Division F - Poster Abstracts


Hypothesis of the massive planet on the periphery of the Solar System

Guliyev, Rustam

The present work reviews selected aspects of the Guliyev's hypothesis about the massive celestial body at a distance of 250-400 AU from the Sun as well as the factor of comets transfer. It is shown, that the conjecture of the point around which cometary perihelia might be concentrated, is not consistent. On the issue of perihelia distribution, priority should be given to the assumption that there is a plane or planes around which the concentration takes place. The search engine for such planes was applied to numerous cometary groups, separated by clusters T (discover date), e, q, H (absolute magnitude), Q, 1/aori, etc. A total of 24 comet groups were investigated. In almost all cases there are detected two types of planes or zones: the first one is very close to the ecliptic, another one is about perpendicular to it and has the parameters: ip = 86°, Ωp = 271.7°. The existence of the first area appears to be related to the influence of giant planets. The Guliyev's hypothesis says that there is a massive perturber in the second zone, at a distance of 250-400 AU. It shows that number of aphelia and distant nodes of cometary orbits in this interval (within statistical confidence) significantly exceeds the expected background. On the basis of collected cometary data, we have estimated orbital elements of the hypothetical planetary body: a = 337 AU; e = 0.14; ω = 57°; Ω = 272.7°; i = 86° Naturally, each value may contain some errors. In order to test the stability of such an orbit, the planet was integrated for 10 million years, assuming that its mass is about 10 Earth masses. The orbits of 33 comets (having aphelia and distant nodes 286-388 AU) are also integrated in the past for a million years in order to trace possible dynamic relationship with the planet. In doing so, we varied the mean anomaly of the planet from 0° to 360° by 10° in each cycle of numerical explorations.

Perseid meteoroids by the Tajikistan fireball network observations. I. Dynamical features

Kokhirova, Gulchehra

Fireball observations were started in the Institute of Astrophysics of the Academy of Sciences of the Republic of Tajikistan in 2006. The network consists of 5 stations situating on the south part of the Tajikistan territory and covering the area of near eleven thousands square kilometers. The mutual distances between them range from 53 to 184 km. The stations are equipped by the all-sky cameras with the Zeiss Distagon "fish-eye" objectives (f=30 mm, D/f =1:3.5) using sheet films and by the digital SLR cameras "Nikon D2X" and "Nikon D300" with the Nikkor "fish-eye" objectives (f=10.5 mm, D/f=1:2.8). The all-sky cameras provide us with photographic data about meteors brighter than -4 magnitudes, which are called fireballs. Astrometric and photometric reduction procedures the same as in the European Fireball Network (EN) are using. Photographic observations of the Perseid meteor shower activity were carried out by the Tajikistan fireball network at the maximum of the shower during 2007-2011. 29 Perseid fireballs were registered over this period. The fireballs were produced by meteoroids with sizes larger than small dust particles which form usual meteor phenomenon. As a result of astrometric and photometric reduction of the obtained observational data the atmospheric trajectories, velocities, orbits, light curves of fireballs as well as the photometric masses and densities of meteoroids were determined. Detected fireballs present sufficient data set for analysis of physical and dynamical properties of the large-sized Perseid meteoroids. The results of investigation of their dynamical features are presented in this paper. It is shown that detected Perseid activity was caused by both the Perseid filament and annual shower activity.

Dynamical and physical properties of presumed meteorite-dropping fireballs photographed by the Tajikistan fireball network

Kokhirova, Gulchehra

The systematic double-station observations of fireballs were started in the Institute of Astrophysics of the Academy of Sciences of the Republic of Tajikistan in 2006 with the aim to study the large-sized meteoroids penetrating the Earth's atmosphere. Obtained experience and results have stipulated the organization of the fireball network in 2008. The network consists of 5 stations situating on the south part of the Tajikistan territory and covering the area of near eleven thousands square kilometers. The mutual distances between them range from 53 to 184 km. The stations are equipped by the all-sky cameras with the Zeiss Distagon "fish-eye" objectives (f=30 mm, D/f =1:3.5) using sheet films and by the digital SLR cameras "Nikon D2X" and "Nikon D300" with the Nikkor "fish-eye" objectives (f=10.5 mm, D/f=1:2.8). The all-sky cameras provide us with photographic data about meteors brighter than -4 magnitudes, which are called fireballs. More than 400 multi-station fireball images including digital ones were photographed by the network in the period 2006-2012. The geometrical conditions for 230 multi-station fireballs were good enough to compute reliable trajectories. Astrometric and photometric reduction procedures the same as in the European Fireball Network (EN) are using. Digital fireball images were measured using the Ascorecord measuring software "FISHSCAN" developed by Dr. J. Borovicka. 25 meteorite candidates, i.e. fireballs that may have dropped meteorites, were identified among processed fireballs. In this work, we present complete and precise data on their atmospheric trajectories, radiants, orbits and light curves. The physical properties such as preatmospheric and terminal masses, densities of the substance of presumed meteorite-dropping meteoroids are considered as well. Strong correlations have found between dynamical and physical features allow describing parameters of typical meteorite event.

Planetary dynamics from observations of planets and spacecraft (ephemerides EPM2017 at IAA RAS)

Pitjeva, Elena

Dynamics of planets have been obtained by constructing high-precision Ephemerides of Planets and the Moon (EPM20017, iaaras.ru/en/dept/ephemeris/epm/2017) at the Institute of Applied Astronomy of the Russian Academy of Sciences, based on 800000 observations of planets and spacecraft in 1913-2015 (Martian orbiters and landers, MESSENGER, Venus Express, Cassini) and LLR data in 1970-2016. The model of planetary motion includes the gravitation interactions between the Sun, planets, the Moon, asteroids and trans-neptunian objects. The most important improvements in EPM at past three years were: the updated model of the orbital and rotation motion of the Moon as an elastic body having a rotating liquid core; updated planetary motion model with Lense-Thirring acceleration, perturbations from the largest 301 asteroids, 30 TNO, and two discrete rotating annuli (the Main asteroid belt and the Kuiper belt); more accurate relativistic barycenter definition; the construction of the long EPM2017H ephemeris covering the timespan of 13000 years. More than 360 parameters of EPM20017 were determined from all observations, including the total masses of the Main asteroid belt and Kuiper belt. EPM ephemerides serve as the basis for the Russian Astronomical and Nautical Astronomical Yearbooks, are planned to be used in the GLONASS and LUNA-RESOURCE programs, and are being used for determination of physical parameters: masses of asteroids, parameters of rotation of planets, the solar gravitation constant (GM_Sun) and its secular variation, PPN parameters, upper limit on mass of dark matter in the solar system. EPM can also be used in search of the remote supposed 9-th planet.

The stellar pulsation timing method to detect substellar companions

Mackebrandt, Felix

Planetary systems undergo their most fateful changes during the pre- and post-main sequence phase of the host star. Subdwarf B stars (sdBs) are laboratories to test how planets survive and influence the late phases of stellar evolution. Those stars are stripped He-burning cores of red giants with a thin hydrogen atmosphere. The canonical model to explain the existence of sdB stars is binary evolution. Formation scenarios for single sdBs are more controversially discussed and can be hard to reconcile with observational properties. Besides the merger of two helium white dwarfs or other merger processes for apparently single sdB stars, an alternative formation channel involves planetary systems. During the RGB the star would develop a common envelope with a giant planet that leads to the loss of the envelope._x000D_ To empirically test this scenario, we have monitored the rapid pulsations of a number of sdBs, which allows to detect sub-stellar companions. Periodic variations in the expected arrival times of the pulsation maxima provide evidence for companions. This timing method is particularly sensitive to planets at large distances and complementary to other exoplanet detection methods which are not efficient for stars with small radii and high gravities. Thus, the timing method opens up a new parameter range in terms of the host stars and helps to understand the formation process of single sdBs. Examples of planetary candidates in sdB-systems are V391 Peg b, HW Vir b, c, HS 0705+67003 b and Kepler-429 b, c, d._x000D_ In consideration of future photometric space missions like TESS or PLATO it is essential to enhance the diversity of potential exoplanet host stars that can be probed. We report on the development of an automated pipeline and simulations to validate this method and to apply it to a variety of both ground- and space-based observations. This allows us not only to probe evolved stars but also other pulsating stars such as main-sequence A stars as exoplanet host stars.

A Transit Timing Variation Analysis of Extra-solar Planetary System Qatar-1

Thakur, Dr. Parijat

We present three new transits of the extra-solar planetary system Qatar-1 observed with the 2-m Himalayan Chandra Telescope at the Indian Astronomical Observatory, Hanle, India between June 2016 and September 2016. In order to examine transit timing variation (TTV), our three transits data are combined with thirty five previously available transit light curves. These thirty eight transit light curves allow us to estimate the physical and orbital parameters, as well as to refine the ephemeris for the orbital period and mid-transit time to investigate the possible transit timing variation (TTV) in this extra-solar planetary system. It is found that there is no evidence of transit timing variation (TTV) to confirm the presence of additional planet in the extra-solar planetary system Qatar-1.

Precise and fast computation of gravitational field of general finite body and its application to gravitational study of asteroid Eros

Fukushima, Toshio

In order to obtain the gravitational field of a general finite body like Ryugu inside its Brillouin sphere, we developed a new method to compute the field accurately (Fukushima 2017, Astron. J., 154:145). First, the body is assumed to consist of some layers in a certain spherical polar coordinate system and the volume mass density of each layer is expanded as a Maclaurin series of the radial coordinate. Second, the line integral with respect to the radial coordinate is analytically evaluated in a closed form. Third, the resulting surface integrals are numerically integrated by the split quadrature method using the double exponential rule. Finally, the associated gravitational acceleration vector is obtained by numerically differentiating the numerically integrated potential. Numerical experiments confirmed that the new method is capable of computing the gravitational field independently of the location of the evaluation point, namely whether inside, on the surface of, or outside the body. Also, it can provide sufficiently precise field values, say of 14--15 digits for the potential and of 9--10 digits for the acceleration, respectively. Furthermore, its computational efficiency is better than that of the polyhedron approximation. This is because the computational error of the new method decreases much faster than that of the polyhedron models when the number of required transcendental function calls increases. As an application, we obtained the gravitational field of 433 Eros from its shape model expressed as the 24x24 spherical harmonic expansion by assuming the homogeneity of the object.

A specific non-gravitational effect in the asteroid belt as a possible main cause of origin of Trojans in the Solar system

Kazantsev, Anatolii

A specific non-gravitational effect (NGE) in the asteroid belt is revealed. This NGE manifests itself in an increase in the semimajor axes of orbits of low-albedo asteroids relative to the semimajor axes of orbits of high-albedo bodies. The increase of semimajor axes of asteroids with albedos ? < 0.1 may be as high as 1.E–7 AU/year. The NGE presently affects the motion of a considerable fraction (not less than 20%) of main-belt asteroids with diameters up to 40 km.            The NGE action can see from results of numerical calculations of the orbital evolution of asteroids from 2005 to 2016. From the numerical calculations there were obtained differences (da) of semimajor axes of asteroid orbits for 10 years, which are not caused by the gravitational influence of the planets. A significant dependence of the da values on the albedos for bodies with sizes of 5-40 km is obtained.     Such result is confirmed by dependences asteroid albedos on proper semimajor axes for individual asteroid families. The physical mechanism behind this NGE should be close in nature to an NGE in comets.      The action of this NGE can explain:- the well-known reduction of the mean albedo across the asteroid belt;- the existence Trojans of Mars, Jupiter and Neptune and the absence Trojans of Saturn;- the origin of the Hilda group asteroids and the low albedos of these bodies, as well as the  Jupiter Trojans.     This mechanism of the Trojans origin involves certain characteristics of small bodies, which can easy verify from observations:- Mars Trojans  should mostly have retrograde rotation;- Hilda group asteroids and Jupiter Trojans should mainly have prograde rotation.

The Trojans distribution in the Solar System

Kazantsev, Anatolii

Orbits of potential Trojans of different planets in the solar system were selected from the MPC catalog on February, 2017. The evolution of those orbits was calculated. The bodies on librating orbits around the points L4 and L5 were determined.            The quantities of real Trojans in the MPC catalog are as follows: Mars - 5, Jupiter - over 4500, Saturn - none, Uranus - 2, Neptune - 15.            A reasoned explanation of such distribution of Trojans in the solar system is proposed.

Morocco Oukaimeden Sky Survey Telescope in the top 10 since 2012

Zouhair, Benkhaldoun

With more than 1.5 million astrometric measurements sent to MPC, 6 NEO and 4 comets, the MOSS (Morocco Oukaimeden Sky Survey) telescope at the Oukaimeden Observatory (IAU code J43) is one of the most successful asteroids program in the world behind the NASA funded American surveys (PanSTARRS, CSS, Spacewatch…). The 1073 rediscoveries credited to MOSS team on Feburary 3 2018 place the Oukaimeden Observatory at the 26th place for all time since the discovery of Ceres in 1801.Morocco Oukaimeden Sky Survey is the most prolific amateur program in the world. During the period 2011-2017 the MOSS 50 cm F/D=3 scope has taken more than 300k images for an accumulate size of more than 5 Tbit of data. This data ought to be check with automatic process for extracting new supernovae, novae and variable stars.Located in the High Atlas mountains in Morocco, the Oukaimeden observatory benefits of good observing conditions: the median number of observable or clear night is around 230 each year. A weather station is installed in situ since 2010 and the seeing is measured continually since 2015. The median zenith seeing is around 1.0 arcsec.We propose here to describe the characteristics of the instrumentation involved, but above all, the observation and data reduction strategy that made this success possible. 

Planetary cores, their energy flux relationship, and its implications

Johnson, Prof. Fred M.

Integrated surface heat flux data from each planet in our solar system plus over 50 stars, including our Sun, was plotted against each object’s known mass to generate a continuous exponential curve at an R-squared value of 0.99. The unexpected yet undeniable implication of this study is that all planets and celestial objects have a similar mode of energy production. It is widely accepted that proton-proton reactions require hydrogen gas at temperatures of about 15 million degrees, neither of which can plausibly exist inside a terrestrial planet. Hence, this paper proposes a nuclear fission mechanism for all luminous celestial objects, and uses this mechanism to further suggest a developmental narrative for all celestial bodies, including our Sun. This narrative was deduced from an exponential curve drawn adjacent to the first and passing through the Earth’s solid core (as a known prototype). This trend line was used to predict the core masses for each planet as a function of its luminosity.

Formation of trans-Neptunian satellite systems at the stage of rarefied condensations

Ipatov, Sergei

The angular momenta used by Nesvorny et al. [1] as initial data in their calculations of contraction of condensations leading to formation of trans-Neptunian binaries could be acquired at collisions of two condensations that were moving before collisions in circular heliocentric orbits [2]. Initial angular momenta of condensations were not enough for formation of binaries. The parental condensation with radius close to its Hill radius that grew by accumulation of small objects could get the angular momentum at which a satellite system of a trans-Neptunian object could form. However, in this case the angular momentum of all satellite systems (e.g., binaries) would be positive. Actually about 40% of discovered trans-Neptunian binaries have negative angular momentum. Depending on heliocentric orbits of two colliding condensations, the angular momentum at their collision can be positive or negative. For the model of formation of binaries at the stage of rarefied condensations, I explained [3] the formation of prograde and retrograde rotation of discovered trans-Neptunian binaries, the inclinations of orbits of secondaries at different ratios of diameters of the secondary to the primary, the inclinations of orbits of secondaries at different orbital elements of heliocentric orbits of binaries, the separation distances at different heliocentric orbits, the orbits of binaries at different separation distances. The work was supported  by the RFBR grant ? 17-02-00507 (angular momenta of condensations needed for formation of binaries) and by the Program of the Fundamental Studies of the Presidium of RAS N 28 as a part of Russian state program for GEOKHI N 00137-2018-0033 (origin of orbits of secondaries in binaries). [1] Nesvorny D. et al. Astron. J. 2010. 140. 785-793. [2] Ipatov S.I. Solar System Research. 2017. 51. 321-343. https://arxiv.org/abs/1801.05217. [3] Ipatov S.I. Solar System Research. 2017. 51. 409–416. https://arxiv.org/abs/1801.05254

Possible relations between outbursts and diamagnetic cavities in comet 67P/Churyumov-Gerasimenko

Voelzke, Marcos Rincon

On 2014 August 06 the Rosetta spacecraft arrived at comet 67P/Churyumov-Gerasimenko. Since then, the spacecraft accompanied the comet on its journey around the Sun (Glassmeier et al. 2007a), until the end of the mission on 2016 September 30. This work tries to understand the possible connections between the 665 reported diamagnetic regions (Goetz et al. 2016), detected from April 2015 to February 2016 around the comet 67P/Churyumov-Gerasimenko, with the fluxgate magnetometer of the Rosetta Plasma Consortium (RPC-MAG), when the heliocentric distance of the comet from the sun varied from 1.8 to 2.4 AU and the 34 reported outbursts (Vincent et al. 2016), detected from July to September 2015, with the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) cameras, when the ESA´s Rosetta spacecraft changed the cometocentric distance from 155 to 817 km.

Gaseous clumps, accretion bursts, and the prospects of giant planet formation in gravitationally unstable protostellar disks

Elbakyan, Vardan

Planets form in gaseous and dusty disks around young stars. A possible scenario for giant planet formation is disk gravitational instability and fragmentation. We use high-resolution grid-based numerical hydrodynamics simulations to compute the formation and long-term evolution of gravitationally unstable protostellar disks around solar-mass stars. We show that gaseous fragments that have formed in the outer regions of a protostellar disk (> 100 AU) through disk fragmentation may later become perturbed by other fragments or disk structures, such as spiral arms, and quickly migrate toward the central star (during ~ few 103-104 years). During inward migration, the fragments first gain mass (up to several tens of Jupiter mass), but then quickly lose most of it through tidal torques when approaching the star. Part of the lost material can be accreted on the central star causing an FU-Ori-type luminosity outburst. This mass loss, or tidal downsizing, helps the fragments t o halt their inward migration at a distance of a few tens of AU. The resulting fragments are heavily truncated both in mass and size compared to their wider-orbit counterparts, keeping only a dense and hot nucleus. During the inward migration, the central temperature in these fragments may exceed the molecular hydrogen dissociation limit (~2000 K) and the central region of the fragment can collapse into a gas giant protoplanet. We argue that FU-Orionis-type luminosity outbursts may be the end product of disk fragmentation and inward fragment migration, ushering the formation of giant protoplanets in the inner parts of protostellar disks.

Near-Infrared atmospheric modelling of Jupiter’s Southern Equatorial Belt (SEB) observed with AAT/IRIS2

Karamiqucham, Behrooz

The low resolution (R ~ 2400, H and K bands) spectra of Jupiter’s Southern Equatorial Belt have been modelled using VSTAR (Versatile Software for Transfer of Atmospheric Radiation) and ATMOF (ATMOspheric Fitting) codes through observation of the Anglo-Australian Telescope’s  Infra-Red Imaging Spectrograph 2 (AAT/IRIS2). By creating a line-by-line radiative transfer model with the most latest ammonia and methane line lists we derived the best models in the Jupiter’s, ammonia depleted, SEB. Using different cloud and haze opacities and distributions resulted from our modelling outputs, we were able to fit our models to the spectra of the planet in the observed region. Our findings enable us to use and define the resulted parameters to uncover the cloud and haze pressure heights and opacities in the spectral H and K bands of Jupiter’s troposphere and stratosphere.

A formation mechanism of 4179 Toutatis-like elongated contact binary configuration

Hu, Shoucun

4179 Toutatis is a near-Earth asteroid with a bifurcated shape and an extremely slow tumbling rotation. The measurements from previous radar models and optical images acquired by Chang’e-2 spacecraft show that Toutatis has an elongated contact binary configuration, composed of two lobes (body and head), with the contact point located along the body’s long axis. We speculate that such configuration may have resulted from a low-speed impact between two components. In this work, we have performed a series of numerical simulations and further compared the results with the images captured by Chang’e-2, to examine the mechanism and better understand the formation of Toutatis. Herein we propose an scenario that an assumed separated binary precursor could undergo a close encounter with Earth, leading to an impact between the primary and secondary, and the elongation of the asteroid is caused by Earth’s tide. The precursor is assumed to be a doubly synchronous binary with a semi-major axis of 4 Rp (radius of primary) and two components are represented as spherical cohesionless self-gravitating granular aggregates. The mutual orbits are simulated in a Monte Carlo routine to provide appropriate parameters for our N-body simulations of impact and tidal distortion due to Earth. We employ the numerical package pkdgrav with a soft-sphere discrete element method (SSDEM) to explore the entire scenarios. The results show that contact binary configurations are natural outcomes under this scenario as long as using proper initial conditions, whereas the shape of the primary is almost not affected by the low-speed impact of the secondary. However, our simulations provide an elongated contact binary configuration best-matching to the shape of Toutatis at an approaching distance rp = 1.4 ~ 1.5 Re (Earth radius), indicative of a likely formation scenario for configurations of Toutatis-like elongated contact binaries.

Deep high-resolution imaging of the field around nearby stars of the Ursa Major moving group

Ammler-von Eiff, Matthias

Results from a search for low-mass companions in the vicinity of 20 nearby Ursa Major group members are reported. The Ursa Major open cluster is the nucleus of this group and coincides with the Big Dipper constellation. Other members are spread over the entire sky and share a common space motion. The selected targets of high proper motion pass the background field quickly so that any comoving companion could be identified easily. The targets are also nearby and young so that low-mass companions would be bright in the near-infrared and separated well from the stellar image. The observations were taken with NAOS-CONICA at the ESO VLT in the Ks band using a semi-transparent coronagraph. The consolidated results of this survey have been published recently.The survey achieved a brightness contrast of typically 13-15 mag and was sensitive to objects as faint as 20 mag at separations between a few arcseconds and up to 25 arcseconds from the star. This is as close as several astronomical units for the nearby eps Eri and up to 600 au and more for the most distant targets. More than 200 faint background sources were identified. We will discuss the observations in the light of similar ground-based direct imaging campaigns and other recent studies of the UMa group.High-resolution imaging is not only a key technique to detect giant planets in wide orbits around nearby stars but is also essential for the follow-up of transit candidates from missions like TESS and PLATO. These monitor wide fields at low spatial resolution so that additional observations are needed to distinguish contaminating sources close to the actual targets. Even though NAOS-CONICA has already been decommissioned, the results presented are considered relevant to the ground-based follow-up of TESS and PLATO targets as those will be bright, potentially nearby, and may display significant proper motion.

Slichter modes of celestial bodies through a variational formalism

Escapa, Alberto

Some bodies of the solar system are thought to have a subsurface global fluid layer. Indeed, it is the case for the Earth, but other planets like Mercury or some icy satellites may also share this situation._x000D_ A particular feature of this kind of bodies is that the barycenters of its solid constituents can perform differential displacements. This internal dynamics has commonly an oscillatory nature. It was considered for the first time in the Earth case by Slichter (1961). Hence, the denomination of Slichter modes for referring to its different normal or oscillation modes. The Slichter modes of other bodies have received less attention in spite of the fact that, if excited, their observation might provide an indirect proof of the existence of an internal fluid layer or constrain its dimensions._x000D_ We revise the necessary steps to implement the variational formalism (Escapa & Fukushima 2011, 2015) to solve this kind of problems. Its main advantage is that the solids and the fluid are considered as a single dynamical system. Its dynamics is obtained from the Lagrangian, involving the computation of the kinetic and potential energies of the solids and the fluid. The dynamics of the fluid, in these circumstances, is captured by solving a Neumann problem that just depends on the dynamical state of the solids (Lamb 1916). Hence, the fluid-solid interaction is automatically incorporated into the kinetic energy of the system without needing the computation of the pressure field of the fluid._x000D_ The theory is exemplified by applying it to two different models of three-layer structures: in the first, both solid constituents are undifferentiated whereas in the second one the inner core is assumed to be differentiated. It allows us to discuss the dependence of the Slichter mode on the rheological properties of the model, as well as to compare the Slichter modes of different celestial bodies. Applications to different models of Mercury, Europa, Titania, Oberon, etc. are provided.

Chemical signatures of rocky accretion in young solar-type stars

Spina, Lorenzo

It is well known that newly formed planetary systems undergo processes of orbital reconfiguration and planetary migration. As a result, planets or protoplanetary objects may accrete onto the central star, being fused and mixed into its external layers. Such dramatic events may result in a modification of the chemical composition of the stellar photosphere in an observable way, enhancing it with elements that were abundant in the accreted mass. Open clusters are groups of stars that formed from the same nebula and started as chemically homogeneous, thus they are the ideal targets for the identification and the study of chemically anomalous stars that may have accreted planets. In this talk I will review our recent results on the chemical content of five solar-type members of Pleiades. Our analysis has revealed that chemical anomalies exist among these cluster members and that the abundance differences between the members are correlated with the condensation temperature. This finding strongly supports that planet engulfment events are frequent among Sun-like stars.

Problems with exoplanets around sdBV snd sdO stars from primary Kepler field

Krzesinski, Jerzy

The existence of exoplanets around evolved objects is one of the most interesting subjects from the viewpoint of planetary systems evolution and their fate. What happens to the exoplanets engulfed in the host star envelope during red giant branch (RGB) phase? What is the fate of planets when the host star enters the asymptotic giant branch (AGB) evolution? Do planet form from the debris of the AGB remnant material or are there any survivors from the original planetary system? These and other questions are crucial for our understanding of the late planetary system evolution.    We do observe planets around giant stars, however, since the discovery of exoplanets around pulsars (Wolszczan and Frail 1992), there are still continuous searches going for exoplanets around white dwarfs and intermediate stage stars – subdwarfs. The last one seems to be successful in terms of finding candidates for giant and earth type planets around extreme horizontal branch stars, but is this a confirmed link for planetary existence between RGB/AGB and white dwarf phase of the stars?  Here we are showing that at least some of the exoplanetary signatures found in the light curves of a couple of sdBV star systems (KIC 5807616 and KIC 10001893) might be of different source than exoplanet light reflection or radiation effects. We point out that at least one signature can be explained by linear combination of pulsating frequencies of the host star and others might be just artifacts. Using simulated light curves we also analyzed frequency changes of the signal around 0.256 c/d (~3.9 day) visible in the Fourier transform of the KIC 10449976 sdO star light curve. Our simulations show that it is difficult to reproduce the observed signal frequency variations by the weather changes in the exoplanet atmosphere.

Thermal conductivity of porous dust aggregates

Arakawa, Sota

The thermal conductivity of dust aggregates is a key parameter in planetary science, including thermal evolution of minor planets and comets. However, the porosity dependence of thermal conductivity for highly porous aggregates is not yet thoroughly understood.We numerically investigated the thermal conductivity of fluffy dust aggregates. In our calculation, we used the snapshot data of N-body simulations of static compression in the periodic boundary condition and determined the temperature structure and heat flux of the porous dust aggregates.We derived an empirical formula for the solid thermal conductivity as a function of the filling factor of dust aggregates. The results reveal that the solid thermal conductivity is approximately proportional to the square of the filling factor. For the case of dust aggregates with the filling factor in the range of 0.1-0.5, our results are well consistent with the experimental data. Moreover, we also found that the solid thermal conductivity is significantly lower than previously assumed for highly porous aggregates whose filling factor is lower than 0.1. In light of these findings, we will reexamine the thermal histories of small planetary bodies.

Exocomets in the Proxima Centauri system and their importance for water transport

Schwarz, Richard

The scenario and the efficiency of water transport by icy asteroids and comets are still amongst the most important unresolved questions of planetary systems. The detection of Proxima Centauri b (PCb), which moves in the habitable zone of this system, triggered a debate whether or not this planet can be habitable depending on its formation history and available water content. A better understanding of cometary dynamics in extrasolar systems shall provide information about cometary reservoirs and give an insight into water transport especially to planets in the habitable zone.In our study we perform numerous N-body simulations with PCb and an outer reservoir of comets. We investigate close encounters and collisions with the planet, which are important for the transport of water. Observers found hints for a second planet with a period longer than 60 days. Our studies show, that from the dynamical point of view, two planets are stable even for a massive second planet with up to ~ 12 Earth masses. In a third model we perform simulations including exocomets, a second planet, and the influence of the binary alpha-Centauri.The studies on the dynamics of exocomets reveal that the outer limit for water transport is between 100 and 200 au. In addition we could show that water transport would be possible for a close in planetesimal cloud (1-4 au) which was detected by Anglada et al. 2017. From our simulations we estimate the water mass delivered to the planets to be between 0 and 30 Earth oceans.Anglada G., et al., 2017, ApJ, 850, L6

Observations of near-Earth object 2012 TC4 — The high-time resolution lightcurve with the Tomo-e Gozen camera

Urakawa, Seitaro

Explorations of Itokawa by Hayabusa space probe revealed that asteroids can take a rubble pile structure in which numerous pieces of the rock are weakly constrained by gravity. On the other hand, asteroids that are constructed from a piece of rock itself are called monolithic asteroids. The monolithic asteroids can be said to be the smallest unit object constructing rubble pile asteroids. To clarify the structural strength and/or the constituting substance of the monolithic asteroids help us to understand the physics of asteroids more deeply.  A near-Earth object 2012 TC4 (hereafter TC4) was observed in 2012, and the rotation period was to be 12.24 minutes. The fast rotation indicated that TC4 was a monolithic asteroid. The observation opportunity of TC4 had come again in October 2017. This apparition was a very good observation opportunity to investigate the surface of monolithic asteroid that was not covered with the regolith layer. We conducted the observation campaign of TC4 at the Kiso Observatory, the Bisei Spaceguard Center, the Nishi-Harima Astronomical Observatory, the Nayoro City Astronomical Observatory, and the Anan City Astronomical Observatory. In particular, we succeed to obtain the high-time resolution lightcurve of TC4 with the Tomo-e Gozen camera. The Tomo-e Gozen camera is the world's first wide-filed CMOS camera mounted on the 1.05 m Schmidt telescope at the Kiso Observatory. The power spectrum from the period analysis shows the rotation period of 12.252 minutes, and the precession period of 8.479 minutes. Thus, TC4 is a tumbling asteroid. We made the shape model of TC4 from the lightcurve. When we assume TC4 is an ellipsoidal body, the normalized axis lengths are around 2.4, 1.6, and 1.0. Moreover, the visible and near-infrared photometry shows that the taxonomy class of TC4 is X-type. In this presentation, we present the observation results of TC4 and discuss the structural strength and/or the constituting substance of TC4.

Planetesimals role in habitability of TRAPPIST-1 planets

Ðošovic, Vladimir

Minor planets (aka asteroids and comets) are widespread in the solar system, and theobservational evidence suggests that similar planetesimal objects exist also in other planetary systems. Existence of minor planets is also predicted by planet formationmodels. These remaining planetesimals may however play a very important role for ahabitability of the planets within a planetary system. In this work we investigated the role of a hypothetical planetesimal belt locatedclose to the snow line in the Trappist-1 system. We performed N-body simulations to estimate theflux of the small objects towards the planets, focusing on two possible consequences ofthis transport.First, we analyzed the amount of water that may by transported by icy planetesimalsto planets.Second, we estimated the impact risk for each planet, and discussed how these mayaffecthabitability of the planets within the Trappist1 system. Our results showed that during the early phases of the system formation, flux of theplanetesimals from the belt to the region of planets may be significant under certain conditions,allowing significant amount of water to be transported to the planets. The transportis mainly caused bymean motion resonances, although in some cases secular resonances may play acritical role. During the later phases, the flux is significantly reduced, making the impact riskfor potentially habitable planets very small. This is primarily because the non-gravitationaleffects are inefficient in the systems around dwarf stars.

Habitable Zones in Binary Star Systems: New Analytic Estimates

Eggl, Siegfried

A large fraction of stars in our galactic neighborhood have close stellar companions. Whether or not terrestrial planets can retain Earth-like conditions in such systems largely depends on the interplay between stellar radiation, orbital dynamics and a planet’s “climate interia.” The latter is a measure of how quickly a planet’s climate adapts to time dependent radiative orbit forcing. In this contribution I present new analytic estimates that accurately predict the existence and extent of dynamically stable habitable zones in binary star systems by fully accounting for the interaction between the stars and the planet. Analytically derived habitable zone borders are, furthermore, compared to current state-of-the-art climate simulations using 3D General Circulation Models (GCMs).

SPHEREx: Exploring the Origin and Evolution of Interstellar and Biogenic Ices

Unwin, Stephen

Many of the most important building blocks of life are locked in interstellar and protoplanetary ices including H2O, CO, CO2, and CH3OH. The cores of dense molecular clouds and the mid-plane of protoplanetary disks contain much more of these species in the form of ices rather than the gas phase. These key species are thought to be delivered to young planets through collisions with ice-bearing bodies. We wish to understand the role of cloud density and temperature, presence or absence of embedded sources, external FUV and X-ray radiation, gas-phase composition, and cosmic-ray ionization rate, on the ice composition of clouds at similar stages of evolution. Ultimately, our goal is to understand how these findings connect to our own Solar System.  Currently, there are too few ice absorption spectra toward Galactic molecular clouds, less than 250, to permit an exploration of these effects and understand their contributions.SPHEREx would change that in a major way. It is an all-sky spectroscopic survey, currently in Phase A study, and it would provide optical and near-IR spectra, including the 2.5 to 5.0 µm region which encompasses the above biogenic ice features. With a spectral resolution of R=135 at the long-wavelength end, SPHEREx would deliver more than 105 spectra of illuminating background continuum sources for absorption spectroscopy with SNR = 100 per spectral resolution element, allowing detection and abundance measurement of several ice species. Having a huge number of such high-SNR ice absorption spectra would allow us to explore a wide variety of regions distributed throughout the Galaxy and reveal correlations between ice content and environment not possible with the limited sample currently available. SPHEREx would overlap with JWST beyond 2022, allowing SPHEREx to identify the most valuable ice sources for JWST follow-up.

Climate model for habitable locked planets (Mini conference on planetary astronomy)

Wandel, Amri

Habitable Zone planets of M-dwarfs are likely to synchronously orbit their host star. Recent detections of planets in the habitable zone of Proxima Centauri, Trappist-1, and many other nearby M-type stars, as well as the easier detection of bio-signatures of planets orbiting M-dwarfs by future telescopes, raise the need for a simple climate model for such planets, that can calculate actual habitability limits for many atmosphere types. We derive a simple 1-D semi-analytical model for the surface temperature distribution of synchronously rotating planets, taking into account their atmospheric properties. The atmospheric impact on the temperature is quantified in terms of the greenhouse heating, stellar irradiation, albedo and heat redistribution (Wandel 2018, ApJ). The results suggest that planets orbiting M-type stars may have life-supporting temperatures, at least on part of their surface, for a wide range of atmospheric properties.

Vortex stretching in self-gravitating protoplanetary discs

Regaly, Zsolt

Horseshoe-shaped brightness asymmetries of several transitional discs are thought to be caused by large-scale anticyclonic vortices. This vortices can efficiently collect dust particles, therefore they can play a major role in planet formation. Former studies suggest that the disc self-gravity weakens vortices formed at the edge of the gap opened by a massive planet in discs whose masses are relatively large, e.g. being in the range of 0.01 = Mdisc/M* = 0.1. In my talk, i present our investigation on the role of disc's self-gravity in the evolution of large-scale vortices excited at discs' dead zone outer edge. We performed our study by means of 2D numerical hydrodynamical simulations taking into account the disc's self-gravity in a locally isothermal approximation. Interestingly, vortices are found to be strongly affected by the disc's own gravitational field even for low mass discs, Mdisc = 0.005M* (Q<=50 initially) for which case the effect of disc's self-gravity was thought to be negligible. As a result of this azimuthal stretching, vortices have weaker azimuthal density contrasts and prone to decay faster than in non-self-gravitating discs. The vortex stretching can be explained by the combined action of a non-vanishing gravitational torque caused by the vortex itself, and the Keplerian shear of the disc. Based on our results, we conclude that the formation of long-lasting vortices requires a relatively small disc-to-star mass ratios being less than 0.5 percent and low disc viscosity. We also conclude that a former scenario in which a gravitationally stable disc fragments inside vortices, can not be a plausible pathway to planet formation, because of the vortex stretching tends to decrease the density enhancement at the vortex centre before fragmentation occurs. 

Simulating the Water Vapor Flow through Enceladus' South Polar Cracks

Sakuler, Wolfgang

A plume of water vapor and ice particles has been discovered by the Cassini spacecraft orginating from the south polar terrain (SPT) of Saturn's icy moon Enceladus [1]. The observations by Cassini showed evidence that water vapor and ice particles are evaporating from a subsurface liquid ocean [2-4]. These particles flow through cracks in the ice shell, that have a crack depth between several 100 m and a few km [5] and an estimated crack width of ~0.1 - ~1 m [5].We analysed the water vapor flow through the vents via numerical simulations of the 2-dim Navier-Stokes equations. The distributions of pressure and the 2-dim velocity vector field inside the cracks have been computed. For the numerical simulations the open-source computing platform FEniCS (Finite Element Computational Software) [6] for solving partial differential equations (PDEs) has been employed. Simulations have been performed for different crack lengths and crack widths, and for various vent geometries, ranging from simple rectangles, i.e. having a constant crack width, up to more complicated structures with varying crack widths including throats, discontinuities, kinks, zig-zag lines, and forking branches.The calculations show that the distribution and magnitude of the velocity strongly depend on the vent geometry. Vents with varying crack widths experience strong velocity boosts around throat-like narrowings. The simulations for the more realistic vent geometries including throats and discontinuities provide velocity distributions at the upper vent opening that are consistent with observations.[1] Porco, C.C., et al., Science 311, 1393-1401, 2006.[2] Thomas, P.C., et al., Icarus 264, 37-47, 2016.[3] Cadek, O., et al., Geophys. Res. Lett. 43(11), 5653-5660, 2016.[4] Le Gall, A., et al., Nature Astronomy 1, 0063, 2017.[5] Nakajima, M., Ingersoll, A.P., Icarus 272, 309-318, 2016.[6] "The FEniCS Project page", https://fenicsproject.org

New insight into the coma of comet 2P/Encke: apparitions of 2013 and 2017

Rosenbush, Vera

We present new results of photometric, polarimetric, and spectroscopic observations of comet 2P/Encke performed at the 6-m telescope of the SAO RAS during apparitions of 2013 and 2017. We observed the comet through the narrow-band filters isolating dust continuum domains BC (blue) and RC (red) and the emission band of NH2 as well as with broad-band SED500, V, and r-sdss filters to provide the best images. The full filter set of Encke images shows different morphology of the coma and variations in its size and structure as a function of wavelength that yields insight into the chemistry of the coma.As in the case of comet 67P/Churyumov–Gerasimenko (Rosenbush et al. 2017, MNRAS469), we found that the near-nucleus area of comet Encke is redder and more polarized than the adjacent coma. The dust color gradually changed from 1.0m in the innermost coma to about 0.3m in the outer coma. At the same time, the corrected for gas contamination radial profiles of polarization showed that the polarization in the near-nucleus area was almost 12%, dropped sharply to 6% at the distance 3000 km, and then gradually increased with projected distance from the nucleus, reaching 12% at 12000 km. Such radial variations of polarization and color in both comets, dust-poor comet Encke and dust-rich comet 67P/C-G, suggest a change in the particle properties and, hence, in the mean scattering properties of the grains on a time-of-flight timescale. To calculate the light scattering properties of individual scattering particles, the Sh-matrix method (Petrov et al. 2012, JQSRT 113) was used. Our simulation allowed us to determine the microphysical parameters of the model particles and describe the observed changes in color and polarization.We will demonstrate results of observations of comet Encke and discuss the possible reasons of diversity and similarity of physical characteristics of gassy comet Encke and dusty comet 67P/C-G.

Visible spectra of ETNOs using the 10.4m Gran Telescopio Canarias

de Leon, Julia

The so-called extreme trans-Neptunian objects (ETNOs) are very distant minor bodies presenting orbits with semi-major axes larger than 150 au, and perihelion distances larger than 30 au. Due to their distance, there are less than 30 ETNOs discovered so far, the first one identified in 2000. This is a very interesting population that is currently generating some debate about the possibility on the existence of a yet-to-be-discovered planet in the outer regions of our solar system (Planet X). With the aim of shedding some light to this controversy, we initiated a spectroscopic survey in 2016 to obtain visible spectra of ETNOs using the unique capabilities of the 10.4-meter Gran Telescopio Canarias (GTC), located at the El Roque de Los Muchachos Observatory, in the island of La Palma (Spain). Here we present our most recent results and the current status of this spectroscopic survey.

Atmospheric Mass Loss due to XUV radiation from Sgr A* in Planetary Lifetime

Wislocka, Agata

In recent years, there has been a noticeable rise in interest in the damage caused to planetary atmospheres as a result of exposure to XUV radiation (capable of driving hydrodynamic winds) emitted by super massive black holes (SMBH) as they accrete matter. These studies have mainly concentrated on the theoretical mass loss of Earth-like planets as a function of distance from our own SMBH, Sgr A*, located at the centre of the Milky Way Galaxy. The focus of our work is the quantification of total mass loss as a function of planet distance, bulk density and age experienced by all Earth-like planets discovered to date, as well as the 16 Sagittarius Window Eclipsing Extrasolar Planet Search (SWEEPS) exoplanets known to reside in the bulge of the Milky Way Galaxy. Based on the current body of evidence, Sgr A* went through an active phase approximately 8 Gyrs ago. This would indicate a more severe loss of atmosphere for some planets in our sample, with ages of host stars exceeding 8 Gyrs. For planets orbiting stars younger than 8 Gyrs, we find the mass loss to be negligible under the assumption that Sgr A*’s luminosity has remained constant, at its current value LSgr A* = 10-8.5 LEdd since the end of its active galactic nucleus (AGN) stage.

A new perspective for understanding the Hyperbolic Meteors type after interstellar object Oumuamua discovery


Hyperbolic meteors are a subset of meteoroids encountering the Earth's atmosphere, which some of them could have an interstellar origin, characterized by orbital elements possessing a<0 and e>1. Hyperbolic meteors have been identified in many meteors surveys [1,2]. Maria et.al [2] calculated a total number of 484 hyperbolic orbits from 64,650 meteors within the SONOTACO catalogue [4], representing 3.28% of all orbits.There are often significant errors when estimating heliocentric velocities of a meteor due to inaccuracy of measurements, pertubation from recent close planetary encounters, and solar radiation that could generate false hyperbolic orbits in the parameters estimated. After accounting for these, there still remains a small fraction of hyperbolic solutions that could still be interstellar meteoroids, as demonstrated by Maria [2] with an upper frequency limit of 1 in 1000 meteors.After the discovery of the first confirmed extrasolar object crossing our Solar System, 1I/2017 U1 ('Oumuamua), on 2017 October 19 [3], the discussion was renewed about the presence of such objects, suggesting the previous number density may be understimated.Thus a meteor surveillance system that improves hyperbolic identification for meteoroid candidates through the use of better measurement accuracy for heliocentric velocity, will help obtain orbital information with higher reliability and be used as a way to search for signatures of parent objects with extrasolar origins. With reliable orbital data, a better estimate for the number density of interestellar objects could be achieved.[1] Hajduková, M., Kornoš, L., and Tóth, J. (2014). Frequency of hyperbolic and interstellar meteoroids. Meteoritics and Planetary Science, 49:63–68.[2] Meech, K.J., Weryck, R., Micheli, M., et al. (2017). A brief visit from a red and extremely elongated interstellar asteroid.Nature, 552:378.[3] SonotaCo. (2009). A meteor shower catalogue based on video observations in 2007–2008. WGN 37:55–62.

Dynamical evolution of comet pairs

Sosa, Andrea

Some Jupiter family comets in near-Earth orbits (thereafter NEJFCs) show a remarkable similarity in their present orbits, like for instance the comets 169P/NEAT and P/2003 T12 (SOHO), or the comets 252P/LINEAR and P/2016 BA14. By means of numerical integrations we studied the dynamical evolution of these objects. We integrated the orbits of the objects plus 1000 clones for each one of them, for 10,000 years in the past and in the future. We found that 169P and P/2003 T12 move on stable orbits for the past 10,000 years, avoiding very close encounters with Jupiter, in good agreement with Fernandez and Sosa 2015 ( Planetary & Space Science 118, pp. 14-24). By the contrary, we found that 252P and P/2016 BA14 move on highly unstable orbits, with frequent very close encounters with Jupiter.  For 169P and P/2003 T12 we found some well defined minima of their relative spatial distance, almost coincident with a minimum of their relative velocity. In order to study if a breakup of a parent body could be the most probably origin for this comet pair, we simulated the orbital evolution of hypothetical fragments of 169P. Our aim is to reproduce the actual orbit of P/2003 T12 by modeling a fragmentation of 169P.  Might be exist several causes for the fragmentation of the parent body, like thermal stress, rotational instability, collisions, or tidal forces if the object pass too close to a masive body (like the Sun or Jupiter). Some of the main model parameters are the relative ejection velocity (a few m/s), the orbital point at what the fragmentation could have happened (e.g. perihelion), and the elapsed time since fragmentation. Tentative values for this last parameter were based in the minima of the relative distance and velocity that we found in the past dynamical evolution of the comet pair. The robustness of the results are also evaluated.

Sizing up small bodies: New technologies, new challenges

Conrad, Albert

In recent years the exploration, characterization, and mapping of small bodies via remote sensing has continued at an ever-quickening pace. Advances in adaptive optics on bigger telescopes now allow researchers to study the shape of main belt asteroids like (16) Psyche at the resolution of a few kilometers from ground-based facilities [Drummond, et al (2018), Shepard, et al (2017)].  Spectrographs, optimized for the purpose, can determine the composition of small bodies as faint as 21st magnitude, in some cases only 50 meters in diameter [Reddy, et all (in prep)].  Advances in radar, stellar occultation, and light curve methods also continue; and all of these methods can often be combined to make accurate shape measurements of an increasingly large population of worlds that can be mapped [Carry, et al (2012)].With new technologies come new challenges, for example "big data" and complex data products that can only be interpreted by sophisticated software pipelines.  In our presentation, we report on new methods and policies for meeting these challenges.  In particular, we look at how the community is coping with the rapid increase in the reported measurements of small body properties; with special attention to those bodies that are the intended destination for spacecraft missions, such as the NASA Discovery Class mission to (16) Psyche.

Understanding internal structure of planetary satellites through astrometry

ARLOT, Jean-Eudes

The internal structure of the natural planetary satellites have an influence on the motion of these objects. Careful observations may lead to constraints on this structure. However, in spite of the high accuracy of recent space probe observations, the observations are not made on a sufficient interval of time to put into evidence the effects due to the internal structure. These effects are cumulative and we need long period observations. In order to solve that problem, we digitized old photographic plates and reduced them with the Gaia reference star catalogue providing old data with today accuracy. This method is very promising for the understanding of the formation, evolution and structure of the natural planetary satellites.

Analysis of gas/dust productivity and molecular composition of cometary comae, which were investigated in 2008-2017

Ponomarenko, Vasyl

In 2008-2017 years we estimated the gas and dust productivity of comets 8P/Tuttle, 46P/Wirtanen, 81P/Wild 2, 103P/Hartley 2, ?/2009 K5 (McNaught), C/2009 P1 (Garradd), C/2013 US10 (Catalina), C/2014 Q2 (Lovejoy). The research has been performed on the basis of the optical spectra with an average resolution (?/?? ˜ 1300 and ?/?? ˜ 14000). The spectra were obtained on the mountain observatory «Peak ??rsk?l» (MPC code B18) and at the observation station "Lisnyky" (MPC code 585) with the help of the reflecting telescopes Zeiss-2000 (D = 2.0 m; F2 = 16 m) and AZT-14 (D = 0.48 m; F2 = 7.7 m). Also on the basis of obtained spectral material has been carried out the identification of the spectral emission lines and bands of molecules CN, C2, C3, NH2 and other. With the help of Haser and Shulman models were calculated some physical parameters of neutral gaseous and dust cometary atmospheres. The distributions of general and reflected energy along the slit of the spectrograph have been built.The obtained data have been analysed. The performed analysis has showed that the ratio of gas productivity to relative dust productivity (Q/Af?) of comets can indicate on the size of the cometary nucleus. Probable for most large nuclei (D > 4 km) the ratio (Q/Af?) at the heliocentric distances (1 AU < r < 2 AU) has a much smaller value than for small nuclei (D < 0.6 km).

Cloud density for Equilibrium Cloud Condensation Model of Jupiter's atmosphere

Takeuchi, Satoru

Equilibrium Cloud Condensation Model (ECCM) is a popular and simple one-dimensional model for studies of vertical structures of Jovian atmospheres (Weidenschilling and Lewis, 1973). The model predicts vertical distributions of temperature, pressure, mixing ratios of some condensable vapors, and ones of cloud densities after condensations at each altitude. Wong et al.(2014), however, pointed out that the cloud densities predicted by the ECCM exceed vapor's densities before condensations and that the ECCM violates consavation law of mass. In this study, we attempt to introduce more relevant formula of cloud density for the ECCM to keep mass conservation.We think that there are some confused uses between total column values above an altitude and volume values on same altitude in discussion of cloud density of Weidenschilling and Lewis (1973). So, to avoid this confusion, we will construct new formula of cloud density without use of any column values.As a first step, a term of cloud density is added in equation of hydrostatic equilibrium. This term corresponds to pressure decrese by condensation, which is equal to difference between over-saturated partial pressure of an apor before condensation and saturated pressure of same vapor deteremined by temperature at an altitude. Thus, cloud density can be estimated from this connection. The new formula can estimated cloud densities, which don't exceed vapor densities before condensation, and can save conservation law of mass.

What tell close-in brown dwarfs about planetary system's evolution and formation?

Csizmadia, Szilárd

While there are thousands of transiting exoplanets (confirmed or suspected), transiting brown dwarfs are extremely rare and their number is well below 20. However, discovery of brown dwarfs in orbits with orbital period less than 10 days by CoRoT, Kepler, K2 and ground-based surveys caused a surprise because they are in the so-called 'brown dwarf desert' where their occurrence was not expected. Brown dwarfs are suspected to be just high mass giant-planets, the deuterium- or lithium burning are so episodic events that the brown dwarfs can be considered identical to giant planets in the mass-radius diagram (Hatzes and Rauer 2015). Accepting this picture, brown dwarf occurence rates should be studied jointly with the occurence rates of giant planets.Since small mass brown dwarfs may form in the same way as giant planets, close-in brown dwarfs can be test objects: are planet formation theories are generally valid for all mass ranges?Our study showed that the true frequency of brown dwarfs close to their host stars (P< 10 d) is estimated to be approximately 0.2% which is about six times smaller than the frequency of hot Jupiters in the same period range. This result was based on the CoRoT survey. We suspected that the frequency of brown dwarfs declines faster with decreasing period than that of giant planets. We presented an occurrence rate - binary separation relationship for brown dwarf-solar like star systems based on transiting, radial velocity and adaptive optic techniques, and discuss this relationship from a planetary system formation point of view. We point out that our predicted relationship was later fully confirmed by Kepler and by other radial velocity surveys.

Chaotic clearing of the vicinity of rotating small bodies

Lages, José

Asteroids, cometary nuclei, trans-Neptunian objects, planetary satellites, with diameter below 1000km, are usually irregular shape bodies which appear like contact binaries. We show that the rotation of such gravitating bodies creates in their vicinity a zone of chaotic orbits. We determine the chaotic zone extent analytically and numerically. The slower is the rotation rate of the small body, the wider is the chaotic zone. In particular, the chaotic zone swells more than twice if the rotation rate is decreased 10 times with respect to the contact binary “centrifugal breakup” threshold. We precisely determine the properties of the chaotic orbital zones and of the global orbital dynamics about the asteroids; 243 Ida (which has a moon, Dactyl, orbiting near the edge of the chaotic zone), and 25143 Itokawa; and about the cometary nuclei of 67P/Churyumov–Gerasimenko, 1P/Halley, 8P/Tuttle, 19P/Borrelly, and 103P/Hartley. In the case of Comet 1P/Halley, the circumnuclear chaotic zone seems to engulf an essential part of the Hill sphere, at least for orbits of moderate to high eccentricity.References:J. Lages, I. Shevchenko, G. Rollin, Chaotic dynamics around cometary nuclei, accepted in Icarus (https://doi.org/10.1016/j.icarus.2017.10.035)J. Lages, I. Shevchenko, D. Shepelyansky, Chaotic zones around rotating small bodies, The Astronomical Journal 153:272 (2017)L. Maltagliati, Research Highlights: Cloud of chaos, Nature Astronomy 1, 0168 (2017) (highlight of article [2])

Free-floating planets with K2 (and other topics)

McDonald, Iain

Free-floating exoplanets (FFP) are generated by orbital dynamical evolution, mostly at the start and end of stellar evolution. thus their abundance traces migration patterns within planetary systems. Tension exists between occurrence rates of FFPs derived by OGLE and MOA. I describe our blind search for FFPs in data from the K2 Campaign 9, which targetted the Galactic Bulge, and our attempts to resolve this tension. I will finish by summarising other research into planetary migration, evolution and atmospheric characterisation being performed by the SpearNet Manchester-Thai collaboration.

The shapes of fine fragments with several tens of micrometers in impact experiments and influence of petrographic textures: Comparison with Itokawa regolith particles.

Michikami, Tatsuhiro

The shape distribution of Itokawa particles less than 120 µm is distributed around the mean values of the axial ratio 2: v2: 1, which is similar to those of laboratory impact fragments larger than several mm in catastrophic disruption. Thus, the Itokawa particles are considered to be the impact fragment on the asteroid surface. However, there have never been laboratory impact experiments investigating the shapes of fine fragments less than 120 µm, and little is known on the relation between the petrographic textures and the shapes of fine fragments. In this study, we have primarily investigated the shapes of fine fragments smaller than 120 µm (S-sized fragments) created in impacts in the range from cratering to catastrophic disruption (Q = 230 to 8540 J/kg in basalt targets; Q = 1930 and 13540 J/kg in L5 chondrite targets) using synchrotron radiation-based microtomography at SPring-8. The shape distributions of S-sized fragments of basaltic and L5 chondrite targets are similar, distributed around the mean values of the axial ratio 2: v2: 1. The shape distributions of these small fragments are independent of Q which means that the degree of target fragmentation does not affect their shapes.Moreover, we found that concluded the petrographic textures and the crystal grain boundaries do not significantly affect the shapes of S-sized fragments by impacts. On the other hand, in thermal fatigue caused by the day-night temperature cycles on an asteroid surface, the petrographic textures and the crystal grain boundaries would affect the shapes of the fragments (Molaro et al., 2015). As the shape distribution of the Itokawa particles is similar to those of S-sized fragments from impacts, we therefore conclude that the Itokawa particles have not been produced by thermal fatigue and are likely to be impact fragments on the asteroid surface.

Is WASP-12 b falling onto its host star?

Maciejewski, Gracjan

With an orbital period as short as 26 hours, the transiting giant planet WASP-12 b belongs to a group of planets on the tightest orbits. We detected the apparent shortening of its orbital period that could be caused by orbital decay or apsidal precession due to tidal interactions. The reanalysis of available data allowed us to identify an alternative scenario that explains the departure of transit timing from a linear ephemeris. We have found a solution with an additional planet from a Neptune-mass regime and an orbital period of 3 days. Numerical simulations show that this planet can perturb the orbital motion of WASP-12 b that manifests as the apparent orbital decay. The proposed planet is likely to transit the host star. This finding rises an opportunity to confirm the existence of the planet via the transit method.

Characterization of extrasolar multi-planet systems by Transit Time Variation

Korth, Judith

Transit Time Variation (TTV) is the earlier or later occurrence of a planetary transit across the stellar disk relative to the time of a reference transit. TTV is dominantly caused by third body orbit perturbations by attracting forces acting on the transiting planet by at least one another planet inside or outside of the orbit of the known transiting planet. Gravitational interactions perturb the velocity of the transiting planet in its orbit which manifests in a periodical perturbation of the revolution period. Measurements of the transit times and the identification of differences from a mean transit period may prove the existence of further planets. The TTV is therefore a tool to confirm planetary candidates in multi-planet systems. Even non-transiting planets can be detected by the analysis of the TTV of a transiting planet. Their orbital elements can be estimated if the TTV is sufficiently resolved. The shape of the TTV curve, the sequence of the individual transit time differences as a function of observing time, depends on the orbital elements of the planet(s) in the system and may show very complex structures.Upcoming spaced-based surveys will observe various stars for which the usual planetary mass determination by ground-based radial velocity observation is not always possible. TTV is an alternative method for orbit determination which uses only the information from the light curve.

Protoplanetary disc vortices strengthened by gas thermodynamics

Tarczay-Nehéz, Dóra

Large-scale horseshoe-like brightness asymmetries in transitional protoplanetary discs are thoughtto be caused by anticyclonic vortices. These vortices can play a key role in planet formation asmm-sized dust the building blocks of planets can be accumulated inside them. Anticyclonicvortices form by Rossby wave instability, which can be excited at gap edges of giant planets or atsharp viscosity transitions of accretionally inactive region edges. It is known that vortices proneto stretching and later dissolving due to disc self-gravity for canonical disc masses by assuminglocally isothermal gas. To improve the hydrodynamic model of protoplanetary discs, we includethe disc thermodynamics too. In my talk, I present our results on the evolution of the vorticesformed at the outer edge of an accretionally inactive region (dead zone) assuming politropic equa-tion of state for the gas and self-gravitating disc. We found that disc thermodynamics results inlonger lifetime and stronger vortices mitigating the vortex weakening effect of disc self-gravity.Our results suggest that the hypothetical vortex-aided planet formation scenario is favored indiscs where thermodynamics are important.

YORP classification of asteroids revisited

Golubov, Oleksiy

We analyze the YORP evolution of asteroid rotation states depending on their shapes, and discover yet unknown symmetries between different components of the YORP effect. We find a simple theoretical background behind the phenomenological classification of asteroids into four types depending on their YORP behavior by Vokrouhlický and Capek (2002, Icarus 159, 449). Although it has long been known that the obliquity component of YORP can change sign as the rotation rate increases (Capek and Vokrouhlický, 2004, Icarus 172,.526), we find that the number of sign alterations is always even, so that the signs of YORP at very slow and very fast rotation rates is always the same. The points of sign alteration can serve as YORP equilibria and attractors. Unexpectedly, it turns out that even a symmetric asteroid can experience the obliquity component of the YORP effect. We also describe the simplest and most generic evolutionary tracks of asteroids, as well as more subtle effects capable of changing the topology of the evolutionary trajectories and creating stable rotational equilibria for asteroids.

Magrathea: A proposal for a satellite mission on protoplanetary dust growth experiments

Greif, Jonas

The physics of particle growth in protoplanetary disks is still not fully understood, e.g. the growth gap between dust grains and mm-sized particles. Additionally, current methods cannot model the full complexity of interactions in this phase of planet formation. Therefore, experiments in microgravity are crucial to revealing the underlying physics. Previous experiments have several limitations in particular their short duration and constrained dimensions. Accurately representing the conditions in the protoplanetary disk, such as the dust particle mean free path and large spatial extent of the dust, longer duration experiments are needed.In order to create the best conditions for these experiments, here we present a concept satellite with a 6m3 chamber. The payload bay provides different measurements of ongoing collision processes, and samples of collision products. Its modularity and capacity is designed to carry several instruments in a carrousel, with 28 experiment canisters. Those experiments have a range of compositions (including Silicate and Fayalite, both with or without ice layers), and size distribution (between 1µm and 100mm), probing the conditions that could benefit grain growth. Each experiment will last up to one month allowing the record of approximately 106 collisions, with relative velocities of up to 5mm/s, obtaining statistically meaningful results.With the science objectives and requirements formulated, we consider the experiment phase will last up to 5 years. During that time external influences should be minimised, in respect to the structure, thermal control, and attitude control. Therefore, we suggest a 1000kg spacecraft solution, set on a 800km Sun-synchronous orbit. The mission would cost around 438MEuros.The full work was developed during 10 days of the 2017 Alpbach Summer School, by a group of fifteen young scientists and engineers, with various backgrounds, from all across Europe, with the support of two dedicated tutors.

Long-term tidal evolution: the role of mantle convection

Walterova, Michaela

The long-term orbital evolution of planets and moons is closely linked to their internal evolution: the tidal deformation of the planet and the corresponding torque depends on its temperature-dependent rheological properties. As the planet evolves, the heat is transported from the deep parts of the body to the surface and the internal temperature tends to decrease, making the planet less deformable. At the same time, the tidal deformation of the planet can lead to a significant internal heating and to the increase in temperature, together with decrease in the mantle viscosity. This would, on the other hand, result in a more deformable body.The aim of this study is to assess the role of internal dynamics in the long-term orbital evolution of differentiated terrestrial (exo)planets and icy moons subjected to tides. The thermal evolution is investigated by a model of parameterized (1D) subsolidus convection (see e.g. [1]), while the tidal response of the planet is described by the set of partial differential equations derived in [2]. This enables the prescription of arbitrary linear viscoelastic rheology with different temperature-dependent material parameters in each layer (see also [3]) and the computation of frequency-dependent complex Love numbers. These parameters govern the evolution of both the spin rate and the orbit, as described in [4]. We perform several parametric studies concerning the dependence of the Love numbers and stable spin states on the internal structure and compare them with a time-evolving, convecting model. Semi-analytical results are also compared to a fully numerical 3D model [5].[1] Hussmann, H., Spohn, T. (2004). Icarus, 171(2), 391-410.[2] Wu, P., Peltier, W. R. (1982). Geoph. J., 70(2),435–485.[3] Tobie, G., et al. (2005). Icarus, 175(2), 496-502.[4] Kaula, W. M. (1964). Rev. Geophys., 2(4), 661–685.[5] Walterová, M., Behounková, M. (2017). Celest. Mech. Dyn. Astr., 129(1-2), 235–256.

Coorbital evolution during the primordial migration in systems of natural satellites. Implications for Janus and Epimetheus

Rodriguez, Adrian

We analyze the orbital motion of two natural satellites initially in coorbital con g-uration with a third (guiding) migrating satellite embedded into a circumplanetary gasdisk. Through the solution of the exact equations of motion, including the effect of thedisk and the mutual gravitational perturbations, we investigate the orbital behaviorof the system after the guiding satellite crosses its Roche limit with the central planetdue to the induced orbital decay. The application is done for a system consideringSaturn as the central planet and Janus and Epimetheus as being the two coorbitals.By performing a large set of numerical simulations, varying the mass and the initialdistance of the main satellite, we compute the nal orbital con guration of Janus andEpimetheus and show that the horseshoe mutual coorbital motion appears as a naturaloutcome in the simulations.

Water delivery to the TRAPPIST-1 planets

Dencs, Zoltan

Three of the seven rocky planets (e, f, and g) in TRAPPIST-1 system orbit in the habitable zone of the host star. As a result, water can be in liquid state at their surface being essential for life. Recent studies suggest that these planets began to form beyond the snowline, where they could gather water. However, water frozen in asteroids may be lost due to frequent collisions during the formation of planets. A potential water delivery event resembling to the late heavy bombardment in the Solar System, can reproduce the water reservoir on these planets. To simulate this water delivery process, we ran a series of N-body simulations incorporating the seven known planets and a putative planet whose mass are in the range of 5 M_Earth-50 M_Earth orbiting beyond the snowline embedded in a water-rich asteroid disc. We used our own developed GPU-based N-body integrator, HIPERION to model the dynamics of half a million asteroids interacting with the expanded planetary system. To test long-term stability of the expanded system, we applied IAS15 integrator for 10^8(10^7) orbits of the innermost(outermost) known planet. Expanded systems with the putative planet orbiting beyond 0.17 au are all found to be stable. We found that the longevity of the accretion events occurring on planets increases with the orbital distance of the accreting planet. The amount of asteroid accreted also increases with the accreting planet's orbital distance and decreases with the distance and orbital inclination of the perturber. The highest accreted-to-initial number of asteroids measured in stable systems is maximum 5% in total, 1.5% for the habitable planets, and peaks at 3.5% for TRAPPIST-1h, supporting the idea that it can host significant amount of water. By applying a plausible assumption for the water mass contained by the unperturbed asteroid belt, the amount of water accreted by TRAPPIST-1h can reach several 10% of planet mass.

Structure of meteoroids producing double-peaked light curves

Campbell-Brown, Margaret

The structure of small meteoroids (in the millimeter size range) can provide important information about their parent asteroids and comets. Faint meteors normally have symmetric light curves, but a small percentage of meteors show two distinct peaks. The Canadian Automated Meteor Observatory (CAMO) can resolve details of ablating meteors at meter scales. Of twenty-five observed double peaked light curves, all but one showed a single ablating object with very little wake. This is in contrast to the majority of CAMO meteors, of which 90% show long wakes or distinct fragments indicative of the shedding of significant mass in fragments. This contradicts the current model of double peaked light curves (Roberts et al., 2014), in which two separate fragmentation events are responsible for the two peaks.Roberts, I., Hawkes, R., Weryk, R. et al., 2014. Proceedings of Meteoroids 2013, Poznan, Poland, AM University Press, 155.

Isotope fractionation in the photochemical escape from Early Mars

ZHAO, Jinjin

The isotope ratios of C and O on Mars record important information about the past atmosphere evolution of the planet. 13C/12C and 18O/16O in the modern Martian atmosphere have been measured by multiple planetary missions. Martian meteorites are the most important isotopic composition indicator for the early Martian atmosphere. In this work, a 3-D Monte Carlo Model built to investigate isotope fractionation of C and O during the photochemical escape. Ionosphere and thermosphere structures for 1, 3, 10, and 20 times the present solar XUV flux, corresponding to solar activity levels at 2.5, 3.8, and 4.1 Gyrs ago, are considered in this model. Preliminary results show that the fractionation factor for 18O relative to 16O is constant ˜0.65, while that of 13C relative to 12C from 0.5 to 0.8 with solar XUV flux increasing. To make the observed C and O isotopic ratios consistent with the values of d13C=46 (VPDB) and d18O=48 (VSMOW) from Curiosity, our model suggests that ˜40 mbar CO2 and ˜180 mbar H2O have been lost to space due to DR-induced photochemical escape. Such estimates are lower limits because other important loss mechanisms such as photodissociation, sputtering, carbonate deposition for C, and iron oxidation for O, are not considered. Besides, the present C isotopic ratio in Mars atmosphere could be dominated by the contribution of CO2 released to the atmosphere through volcanism or polar cap sublimation during the period of DR-induced escape.Based on the D/H isotope fractionation factor observed by Curiosity, >120 m GEL of water could have been lost, but most of the oxygen sink could have been iron oxidation (e.g. through serpentinization of the crust). Based on estimates of volcanic outgassing rates, >400 mbar CO2 could have been released into the atmosphere, but most carbon loss could be due to carbonate formation in subsurface hydrothermal. Our results provide a preliminary estimate of the contribution of non-thermal escape to Mars atmosphere evolution.

Immersed Moonlets and the lifetime of Saturn's ring arcs

Giuliatti Winter, Silvia

Data obtained by Cassini spacecraft showed the existence of three tiny moons around Saturn Anthe, Methone and Aegaeon  coorbital to planetary arcs. The existence of these systems is assign to corotation eccentric resonance (CER) with the satellite Mimas: 10:11 to Anthe's arc, 14:15 to Methone's arc and 7:6 to G ring arc (Aegaeon's arc). A corotation resonance m+1:m is responsible to create m sites where the particles will be azimuthally trapped. This can explain the existence of the planetary arcs.  Based on the results presented by Madeira et al. (2018, in press) which shows that the main contribution of Aegaeon is to act as a sink for the arc population,  we propose that the 7:6, 14:15 and 10:11 CER regions present only one arc  (the other sites are empty)  because the other sites would have tiny moonlets which help to clean these regions populated by micrometer sized particles.The numerical simulations were performed using the Mercury integrator package  (Chambers 1999). The dynamical system ir formed by Saturn and its gravitational coefficients (J2, J4 and J6), Mimas, tiny moons  and a set of ring arc particles.Our results showed that without dissipative forces the particles remain confined in the sites for more than 100000years. If the arcs are formed by micrometer sized particles,  the effects of the solar radiation force   reduce this lifetime  for  less than 1000 years. The gravitational  effects of a tiny moon immersed in the arc help to reduce its  lifetime. The mass production due to collisions between interplanetary debris onto the surface of the moons  can not  supply  the arc with micrometer sized particles  in order to maintain it in a steady state. Therefore the arcs seem to be transient features even in a presence of tiny moons. We will discuss the size of the tiny moons and its role in the lifetime of the arcs.The authors thank CNPq (309714/2016-8) and Fapesp (2016/24488-0) for the financial support.

Analysis of Dawn Framing Camera images of Ceres in preparation for OSIRIS-REx encounter with Bennu.

Licandro, Javier

The IAC Solar System group has been cooperating with NASA’s OSIRIS-REx mission since 2011. In 2015 we came to an agreement to be members of the Image Processing Working Group (IPWG) to perform two main tasks: produce and analyze the Color-ratio Maps and participate in the in-flight calibration of the cameras (OCAMS). Currently four members of our group are participating in the IPWG.OSIRIS-REx was launched in 2016 and will visit near-Earth asteroid Bennu. It will completely characterize this object during 2018-2019, take a sample of material from its surface, and bring it back to Earth for detailed study in 2023. Bennu is the most accesible primitive near-Earth asteroid and is also one of the Potentially Hazardous Asteroids most likely to collide with Earth. It is well established that primitive class (eliminar) asteroids are the parents of carbonaceous chondrite meteorites, those with the most primitive known composition. Their study is of cosmogonic and astrobiological interest due to their primitive nature and their content in water and complex organics.In preparation for the analysis of Bennu’s color-ratio maps we have been analyzing Dawn Framing Camera images of different regions of Ceres using a spectral clustering technique to search for regions with different spectrophotometric properties. We have also derived Ceres' global photometric parameters following Schroder et al. (2017). In this talk we present our preliminary results on the clustering analysis of Ceres images and the derived global photometric models. We finally discuss the potential of the application of these techniques to OSIRIS-REx/OCAMS images of Bennu in the framework of our contribution to the IPWG.

Characterizing of Polygonal Impact Craters on Rhea, Dione, Tethys, Ceres, and Vesta

Neidhart, Tanja

A polygonal impact crater (PIC) is a crater that does not have a circular shape but consists of at least two straight crater rim segments including a discernable angle. We examined all approved impact craters from the IAU/NASA/USGS Planetary Database on Rhea, Dione, Tethys, Ceres, and Vesta and performed statistics concerning their number of straight rims, diameters, and distribution [1]. We also measured the unknown diameters of 48 craters on Rhea.In total, 431 approved impact craters were studied. On Rhea about 48% of craters were classified as polygonal, on Dione 59%, on Tethys 34%, on Ceres 70%, and on Vesta 56%. The results regarding the mean number of straight rims and the angles between them accord well with previous studies [2,3]. Also, the assumption that PICs seem to favour small to midsized diameters has been proved [2,3]. As there are many more unapproved than approved impact craters on these objects, all impact craters between a latitude of 60° and -60° were examined yielding about 44% for Rhea, 50% for Dione, 51% for Tethys, 61% for Ceres, and 55% for Vesta. Furthermore, no correlation between the diameters and the number of straight crater rim segments was found.However, why the percentage of PICs on these objects is much higher than on the terrestrial planets and the Moon remains unclear. One possible explanation could be the different surface composition in comparison to the terrestrial planets and the Moon but for definite answers to this question further understanding of the formation process of PICs, which is still unclear, is necessary.References: [1] IAU/NASA/USGS Planetary Database. (2016), planetarynames.wr.usgs.gov. [2] Öhman et al. (2010) Geol. Soc. Spec. Pap., 465, 51-65. [3] Weihs G. T. et al. (2015) Planet. Space Sci., 111, 77-82.

Observing with CHEOPS: the CHEOPS Guest Observers Programme

Isaak, Kate

CHEOPS (CHaracterising ExOPlanet Satellite) is the first exoplanet mission dedicated to the search for transits of exoplanets by means of ultrahigh precision photometry of bright stars already known to host planets. It is the first S-class mission in ESA’s Cosmic Vision 2015- 2025. The mission is a partnership between Switzerland and ESA’s science programme, with important contributions from 10 other member states.Foreseen to be ready to launch at the very end of this year, CHEOPS will provide the unique capability of determining radii of planets in the super-Earth to Neptune mass range to 10% precision. It will also provide accurate radii for new planets discovered by the next generation of ground-based or space transit surveys (from super-Earth to Neptune-size). The high photometric precision of CHEOPS will be achieved using a photometer covering the 0.33 - 1.1um waveband, designed around a single frame-transfer CCD which is mounted in the focal plane of a 30 cm equivalent aperture diameter, f/5 on-axis Ritchey-Chretien telescope.20% of the observing time in the 3.5 year nominal mission will be available to the Community through the Guest Observers Programme that will be run by ESA. for the first year of observing will come out in Summer 2018.In this contribution  I will give an overview of observing with CHEOPS, with a particular focus on the ESA-run CHEOPS Guest Observers Programme. 

Growing Plants on Mars - Mars Gardens in the University: Growing Vegetables in Martian regolith simulant.

Guinan, Edward

Over the next few decades NASA and private enterprise missions such as SpaceX-Mars plan to send human missions to Mars with the ultimate aim to establish a permanent human presence on this nearby planet. For a self-sustaining colony on Mars it will be necessary to provide food by growing plants in heated/sheltered greenhouses. As part of an undergraduate student project in Astrobiology at Villanova University, experiments are being carried out, testing how various plants grow in the Martian regolith (soil).  The plants are being grown and tested in Mars regolith simulant commercially available from The Martian Garden (TheMartianGarden.com). This Mars regolith simulant is based on Mojave Mars Simulant (MMS) developed by NASA and JPL for the Mars Phoenix mission. The MMS is based on the iron-rich Mojave Saddleback basalt. Additional reagents were added to this iron-rich basalt to bring the chemical content close to the actual Martian regolith. It is ~90% similar to regolith found on the surface of Mars - excluding poisonous perchlorates commonly found on actual Mars surface. Since Mars is 1.52 a.u. from the Sun, the ambient surface solar light insolation is about ~43% Earth.A wide variety of plants and vegetable are being grown and tested. These include carrots, spinach, dandelions, kale, soy beans, peas, onions, garlic, peanuts, Jerusalem artichokes, and of course potatoes, and sweet potatoes. In Spring 2018 barley and hops have been planted in the MMS in larger quantities with the hope of making Martian beer. Also earthworms and red worms have been introduced to test their viability. The worm castings (excrement) will be used to enrich the Martian soil. The results of this project will be discussed from an educational viewpoint as well as from usefulness in Martian botany research.We thank the Dept. of Astrophysics and Planetary Science (Villanova University) for financial support and the Biology Department for the use of their campus greenhouse.

Experimental light scattering by ultrasonically controlled small particles

Gritsevich, Maria

Electromagnetic scattering is a fundamental physical process that allows inferring characteristics of an object studied remotely. This possibility is enhanced by obtaining the light-scattering response at multiple wavelengths and viewing geometries, i.e., by considering a wider range of the phase angle (the angle between the incident light and the light reflected from the object) in the experiment. Planetary environments represent numerous examples of scattering media composed of particles. There is a fundamental difficulty, however, in bridging the gap between the light-scattering theory and experiment: while existing theoretical models can be used reliably to simulate scattering by a fixed finite object or random particles, thorough experimental work has mostly been performed with light scattered from surfaces. We present an overview of our newly developed 3D scatterometer — a setup for precise multi-angular measurements of light scattered by mm- to µm-sized samples held in place by sound. The measurements obtained with the scatterometer can be cross-validated against the modeled light-scattering characteristics of the sample, i.e., the intensity and the degree of linear polarization of the reflected light, calculated with state-of-the-art electromagnetic techniques.

Consequences of meteoroid impacts based on atmospheric trajectory analysis

Gritsevich, Maria

One of the important steps in the prediction of an impact threat to Earth raised by potentially hazardous asteroids is the understanding and modeling of the processes accompanying the object’s entry into the terrestrial atmosphere. Such knowledge enables characterization, simulation and classification of possible impact consequences. For observed meteor events the reconstructed atmospheric trajectory is the key to deriving the pre-impact meteoroid's orbit in the Solar System on one hand, while on the other hand, it is also required for dark flight simulations which enables to locate surviving meteorite fragments on the ground. Using dimensionless expressions, which involve the pre-atmospheric meteoroid parameters, we have built physically based parametrisation to describe the changes in mass, height, velocity and luminosity of the object along its atmospheric path. The developed model is suitable to estimate a number of crucial unknown values including the shape change coefficient, ablation rate, and surviving meteorite mass. The model is also applicable in the  prediction of the terminal height of the luminous portion of flight and therefore, the duration of the fireball. Besides the model description, we demonstrate its application using the wide range of observational data from meteorite-producing fireballs appearing annually (such as e.g. the Annama, Košice, Neuschwanstein and Osceola fireballs) to larger scale impacts (such as the Chelyabinsk, Sikhote-Alin and Tunguska event). In particular, this approach enabled us to successfully recover the Annama meteorite based on the analysis of the fireball observed by the Finnish Fireball Network on 19 April 2014.

Exoplanetary Science and Instrumental Developments at LBTO

Veillet, Christian

With its pair of 8.4m mirrors on a single mount, the Large Binocular Telescope (LBT) offers the gathering power of an 11.8m telescope and the angular resolution of a 22.8m telescope. With its pair of deformable secondary mirrors, it offers excellent adaptive optics (AO) performance, as demonstrated by the imaging of extrasolar planets in the early days of its AO operations.Since then, various programs in Exoplanetary Science were launched, including the NASA HOSTS mission using the LBT Interferometer (LBTI). We will describe the main scientific objectives of the currently ongoing programs, which also include high spectral resolution transit observations.We will close the presentation with an overview of the new instruments in development, such as visible and near-IR extreme-AO imagers and a near-IR AO-fed high-resolution and high-stability spectrograph, or in their infancy (interferometry in the visible). They all have exoplanets are targets of choice!  Extrasolar Science will contribute to establish LBT as a forerunner of the ELTs, which are still a decade or more away from their full operation.

The brightness variations of Boyajian's star: Dusty planetesimals, temperature variations, or something else?

Deeg, Hans

KIC 8462852, also known as the Boyajian's star, was observed by the Kepler mission during 4 years. During that time, this star underwent several events of strong brightness variations that are unlike that of any other known astronomical object. Since 2017, an intense ground-based observing campaign has been under way to closely survey this target for further brightness variations. The coverage of several minor such variations from both multicolor photometry and spectrophotometry showed that these events have a color-signature. This observation is compatible with the hypothesis by Neslušan & Budaj of a pool of dusty planetesimals that may occasionally pass close to the star. Their  optically thin dust shroud might then generate the observed colors. However, while current observations support this scenario, they do not prove it. Alternative explanations for the star’s behavior will be revised, and in particular, variations in the temperature of the stellar surface will be evaluated for their compatibility with the observations. Furthermore, an update on the observing campaign of Boyajian’s star will be given, possibly with input from new data acquired in the first half of 2018.

Photometry of high-albedo outer main-belt asteroids

Belskaya, Irina

The parameters characterizing magnitude phase dependences of asteroids are found to be very similar for objects belonging to the same composition type. The discovered correlation  of the photometric parameters such as the amplitude of the opposition effect and phase slope on albedo gives an alternative way to estimate asteroid's albedo (Belskaya and Shevchenko, Icarus 197, 94, 2000). Thus, the measurement of magnitude-phase dependence of an asteroid can provide complimentary information on its albedo and composition type. We present new photometric observations of the selected asteroids from the outer part of asteroid belt. The asteroids were selected based on their high values of radiometric albedos given by the WISE and/or AKARI infrared surveys. Our aim is to compare their magnitude phase dependences with those from the inner part of asteroid belt and to provide an independent check of surface albedo and composition type of these asteroids. Knowledge of the fraction of high-albedo asteroids in the outer asteroid belt where majority of asteroids have low albedo surfaces is important for understanding the formation and evolution of our Solar system.

Modeling instrumental systematics in exoplanets transmission spectras using Gaussian Processes

Estrela, Raissa

Several transiting exoplanets, from Hot Jupiters to Super-Earths, are having their atmospheres investigated using the most powerful technique to date: transmission spectroscopy. This technique measures the wavelength-dependent absorption of starlight by the planet's atmosphere during a transit revealing the atmospheric composition. However, instrumental systematics can significantly affect the transmission spectra leading to some spurious detections. This is an important issue that has been overlooked in the scientific community due to the presence of instrumental systematics produced by many instruments (Hubble/NICMOS, FORS2, etc).  The recently introduced technique of using Gaussian Processes (GP), also widely used  in machine learning and Bayesian regressions, has been successfully used to model systematic or correlated noise and to infer accurate planet-to-star ratios and realistic precisions. In this work we develop a technique using such GPs to better analyse systematic trends in exoplanet transmission spectra taken in either MOS/MXU modes caused by the GRIS_600z grism of FORS2. Our method can provide an effective tool to interpret transmissions signals in future observations with other telescopes in the presence of instrumental systematics.

The Ever Changing Centaur: Relating Activity, Orbital and System Evolution of Minor Bodies in the Giant Planet Region

Sarid, Gal

Centaurs roam the outer solar system region, mostly between the heliocentric distances of Jupiter and Neptune. The dynamical lifetime of the population is much shorter than the age of the solar system and these bodies may encounter many gravitational perturbations from the outer planets, thus making it a transient population (akin to the inner solar system's NEAs). Centaurs are transition objects not just by virtue of their dynamics, but also because they can exhibit both asteroid and cometary properties – Observed activity, surface composition, density. Several such objects have been observed to show cometary activity, in the form of observable comae, at least 2 objects (Chariko and Chiron) have a sustained ring system, and at least 2 known binary systems (Ceto/Phorcys and Typhon/Echidna) have derived densities between those of large and small KBOs. Notably there has been some tentative evidence for 2 active objects (29P and Echeclus) to also have a signature of a fragment or small moon associated.We develop a modeling scheme that connects sublimation-driven outgassing of species more volatile than water (CO, CO2, CH4, CH3OH) with the formation and retention of extended components (rings, moons, binaries), as a function of an object's dynamical environment (orbital variation, surface impacts). We utilize thermos-physical, dynamical and hydrocode calculations to track the outcome in terms of activity patterns, color/composition variations, sustained ring systems and effects of secondary bodies.Centaurs have a potentially crucial role in understanding the feedback between outer and inner solar system asteroid/comet populations. In addition, the process of initiating and maintaining activity beyond the water-activation distance is related to our basic understanding of how volatile species behave, both in the interior and surface of icy-rocky bodies


Krugly, Yurij

The main goals of our survey are regular photometric observations of near-Earth asteroids (NEAs) in order to investigate:(1) newly discovered and/or closely approaching the Earth NEAs, with impact on potentially hazardous asteroids;(2) rotation properties of NEAs, which are expected to show an evidence of the YORP effect influence;(3) well-known binary NEAs for the BYORP effect determination as well as to search for new binaries;(4) very fast rotation of small NEAs with diameters smaller 200-300 m;(5) physical properties of NEAs which are radar targets.The survey is based on facilities of International Scientific Optical Network (ISON). The Network includes more than 100 telescopes with the apertures from 20 cm up to 2.6 m located at 43 observatories in 17 countries. Ten largest telescopes are used for regular photometric observations of asteroids.We present the results of our observations of 70 NEAs carried out during more than 250 nights in 2017. Among them, we observed 18 newly discovered NEAs and the known binaries (66391) 1999 KW4 and (137170) 1999 HF1 to study the BYORP effect. The rotation peroids were determined or improved for more than 20 asteroids. We obtained the lightcurves of many asteroids suitable to investigate an influence of the YORP effect. Several NEAs were found as suspected to be a binary.  We also discuss future development of the ISON network for photometry of asteroids.

Observation campaigns of (3200) Phaethon and (155140) 2005UD for the DESTINY+ mission

Yoshida, Fumi

The  DESTINY+  (Demonstration  and Experiment of Space Technology for INterplanetary voYage,  Phaethon  fLyby  and  dUSt  science)  is  an  upcoming JAXA/ISAS  flyby  mission  to  asteroid  (3200)  Phaethon, the  parent  body  of  Geminid  meteor  shower.  The  spacecraft  will  investigate  the  dust  trail  of  Phaethon,  a  dust distribution   and   compositions   of   the   dust   nearby Phaethon, surface/geology of Phaethon, and so on.We organized the ground-based observation campaign of Phaethon in 2017 for gathering  as  much  scientific  knowledge  about  Phaethon as possible before the spacecraft launch. And we will host another ground-based observation campaign for 2005UD in 2018, which is a possible breakup body of Phaethon and a possible second flyby target of DESTINY+.

CCD Photometry of Main Belt Comets 176P/LINEAR, 238P/Read and 288P/2006 VW139

Shi, Jianchun

The study of Main Belt Comets (MBCs) has attracted a great deal of interest in recent years since the recognition of MBCs as a new class of comets in 2006. To study activity and physical properties of three MBCs 176P/LINEAR, 238P/Read and 288P/2006 VW139, we carried out broadband CCD photometry of three MBCs. The upper limit of the nucleus radius, the color index, the Afrho values and the dust production rates were derived. Finally,the activity of three MBCs were discussed.

Low Frequency Radio Spectrometer on board Chinese CE-4 lunar lander

Su, Yan

Low Frequency Radio Spectrometer(LFRS) is a scientific paylad hosted by the Chinese Chang'e-4 (CE-4) lunar lander, expected to be launched in 2018. The main mission consists of three parts, a relay around the Earth-Moon L2 point, a lander and a rover on the far said of the Moon. The LFRS is a low frequency radio instrument that serves as a pathfinder for space-based exploration. Its frequency range is 100kHz up to 40MHz. As quiet radio zone of the far side of the moon preventing from Earth's ionosphere and interference from the earth, its sciences goals include observing solar activities and Characterizing the radio interferences environment around the moon.  The LFRS system consists of three 5m long monopole antennas mounted at the outer wall of the lander connected to a low noise amplifier and a digital receiver system. Cross-correlating signals from all polarization could be captured. The analogue signals are fed into three high-resolution (14 bit, 100 M samples per second)  analogue to digital converters. EMC tests have been done and there is strong self-generated interference originating from the lander unfortunately, one 20cm short dipole is designed to measure the background interference. It is expected to reduce the noise by approaches correlating signals to extent. If this problem could be sorted out successfully, the LFRS could cover wider science cases that include observing Jupiter, pulsars even dark ages signal.   


Milic Zitnik, Ivana

The subject of our research is interaction between the mean motion resonance (MMR) and the Yarkovsky effect. This interaction occurs when an asteroid due to the changes of its orbital semimajor axis (caused by the Yarkovsky effect) reach the resonance. The resonance induces a periodic oscillations in the asteroid's semimajor axis around its center. The Yarkovsky effect exactly causes the permanent (secular) evolution of the orbital semimajor axis. As a result of their interaction, the mean semimajor axis drift speed is modified with respect to the one caused solely by Yarkovsky. One of the main goals of this investigation was to study this interaction, and to define how the time that an asteroid spend in the MMR depends on some characteristics of this resonance, as well as of the asteroid itself. So far, the impact of the resonance on the semimajor axis drift speed has not been studied to that extent neither from that point of view. We established our findings about the effect of 11 two-body MMRs with Jupiter, on the mobility of an asteroid's semimajor axis caused by the Yarkovsky effect. This study was accomplished using numerical integrations of test asteroids. The obtained results revealed that MMRs could either speed up or slow down the drift in the semimajor axis. This allowed us to determine the distribution that represents the best data obtained for time delays, dtr, caused by the resonances on the mobility of an asteroid. Also, we established the certain functional relation that describes dependence of the average time lead/lag <dtr> on the strength of the resonance, SR, and the semimajor axis drift speed, da/dt. Also, we analyzed how the time spent inside the resonance depends on orbital eccentricity, and proposed the relation that taking this parameter into account as well. As the Yarkovsky effect scales as 1/D, an important consequence of this relation was that average time lead/lag <dtr> is directly proportional to the diameter D of an asteroid.</dtr></dtr>

Long-Term evolution of planetary system in stellar clusters

Flammini Dotti, Francesco Maria

Most stars, and perhaps even all stars in the Galaxy, form in crowded stellar environments. Most of such star forming regions typically dissolve within ten million years, while others remain bound stellar groupings for hundreds of millions to billions of years, and then become the open clusters or globular clusters that are present in our Milky Way galaxy today. It is commonly accepted in that a large fraction of stars in the Galaxy hosts planetary companions; even binary star systems are known to host exoplanets. To understand the origin and dynamical evolution of exoplanet systems, it is necessary to carefully study the effect of their environments, i.e., that of the star forming region in which they formed and in which spent their first millions of years, and that of the Galactic field, open cluster, or globular cluster in which they spend the remaining part of their lives. Our study combines theoretical estimates with state-of-the-art numerical simulations. Here, we present the initial results of our numerical study of the evolution of planetary systems in star clusters, in which we model the effects of neighbouring stars and the external Galactic tidal field on existing planetary systems. We aim to study a wide variety of planetary systems and surrounding environments, to obtain a comprehensive picture of the conditions under which external perturbations are important or negligible. To carry out our simulations, we combine the planetary systems N-body evolution code REBOUND with the NBODY6++ star cluster evolution code in the AMUSE multi-physics environment. With our study we will be able to constrain the effect of external perturbations of different environments on the planets and debris structures of a wide variety of planetary systems, which may play a key role for the habitability of exoplanets in the Universe. 

4-D dust trail calculation of 2018 October Draconid

Sato, Isao

October Draconid is a meteor shower originated from 21P/Gicobini-Zinner. It is predicted to be seen from Europe this year. In primary dust trail theory in one dimension, a meteoroid is supposed to be ejected from the parent comet at the perihelion with a velocity in the direction of the velocity vector. But the author calculated a prediction with a dust trail theory in 4 dimensions, namly, a meteoroid is supposed to be ejected from any time on the orbit in 3-D velocity vector. As the result, the minimum ejection velocity to colide the Earth from the parent comet is 20m/s at 200 days after the perihelion passage of the 1946 dust trail. The peak time of apparition will be October 8th 22h50m.

Some properties of motion of resonant asteroids with very slow Yarkovsky drift speeds

Milic Zitnik, Ivana

We investigated the effect of mean motion resonances (MMRs) with Jupiter, on the mobility of an asteroid's semimajor axis caused by the Yarkovsky effect. We observed only asteroids that entered and exited from the MMR. One of the main goals of our research was to study this interaction between gravitational and non-gravitational force, and to define how the time that an asteroid spend in the MMR depends on some characteristics of this resonance and of the asteroid itself. In the begining, for 9 (out of 10) values of Yarkovsky drift speed (da/dt) that we analyzed (in range from 0.00004 AU/Myr to 0.001 AU/Myr), we found that time increases when strength of resonances (SR) is increasing and vice versa. For our the slowest Yarkovsky drift speed, an opposite trend is observed: test asteroids very fast move across MMRs in comparing with resonant asteroids with da/dt larger and equal than 0.0001 AU/Myr (our the second smallest da/dt). This results might indicate that below some limiting value of da/dt, objects typically quickly jump across the MMR. Analyzes of additionally four values smaller than 0.00004 AU/Myr (0.00003, 0.00002, 0.00001, 0.000007 AU/Myr) were necessary and have confirmed our previous results. Asteroids very fast cross the MMR in this way: with smaller speed da/dt we got smaller time spent in the resonance. We concluded that limit value of Yarkovsky drift speed exists between 0.00004 and 0.0001 AU/Myr, approximately on 0.00007 AU/Myr (we took medium of previous interval). Possible explanation about results of our research is that MMRs have more powerfully influence than very slow Yarkovsky drift speeds on motion of resonant asteroids. Also, the mentioned effect on time is more expressed in stronger MMR because combination of larger oscillation in semimajor axis values with very slow da/dt helps resonant asteroid to reach easier border of MMR and came out earlier from MMR.

Correlation of CCD aperture photometry and Herschel photometry of 29P/Schwassmann-Wachmann from the Herschel Catalogue of Solar System Object Observations

Kidger, Mark

Comet 29P/Schwassmann-Wachmann is an object of great interest due to the fact that despite orbiting in a low-eccentricity orbit between Jupiter and Saturn it shows frequent outbursts that can be of amplitude up to 6 magnitudes. The Herschel Science Archive reveals that twelve observations of Comet 29P/Schwassmann-Wachmann were made with the Herschel Space Observatory on six Operational Days between April 19th 2010 and February 17th 2013, all within the HssO Guaranteed Time Key Programme, “Water and related chemistry in the Solar System”. Three of the observations were high-resolution spectroscopy of the 110-101 o-H2O line at 557GHz taken with HIFI, four were imaging observations in mini-scanmap mode (scan and cross-scan) with the PACS photometer at 70 and 160 microns (obtained on 10/06/2010, 02/01/2011 & 17/02/2013) and one observation was SPIRE imaging photometry simultaneously at 250, 350 and 500 microns (obtained on 10/06/2010).The HIFI observations on April 19th 2010 are particularly interesting as they were made close to the peak of an outburst with maximum at R=12.5 (within a 30 arcsecond aperture) on April 16th. The HIFI observation shows a strong detection of the 557 GHz water line with a FWHM of ˜130m/s. A second observation, taken on May 11th, with the magnitude in a 10 arcsecond aperture down 2.5 magnitudes from the peak, shows a weak detection of a much broader 557 GHz line of FWHM 700m/s (Bockelée-Morvan et al., 2010DPS....42.0304B).We present the HIFI spectra and photometry of 29P at 70, 160, 250, 350 and 500 microns taken from the Herschel Catalogue of Solar System Object Observations that we correlate with the visible light curve of the comet as determined from an archive  of 18500 historical CCD measures of the comet obtained by Spanish observers between 2002 and 2017 by the “Observadores_cometas” Group.

The Herschel Catalogue of Solar System Object Observations

Kidger, Mark

The European Space Agency's Herschel Space Observatory has been the only space facility to date to cover a spectral range from the far infrared to sub-millimetre (55-672µm). Herschel performed photometry and spectroscopy with its 3 on-board instruments: 2 diffraction-limited cameras - PACS (simultaneous observations in 70µm or 100µm and 160µm) and SPIRE (simultaneous observations in 250µm, 350µm, 500µm), each with a low-to-medium resolution spectrograph and a one very high resolution heterodyne spectrometer, HIFI.Herschel performed ˜37000 science observations of which 1693 were from Solar System objects (4.5% of the total) which represent 170 individual objects, including 5 planets and 6 of their satellites, 14 comets, 107 TNOs and 38 other asteroids. These measurements have been only partially exploited and to facilitate their analysis we have compiled these observations in the Herschel Catalogue of Solar System Object Observations (SSOO). We have included fluxes for each photometric observation, as well as complete ancillary information, a detailed classification of the observed bodies and the physical circumstances of the observation (phase angle, heliocentric distance, etc.) to facilitate a search for correlations between properties.We have analysed all the photometric observations from PACS and SPIRE using the science ready maps in the Herschel Interactive Processing Environment (HIPE) v15.0.1 and performed point source aperture photometry. Due to the diversity of the 170 SSOs (e.g. TNOs, planets) we developed a pipeline to apply to both faint and bright sources. The quality of the measurements has been analysed taking into account the source flux, sky background and published results from different types of bodies.We aim to facilitate the analysis of Herschel SSO data and help the scientific community to use the archive to widen our knowledge of the Solar System. Our own analysis of the data in this catalogue will be presented.

Can the planetary system HD 141399 harbor habitable planets?

Dvorak, Rudolf

Our aim was to find whether terrestrial planets could have been formed in the habitable zone of the 4 planet system of HD 141399 (found by Vogt et al (2014)). The system consists of 4 gas giants with approximately 0.5 to 1.4 Jupiter-masses orbiting between 0.4 and 5 AU. In our investigations we concentrated on the habitable zone around the late K-type star.In numerical n-body simulations with initially 500 bodies with masses between 0.5 to 2 Moon-masses we let the bodies interact with the gas giants and each other and monitored the growth by collisions and merging. In our initial conditions we also took care of the possible water content of the protoplanets with respect to theirlocation in the 'habitable ring' between the gas giants HD 141399 c and HD 141399 d.It turned out that after millions of years terrestrial planets on stable low eccentric orbits can be formed in the habitable zone of HD 141399 containing a high enough amount of water to make these planets capable of supporting life.

Space Mission Geometry for Almost Every Purpose

Acton, Charles

Every space mission needs some form of space geometry–positions, velocities, orientations and more–from the very earliest design stages through the analysis of science or other results that may extend to many years after the end of operations.   These kinds of space geometry computations can be rather difficult to make given that everything is moving or rotating; given that a number of reference frames and coordinate systems come into play; given that estimates of size, shape and orientation of target bodies are frequently revised; and given that several time systems are used.      Realizing the challenges and also the importance of making accurate space geometry computations, NASA established an organization–the Navigation and Ancillary Information Facility (NAIF) to implement a multi-mission, enduring process, named SPICE1, for computing space mission geometry.   SPICE comprises both ancillary data files, called “kernels,” and a suite of software used to produce those kernels and to compute derived quantities such as altitude, latitude/longitude, lighting angles, etc. from the data contained within the kernels. The SPICE software is available in six languages, and for most popular computing environments. The software is extensively documented and throughly tested; tutorials and training classes on its use are offered. NASA offers SPICE free of charges, export restrictions and licensing arrangements: literally anyone, worldwide, can obtain and use the SPICE components.   This presentation will provide examples of where and how SPICE has and is being used and it will look to the future of SPICE–what new capabilities are being added and where it might be helpful in new solar system engineering and science activities.1Spacecraft, Planet, Instrument, Camera-matrix, Events

NEOCam: The Near-Earth Object Camera

Masiero, Joseph

The Near-Earth Object Camera (NEOCam) is NASA-funded mission concept that would discover and characterize the majority of potentially hazardous asteroids, allowing us to constrain the threat posed to Earth from an asteroid impact.  The NEOCam mission would place a 50 cm, passively-cooled, infrared telescope at the Earth-Sun L1 point, where it would carry out a survey of the inner Solar system for nearby asteroids and comets.  Here, we describe the details of the NEOCam mission, the nominal planned survey, and discuss predictions of the survey performance over the planned 5-year mission life.

Titan’s polarization phase curves with Cassini/ISS

Ilic, Nikoleta

The sunlight reflected by Titan’s atmosphere is strongly polarized at phase angles near quadrature. This Rayleigh-like behavior has been a key clue for the understanding of the aggregate nature of Titan’s ubiquitous atmospheric haze. We are preparing Titan’s polarization phase curves with data collected with Cassini’s Imaging Science Subsystem. The Cassini/ISS dataset covers the spectrum from the UV to the NIR, and phase angles from nearly zero degrees (full illumination) to 150 degrees, thereby extending the observations made by the Voyager and Pioneer spacecraft decades ago. The Cassini/ISS dataset confirms the older trends in Titan’s polarization, but also shows new insight thanks to the relatively good phase sampling and to the availability of data at wavelengths affected by methane absorption. Since we now have spectrally-resolved phase curves in both brightness and polarization, we are investigating the optimal way to combine that information towards the optimal characterization of Titan’s atmosphere. The question is also relevant to the prospective characterization of exoplanets.

Binary Star Systems with Circumstellar Habitable Zones Affected by Resonances

Bazso, Akos

Extrasolar planets have been detected in a vast diversity of orbital configurations. Among them, wide separation binary star systems with circumstellar extrasolar giant planets have been shown to successfully form terrestrial planets in the host star's habitable zone (HZ). We focus on binary star systems with stellar separations from 20 AU up to several hundreds of AU. In this study we demonstrate that under suitable circumstances secular resonances (SR) might fall into the HZ and cause highly eccentric motion of terrestrial planets. We analyse the circumstances for which an SR is present in the HZ, and show the dependence on various system orbital and physical parameters. By applying a combination of simple analytical models we determine the orbital precession frequency of the giant planet and relate it to the corresponding frequencies of test planets in the HZ. We focus on the spectral type of the host star for different HZ ranges, and treat the orbital distance and eccentricity of the secondary star (which are often poorly constrained from observations) as free parameters. Our study shows that for any given location of the giant planet there exist configurations in which an SR appears somewhere in the HZ. Even for relatively distant secondary stars the giant planet's precession frequency might push terrestrial planets in the HZ to become eccentric. In summary, in wide binary systems with a giant planet exterior to the HZ, secular perturbations can affect the HZ. These perturbations drive terrestrial planets to more eccentric orbits, which increases the insolation received by the planet and could lead to uninhabitable conditions on the planet.

Seasonal variation of radial brightness contrast of Saturn's rings viewed in mid-infrared by Subaru/COMICS

Fujiwara, Hideaki

To investigate the mid-infrared (MIR) characteristics of Saturn’s rings, we collected and analyzed MIR high spatial resolution images of Saturn’s rings obtained in January 2008 and April 2005 with COMICS mounted on Subaru Telescope, and investigated the spatial variation in the surface brightness of the rings in multiple bands in the MIR. We also composed the spectral energy distributions (SEDs) of the C, B, and A rings and the Cassini Division, and estimated the temperatures of the rings from the SEDs assuming the optical depths. We find that the C ring and the Cassini Division were warmer than the B and A rings in 2008, which could be accounted for by their lower albedos, lower optical depths, and smaller self-shadowing effect. We also find that the the C ring and the Cassini Division were considerably brighter than the B and A rings in the MIR in 2008 and the radial contrast of the ring brightness is the inverse of that in 2005, which is interpreted as a result of a seasonal effect with changing elevations of the sun and observer above the ring plane.

Dynamics of the Oort Cloud in the Gaia Era

Torres, Santiago

Comets in the Oort cloud evolve under the influence of internal and external perturbations, from giant planets to stellar passages, the Galactic tide, and the interstellar medium. Using proper motions, parallaxes and radial velocities from Gaia DR2 and combining them with the radial velocities of several catalogues, we constructed a catalogue of the closest stars to the Sun within 50pc. Then we calculated the closest encounters that the Sun has had in the recent past and will have in the near future, with a special focus on the stars within 2pc from the Sun, for being the ones with major impact to the Oort cloud.  We constructed an artificial Oort cloud and by using the closest stars found it, we investigated the secular effect over the Oort cloud in +/-10Myr. We will present our latest results.

Water transport and loss in planet formation: a collision outcome parameter study

Maindl, Thomas I.

As it is well established, the formation of terrestrial planets involves a long sequence of collisions of protoplanetary bodies. Water in particular may have been brought to the accretion zone of Earth by water-carrying planetesimals and planetary embryos from outer regions of the asteroid belt. In most simulations of planet formation, these collisions are treated as perfect inelastic merging events and consequently ignore fragmentation and the loss of volatiles such as water. Compared to the actual outcome of realistic, physical collisions, the masses as well as the water contents of the final terrestrial planets are significantly overestimated.In order to arrive at a more realistic estimate of the amount of water transported to Earth’s accretion zone, we performed a suite of several hundred collision simulations with our 3D smooth particle hydrodynamics (SPH) code. We discuss the outcome of our simulations in terms of mass and water content of final bodies and for different parameters of the system including collision velocity, impact angle, and the masses and water-mass fractions of the projectile and target. Our results present a more realistic estimate of water transport rates in dynamical studies of planet formation.

Habitable zones of hot stars

Briot, Danielle

The classical figures of habitable zones versus stellar spectral types generally do not apply to hot stars. The aim of this study is to extend the determination of habitable zone to hot and very hot stars. We know that planets orbiting hot stars are hardly detected. The short life time of those planets does not probably allow very evolved life species. In addition, due to the short wavelength radiation of hot stars, atmospheres of potentially inhabited  planets orbiting hot stars must be very opaque to photodissociative processes harmful to biomolecular links. We attempt to identify some possible niches for such life abodes.

Application of fuzzy logic in the study of exoplanets

Girola Schneider, Rafael

: In recent years, the number of exoplanets discovered involves the use of computer codes that allow us to differentiate both the environmental characteristics of the star system and those that are intrinsic to the exoplanet. In a scenario of uncertainty about the reliability of the data to ensure that an exoplanet may or may not have consistent physical conditions for the development of life, we use a computational tool that works with a fuzzy logic code, which provides a mechanism for Inference, and a mathematical framework that allows to model the uncertainty of cognitive processes, elaborating formal tools for its treatment. In a set of environmental contexts of exoplanets, the research group needs to distinguish reliable results, when the uncertainty of the measures generates an ambiguity in the decision making, reach a consensus to classify or accept a result that is not entirely reliable if other usual techniques are applied. For example, error bars for mass, temperature and atmospheric models. This paper shows how fuzzy logic can be useful in making decisions from ambiguous predicates, using a fuzzy computer code, obtaining numerical data associated with indeterminate variables.Keyword: Exoplanets, Fuzzy logic, Models, classification.

Noble gases and volatiles delivery from comets to Earth

Laufer, Diana

Direct measurements by the Rosetta spacecraft on Comet 67P/C-G composition together with our laboratory experiments of gas trapping in amorphous ice improve our understanding of the gas composition and the formation condition of the ice grains in the protosolar nebula (PSN) and the source of the Earth's atmosphere and the building blocks of life.For the first time in comet research, the Rosetta spacecraft detected O2, N2 and also noble gases: argon, krypton and xenon and their isotopes, and absence of neon. Comparing these measurements to our experimental results of gas-laden amorphous ice, the formation temperature of the cometary ice grains was =35 K. This temperature is close to the temperatures observed for the circumstellar dust shells around a PsA (55 K), e Eri (45 K) and Ori A PPD Class II (40-65 K).Noble gases are key tracers for understanding the origin and their contribution to the planetary atmospheres. The ROSINA mass spectrometers of the Rosetta spacecraft measured their isotopic abundances. Argon isotopes are depleted as compared to solar. This can be explained by our experimental results of trapping of argon in amorphous ice, being strongly dependent on the formation temperature of the ice. At 35-50 K, not all the argon was trapped in the amorphous ice, as krypton and xenon, with a depletion factor of up to 2. The xenon isotopes in 67P/C-G are significantly different from solar.A possible explanation can be xenon being trapped also in CO2 ice or recondensed on the night side.For other volatiles, N2 and Ar are depleted as compared with O2, as derived also from our experiments. CO and CO2 vary for different comets as also the D/H ratio, being explained by inhomogeneity in the PSN.The measurements of comet 67P/C-G together with our experimental results set a limit to the formation conditions and abundances of the volatiles delivered to the Terrestrial planets.This research was supported by the Israel Space Agency, Ministry of Science and Technology.

The Juno gravity science experiment

Folkner, William

The Juno spacecraft entered orbit around Jupiter in July 2016 in a 53-day orbit. At closest approach to Jupiter, perijove, measurements of the Doppler shift of the Juno radio signal are made by the NASA Deep Space Network. These measurements have been used to estimate the Jupiter gravity field, tidal response to the Galilean satellites, and the precession and nutation of the Jupiter spin axis. Doppler data from the first few perijoves provided estimates of the low-order even zonal harmonics that provided significant improvements on previous estimates from Pioneer, Voyager, and Galileo missions. Subsequent date showed clear evidence of odd low-order zonal harmonics, that are explained by the zonal winds observed from images of the cloud tops extend to a depth of 3,000 km. The estimated harmonics provide significant constraints on the interior structure of Jupiter. We report on the current status of the gravity estimates and the expected results from the rest of the mission duration.

How bright are the brightest stars with transiting exoplanets?

Masuda, Kento

We discuss the expected properties of nearby transiting exoplanets, based on the planet occurrence rate from the Kepler mission as well as the properties of nearby stars from the second data release of Gaia. We especially focus on estimating how bright the brightest stars hosting various types of transiting planets are, to inform future missions.

Material properties and momentum transfer uncertainty for DART

Maindl, Thomas I.

Kinetic impactors are one possible option to deflect sub kilometer sized asteroids that may collide with planet Earth. The momentum delivered by such a spacecraft would change the potentially hazardous asteroid's orbit so as to avoid an impact on our home world. Near-Earth asteroids with diameters the order of 100m are believed to be very common and consist of a wide variety of materials with varying bulk densities. A kinetic impact on such targets would not only entail a direct momentum transfer from the spacecraft to the target, but also post-impact effects caused by ejected material resulting in a momentum transfer efficiency ß>1. The latter is only weakly constrained, however. We study the momentum transfer onto an asteroid after it is hit by a kinetic impactor comparable to the Double Asteroid Redirection Test (DART) mission concept's projectile. The notional target is an asteroid similar in size to the secondary body of the binary near-Earth asteroid (65803) Didymos (approx. 150m) consisting of a variety of different materials such as solid basaltic rock, carbonaceous chondrite, porous rock, a blend of porous rock and water ice, and – as an extreme case – solid iron. Impact simulations are conducted within a state-of-the-art 3D smooth particle hydrodynamics framework that allows us to present likely ß factors for different target materials. We compare our results to other published work and discuss potential consequences for DART.

A radial velocity study of possible planets around A-type stars - can they really explain the strange signatures in 166 Kepler light-curves?

Sabotta, Silvia

Up to now very little is known about close-in planets of stars that aremore massive than the Sun. Detecting such planets is important because they challenge our current understanding of planet formation and migration.Balona (2014) identified 166 possible short-period planets around A-stars in the Kepler-survey based on strange features in their periodograms. He explains them as the consequence of differential rotation of the star and an orbiting exoplanet. The exoplanets do not show transits but the variations could be caused by the ellipsoidal, beaming and reflection effects on a Jupiter size planet. We have obtained about 230 spectra of a small subsample of those "Balona Stars" with the two echelle spectrographs at the Tautenburg and Ondrejov 2m telescopes. In ourposter, we provide upper limits for the masses of those possible planets and show if the upper limits agree with the variation of the lightcurves.

bRing: Constructing a PSF Map

Khorshid, Niloofar

The MASCARA and bRing instruments are the first ground based instruments searching all sky for transiting exoplanets around bright stars with a magnitude of 4 to 8. The southern MASCARA and bRing network continuously covers a large area of the southern hemisphere between declination bands of -30 and -80 and the northern MASCARA instrument covers the northern hemisphere.Stellar flux seen by the detector is influenced by a variety of noise factors which results in lower signal to noise and photometry precision. The photometric precision of bRing is around 0.5% for ß Pictoris over 5 minutes. With this precision it is possible to detect planets on the order of Jupiter masses for every star. In order to push our limits we constructed a new method based on Point Spread Function (PSF) fitting to better reduce the raw data from bRing.We build a super resolved PSF map for the instrument so that each star is assigned a PSF which is dependent on the position of the star on the detector. There are two major assumptions upon which we build the PSF map: the PSF does not change significantly for a star within a short period of time, and the PSF shape does not change quickly over the detector area, meaning that neighbouring stars have similar PSF shapes. To construct the PSF map we average over all the frames we have for each star at the same siderial time.Comparing the results for ß Pictoris, this method works 40% better than the current method that is used for bRing and MASCARA, which is approximating the PSF by a circular aperture and calculating the flux within that aperture. The aperture photometry requires corrections around the edges which mostly come from coma aberrations, where the PSF spreads out of the aperture. At the edges, the average flux over the PSF becomes much lower and the signal to noise drops. This PSF method can be easily reapplied to any wide-field instrument, as it is independent to any unique characteristics of the detector.

Constraints on Circumbinary Planet Formation From ALMA and Sphere/IRDIS Imaging of V4046 Sgr.

Ruiz-Rodriguez, Dary

We present the highest-resolution continuum and scattered-light images obtained to date of the circumbinary disk orbiting V4046 Sgr, an actively accreting, close binary (K5+K7) T Tauri star system located a mere 72.4 pc from Earth. We observed the disk with the Atacama Large Millimeter/submillimeter Array (ALMA) at 850 µm (Band 7) during Cycle 4, and we analyze these data in conjunction with archival H band polarimetric images taken with the Sphere/IRDIS on the ESO Very Large Telescope (VLT). At 0.25" (20 au) resolution, the 850 µm emission reveals a ring with a maximum at 33 au and with an extension of ~ 90 au, while analysis of the 50 mas (4 au) resolution scattered light imaging confirms the presence of two dust rings peaking at ~ 15 and 25 au (see also Rapson et al. 2015; Avenhaus et al. 2018). From the 850 µm continuum emission, we infer a dust mass of ~ 64.0 MEarth for the 33 au radius ring. In addition, we combine two-dimensional two fluid (gas + particle) hydrodynamical calculations with three-dimensional Monte Carlo Radiative Transfer simulations to simultaneously model the potential observational signatures of protoplanet-induced gaps at millimeter and near-infrared (NIR) wavelengths. We find that a single planet with a mass in the range between 0.2 and 1  MJup orbiting at ~ 18 au from the central star can well reproduce the combination of a deep gap in scattered light and a surrounding bright 850 µm ring. The comparison of NIR and millimeter extensions suggests a flat disk with efficiently settling down of the grain particles to the midplane, as expected given V4046 Sgr's advanced age of ~ 20 Myr.

Analysis of the exoplanet containing system Kepler-13

Püsküllü, Çaglar

We have applied the close binary system analysis program WINFITTER, with its physically detailed fitting function, to an intensive study of the complex multiple system Kepler-13 using photometry data from all 13 short cadence quarters downloaded from the NASA Exoplanet Archive (NEA) (http://exoplanetarchive.ipac.caltech.edu). The data-point error of our normalized, phase-sequenced and binned (380 points per bin: 0.00025 phase interval) flux values, at 14 ppm, allows the model’s specification for the mean reference flux level of the system to a precision better than 1 ppm. Our photometrically derived values for the mass and radius of KOI13.01 are 6.8 ± 0.6 MJ and 1.44 ± 0.04 RJ. _x000D_ The star has a radius of 1.67 ± 0.05 Ro. Our modelling sets the mean of the orbital inclination i at 94.35 ± 0.14 degree, with the star’s mean precession angle φp = 49.1 ± 5.0 and obliquity θo = 67.9 ± 3.0 deg, though there are known ambiguities about the sense in which such angles are measured. We could confirm a small but steady diminution in the cosine of the orbital inclination over the 17 quarter timespan. This is accompanied by a slight increase of the star’s precession angle (less negative), but with no significant change in the obliquity of its spin axis. There are suggestions of a history of strong dynamical interaction with a highly distorted planet rotating in a 3:2 resonance with its revolution, together with a tidal lag of ~30 deg. The mean precessional period is derived to be about 1000 y, but at the present time the motion of the star’s rotation axis appears to be supporting the gravitational torque, rather than providing the balance against it that would be expected over long periods of time. The planet has a small but detectable backwarming effect on the star, which helps to explain the difference in brightness just after transit and just before occultation eclipses. In assessing these findings it is recognized that sources of uncertainty remain.

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