Focus Meeting 5 - Abstracts
Historical Observations of Novae: Guest Stars to Glass Plates (and Beyond)
Pagnotta, Ashley
Guest Star observations noted by early Asian astronomers can be identified as novae and other cataclysmic variables (accreting white dwarfs) by connecting them to modern observations, where "modern" can be broadly interpreted to include both archival glass plate and CCD images. I will discuss our recent identification of the cataclysmic variable associated with a nova that erupted in Scorpius in 1437, which we determined by combining Korean observations, Harvard Plate data, and new observations our collaboration took in 2016, as well as other historical observations of Guest Stars we believe to have been novae and their modern counterparts.
Cuneiform Descriptions of Transient Phenomena
Hunger, Hermann
In sources from Ancient Mesopotamia, transient astronomical phenomena occur in two contexts: in records of observations, many of which can be dated; and in collections of omens, which use the appearance of such phenomena to find in them predictions of future events. These omens consider quite a range of phenomena, but with rare exceptions they cannot be dated in a precise way. The paper will describe how transient phenomena are handled in both kinds of texts.
Historical Meteor outbursts and its parent comets
Ahn, Sang-Hyeon
Comets emit debris at their perihelion passage, and such debris initially form meteor streams. When the Earth encounters with those streams during its revolution, the cometary debris fall into the Earth's atmosphere and form a meteor showers. If the encounter were made with a fresh meteor-stream, a large number of meteors occur intensively in a short time scale, which are called meteor outbursts. This astronomical phenomena are so brilliant that they have attracted human interest from the early time of history to be recorded in historical archives. Usually meteors form at the altitude of 70-100km, while a small fraction of them survive to fall to the ground and found to be called meteorites. These have been witnessed and collected to be left in history books. A little bit larger impact formed craters on ground. Impact craters on the surface of the Earth, as well as on the Moon, give us precious data to investigate the solar system activity from tens of thousands years ago to hundreds of millions years ago. Likewise, Historical records can give us unique chance investigate the thousand-years-term variations of meteor activity in the Solar system, which must be closely related with the orbital variations of minor bodies in the Solar system. Here in this presentation, I will report the results for meteor outbursts identified from historical archives all around the world throughout the human history, and additionally historical records of meteorites written in Korean royal chronologies. Due to the precession of parent comets, the appearance dates of meteor outbursts also show temporal variations. From these observations, we can pick out at least 12 meteor outbursts that can be identified with their own parent comets. In addition, a couple of Korean records for meteorites give detailed information to be analyzed physically to give us a hint for their type.
Ambiguity, Scope, and Significance: Difficulties in Interpreting Celestial Phenomena in Chinese Records
Chapman, Jesse
This paper examines three factors that contribute to the misinterpretation of records of astronomical and meteorological phenomena in the Chinese historiographical tradition. First, it shows that certain types of records, particularly those describing light, bows, or qi (variously translated as ether, material force, and psychophysical stuff) in fact refer to disparate types of phenomena ranging from oddly-shaped clouds, to halo effects, comets, and aurora. Position words, such as pang (“beside” or “on the side of”) and guan (“encircle” or “penetrate”), are likewise often ambiguous. Second, it describes the range of phenomena and events included in Chinese categories roughly corresponding to astrology and mathematical astronomy, tianwen (celestial patterns) and lüli (calendars and pitchpipes), as well as a third category which includes extensive records of celestial phenomena, wuxing (general omenology, lit. “five phases”). Finally, it turns to the political and religious significance of the practice of observing the sky and modeling the movements of celestial bodies in premodern Chinese records. To avoid miscategorization and misinterpretation, it is necessary to have a working understanding of the problems of ambiguity, scope, and significance.
Transient astronomical phenomena in Australian Indigenous oral traditions: 65,000 years of oral history
Hamacher, Duane
Descriptions of transient phenomena are commonplace in the oral traditions of Indigenous cultures around the globe, particularly Australia. These traditions describe bright meteors, airbursts, haloes, eclipses, aurorae, variable stars, comets, and other related phenomena. Specifically, Aboriginal Australians have detailed oral traditions about different types of variable stars: including descriptions about the sudden appearance, and gradual fading, of bright new stars in the sky, suggesting observations of novae/supernovae. In the 1840s, Aboriginal people in western Victoria observed the Great Eruption of Eta Carinae and incorporated the event in to their traditions. Similarly, Aboriginal communities in southern Australia describe the variability of the pulsating red giants Antares, Betelgeuse, and Aldebaran. This paper will address Indigenous oral and historical records of variable star phenomena in Australia. We will explore how observations of these phenomena are described in oral tradition, including changes in brightness and periodicity, as well as testing claims of supernovae in oral and material culture. We will explore methodologies for identifying these objects and examine ethnographic and ethnohistoric research, how Western science can learn from these traditions, and how this knowledge can be shared by Indigenous elders and applied to the new era of Terra-Astronomy.
What is Terra-Astronomy? An introduction
Neuhäuser, Ralph
There is a large number of historical observations of transient celestial phenomena, often considered sub-lunar, or atmospheric. In what we call Terra Astronomy, we study transient astrophysical processes which potentially affect Terra (e.g. climate, biosphere, etc.) such as solar activity and nearby supernovae - and we investigate them with terrestrial archives, both natural archives (e.g. 14C in trees and 10Be in polar ice) and historical archives (observations recorded in previous centuries to millennia). Written records from various civilizations offer high temporal and spatial resolution, e.g. aurora observations to reconstruct solar activity. Transient phenomena were often recorded in portentous connection: the question was not why and how it happened, but what it could presage. It has been proven challenging to connect or convert qualitative generic text statements to quantitative data. This still holds in the Early Modern Period until the 18th century and is relevant for a better understanding of evolution and depth of the Maunder Minimum.This presentation will discuss challenges and open questions such as: Can we predict solar activity by studying the past? How do cometary plasma tails inform us about solar wind? Given ~10 supernovae in the last two millennia, can we expect to find more? Can the problem of nova evolution be solved with historical observations? How can we go about to find and study additional textual sources, e.g. from Arabia or Korea? What are the advantages and limitations of digital search techniques in a large text corpus?Collaboration with philologists and historical critical methods are essential for a full comprehension of the texts, often in old to ancient languages using different terms, leading to a correct classification of the reported phenomena. Terra Astronomy is truly trans-disciplinary. Synergy is also possible with history of astronomy, historical climatology, and geology (earthquakes, geomagnetic field, volcanic eruptions).
The solar observations during the Maunder minimum: recent advances
Vaquero, José Manuel
John A. Eddy named the Maunder minimum (a period of very low solar activity around the second part of the 17th century) more than forty years ago. However, the exact level of solar activity during this grand minimum of solar activity remains unclear (although several studies have confirmed a low level of solar activity proposed by Eddy). In the last years, some authors have speculated with different scenarios for the Maunder minimum. In this work, we propose to re-analyze the sunspot observations recorded during the MM, also taking into account the knowledge of historians of science and linguists. We must avoid speculations not based on contrasted facts. The sunspot observations made by Hevelius in the onset of the Maunder minimum will be revisited. Also, some sunspot drawings made during the Maunder minimum have been analyzed in detail (computing the ratio umbra-penumbra). Finally, some considerations about the measurements of the solar radius made during the Maunder Minimum will be stablished revisiting the measurements made in the Basilica of San Petronio in Bologna.
Aurora catalogs revisited - with a focus on European records from the Early Modern Period
Neuhäuser, Dagmar L.
In the first half of the 18th century, catalogs were published in Europe for the first time aiming at a compilation of Aurora Borealis records (e.g. de Mairan 1733 and 1754, Frobesius 1739), they were now observed more often; the auroral phenomenon was studied by investigating locations, durations, and variations within and over the years - the connection to the variable Sun or the interpretation as geomagnetic disturbance moved into the focus of the discussion during the 19th century (e.g. Fritz 1873).From the very beginning of compiling current observations, historical sightings were added: many previous observations were found in collections of prodigies from antiquity and the Early Modern Period (e.g. Obsequens and Lycosthenes, respectively), mostly written in Latin. Thereby, two problems occurred, which made their way into publications until today: new and old collections of portents include all kinds of celestial signs, both day- and night-time, both astronomical and meteorological, and they seldom cite the original sources, so that they suffer from many shortcomings regarding text and dating. For distilling a credible aurora catalog for Europe, one needs cultural knowledge, clear criteria regarding the diverse phenomena recorded, as well as collaboration with scholars of philology and history.At the beginning of the Early Modern Period (16th and 17th centuries), an apocalyptic zeitgeist spreads throughout Europe, transient celestial signs are recorded with patience and details - in particular halo phenomena, from simple effects to elaborated displays, published and widely distributed in broad sheets, an early version of newspapers. Therefore, in particular for the period of the Maunder Minimum, one has to expect that aurora catalogs are contaminated by such signs; furthermore, in this time period, calender confusion between the Julian and Gregorian styles (reform 1582 implemented slowly) led to dating errors and duplications.
First and last visibility of the lunar crescent
Gautschy, Rita
The first or last visibility of the lunar crescent is the decisive phenomenon for the start of a new month in various calendars, e.g. the Islamic, Jewish or lunar Egyptian calendar. In order to correctly convert the dates of astronomical observations documented by these cultures into Julian or Gregorian dates, it is necessary to compute the beginnings of the lunar months. Various criteria for the first visibility of the lunar crescent have been proposed based on ancient as well as on modern observational data. For my computations, I use the criterion of Yallop (Yallop 1997) adapted for topocentric calculations. This criterion makes use of the so-called "best time" of observation when the Moon is still some degrees above the horizon – hence, effects of the local horizon can be neglected as long as the horizon is not higher than about three degrees. In the calculations the slowing down of Earth’s rotation is accounted for as well as for standard values of refraction. However, a successful sighting of the lunar crescent is highly dependent on the prevailing seeing conditions: dust in the air or slight fog can easily cause delayed first sightings. Especially in cases where the visibility parameter is close to the critical threshold a lunar crescent may be missed even if the seeing is good. I will discuss the uncertainties of the calculations for different periods of time and show how they may be dealt with. References B. D. Yallop, A Method for Predicting the First Sighting of the New Crescent Moon, NAO Technical Note No. 69, 1997. HMNAO’s Moon Watch web site: astro.ukho.gov.uk/moonwatch/index.html Islamic Crescents’ Observation Project: www.icoproject.org
Applying historical observations to study transient phenomena
Griffin, Elizabeth
Astronomy has an enviable wealth of historic observations. Some verge on the archaeological, and bear important information about rare events such as novae and supernovae; many others range up to $\sim$100 years old, and bear unique information about events that will never repeat in detail. Historic data were obtained in analogue formats, and in the present era of born-digital data they are often regarded as hailing from a culture that has historical significance only. That is a serious misrepresentation of the facts: our archives of photographic observations, in particular, are invaluable and irreplaceable resources. The technology change to electronic data was abrupt and in some ways cathartic, but it left most of today's astronomers unable to handle photographic data, let alone to comprehend the feasibility of including such "old-fashioned" technological output in the service of research. What is not widely recognized, or believed, is that any of those photographic observations has the potential to contribute unique and unrepeatable information to {\it present-day} studies of variability in the cosmos. The older the data, the more reliable the base-line against which one can measure new trends, determine orbital parameters, etc. Efforts have been discussed for some time as to how to rescue that vital information from loss as the plates age, or (in some cases) get discarded "for lack of interest". The necessary technology for scanning plates correctly is becoming available, and it is now up to us to find the necessary funding to carry through a major digitizing programme. The talk will outline plans for such a project.
Eclipses and the Earth's Rotation
Morrison, Leslie
Historical records of eclipses of the Sun and Moon in the period 720 BC to AD 1600 provide vital information about the rotation of the Earth. The extant records come from the ancient civilisations of Babylonia, China, Greece, Arab Dominions, and medieval Europe. Generally, the record of an eclipse allows the place of observation to be established, and contains sufficient local calendrical information for the Julian date to be determined unequivocally. The record also contains an estimate of the local time, from which the Universal Time (UT) of the circumstance of the eclipse can be calculated. In the particular case of total solar eclipses, where the track of totality is very narrow on the Earth’s surface, the possible range of UT is defined by the sharp boundaries of the track. Given the place, date and UT, the local circumstances of the eclipse in Terrestrial Time (TT) can be calculated from the gravitational theories of the motion of the Earth and Moon. The difference, TT-UT, commonly referred to as ΔT, measures the cumulative discrepancy in UT due to fluctuations in the Earth’s rate of rotation, which is conveniently measured by changes in the length of the mean solar day (lod). We have measured the quantity ΔT in the period 720 BC to AD 1600 from observations of several hundred solar and lunar eclipses. The slope on a curve fitted to these data is a measure of the lod. The average long-term increase in the lod is found to be $+1.78$ milliseconds per century (ms/cy), which is significantly less than the increase of $+2.3\,$ms/cy expected on the basis of tidal friction. This implies an accelerative component decreasing the lod by $-0.5\,$ms/cy since 720.
I,II,III,IV,V: Types of Historical Supernovae and what you, I, and LIGO might have seen
Trimble, Virginia
First the good news: The historical supernovae (of which there are 7-14) can tell us something about rates (small number statistics), types (no two are the same), parent populations, 3-D structures, what SNe put into the ISM, formation, initial rotation and magnetic fields, and early evolution of neutron stars, ditto for black holes, late mass loss from massive stars, nucleosynthesis, kick velocities, and whatever I've left out. Now for the bad news: CM Tau (SN 1054, NGC 1952, 3C144, Tau X-1, NP0532, etc.) has aged 5.6% since I and Jeff Scargle began looking at images of it for our Caltech PhD dissertations (with thanks to Walter Baade and Guido Munch). In the interim, its observed mass has fluctuated more than a factor two, it has added a pulsar (with rather slow initial rotation), a fairly useless jet off to one side (though everything else discovered by Sidney van den Bergh over the years has been highly useful), a gamma ray source, and many models of particle acceleration, of which at most one can be correct. And this is the historical SN about which we know most. The ensemble includes 1572 (Tycho), 1604 (Kepler), Cas A (not Flamsteed), SN 1006, the progentor of SNR 0519-76.5 (not Magellan), S And, RCW86 = SN 185, 1987A, etc. Eta Carinae was a Zwicky Type V and doesn't count. These suggest, first, that we are overdue for another Galactic event and, second, that successful clasification of events is considerably assissted by not knowing too much about them. The Crab Nebula was also the first identified remnant of an event that had been recorded when it occurred (credit Lundmark and assorted anonymous Chinese sky-watchers). The identification was, of course, then disputed, until many astronomers had written either that they had always known about it, or that it wasn't very important, or that they thought of it first."
Revisiting the historical sunspot number back to 1610: latest progresses
Clette, Frédéric
Due to its unique 400-year duration, the sunspot number is a central reference for understanding the long-term evolution of solar activity and its influence on the Earth environment and climate. Following a 4-year effort, a first end-to-end re-calibrated series of the sunspot number (SN) series was released in 2015. It reduced the main inconsistencies between the SN series and its closest counterpart, the sunspot group number (GN). As it also showed that further improvements are possible, this revision led to the publication of several new alternate reconstructions of either the SN and GN series, leading to some confusion among scientific users. We will first review the main results, which rest either on new improved databases of historical sunspot observations, or on alternate statistical approaches like the active-day method, non-parametric cross-matrices between pairs of observers, expectation minimization, etc. Over recent months, coordinated investigations in the framework of ISSI Team Meetings allowed to identify some flaws or limitations in the applicability of those recent methods and to envision the combined application of multiple approaches. This coordinated work also aims at a better determination of uncertainties in the reconstructed series by each method, where error bars were totally absent in the orignal sunspot numbers. We report on those ongoing progresses. The current international synergy for the preparation of SN version 3, can actually become the fundation of a continuous quality assurance and of a community-wide sanctioning of future updates. We propose such a permanent version-development and supervision scheme under the official IAU framework. With its origins rooted in the 17th century, the sunspot number is thus called upon to become a modern astronomical standard for the 21st century.
Study of Sanskrit inscriptions of South East Asia as sources of records of celestial events.
B S, Shylaja
Inscriptions in Sanskrit are seen in Cambodia,Nepal, Srilanka, in general all over South East Asia from about 4th Century CE till about 13th century. These are records of grants and other religious deeds with valuable documentation of celestial events like eclipses, planetary conjunctions and even comets. A study of these records also throws light on the evolution of the calendar and influence of other types of calendars. Possible mention of the 1054 supernova event also is discussed.
An Extended Moonwatch in the Middle East in 860 CE for Determining Empirically a Critical Value for Lunar Crescent Visibility
Thomann, Johannes
In the years from 1987 to 1990, five organised Moonwatches took place in North America. The results were used to evaluate different models for the visibility of the lunar crescent, including historical criteria from Babylonian and Arabic astronomers (Doggett/Schaefer 1994). Already in the 9th century this empirical method was in use. The ingenious astronomer ?abash al-?asib established in his Damascene Zij the most elaborate model for predicting visibility ever formulated in pre-modern times. It was praised by al-Biruni in the Masudic Canon as the best available criterion. However, despite ?abash’s fame, his Zij remains unpublished. ?abash begins by describing his model in general terms and introducing a threshold value, for which he gives no explanation. Then, he explains the model by providing an example for November 860 CE. Finally, ?abash reports that the moon was seen in Kufa, Anbar and cities in Syria, but not in Baghdad and Samarra. Obviously, his threshold value was chosen to match these data points. According to a modern estimation, the crescent could have been seen in Baghdad. Weather conditions might have not been favorable in November 860. Indeed, the historian al-?abari recorded heavy showers in Baghdad for that month. This leads to more general considerations. The Muslim calendar was regulated by sighting of the lunar crescent at the evening of the 29th of each month. Every historical record of a month of 29 days is a witness of a positive observation of the crescent, and every record of a month of 30 days is a negative one. Calendars were regulated locally and differed from city to city. Therefore, the enormous annalistic Arabic literature is a huge archive of thousands of Moonwatches undertaken in a large territory from the Atlantic to Aral sea and beyond, which could be used as proxy data for atmospheric phenomena.
Using Byurakan Plate Archive records for revelation of transient objects
Mikayelyan, Gor
We use Byurakan Plate Archive records for revelation of transient phenomena. The Byurakan Astrophysical Observatory (BAO) Plate Archive Project (https://www.aras.am/PlateArchive/) is aimed at digitization of all 37,500 plates obtained during 1947-1991, their astrometric solution, creation of extraction and analysis software, electronic database, webpage and interactive sky map. The famous Markarian Survey (or the First Byurakan Survey, FBS) 2000 plates were digitized in 2002-2007 and the Digitized FBS (DFBS, www.aras.am/Dfbs/dfbs.html) was created. New science projects have been conducted based on this low-dispersion spectroscopic material. Armenian Virtual Observatory (ArVO, www.aras.am/Arvo/arvo.htm) database will accommodate all new data. ArVO will provide all standards and tools for efficient usage of the scientific output and its integration in international databases. One of the most interesting science projects that is possible based on BAO Plate Archive data, is the search for transients by comparison of the same fields from different epochs, including both comparison of BAO plates between each other and BAO and POSS 1/2 (DSS 1/2) records. BAO observations are significant contribution for the years gap between POSS1 and POSS2 and may reveal numerous new transients and variables, such as Novae and Supernovae, as well as comets and asteroids. One of our small projects in collaboration with IMCCE (France) was already applied for search and study of asteroids using the VO software SkyBoT and 700 known asteroids were revealed at previously not detected positions, which helped to correct their ephemeris and develop low-dispersion model spectra for search for new asteroids. 7 extremely high amplitude variables (7m-8m and larger differences between two epochs) were discovered by comparison with DSS fields. We will give examples of transients found by means of Byurakan archival observations.
X-ray Ejecta Kinematics in the Remnants of Historical Supernovae 1604 and 1572
Park, Sangwook
Based on our Chandra High-Energy Transmission Grating Spectrometer (HETGS) observations, we measure the bulk radial velocities of numerous small X-ray emission features from the shocked metal-rich ejecta gas in the remnants of historical supernovae 1604 (Kepler’s supernova remnant) and 1572 (Tycho’s supernova remnant). We measure the Doppler shifts in the K-shell electron transition lines in highly-ionized, He-like Si ions in the spectra of these overabundant ejecta “knots” to estimate their radial velocities. We present our results from a sub-sample of ejecta knots in these remnants. We estimate high radial velocities up to ~10,000 km/s for some of these ejecta knots, indicating the presence of nearly “freely-expanding” stellar debris after ~400 years of the explosions. We discuss the implications of these velocity measurements for the distances to these historical supernovae. This work has been supported in part by NASA Chandra Grants GO6-17060X, AR7-18006X, and GO7-18061X.
Reconstructing the geomagnetic field from historical aurorae
Wagner, Daniel
For studying secular variations of solar activity over centuries fromthe satellite to the pre-telescopic era, homegeneous time series areneeded. Observations of aurorae as solar wind proxy could provide acontinuous time series overlapping with various discontinuities anderas. While aurorae were documented all over the world for the lastfew centuries, a critically checked and homogeneous dataset is notavailable. Here, we have started new initiatives to compile suchdatasets (we have obtained experience with historically observedaurorae from the pre-telescopic era). It is well-known that auroraetrace solar wind and, hence, are correlated to geomagnetic indices(e.g. aa-index measured since 1868); a full understanding of theconnection between auroral displays, observed from the ground by thenaked eye, and, e.g., the aa-index is still missing.Therefore, we investigated the size of the auroral oval as well as its offset fromthe geomagnetic pole for different magnetic activity levels describedby the Kp-index during solar maximum and minimum. We used imaging datafrom 1981 to 1991 from the Spin-Axis Auroral Imager mounted on theDynamics Explorer 1 satellite. We found a linear dependence betweenthe Kp-index and the oval radius and a nearly constant shift of theoval center towards the midnight sector of around 4.5 degrees.Currently, we derive the aurora oval size and radius from ground-basedaurora observations of the last few decades to compare them withsatellite data of the oval. Next, we plan to derive the geomagneticfield (strength and location of poles) from historical aurorae of thelast two centuries to compare with direct measurements of the magneticfield; if this would work, we can apply the same technique to previouscenturies to obtain an independent reconstruction.
What can say observations of comets about the solar wind at the Maunder minimum?
Zolotova, Nadezhda
We consider the question of whether observers in the 17th century left historical records on the monitoring of the plasma tails of comets, which would allow us to judge the physical parameters of the solar wind. The magnitude of the deviation angle of the comet tail from the prolonged radius-vector of a comet defines the type of the comet tail: plasma or dust. We consider Bessel's and Bredikhin's calculations of trajectories of 10 comets during the Maunder minimum (1645-1715). For these comets the value of the angle between the tail axis and the prolonged radius-vector on the average exceeds 10 degrees that is typical of dust tails. Also note that visual observations of the ion tails of comets are very difficult due to the spectral composition of their radiation. This confirms our conclusion that the comet tails observed in the 17th century are not suitable for discussion about the physical parameters of the solar wind in the past.
New orbits for perihelion passages of comet 1P/Halley in AD 760 and 837
Mugrauer, Markus
Orbital elements of comets can be deduced from historical observations, where positions on sky and dates of observations are given, as was done e.g. for comet 1P/Halley back to the first centuries BC (e.g. Yeomans & Kiang 1981, MNRAS 197, 633). We critically review the Chinese records for AD 760 and 837, which were previously used to estimate the orbital elements for comet 1P/Halley. Then, we add more dated positions for the perihelion passage of AD 760 also from the Syriac Chronicle of Zuqnin (Harrak 1999, D.L. Neuhäuser et al. 2018, in prep.), whose author had observed and drawn this comet as eyewitness. For AD 837, we also added the positions from al-Kindi's observations (Yazdi 2015, JHA 45, 61) as well as dated positions from Carolingian observations, which were not used before for orbital reconstruction. Several of the dated positions do not agree with the previously published orbits. We then determined a new orbital solution for the AD 760 perihelion passage and are currently working on the AD 837 perihelion - using the method of least squares, taking into account several gravitational perturbers in the solar system. We discuss the light curve of the comet (obtained for the new orbital elements) with records for first and last sighting around conjunction with the Sun as well as the very first and last sightings. The observed comet brightness and tail length (blown by solar wind) depend on cometary and solar activity for the time of observation, the latter is known to be rather high around AD 760 and 837 (Neuhäuser & Neuhäuser 2015 AN 336, 225). Precise orbital elements of these two perihelia are important for going back into the more distant past, because comet 1P/Halley had a close encounter with a planet (Earth within 0.0335 au) in AD 837 April, which should have modified the orbit. A re-assessment of historical records should be done also for the other perihelia passages of 1P/Halley and also for other comets.
The Maunder minimum of solar activity as documented by historical sunspot observations
Arlt, Rainer
A period of very low solar activity in the 17th century was identified already 130 years ago from the inspection of historical sunspot observations. The minimum lasted from about 1650 to 1710. This talk will give an overview of our present knowledge of these observations and the interpretation of them. Physical quantities can actually be derived from the drawings of the solar disk. The differences in behaviour of the solar cycle from today may be the key to understand the mechanism behind the solar magnetic variability, the solar dynamo.
Changes in the Unchangeable: Simulation of Transient Astronomical Phenomena with Stellarium
Zotti, Georg
Since the 1980s, desktop planetarium programs have been a great help for visualizing the sky and computing the positions of the planets and other objects in present and past times. Advances in graphical capabilities of affordable personal computers allowed the development of ever more visually realistic simulations, and the development of the world-wide web, broadband communication and open-source movement of software development have brought forth high quality cost-free or affordable software for many application fields.One of those projects is the open-source desktop planetarium Stellarium. Its original purpose was to visualise the current skies as realistically as possible. With its high quality physics-based sky brightness and colour simulation it gained also high popularity as astronomy outreach tool during IYA2009.Although it was geared towards contemporary amateur astronomers and laypeople, some of its original features, such as its visual quality of simulation and easily exchangeable sky cultures (constellation patterns), as well as its simple usability and free availability, also made the program very attractive to researchers in the fields of historical and also ethnoastronomy. Stellarium has also become a well-known educational tool in schools, colleges, universities and planetariums around the world.A powerful aspect of Stellarium is the possibility to extend the program with plugins for special --- educational or scientific --- purposes without deep changes in the core code. Several of those, including a 3D mode to explore potentially astronomically oriented buildings in their surrounding landscape, have been developed for purposes of visualisation and research in historical astronomy and archaeoastronomy.In this paper we want to highlight several features which can be used to simulate for research, but also and especially for outreach, several transient astronomical phenomena:Solar and Lunar eclipses, Comets, and Supernovae and Novae.
Galileo's account of Kepler's supernova (SN1604): a Copernican assessment
Cosci, Matteo
The supernova that appeared in the constellation of Ophiuchus on the 9th of October 1604 is known today as "Kepler's supernova" because of the long and detailed study that the German astronomer devoted to the understanding of the exceptional event (De Stella Nova, Prague 1606). However, at that time Kepler was not the only astronomer whose eyes were turned to the scientific study of that unexpected astronomical event. A few years before than the telescope was invented, also Galileo Galilei was involved in the debate regarding the nature, appearance, position, distance, and overall meaning of the "anomalous" phenomenon. Although he did not publish anything specific on the subject, it is possible to reconstruct his take on the supernova from scattered sources, whose temporal extension start from the first weeks after the stellar outburst and last up to the final years of life of the Pisan astronomer. Therefore it can be affirmed that actually Galileo never stopped his survey on the stella nova. In fact, he lectured on it, took fragmentary notes, drew some diagrams, kept a scientific correspondence, inserted dedicated sections within his major works, commented on the margins of the pages of his copies of his competitors' books and replied under pseudonyms to many of his critics. The present contribution aims at solving the puzzle of Galileo's account on Kepler's supernova, arranging all the extant pieces of evidence in their right chronological order. Galileo's sources will be set in context and the network of his informers will be tracked in order to frame in a comprehensive way one of the most original and influential understanding of the SN1604 of that time. In conclusion it will be evident how Galileo intended to use his set of data for an early, albeit unsuccessful, confirmation of the Copernican model of the solar system (cf. J.L Heilbron, Galileo, Oxford 2010, pp.119-126), almost managing to make the star known as the "Galileo's Supernova".
Definition and epistemology of terra-astronomy
Posch, Thomas
Terra-astronomy is a relatively recent discipline of astronomy, a fact that calls for its precise definition (1) and for a reflection on its epistemological basis (2).(1) I shall argue that terra-astronomy is most clearly defined as the study of individual astronomical objects and phenomena (e.g. the Sun, the Earth’s rotation eclipses, aurorae, particular supernovae, particular comets etc.) based on historical records. Its focus on past events and old pieces of evidence is a feature that it shares with astronomical historiography. However, the aspiration of terra-astronomy is different from many merely historical investigations, namely to ultimately derive conclusions of relevance to contemporary astrophysical research (e.g. a deeper understanding of the solar dynamo or a refinement of the laws governing supernova explosions).(2) This leads to some basic epistemological considerations. I shall base them on Heinrich Rickert’s view according to which there are two prototypical approaches to empirical reality: the ‘historical’ approach and the natural scientific approach, the latter being most distinctly represented by theoretical physics. The first, far from being restricted to ‘data on past events’, focusses on individual phenomena and cultural values. The second, by contrast, usually does not refer to (i.e. it abstracts from) cultural values and aims at establishing universal laws of nature. As I finally try to demonstrate, both astronomy in general and terra-astronomy in particular need to rely on conceptual elements from both approaches.
AI-generated magnetogram of the Carrington event in 1859 and the estimation of its Dst value
Lee, Harim
We apply an image-to-image translation model, which is a popular deep learning method based on conditional Generative Adversarial Networks (cGANs), to the generation from sunspot drawings to the corresponding magnetograms. For this, we train the model using pairs of sunspot drawing from Mount Wilson Observatory (MWO) and their corresponding SDO/HMI line-of-sight magnetogram from 2012 to 2013. We test the model by comparing pairs of actual SDO/HMI magnetogram and the corresponding AI-generated one in 2014. Our results show that bipolar structures of the AI-generated magnetograms are consistent with those of the original ones and their unsigned magnetic fluxes are well correlated with those of the original ones with a good correlation coefficient of 0.78. Using this model with the Carrington sunspot drawing, we successfully produce AI-generated magnetogram and estimate unsigned magnetic fluxes. Using several empirical relationships (magnetic flux vs. CME speed, CME speed vs. ICME speed, and ICME speed vs. Dst) in 23 and 24th solar cycle, we conjecture the Dst value of the Carrington event, about -1,100 nT, which is between two estimations of Bombai magnetometer.
Scaling Historical Space Weather Events: Case Studies of Events in 1859 and 1770
Hayakawa, Hisashi
This presentation aims at providing insights on scaling the historical space weather events before magnetic observations. It is well known that the Carrington event is considered one of the most extreme space weather events in the coverage of magnetic observations. However, this coverage spans no more than 2 centuries and it is not clear if this event is that “extreme” in historical time span. On the other hand, it is known that equatorward boundary of auroral oval has correlation with scale of magnetic storms. Therefore, in this presentation, we review historical records in 1859 and see its relation with magnetic observations (Hayakawa et al., 2016). Then, we apply the same approach to another historical space weather event in 1770. In this presentation, we examine the equatorward extension of auroral visibility, elevation angle of auroral display, and longevity of the low latitude aurorae, to compare this event with the extreme space weather event in 1859 (Hayakawa et al., 2017; Ebihara et al., 2017; Kataoka and Iwahashi, 2017).Ebihara, Y., et al. 2017, Space Weather, 15, 1373Hayakawa, H., et al. 2016, PASJ, 68, 99.Hayakawa, H., et al. 2017, ApJL, 850, L31 Kataoka, R., Iwahashi, K. 2017, Space Weather, 15, 1314
Great historical events of space weather from Spanish documents: a review
Gallego, María Cruz
Northern lights observed from Spain are generally related to great space weather events due to its location in southern Europe. In this contribution, we review the auroras observed from the Iberian Peninsula in the last millennium. Great events of space climate (such as Maunder minimum) are well-characterized in this set of auroral observations. The maximum number of auroral observations occurred in the 18th century when the geomagnetic latitude of the Iberian Peninsula was higher. In fact, we analyze in detail the evolution of the geomagnetic latitude of the Iberian Peninsula during the last centuries. Some cases of interest are analyzed in detail such as the Carrington storm or the 1903 geomagnetic storm (that was the first geomagnetic storm that significantly affected the telegraph in Spain). We also briefly discuss other historical cases of auroras or geomagnetic storms observed in Spanish colonies.