List of possible dwarf planets

The number of dwarf planets in the Solar System is unknown. Estimates have run as high as 200 in the Kuiper belt and over 10,000 in the region beyond.
However, consideration of the surprisingly low densities of many dwarf-planet candidates suggests that the numbers may be much lower (e.g. at most 10 among bodies known so far). The International Astronomical Union (IAU) notes five in particular: in the inner Solar System and four in the trans-Neptunian region: , , , and , the last two of which were accepted as dwarf planets for naming purposes. Only Pluto is confirmed as a dwarf planet, and it has also been declared one by the IAU independently of whether it meets the IAU definition of a dwarf planet.
IAU naming procedures.
In 2008, the IAU modified its naming procedures such that objects considered most likely to be dwarf planets receive differing treatment than others. Objects that have an absolute magnitude (H) less than +1, and hence a minimum diameter of if the albedo is below 100%, are overseen by two naming committees, one for minor planets and one for planets. Once named, the objects are declared to be dwarf planets. Makemake and Haumea are the only objects to have proceeded through the naming process as presumed dwarf planets; currently there are no other bodies that meet this criterion. All other bodies are named by the minor-planet naming committee alone, and the IAU has not stated how or if they will be accepted as dwarf planets.
Limiting values.
Beside directly orbiting the Sun, the qualifying feature of a dwarf planet is that it have "sufficient mass for its self-gravity to overcome rigid-body forces so that it assumes a hydrostatic equilibrium (nearly round) shape". Current observations are generally insufficient for a direct determination as to whether a body meets this definition. Often the only clues for trans-Neptunian objects is a crude estimate of their diameters and albedos. Icy satellites as large as 1500 km in diameter have proven to not be in equilibrium, whereas dark objects in the outer solar system often have low densities that imply they are not even solid bodies, much less gravitationally controlled dwarf planets.
, which has a significant amount of ice in its composition, is the only confirmed dwarf planet in the asteroid belt although Hygeia may possibly also be one. 4 Vesta, the second-most-massive asteroid and one that is basaltic in composition, appears to have a fully differentiated interior and was therefore in equilibrium at some point in its history, but no longer is today. The third-most massive object, 2 Pallas, has a somewhat irregular surface and is thought to have only a partially differentiated interior; it is also less icy than Ceres. Michael Brown has estimated that, because rocky objects such as Vesta are more rigid than icy objects, rocky objects below in diameter may not be in hydrostatic equilibrium and thus not dwarf planets.
Based on a comparison with the icy moons that have been visited by spacecraft, such as Mimas (round at 400 km in diameter) and Proteus (irregular at 410–440 km in diameter), Brown estimated that an icy body relaxes into hydrostatic equilibrium at a diameter somewhere between 200 and 400 km. However, after Brown and Tancredi made their calculations, better determination of their shapes showed that Mimas and the other mid-sized ellipsoidal moons of Saturn up to at least Iapetus (which is of the approximate size of Haumea and Makemake) are no longer in hydrostatic equilibrium; they are also icier than TNOs are likely to be. They have equilibrium shapes that froze in place some time ago, and do not match the shapes that equilibrium bodies would have at their current rotation rates. Thus Ceres, at 950 km in diameter, is the smallest body for which gravitational measurements indicate current hydrostatic equilibrium. Much larger objects, such as Earth's moon, are not near hydrostatic equilibrium today, though the Moon is composed primarily of silicate rock (in contrast to most dwarf planet candidates, which are ice and rock). Saturn's moons may have been subject to a thermal history that would have produced equilibrium-like shapes in bodies too small for gravity alone to do so. Thus, at present it is unknown whether any trans-Neptunian objects smaller than Pluto and Eris are in hydrostatic equilibrium.
The majority of mid-sized TNOs up to about in diameter have significantly lower densities (~ ) than larger bodies such as Pluto (1.86 g/ml). Brown had speculated that this was due to their composition, that they were almost entirely icy. However, Grundy "et al". point out that there is no known mechanism or evolutionary pathway for mid-sized bodies to be icy while both larger and smaller objects are partially rocky. They demonstrated that at the prevailing temperatures of the Kuiper Belt, water ice is strong enough to support open interior spaces (interstices) in objects of this size; they concluded that mid-size TNOs have low densities for the same reason that smaller objects do—because they have not compacted under self-gravity into fully solid objects, and thus the typical TNO smaller than in diameter is (pending some other formative mechanism) unlikely to be a dwarf planet.
Tancredi's assessment.
In 2010, Gonzalo Tancredi presented a report to the IAU evaluating a list of 46 candidates for dwarf planet status based on light-curve-amplitude analysis and a calculation that the object was more than in diameter. Some diameters were measured, some were best-fit estimates, and others used an assumed albedo of 0.10 to calculate the diameter. Of these, he identified 15 as dwarf planets by his criteria (including the 4 accepted by the IAU), with another 9 being considered possible. To be cautious, he advised the IAU to "officially" accept as dwarf planets the top three not yet accepted: Sedna, Orcus, and Quaoar. Although the IAU had anticipated Tancredi's recommendations, a decade later the IAU had never responded.
Brown's assessment.
Mike Brown considers 130 trans-Neptunian bodies to be "probably" dwarf planets, ranked them by estimated size. He does not consider asteroids, stating "in the asteroid belt Ceres, with a diameter of 900 km, is the only object large enough to be round."
The terms for varying degrees of likelihood he split these into:
Beside the five accepted by the IAU, the 'nearly certain' category includes , , , , and .
Grundy "et al".’s assessment.
Grundy "et al". propose that dark, low-density TNOs in the size range of approximately are transitional between smaller, porous (and thus low-density) bodies and larger, denser, brighter and geologically differentiated planetary bodies (such as dwarf planets). Bodies in this size range should have begun to collapse the interstitial spaces left over from their formation, but not fully, leaving some residual porosity.
Many TNOs in the size range of about have oddly low densities, in the range of about , that are substantially less than dwarf planets such as Pluto, Eris and Ceres, which have densities closer to 2. Brown has suggested that large low-density bodies must be composed almost entirely of water ice, since he presumed that bodies of this size would necessarily be solid. However, this leaves unexplained why TNOs both larger than 1000 km and smaller than 400 km, and indeed comets, are composed of a substantial fraction of rock, leaving only this size range to be primarily icy. Experiments with water ice at the relevant pressures and temperatures suggest that substantial porosity could remain in this size range, and it is possible that adding rock to the mix would further increase resistance to collapsing into a solid body. Bodies with internal porosity remaining from their formation could be at best only partially differentiated, in their deep interiors. (If a body had begun to collapse into a solid body, there should be evidence in the form of fault systems from when its surface contracted.) The higher albedos of larger bodies is also evidence of full differentiation, as such bodies were presumably resurfaced with ice from their interiors. Grundy "et al". propose therefore that mid-size (< 1000 km), low-density (< 1.4 g/ml) and low-albedo (< ~0.2) bodies such as Salacia, Varda, Gǃkúnǁʼhòmdímà and are not differentiated planetary bodies like Orcus, Quaoar and Charon. The boundary between the two populations would appear to be in the range of about .
If Grundy "et al". are correct, then among known bodies in the outer Solar System only Pluto–Charon, Eris, Haumea, Gonggong, Makemake, Quaoar, Orcus, Sedna and perhaps Salacia (which if it were spherical and had the same albedo as its moon would have a density of between 1.4 and 1.6 g/cm3, calculated a few months after Grundy et al's initial assessment, though still an albedo of only 0.04) are likely to have compacted into fully solid bodies, and thus to possibly have become dwarf planets at some point in their past or to still be dwarf planets at present.
Likeliest dwarf planets.
The assessments of the IAU, Tancredi et al., Brown and Grundy et al. for the dozen largest potential dwarf planets are as follows. For the IAU, the acceptance criteria were for naming purposes. Several of these objects had not yet been discovered when Tancredi et al. did their analysis. Brown's sole criterion is diameter; he accepts a great many more as highly likely to be dwarf planets (see below). Grundy et al. did not determine which bodies were dwarf planets, but rather which could not be. A red marks objects too dark or not dense enough to be solid bodies, a question mark the smaller bodies consistent with being differentiated (the question of current equilibrium was not addressed).
Iapetus, Earth's moon and Phoebe are included for comparison, as none of these objects are in equilibrium today. Triton (which formed as a TNO and is likely still in equilibrium) and Charon are included as well.
Largest candidates.
The following trans-Neptunian objects have estimated diameters at least and so are considered "probable" dwarf planets by Brown's assessment. Not all bodies estimated to be this size are included. The list is complicated by bodies such as 47171 Lempo that were at first assumed to be large single objects but later discovered to be binary or triple systems of smaller bodies.
The dwarf planet Ceres is added for comparison. Explanations and sources for the measured masses and diameters can be found in the corresponding articles linked in column "Designation" of the table.
The "Best diameter" column uses a measured diameter if one exists, otherwise it uses Brown's assumed-albedo diameter. If Brown does not list the body, the size is calculated from an assumed-albedo of 9% per Johnston.
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Sion astronomical clock

The Sion astronomical clock is an astronomical clock at the town hall of Sion in the canton of Valais, Switzerland. The clock was first installed in 1667–68; the present mechanism dates from 1902.
The clock has five dials: on the two lateral sides of the clock tower, there are 12-hour dials. The principal dial on the front of the tower indicates, from the outer to the inner ring:
The position of the sun in the zodiac and the month are both indicated by a hand with a golden sun. The other end of this hand, with a star, indicates the constellation which passes through the meridian at Sion in the middle of the night.
The two smaller dials underneath the principal dial indicate the day of the week, represented by an illustration of its classical deity, and the lunar phase by means of a rotating moon ball.


Andrew Ballard

Andrew Edgar Ballard (born 14 January 1944) is an Anglican priest. He was Archdeacon of Rochdale from 2000 to 2005; and Archdeacon of Manchester from 2005 to 2009.
He was educated at Rossall School, St John's College, Durham and Westcott House, Cambridge. He was ordained in 1969. After curacies at St Mary's, Bryanston Square and St Mary's Portsea, the largest parish in that city, he held incumbencies in Haslingden, Walkden, Little Hulton and Farnworth before his appointment as Archdeacon.
His father was also Archdeacon of Rochdale, from 1966 to 1972.


Jessica Leigh Jones

Jessica Leigh Jones (born 1994) is a Welsh Engineer and Astrophysicist from Cardiff, Wales. She is credited with becoming the first female to win the UK Young Engineer of the Year Award in 2012 for her work designing a portable uterine contraction monitor which cut manufacturing costs by 99%. She was later rewarded for her efforts to commercialise the technology, receiving the IET Intel Inspiration Award for Entrepreneurship in the same year.
From January 2016 Jones has been employed at the Sony UK Technology Centre, Pencoed, Wales, leading the development of advanced manufacturing technology with Japan for which she was recognised in The Telegraph Top 50 Women in Engineering under 35 list 2017. She also holds positions as Director, Engineering Education Scheme Wales and Patron, Alton Convent School, Hampshire, England. Jones is a Liveryman (by Servitude) of the Worshipful Company of Scientific Instrument Makers, the 84th Livery Company in the City of London.
Jones was appointed Member of the Order of the British Empire (MBE) in the 2020 Birthday Honours for services to women in engineering in Wales.
Early life.
Jones was born in Cardiff on 22 July 1994. As a young child, her father worked at MOD St Athan, Vale of Glamorgan, as an Aircraft Electrician. Jones attended Willows High School in Tremorfa, Cardiff until age 15, where she was taught electronics at GCSE level by Keith Allen, whom she described as one of her role models.


Elsa van Dien

Elsa van Dien (12 July 1914 – 15 October 2007) was an astronomer. She received her Ph.D. from Harvard University. She married Gale Bruno van Albada who was also an astronomer. <br>
Biography.
Elsa van Dien was born in Paramaribo (Surinam) on 12 July 1914. She was the daughter of Rebecca da Silva and Gerrit van Dien. The family moved to the Netherlands in 1923. Elsa began studying astronomy at the University of Amsterdam in 1932. She also registered at the University of Leiden (The Netherlands) in 1935, to have access to its observatory.
After her studies, she started to teach at the Gemeentelijk Lyceum in Zaandam. On 21 November 1940, she was fired for being Jewish. When the deportations started, she went into hiding at reverend J.C.S. Locher in Leiden, and managed to survive the war.
She was awarded a scholarship by Radcliffe College for September 1939, but due to the Second World War she could only commence her PhD there in September 1945, also with support of the American Association of University Women (AAUW). Her thesis, supervised by Donald Menzel, discussed the Stark effect in the Balmer lines of early type stars.
After her PhD, she initially stayed at the Dominion Astrophysical Observatory in Victoria, Canada. In 1948 she moved back to the Netherlands. In August 1948 she was appointed at the Bosscha Observatory near Bandung, Indonesia. There she met and married Gale Bruno van Albada. She continued her astronomical research until 1958, when the family returned to the Netherlands. She edited the Dutch journal "Wetenschap en Maatschappij" from 1965 to 1972. In the 1970s and 1980, after the death of Van Albada in 1972, she once again resumed her astronomical research.


Neutrino Array Radio Calibration

The Neutrino Array Radio Calibration (NARC) experiment was the successor to the Radio Ice Cherenkov Experiment (RICE) which served as a testbed for future development of an eventual large-scale neutrino radio-detection array. NARC involved detecting ultra high energy electron neutrinos through their interactions with ice molecules in the Antarctic icecap, based on the principle of radio coherence. Experimentally, the goal was to detect and measure long-wavelength (radiofrequency) pulses resulting from this interaction. The experiment ended 2012 (end of data-taking 2010). The experiment is succeeded by the Askaryan Radio Array (ARA) experiment.


Three College Observatory

Three College Observatory (TCO) is an astronomical observatory owned and operated by The University of North Carolina at Greensboro (UNCG), North Carolina Agricultural and Technical State University (N.C. A&T), and Guilford College (GC). Built in 1979, it is located south of Graham, North Carolina (USA), in the Cane Creek Mountains. The observatory, designed by W. Edward Jenkins, was funded with a $250,000 grant, however, it would cost $1.5 million to replace it today. The observatory's primary instrument is a Ritchey-Chrétien reflecting telescope attached to an equatorial mount. It was built by Sigma Research and installed at TCO in 1981. TCO is used by UNCG for instruction and outreach. It continues to be the largest telescope in North Carolina and ones of the largest telescopes in the southeast.


93P/Lovas

93P/Lovas, also called Comet Lovas or Lovas's Comet, is a Jupiter-family comet discovered in 1980.


Sinus Sabaeus quadrangle

The Sinus Sabaeus quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. It is also referred to as MC-20 (Mars Chart-20).
The Sinus Sabaeus quadrangle covers the area from 315° to 360° west longitude and 0° to 30° degrees south latitude on Mars. It contains Schiaparelli, a large, easily visible crater that sits close to the equator. The Sinus Sabaeus quadrangle contains parts of Noachis Terra and Terra Sabaea.
The name comes from an incense-rich location south of the Arabian peninsula (the Gulf of Aden).
Layers.
Wislicenus Crater and the Schiaparelli basin crater contains layers, also called strata. Many places on Mars show rocks arranged in layers. Sometimes the layers are of different colors. Light-toned rocks on Mars have been associated with hydrated minerals like sulfates. The Mars Rover Opportunity examined such layers close-up with several instruments. Some layers are probably made up of fine particles because they seem to break up into fine dust. Other layers break up into large boulders so they are probably much harder. Basalt, a volcanic rock, is thought to in the layers that form boulders. Basalt has been identified on Mars in many places. Instruments on orbiting spacecraft have detected clay (also called phyllosilicates) in some layers. Scientists are excited about finding hydrated minerals such as sulfates and clays on Mars because they are usually formed in the presence of water. Places that contain clays and/or other hydrated minerals would be good places to look for evidence of life.
Rock can form layers in a variety of ways. Volcanoes, wind, or water can produce layers. Layers can be hardened by the action of groundwater. Martian ground water probably moved hundreds of kilometers, and in the process it dissolved many minerals from the rock it passed through. When ground water surfaces in low areas containing sediments, water evaporates in the thin atmosphere and leaves behind minerals as deposits and/or cementing agents. Consequently, layers of dust could not later easily erode away since they were cemented together. On Earth, mineral-rich waters often evaporate forming large deposits of various types of salts and other minerals. Sometimes water flows through Earth's aquifers, and then evaporates at the surface just as is hypothesized for Mars. One location this occurs on Earth is the Great Artesian Basin of Australia. On Earth the hardness of many sedimentary rocks, like sandstone, is largely due to the cement that was put in place as water passed through.
Schiaparelli Crater.
Schiaparelli is an impact crater on Mars located near Mars's equator. It is in diameter and located at latitude 3° south and longitude 344°. Some places within Schiaparelli show many layers that may have formed by the wind, volcanoes, or deposition under water.
Other Craters.
When a comet or asteroid collides at a high rate of speed interplanetary with the surface of Mars it creates a primary impact crater. The primary impact may also eject significant numbers of rocks which eventually fall back to make secondary craters. The secondary craters may be arranged in clusters. All of the craters in the cluster would appear to be equally eroded; indicating that they would all are of the same age. If these secondary craters formed from a single, large, nearby impact, then they would have formed at roughly the same instant in time. The image below of Denning Crater shows a cluster of secondary craters.
Impact craters generally have a rim with ejecta around them, in contrast volcanic craters usually do not have a rim or ejecta deposits. As craters get larger (greater than 10 km in diameter) they usually have a central peak. The peak is caused by a rebound of the crater floor following the impact. If one measures the diameter of a crater, the original depth can be estimated with various ratios. Because of this relationship, researchers have found that many Martian craters contain a great deal of material; much of it is believed to be ice deposited when the climate was different. Sometimes craters expose layers that were buried. Rocks from deep underground are tossed onto the surface. Hence, craters can show us what lies deep under the surface.
White rock in Pollack crater.
Within the region is Pollack crater, which has light-toned rock deposits. Mars has an old surface compared to Earth. While much of Earth's land surface is just a few hundred million years old, large areas of Mars are billions of years old. Some surface areas have been formed, eroded away, then covered over with new layers of rocks. The Mariner 9 spacecraft in the 1970s photographed a feature that was called "White Rock.". Newer images revealed that the rock is not really white, but that the area close by is so dark that the white rock looks really white. It was thought that this feature could have been a salt deposit, but information from the instruments on Mars Global Surveyor demonstrated rather that it was probably volcanic ash or dust. Today, it is believed that White Rock represents an old rock layer that once filled the whole crater that it's in, but today it has since been mostly eroded away. The picture below shows white rock with a spot of the same rock some distance from the main deposit, so it is thought that the white material once covered a far larger area.
Pollack crater's white rocks:
Channels in Sinus Sabaeus quadrangle.
There is enormous evidence that water once flowed in river valleys on Mars. Images of curved channels have been seen in images from Mars spacecraft dating back to the early seventies with the Mariner 9 orbiter. Indeed, a study published in June 2017, calculated that the volume of water needed to carve all the channels on Mars was even larger than the proposed ocean that the planet may have had. Water was probably recycled many times from the ocean to rainfall around Mars.


Kristine Spekkens

Kristine Spekkens (born September 28, 1977) is a Canadian astronomer, and is the Canadian science director for the Square Kilometre Array. She is a professor at the Royal Military College of Canada and Queen's University.
Early life and education.
Spekkens was born in Hamilton, Ontario, and grew up in Burlington, Ontario. She represented Canada in netball at the 1998 Commonwealth Games and at the 1999 World Championships.
Spekkens received her B.Sc. from Queen's University in 2000 and her PhD from Cornell University in 2005.
Career.
After finishing her PhD work, Spekkens received a prize Jansky Postdoctoral Fellowship at the National Radio Astronomy Observatory and Rutgers University. In 2008 she became an assistant professor at the Physics department of the Royal Military College of Canada (RMC). In 2013 she was cross-appointed as an assistant professor in the Department of Physics, Engineering Physics and Astronomy at Queen's University. In 2015 she was promoted to associate professor at RMC.
Spekkens' research focuses on the structure and evolution of nearby galaxies.
She is currently on the board of directors of the Square Kilometre Array, representing Canada.


Daniel Barbier

Daniel Barbier (10 December 1907 – 1 April 1965) was a French astronomer born in Lyon.
Between 1930 and 1965 he published nearly 100 scientific papers on astronomy. Among his works were studies of stellar atmospheres and lunar occultations and eclipses. He performed studies of the upper atmosphere, Aurora Borealis, the zodiacal light and the night airglow.
His name remains associated to the famous Eddington-Barbier relationships of analytical radiative transfer (see Barbier 1943 and Paletou 2018).


Shirley Ho

Shirley Ho is an American cosmologist and astrophysicist, currently at the Center for Computational Astrophysics (Flatiron Institute) in NYC and at the New York University and the Carnegie Mellon University. Ho also has visiting appointment at Princeton University.
A cited expert in cosmology, machine learning applications in astrophysics and data science, her interest are using deep learning accelerated simulations to understand the Universe, and other astrophysical phenomena.
She significantly contributed to the development of several fields, including: cosmic microwave background, cosmological models, dark energy, dark matter, spatial distribution of galaxies and quasars, Baryon Acoustic Oscillations, cosmological simulations and applications of machine learning to cosmology. More recently, Shirley Ho has led her team on a series of papers on accelerating simulations using modern deep learning techniques.
Education.
After having completed a Bachelor of Arts (with Highest Honors) in Physics and Computer Science at the University of California at Berkeley, Shirley Ho moved to Princeton University to pursue her Ph.D. at the Department of Astrophysical Sciences of Princeton Universitybetween 2004 and 2008. Astrophysicist and cosmologist David Spergel was her advisor. In 2008 she obtained her Doctorate in Astrophysical Sciences, with a Thesis entitled "Baryons, Universe and Everything Else in Between".
Career.
After her Ph.D., she moved to the Lawrence Berkeley National Laboratory between 2008 and 2012, in a postdoctoral position as a Chamberlain and Seaborg Fellow. Later on, she moved to the Carnegie Mellon University, first as an assistant professor and then as an associate (with indefinite tenure) professor in Physics. Shirley Ho became the Cooper-Siegel Chair Professor in 2015 at Carnegie Mellon University.
In 2016, Shirley Ho joined Lawrence Berkeley National Laboratory as a Senior Scientist while being on leave from Carnegie Mellon University. In 2018, Shirley Ho joined the Simons Foundation as leader of the Cosmology X Data Science group at Center for Computational Astrophysics (CCA) at the Flatiron Institute in NYC. She also currently holds faculty positions at New York University and Carnegie Mellon University.
Prizes.
Shirley Ho won several prizes for her significant contributions to the fields of cosmology and astrophysics. The list includes:


Hyder flare

A Hyder flare is slow, large-scale brightening that occurs in the solar chromosphere. It resembles a large but feeble solar flare and is identifiable as the signature of the sudden disappearance of a solar prominence (a "disparition brusque"). These events occur in the quiet Sun, away from the active regions or sunspot groups, and typically in the polar crown filament zone. Hyder flares have a two-ribbon morphology and can be faintly observed in chromospheric emission lines such as Hα or as enhanced absorption in He I 1083 nm line.
Hyder flares are caused by the unstable eruption of a magnetic filament channel; the filament rises and may escape from the Sun as a part of a coronal mass ejection, and the visible flare marks the magnetic connectivity of the coronal disturbance.
Unlike solar flares, Hyder flares take a much longer time to reach peak intensity, as much as 30 to 80 minutes and then can continue for several hours. They have not caused any interference with Earthly communications like solar flares, and are rather weak.
The discovery of Hyder flares has been mainly associated with Charles Hyder who developed the mechanism describing them in 1967. Some disagree with Hyder's findings and his mechanism, on what actually produces the flare.
Although rare, a notable occurrence that took place November 1, 2014, confirmed that they display special characteristics distinguishing them from solar flares.
Cause.
The explanation for these solar flares comes from Hyder's two-fold observations. One, flares tended to have a parallel ribbon shape to them with one on either side of the filament channel. Two, these flares were not caused by or associated with geomagnetic storms.
Quiescent filaments have been believed to belong to a magnetic trough, which can disappear due to the field's reconfiguration. When this happens, the filamentary material is said to be thrown into the corona, creating a typical solar flare. Hyder explains that the process for Hyder flares differs, in that sometimes the filamentary material instead cascades down the outer sides of the elevated magnetic trough, or ridge, to interact with the lower chromospheric material that is producing the flare. If this falling process is not symmetrical on either side, then there will be a double parallel ribbon shape form, whereas a symmetrical fall will produce only a single parallel ribbon. A sporadic or insufficient fall of filamentary material will cause bright knots of solar flares to be produced.
History.
Hyder flares were first noted by Max Waldmeier in 1938, who wrote a paper describing the phenomenon of suddenly disappearing filaments (disparition brusque), and mentioned that these can be associated with flare-like brightenings, but it was left to Charles Hyder to postulate the first comprehensive mechanism for such flares.
Following on work from his doctoral thesis with the University of Colorado in Boulder (1964), Hyder published two papers in the second volume of the journal Solar Physics (1967) in which the mechanism by which Hyder flares might occur was discussed in detail. Hyder was then on the staff of the (US) Air Force Cambridge Research Laboratories at the Sacramento Peak Observatory in New Mexico.
It was these papers in Solar Physics by which Hyder's name became associated with the flares in question, even though he was by no means the first to observe them.
Occurrences.
As Hyder flares are notably rare, few occurrences have been recorded since their discovery, the first being on August 31, 2012, the second being on June 4, 2014. This solar flare occurred in the Southeastern Galactic quadrant. This flare spanned more than . It was recorded to have happened around 14:30 Coordinated Universal Time (UTC). After the flare took place, solar activity was low for 24 hours.
Another occurrence took place later that year on November 1, 2014. This flare was defined as a C-Class flare and happened between 0400 and 0600 UTC. Scientists noted that some material was sent back into the sun, which then caused several flashes of x-rays wherever they hit the surface of the sun. The remaining material flew out into space that formed a large core of Coronal Mass Ejection (CME) and gravitated away from the sun. It was not projected to hit Earth. Unlike the flare of June 2014, solar activity was high after the event even when no sunspots were detected.
Hazards/controversy.
Despite their size, Hyder flares generally do not have a high intensity. It is commonly accepted that there is no immediate threat to Earth from a solar flare 93 million miles away. These flares can potentially affect space weather, however, which could disrupt electronics. Because of this, many precautions must be taken into account to prevent damages to airplane navigation and/or government technologies.
Recently, the Hyder mechanism has come under question, most notably by Harold Zirin. Zirin questioned the filament falling down the side of the magnetic ridge, stating that magnetic reconfigurations will always create ejection. Comparisons to Hyder's 1968 publications were discussed in Harold Zirin and D. Russo Lackner's Volume 6, Issue 1 of Solar Physics pages 86–103: The Solar Flares of August 28 and 30, 1996.


Springfield Science Museum


Elena V. Pitjeva

Elena Vladimirovna Pitjeva (Елена Владимировна Питьева) is a Russian astronomer working at the Institute of Applied Astronomy, Russian Academy of Sciences, St. Petersburg. She has published over 100 articles, as listed in Google Scholar and the Astrophysics Data System in the field of solar system dynamics and celestial mechanics.
She began employment activity as an engineer-observer at the Astrophysical observation station of the Astronomical Observatory of Leningrad State University in Byurakan (Armenia). Then Pitjeva worked at the Institute of Theoretical Astronomy of the USSA Academy of Science and the Institute Applied Astronomy RAS since the date of its foundation in 1988 as researcher and senior researcher. At present she is head of the Laboratory of Ephemeris Astronomy of this institute.
Major research interests of Dr. Pitjeva include the construction of numerical ephemerides of the planets, the determination of the planets' and asteroids' masses, the parameters of planet rotation and planetary topography, the solar corona and oblateness and general relativity testing. She is one of creators of the numerical Ephemerides of Planets and the Moon (EPM) of IAA RAS that originated in the seventies of the past century and have been developed since that time. The version of the EPM2004 ephemeris has been adopted as the ephemeris basis of Russian Astronomical Yearbook since 2006. The updated EPM2008 ephemerides are available to outside users via ftp.
The works of Pitjeva have recently been used by several scientists to test several models of modified gravity in the Solar System.
Dr. Pitjeva has also contributed to a better understanding an influence of asteroids and Trans-Neptunian Objects on the planets' motion. Recently Dr. Pitjeva collaborated with Dr. Standish and proposed to the IAU Working Group on Numerical Standards for Fundamental Astronomy (NSFA) the values of the masses of the three largest asteroids, the Moon-Earth mass ratio and the astronomical unit in meters, mainly obtained while fitting the constructed DE (JPL) and EPM (IAA RAS) planet ephemerides. These values have been adopted by the 27 General Assembly of International Astronomical Union as Current Best Estimates as the IAU (2009) System of Astronomical Constants.
Pitjeva is a member of the International Astronomical Union: OC of Commission 4 “Ephemerides”,
Commission 52 “Relativity in Fundamental Astronomy”
IAU WG NSFA.”,
Education and Academic degrees.
Pitjeva graduated from the Faculty of Mathematical and Mechanical at Leningrad State University in 1972 in the specialty of astronomy. Pitjeva gained her Ph.D. in the field of "Astrometry and Celestial Mechanics" in 1994, with the thesis “Improvement of ephemerides of the major planets and determination of some astronomical constants by radar observations", and earned the Doctor of Science degree, the highest (after Ph.D.) scientific degree in Russia, with the thesis "Construction of high-precision ephemerides of the major planets and determination of some astronomical constants", in 2005. Dr. Pitjeva is a pupil of Professor G.A. Krasinski and Professor V.A. Brumberg.
Bibliometric information.
According to the NASA ADS database, the h-index of E.V. Pitjeva is 9, with a total number of citations (self-citations excluded) equal to 316.


Uwingu

Uwingu is a private, for-profit company founded by Alan Stern, a former NASA associate administrator. The company lets the public nominate names for exoplanets and craters of Mars on Uwingu's new Mars map, in return for a fee. Uwingu’s mission is to create new ways for people to personally connect with space exploration and astronomy. The profits of the company are dedicated to funding space researchers, educators, and projects.
Since launching the Mars Crater Map feature in February, 2014, over 19,000 craters names have been named on the Uwingu Mars Map. Almost $100,000 has been generated for the Uwingu fund space research, education, and exploration. Uwingu Grant Fund recipients include Astronomers Without Borders, The Galileo Teacher Training Program, SEDS, Allen Telescope Array, International Dark-Sky Association and Explore Mars.
Uwingu has also awarded over $15,000 in Student Research Travel Grants in 2014. The selected students, both men and women, completed their PhDs in 2014. Their research topics range from Martian and lunar science, to astrobiology, to the study of planets around other stars. The awarded Uwingu travel grants will enable these students to report their results and further their professional advancement in the scientific community.
On 3 March 2014, the company announced a partnership with Mars One, which is planning on using Uwingu's map of Mars in its mission. It was announced on 12 June 2014 that a second space mission, Time Capsule to Mars, is carrying Uwingu's Mars Map to Mars as well.
Advisors.
Uwingu’s board of advisors consists of talented and influential thinkers from the astronomy, planetary science, IT, and business worlds:
Criticism.
The International Astronomical Union has strongly condemned Uwingu, calling it a "scam" for charging money to buy planet names, stressing that the IAU is the only official authority on naming astronomical objects. Uwingu denies these accusations, saying it represents the "people's choice" rather than any official position.


Bourges astronomical clock

The Bourges astronomical clock is an astronomical clock in Bourges Cathedral in Bourges, France.
The clock was designed by and installed in November 1424. It was given by Charles VII (the "Little King of Bourges" – at this point of the Hundred Years' War, Charles VII ruled only a small area around his court at Bourges, with Henry VI of England recognised as King of England and France) to the townspeople of Bourges, on the occasion of the baptism of his son the Dauphin (the future Louis XI). It is the oldest extant astronomical clock in France.
History.
The clock was installed on the occasion of the baptism of the future Louis XI. It was designed by , mathematician and canon, and constructed by André Cassart, locksmith. The case was painted by Jean Grangier (or Jean of Orléans).
The clock was initially placed on the cathedral's rood screen, which was removed in 1757. It was then placed in a side aisle of the cathedral until the 19th century, then put into storage in the crypt.
Description.
Housed in a belfry-shaped case, the clock is the oldest surviving astronomical clock in France, and one of the oldest clocks after the 14th century clock in Beauvais Cathedral. Its upper dial, installed in the 19th century, has two hands and shows the 12-hour time; the more complex lower dial shows the following:
All of these are read from the single arrow pointer: the hour on the outer ring numbered I to XII twice in black on white; the day of the lunar month on the ring numbered I to XXIX in gold on blue (with the lunar phase appearing in a circular aperture in this ring), and the annual position of the sun on the inner ring showing the signs of the zodiac.
The bell on top of the case roof chimes the hour. The three bells to the side of the case at the base of the roof chime the quarter hours: A at the first quarter, AD at the half hour, AGD at the third quarter, and AGAD (the first four notes of the "Salve Regina") on the hour.
The clock is very accurate, to within one second per 150 years.
Restorations.
The clock has undergone several rounds of restoration, in 1782, 1822, 1841, and in 1872, when the old mechanism was replaced by a simpler one in the upper part of the clock, which shows only the hours.
The zodiac calendar was restored in 1973. In 1986, a fire caused serious damage to the clock, leading to a thorough restoration project which aimed to return the clock to its original state.
In 1994, the clock was reinstated in the cathedral, after a complete restoration, with the mechanism of 1424 replaced by an exact copy. The original mechanism was conserved, and is on display in the cathedral. In the 1990s, a facsimile of the clock's main dial was made, and placed in the town's tourist office.


Mark Armstrong (astronomer)

Mark Armstrong (born 1958) is a British amateur astronomer, a member of the British Astronomical Association. With his wife Claire Armstrong, he works from Rolvenden (obs. code 960), Kent, England, and, as of 2006, has 58 supernova discoveries (and 12 co-discoveries) to his credit in addition to two asteroids.


Stellar population

During 1944, Walter Baade categorized groups of stars within the Milky Way into stellar populations.
In the abstract of the article by Baade, he recognizes that Jan Oort originally conceived this type of classification in 1926:
Baade noticed that bluer stars were strongly associated with the spiral arms and yellow stars dominated near the central galactic bulge and within globular star clusters. Two main divisions were defined as
with another newer division called
they are often simply abbreviated as Pop. I, Pop. II, and Pop. III .
Between the population types, significant differences were found with their individual observed stellar spectra. These were later shown to be very important, and were possibly related to star formation, observed kinematics, stellar age, and even galaxy evolution in both spiral or elliptical galaxies. These three simple population classes usefully divided stars by their chemical composition or metallicity.
By definition, each population group shows the trend where decreasing metal content indicates increasing age of stars. Hence, the first stars in the universe (very low metal content) were deemed Population III, old stars (low metallicity) as Population II, and recent stars (high metallicity) as Population I. The Sun is considered Population I, a recent star with a relatively high 1.4 percent metallicity. Note that astrophysics nomenclature considers any element heavier than helium to be a "metal", including chemical non-metals such as oxygen.
Stellar development.
Observation of stellar spectra has revealed that stars older than the Sun have fewer heavy elements compared to the Sun. This immediately suggests that metallicity has evolved through the generations of stars by the process of stellar nucleosynthesis.
Formation of the first stars.
Under current cosmological models, all matter created in the Big Bang was mostly hydrogen (75%) and helium (25%), with only a very tiny fraction consisting of other light elements such as lithium and beryllium. When the universe had cooled sufficiently, the first stars were born as Population III stars without any contaminating heavier metals. This is postulated to have affected their structure so that their stellar masses became hundreds of times more than that of the Sun. In turn, these massive stars also evolved very quickly, and their nucleosynthetic processes created the first 26 elements (up to iron in the periodic table).
Many theoretical stellar models show that most high-mass Population III stars rapidly exhausted their fuel and likely exploded in extremely energetic pair-instability supernovae. Those explosions would have thoroughly dispersed their material, ejecting metals into the interstellar medium (ISM), to be incorporated into the later generations of stars. Their destruction suggests that no galactic high-mass Population III stars should be observable. However, some Population III stars might be seen in high-redshift galaxies whose light originated during the earlier history of the universe. None have been discovered, however, scientists have found evidence of an extremely small ultra metal-poor star, slightly smaller than the Sun, found in a binary system of the spiral arms in the Milky Way. The discovery opens up the possibility of observing even older stars.
Stars too massive to produce pair-instability supernovae would have likely collapsed into black holes through a process known as photodisintegration. Here some matter may have escaped during this process in the form of relativistic jets, and this could have distributed the first metals into the universe.
Formation of the observable stars.
The oldest observed stars, known as Population II, have very low metallicities; as subsequent generations of stars were born they became more metal-enriched, as the gaseous clouds from which they formed received the metal-rich dust manufactured by previous generations. As those stars died, they returned metal-enriched material to the interstellar medium via planetary nebulae and supernovae, enriching further the nebulae out of which the newer stars formed. These youngest stars, including the Sun, therefore have the highest metal content, and are known as Population I stars.
Chemical classification by Baade.
Population I stars.
Population I, or metal-rich, stars are young stars with the highest metallicity out of all three populations, and are more commonly found in the spiral arms of the Milky Way galaxy. The Earth's Sun is an example of a metal-rich star and is considered as an intermediate Population I star, while the solar-like Mu Arae is much richer in metals.
Population I stars usually have regular elliptical orbits of the galactic centre, with a low relative velocity. It was earlier hypothesized that the high metallicity of Population I stars makes them more likely to possess planetary systems than the other two populations, because planets, particularly terrestrial planets, are thought to be formed by the accretion of metals. However, observations of the Kepler Space Telescope data have found smaller planets around stars with a range of metallicities, while only larger, potential gas giant planets are concentrated around stars with relatively higher metallicity — a finding that has implications for theories of gas giant formation. Between the intermediate Population I and the Population II stars comes the intermediary disc population.
Population II stars.
Population II, or metal-poor, stars are those with relatively little of the elements heavier than helium. These objects were formed during an earlier time of the universe. Intermediate Population II stars are common in the bulge near the centre of the Milky Way, whereas Population II stars found in the galactic halo are older and thus more metal-poor. Globular clusters also contain high numbers of Population II stars.
A characteristic of Population II stars is that despite their lower overall metallicity, they often have a higher ratio of “alpha elements” (O, Si, Ne, etc.) relative to Fe as compared to Population I stars; current theory suggests this is the result of Type II supernovas being more important contributors to the interstellar medium at the time of their formation, whereas Type Ia supernova metal-enrichment came at a later stage in the universe's development.
Scientists have targeted these oldest stars in several different surveys, including the HK objective-prism survey of Timothy C. Beers "et al". and the Hamburg-ESO survey of Norbert Christlieb "et al"., originally started for faint quasars. Thus far, they have uncovered and studied in detail about ten ultra metal poor (UMP) stars (such as Sneden's Star, Cayrel's Star, BD +17° 3248) and three of the oldest stars known to date: HE0107-5240, HE1327-2326 and HE 1523-0901. Caffau's star was identified as the most metal-poor star yet when it was found in 2012 using Sloan Digital Sky Survey data. However, in February 2014 the discovery of an even lower metallicity star was announced, SMSS J031300.36-670839.3 located with the aid of SkyMapper astronomical survey data. Less extreme in their metal deficiency, but nearer and brighter and hence longer known, are HD 122563 (a red giant) and HD 140283 (a subgiant).
Population III stars.
Population III stars are a hypothetical population of extremely massive, luminous and hot stars with virtually no metals, except possibly for intermixing ejecta from other nearby Population III supernovae. Such stars are likely to have existed in the very early universe (i.e., at high redshift), and may have started the production of chemical elements heavier than hydrogen that are needed for the later formation of planets and life as we know it.
The existence of Population III stars is inferred from physical cosmology, but they have not yet been observed directly. Indirect evidence for their existence has been found in a gravitationally lensed galaxy in a very distant part of the universe. Their existence may account for the fact that heavy elements – which could not have been created in the Big Bang – are observed in quasar emission spectra. They are also thought to be components of faint blue galaxies. These stars likely triggered the universe's period of reionization, a major phase transition of gases leading to the lack of opacity observed today. Observations of the galaxy UDFy-38135539 suggest it may have played a role in this reionization process. The European Southern Observatory discovered a bright pocket of early population stars in the very bright galaxy Cosmos Redshift 7 from the reionization period around 800 million years after the Big Bang. The rest of the galaxy has some later redder Population II stars. Some theories hold that there were two generations of Population III stars.
Current theory is divided on whether the first stars were very massive or not. One possibility is that these stars were much larger than current stars: several hundred solar masses, and possibly up to 1,000 solar masses. Such stars would be very short lived and last only 2-5 million years. Such large stars may have been possible due to the lack of heavy elements and a much warmer interstellar medium from the Big Bang. Conversely, theories proposed in 2009 and 2011 suggest the first star groups might have consisted of a massive star surrounded by several smaller stars. The smaller stars, if they remained in the birth cluster, would accumulate more gas and could not survive to the present day, but a 2017 study concluded that if a star of 0.8 solar masses () or less was ejected from its birth cluster before it accumulated more mass, it could survive to the present day, possibly even in our Milky Way galaxy.
Analysis of data of extremely low-metallicity Population II stars such as HE0107-5240, which are thought to contain the metals produced by Population III stars, suggest that these metal-free stars had masses of 20 to 130 solar masses. On the other hand, analysis of globular clusters associated with elliptical galaxies suggests pair-instability supernovae, which are typically associated with very massive stars, were responsible for their metallic composition. This also explains why there have been no low-mass stars with zero metallicity observed, although models have been constructed for smaller Population III stars. Clusters containing zero-metallicity red dwarfs or brown dwarfs (possibly created by pair-instability supernovae) have been proposed as dark matter candidates, but searches for these types of MACHOs through gravitational microlensing have produced negative results.
Detection of Population III stars is a goal of NASA's James Webb Space Telescope. New spectroscopic surveys, such as SEGUE or SDSS-II, may also locate Population III stars. Stars observed in the Cosmos Redshift 7 galaxy at may be Population III stars.


Lewis Dingle

Lewis Allen Dingle (born 16 September 1988) is an English former first-class cricketer and physician.
Dingle was born at Blackpool in September 1988. He was educated at Rossall School, before going up to Christ Church, Oxford. While studying at Oxford, he played first-class cricket on three occasions for Oxford University against Cambridge University in The University Matches of 2007, 2008 and 2010. After graduating from Oxford, Dingle trained to become a plastic surgeon.
While at Rossall School he was affectionately known as "Ron" for reasons that are now lost to history.


Johann Abraham Ihle

Johann Abraham Ihle (14 June 1627 – c.1699) was a German amateur astronomer who discovered the first known globular cluster, M22, on 26 August 1665 while observing Saturn in Sagittarius.


Achill-henge

Achill-henge is a concrete structure on Achill Island off the northwest coast of County Mayo, Ireland. The term henge is used colloquially only and does not indicate genuine structural or cultural similarity to prehistoric monuments found in Ireland.
Structure.
Achill-henge is over high and in circumference. It consists of a circle of 30 concrete columns topped by a ring of stone. No care was taken to replicate or reference genuine stone circles in the region or the country. The term Achill-henge can be interpreted as a reference to the cultural inaccuracy of the structure in local context as typically henges are simply referred to as stone circles in Ireland.
History.
Achill-henge was constructed over a weekend in November 2011 by Joe McNamara, a property developer and convicted criminal. A team of workers hauled the large concrete slabs up the hill and sank them in the bog.
Mayo County Council requested a court order to force McNamara to remove the edifice as it had been built without planning permission. McNamara claimed that the structure was exempt from planning rules as an "ornamental garden".
Theresa McDonald, Director of the Achill Archaeological Field School, also raised objections on the grounds that the structure may be less than from a Bronze-Age archaeological site.
The High Court required McNamara to cease further work on the site, and, as he was found to be in breach of this, he was jailed for three days for contempt of court. The Court referred the planning decision to An Bord Pleanala, which in July 2012 upheld the Council's decision.
Some local people have expressed admiration for the work as a feat of engineering, and a newspaper poll found a majority of locals in support of keeping the structure.
On 8 January 2012, it was featured as part of the Prime Time programme on RTÉ 1 in Ireland.
Achill Henge is still standing .
Joe McNamara.
Joe McNamara is noted in Ireland for a series of protests against Anglo-Irish Bank and the government's handling of the Irish financial crisis. In particular, he drove a concrete mixer truck into the gates of the Irish parliament building Leinster House, causing minor damage to the paintwork of the gateway. He was found not guilty of criminal damage or dangerous driving.
McNamara described Achill-henge as "a place of reflection".
See also.
In modern times a number of henge type monuments have been built, examples include:


Julius Reichelt

Julius Reichelt (1637–1717) was a German mathematician and astronomer who may have set up the first observatory in the city of Strasbourg.
Biography.
Julius Reichelt was born on 5 January 1637 in the city of Strasbourg. In 1644 at the age of 16 he was enrolled as a student and graduated as Doctor of Philosophy in 1660. He was nominated as Professor of Mathematics in 1667. Reichelt traveled through Northern Europe some time after 1666 and met other notable 17th-century scientists and thinkers such as Jan Hudde, Johannes Hevelius, Andreas Concius, Henrik Ruse, Johannes Meyer, Rasmus Bartholin, and Adam Olearius. After his return from his trip Reichelt may have proposed the building of the "turret lantern" as an astronomical observatory at the top of Strasbourg's Hospital Gate based on the Rundetårn (Round Tower) he saw in Copenhagen. Reichelt died in Strasbourg on 19 February 1717.


Caleuche Chasma

Caleuche Chasma is a Y-shaped chasma on Pluto's moon, Charon. Caleuche Chasma is long. The feature was discovered using stereoscopic processing of "New Horizons" images. At approximately deep, it is the deepest known feature on the natural satellite, and one of the deepest known canyons in the Solar System.
Naming.
Caleuche Chasma got its official name from the IAU along with eleven other surface features of Charon on 11 April 2018 in response to a proposal by NASA's New Horizons team. It is named for the mythical Chilean ghost ship Caleuche. The designation was a part of the Our Pluto initiative by New Horizons, which invited the general public to suggest and vote for names for surface features in the Pluto system. Caleuche was included in the voting on 21 March 2015. It did not make to the initial proposal, sent to the IAU by the New Horizons team on 7 July 2015 but was included later.
In popular culture.
In 2019, composer and Royal Academy of Music professor David Gorton wrote a composition for two cellos titled Caleuche Chasma


SFA Observatory

The SFA Observatory (SFA) is an astronomical observatory located north of Nacogdoches, Texas (USA). The observatory is owned and operated by Stephen F. Austin State University (SFASU), and opened in 1976. It is used for undergraduate instruction and for graduate-level research.


Charles Nordmann

Charles Nordmann (1881–1940) was a French astronomer.


Radio Astronomy Laboratory

The Radio Astronomy Lab (RAL) is an Organized Research Unit (ORU) within the Astronomy Department at the University of California, Berkeley. It was founded by faculty member Harold Weaver in 1958.
Until 2012, RAL maintained a radio astronomy observatory at Hat Creek, near Mt. Lassen. It continues to support on-campus laboratory facilities in Campbell Hall. From 1998 to 2012, the RAL collaborated with the SETI Institute of Mountain View California to design, build and operate the Allen Telescope Array (ATA).
RAL has been central to the creation of several radio observatories, including:


Joseph Bossert

Joseph François Bossert (30 November 1851 – 21 June 1906) was a French astronomer.
Bossert began study at age fifteen at the Paris Observatory. He calculated the orbits of asteroids and comets. He was the main author of three star catalogues:
He was also one of the main contributors to the Astrographic Catalogue project initiated by Mouchez in 1887.
Bossert won the Lalande Prize of the French Academy of Sciences in 1888 and the Valz Prize in 1896.


Catherine Pilachowski

Catherine Pilachowski is an American astronomer, professor and Kirkwood Chair in astronomy at Indiana University Bloomington. She is a fellow at the American Association for the Advancement of Science and former president of the American Astronomical Society.
Early life and education.
Pilachowski was born and raised in California. She has stated that growing up during the Space Race between the United States and the Soviet Union led to her interest in becoming an astronomer.
She received her B.S. in Physics in 1971 from Harvey Mudd College in California and an M.S. and Ph.D. in 1975 from the University of Hawaii.
Career.
Pilachowski is a fellow at the American Association for the Advancement of Science and the American Astronomical Society. She was president of the American Astronomical Society from 2002 to 2004. For over twenty years, she was a staff astronomer at the National Optical Astronomy Observatory's Kitt Peak Observatory in Tuscon, Arizona where she served as Project Scientist for the design and construction of the WIYN Telescope.
Pilachowski became a professor of astronomy at Indiana University and in 2001 was named the Daniel Kirkwood Chair in the Department of Astronomy.
Pilachowski specializes in understanding the spectra of starlight. Her work has included searching for the molecular species hydrogen fluoride.


Joseph Gaultier de la Vallette

Joseph Gaultier de la Vallette (24 November 1564, Rians – 1 December 1647, Aix-en-Provence) was a 17th-century French astronomer. He was a contemporary and friend of Galileo and Peiresc. With Peiresc he observed the moons of Jupiter in November 1610 and earlier that year he had been the second person after Peires to see the Orion Nebula.


Jacobi ellipsoid

A Jacobi ellipsoid is a triaxial (i.e. scalene) ellipsoid under hydrostatic equilibrium which arises when a self-gravitating fluid body of uniform density rotates with a constant angular velocity. It is named after the German mathematician Carl Gustav Jacob Jacobi.
History.
Before Jacobi, the Maclaurin spheroid, which was formulated in 1742, was considered to be the only type of ellipsoid which can be in equilibrium. Lagrange in 1811 considered the possibility of a tri-axial ellipsoid being in equilibrium, but concluded that the two equatorial axes of the ellipsoid must be equal, leading back to the solution of Maclaurin spheroid. But Jacobi realized that Lagrange's demonstration is a sufficiency condition, but not necessary. He remarked:
"One would make a grave mistake if one supposed that the spheroids of revolution are the only admissible figures of equilibrium even under the restrictive assumption of second degree surfaces" (...) "In fact a simple consideration shows that ellipsoids with three unequal axes can very well be figures of equilibrium; and that one can assume an ellipse of arbitrary shape for the equatorial section and determine the third axis (which is also the least of the three axes) and the angular velocity of rotation such that the ellipsoid is a figure of equilibrium."
Jacobi formula.
For an ellipsoid with equatorial semi-principal axes formula_1 and polar semi-principal axis formula_2, the angular velocity formula_3 about formula_2 is given by
where formula_6 is the density and formula_7 is the gravitational constant, subject to the condition
For fixed values of formula_9 and formula_10, the above condition has solution for formula_2 such that
The integrals can be expressed in terms of incomplete elliptic integrals. In terms of the Carlson symmetric form elliptic integral formula_13, the formula for the angular velocity becomes
and the condition on the relative size of the semi-principal axes formula_15 is
The angular momentum formula_17 of the Jacobi ellipsoid is given by
where formula_19 is the mass of the ellipsoid and formula_20 is the "mean radius", the radius of a sphere of the same volume as the ellipsoid.
Relationship with Dedekind ellipsoid.
The Jacobi and Dedekind ellipsoids are both equilibrium figures for a body of rotating homogeneous self-gravitating fluid. However, while the Jacobi ellipsoid spins bodily, with no internal flow of the fluid in the rotating frame, the Dedekind ellipsoid maintains a fixed orientation, with the constituent fluid circulating within it. This is a direct consequence of Dedekind's theorem.
For any given Jacobi ellipsoid, there exists a Dedekind ellipsoid with the same semi-principal axes formula_15 and same mass and with a flow velocity field of
where formula_23 are Cartesian coordinates on axes formula_24 aligned respectively with the formula_15 axes of the ellipsoid. Here formula_26 is the vorticity, which is uniform throughout the spheroid (formula_27). The angular velocity formula_3 of the Jacobi ellipsoid and vorticity of the corresponding Dedekind ellipsoid are related by
That is, each particle of the fluid of the Dedekind ellipsoid describes a similar elliptical circuit in the same period in which the Jacobi spheroid performs one rotation.
In the special case of formula_30, the Jacobi and Dedekind ellipsoids (and the Maclaurin spheroid) become one and the same; bodily rotation and circular flow amount to the same thing. In this case formula_31, as is always true for a rigidly rotating body.
In the general case, the Jacobi and Dedekind ellipsoids have the same energy, but the angular momentum of the Jacobi spheroid is the greater by a factor of


Hilda asteroid

The Hilda asteroids (adj. "Hildian") are a dynamical group of more than 4000 asteroids located beyond the asteroid belt in a 3:2 orbital resonance with Jupiter. The namesake is the asteroid 153 Hilda. Hildas move in their elliptical orbits so that their aphelia put them opposite Jupiter (at ), or 60° ahead of or behind Jupiter at the and Lagrangian points. Over three successive orbits each Hilda asteroid approaches all of these three points in sequence. A Hilda's orbit has a semi-major axis between 3.7 and 4.2 AU (the average over a long time span is 3.97), an eccentricity less than 0.3, and an inclination less than 20°. Two collisional families exist within the Hilda group: the Hilda family and the Schubart family. The namesake for the latter family is 1911 Schubart.
Hildas' surface colors often correspond to the low-albedo D-type and P-type; however, a small portion are C-type. D-type and P-type asteroids have surface colors, and thus also surface mineralogies, similar to those of cometary nuclei. This implies that they share a common origin.
Dynamics.
The asteroids of the Hilda group (Hildas) are in 3:2 mean-motion resonance with Jupiter. That is, their orbital periods are 2/3 that of Jupiter. They move along the orbits with a semimajor axis near 4.0 AU and moderate values of eccentricity (up to 0.3) and inclination (up to 20°). Unlike the Jupiter trojans they may have any difference in longitude with Jupiter, nevertheless avoiding dangerous approaches to the planet.
The Hildas taken together constitute a dynamic triangular figure with slightly convex sides and trimmed apices in the triangular libration points of Jupiter—the "Hildas Triangle". The "asteroidal stream" within the sides of the triangle is about 1 AU wide, and in the apexes this value is 20-40% greater. Figure 1 shows the positions of the Hildas (black) against a background of all known asteroids (gray) up to Jupiter's orbit at January 1, 2005.
Each of the Hilda objects moves along its own elliptic orbit. However, at any moment the Hildas together constitute this triangular configuration, and all the orbits together form a predictable ring. Figure 2 illustrates this with the Hildas positions (black) against a background of their orbits (gray). For the majority of these asteroids, their position in orbit may be arbitrary, except for the external parts of the apexes (the objects near aphelion) and the middles of the sides (the objects near perihelion). The Hildas Triangle has proven to be dynamically stable over a long time span.
The typical Hilda object has a retrograde perihelion motion. On average, the velocity of perihelion motion is greater when the orbital eccentricity is lesser, while the nodes move more slowly. All typical objects in aphelion would seemingly approach closely to Jupiter, which should be destabilising for them—but the variation of the orbital elements over time prevents this, and conjunctions with Jupiter occur only near the perihelion of Hilda asteroids. Moreover, the apsidal line oscillates near the line of conjunction with different amplitude and a period of 2.5 to 3.0 centuries.
In addition to the fact that the Hildas triangle revolves in sync with Jupiter, the density of asteroids in the stream exhibits quasi-periodical waves. At any time, the density of objects in the triangle's apexes is more than twice the density within the sides. The Hildas "rest" at their aphelia in the apexes for an average of 5.0-5.5 years, whereas they move along the sides more quickly, averaging 2.5 to 3.0 years. The orbital periods of these asteroids are approximately 7.9 years, or two thirds that of Jupiter.
Although the triangle is nearly equilateral, some asymmetry exists. Due to the eccentricity of Jupiter's orbit, the side - slightly differs from the two other sides. When Jupiter is in aphelion, the mean velocity of the objects moving along this side is somewhat smaller than that of the objects moving along the other two sides. When Jupiter is in perihelion, the reverse is true.
At the apexes of the triangle corresponding to the points and of Jupiter's orbit, the Hildas approach the Trojans. At the mid-sides of the triangle, they are close to the asteroids of the external part of the asteroid belt. The velocity dispersion of Hildas is more evident than that of Trojans in the regions where they intersect. The dispersion of Trojans in inclination is twice that of the Hildas. Due to this, as much as one quarter of the Trojans cannot intersect with the Hildas, and at all times many Trojans are located outside Jupiter's orbit. Therefore, the regions of intersection are limited. This is illustrated by the adjacent figure that shows the Hildas (black) and the Trojans (gray) along the ecliptic plane. One can see the spherical form of the Trojan swarms.
When moving along each side of the triangle, the Hildas travel more slowly than the Trojans, but encounter a denser neighborhood of outer-asteroid-belt asteroids. Here, the velocity dispersion is much smaller.
Research.
The observed peculiarities in the Hildas' motion are based on data for a few hundred objects known to date and generate still more questions. Further observations are needed to expand on the list of Hildas. Such observations are most favorable when Earth is near conjunction with the mid-sides of the Hildas Triangle. These moments occur each 4 and 1/3 months. In these circumstances the brilliance of objects of similar size could run up to 2.5 magnitudes as compared to the apexes.
The Hildas traverse regions of the Solar system from approximately 2 AU up to Jupiter's orbit. This entails a variety of physical conditions and the neighborhood of various groups of asteroids. On further observation some theories on the Hildas may have to be revised.


Frederick Simpson (historian)

F. A. Simpson (22 November 1883(?) or 1884 - 6 February 1974) was an Anglican priest, historian and a fellow of Trinity College, Cambridge.
Career.
Simpson was educated at Rossall School and Queens' College, Cambridge, graduating B.A. in 1906; and M.A. in 1909. He was ordained deacon in 1909 and priest in 1910, serving his title at St Mary and St Anne, Ambleside. He became a Fellow of Trinity College, Cambridge in 1911, and was a temporary Chaplain to the Forces from 1915 to 1918. While Dean of Chapel at Trinity Simpson controversially queried the divinity of Christ.
He wrote the first two volumes of a life of Louis Napoleon. After this he spent most of the rest of his college life pruning college shrubbery, and was known as "Snipper Simpson".
His change of direction has been attributed to an unfavourable review by Philip Guedalla, but John Polkinghorne ascribes it to an "inner loss of nerve."
Personal life.
Simpson was described as a tall, stooped and craggy-featured figure usually wearing a cloth cap and dangling scarf. He had flown the English Channel in his own Gypsy Moth light aircraft. During the early 1930s he was associated with Guy Burgess when the latter was an undergraduate at Trinity College.


Tamke-Allan Observatory

Tamke-Allan Observatory (TAO) is an astronomical observatory owned and operated by Roane State Community College. Dedicated in 1998, it is located in Harriman, Tennessee.


Carbon-burning process

The carbon-burning process or carbon fusion is a set of nuclear fusion reactions that take place in the cores of massive stars (at least 8 formula_1 at birth) that combines carbon into other elements. It requires high temperatures (> 5×108 K or 50 keV) and densities (> 3×109 kg/m3).
These figures for temperature and density are only a guide. More massive stars burn their nuclear fuel more quickly, since they have to offset greater gravitational forces to stay in (approximate) hydrostatic equilibrium. That generally means higher temperatures, although lower densities, than for less massive stars. To get the right figures for a particular mass, and a particular stage of evolution, it is necessary to use a numerical stellar model computed with computer algorithms. Such models are continually being refined based on nuclear physics experiments (which measure nuclear reaction rates) and astronomical observations (which include direct observation of mass loss, detection of nuclear products from spectrum observations after convection zones develop from the surface to fusion-burning regions – known as dredge-up events – and so bring nuclear products to the surface, and many other observations relevant to models).
Fusion reactions.
The principal reactions are:
Reaction products.
This sequence of reactions can be understood by thinking of the two interacting carbon nuclei as coming together to form an excited state of the 24Mg nucleus, which then decays in one of the five ways listed above. The first two reactions are strongly exothermic, as indicated by the large positive energies released, and are the most frequent results of the interaction. The third reaction is strongly endothermic, as indicated by the large negative energy indicating that energy is absorbed rather than emitted. This makes it much less likely, yet still possible in the high-energy environment of carbon burning. But the production of a few neutrons by this reaction is important, since these neutrons can combine with heavy nuclei, present in tiny amounts in most stars, to form even heavier isotopes in the s-process.
The fourth reaction might be expected to be the most common from its large energy release, but in fact it is extremely improbable because it proceeds via electromagnetic interaction, as it produces a gamma ray photon, rather than utilising the strong force between nucleons as do the first two reactions. Nucleons look a lot bigger to each other than they do to photons of this energy. However, the 24Mg produced in this reaction is the only magnesium left in the core when the carbon-burning process ends, as 23Mg is radioactive.
The last reaction is also very unlikely since it involves three reaction products, as well as being endothermic — think of the reaction proceeding in reverse, it would require the three products all to converge at the same time, which is less likely than two-body interactions.
The protons produced by the second reaction can take part in the proton–proton chain reaction, or the CNO cycle, but they can also be captured by 23Na to form 20Ne plus a 4He nucleus. In fact, a significant fraction of the 23Na produced by the second reaction gets used up this way. In stars between 9 and 11 solar masses, the oxygen (O-16) already produced by helium fusion in the previous stage of stellar evolution manages to survive the carbon-burning process pretty well, despite some of it being used up by capturing He-4 nuclei. So the end result of carbon burning is a mixture mainly of oxygen, neon, sodium and magnesium.
The fact that the mass-energy sum of the two carbon nuclei is similar to that of an excited state of the magnesium nucleus is known as 'resonance'. Without this resonance, carbon burning would only occur at temperatures one hundred times higher.
The experimental and theoretical investigation of such resonances is still a subject of research. A similar resonance increases the probability of the triple-alpha process, which is responsible for the original production of carbon.
Neutrino losses.
Neutrino losses start to become a major factor in the fusion processes in stars at the temperatures and densities of carbon burning. Though the main reactions don't involve neutrinos, the side reactions such as the proton–proton chain reaction do. But the main source of neutrinos at these high temperatures involves a process in quantum theory known as pair production. A high energy gamma ray which has a greater energy than the rest mass of two electrons (mass-energy equivalence) can interact with electromagnetic fields of the atomic nuclei in the star, and become a particle and anti-particle pair of an electron and positron.
Normally, the positron quickly annihilates with another electron, producing two photons, and this process can be safely ignored at lower temperatures. But around 1 in 1019 pair productions end with a weak interaction of the electron and positron, which replaces them with a neutrino and anti-neutrino pair. Since they move at virtually the speed of light and interact very weakly with matter, these neutrino particles usually escape the star without interacting, carrying away their mass-energy. This energy loss is comparable to the energy output from the carbon fusion.
Neutrino losses, by this and similar processes, play an increasingly important part in the evolution of the most massive stars. They force the star to burn its fuel at a higher temperature to offset them. Fusion processes are very sensitive to temperature so the star can produce more energy to retain hydrostatic equilibrium, at the cost of burning through successive nuclear fuels ever more rapidly. Fusion produces less energy per unit mass as the fuel nuclei get heavier, and the core of the star contracts and heats up when switching from one fuel to the next, so both these processes also significantly reduce the lifetime of each successive fusion-burning fuel.
Up to the helium burning stage the neutrino losses are negligible. But from the carbon burning stage onwards, the reduction in stellar lifetime due to energy lost in the form of neutrinos roughly matches the increased energy production due to fuel change and core contraction. In successive fuel changes in the most massive stars, the reduction in lifetime is dominated by the neutrino losses. For example, a star of 25 solar masses burns hydrogen in the core for 107 years, helium for 106 years and carbon for only 103 years.
Stellar evolution.
During helium fusion, stars build up an inert core rich in carbon and oxygen. The inert core eventually reaches sufficient mass to collapse due to gravitation, whilst the helium burning moves gradually outward. This decrease in the inert core volume raises the temperature to the carbon ignition temperature. This will raise the temperature around the core and allow helium to burn in a shell around the core. Outside this is another shell burning hydrogen. The resulting carbon burning provides energy from the core to restore the star's mechanical equilibrium. However, the balance is only short-lived; in a star of 25 solar masses, the process will use up most of the carbon in the core in only 600 years. The duration of this process varies significantly depending on the mass of the star.
Stars of below 8–9 solar masses never reach high enough core temperature to burn carbon, instead ending their lives as carbon-oxygen white dwarfs after shell helium flashes gently expel the outer envelope in a planetary nebula.
In stars with masses between 8 and 12 solar masses, the carbon-oxygen core is under degenerate conditions and carbon ignition takes place in a "carbon flash", that lasts just milliseconds and disrupts the stellar core. In the late stages of this nuclear burning they develop a massive stellar wind, which quickly ejects the outer envelope in a planetary nebula leaving behind an O-Ne-Na-Mg white dwarf core of about 1.1 solar masses. The core never reaches high enough temperature for further fusion burning of heavier elements than carbon.
Stars of more than 12 solar masses start carbon burning in a non-degenerate core, and after carbon exhaustion proceed with the neon-burning process once contraction of the inert (O, Ne, Na, Mg) core raises the temperature sufficiently.


Nyx stream

In astronomy, the Nyx stream is a proposed stellar stream that wraps around the Milky Way galaxy, relatively close to the sun. About 500 stars have been identified in this stream from the Gaia DR2.


Aglaonice

Aglaonice or Aganice of Thessaly (, "Aglaoníkē", compound of αγλαὸς ("aglaòs") "luminous" and νίκη ("nikē") "victory") was a Greek astronomer and thaumaturge of the 2nd or 1st century BC. She is mentioned in the writings of Plutarch and in the scholia to Apollonius of Rhodes as a female astronomer and as the daughter of Hegetor (or Hegemon) of Thessaly. She was regarded as a sorceress for (amongst other extraordinary feats) her (self-proclaimed) ability to 'make the moon disappear from the sky' (καθαιρεῖν τὴν σελήνην : kathaireĩn tìn selénen) which has been taken - first by Plutarch and subsequently by modern astronomers - to mean that she could predict the time and general area where a lunar eclipse would occur.
A Greek proverb makes reference to Aglaonice's alleged boasting: "Yes, as the Moon obeys Aglaonice". A number of female astrologers, apparently regarded as sorcerers, were associated with Aglaonice. They were known as the "witches of Thessaly" and were active from the 3rd to 1st centuries BCE.
In Plato's "Gorgias", Socrates speaks of "the Thessalian enchantresses, who, as they say, bring down the moon from heaven at the risk of their own perdition."
Plutarch wrote that she was "thoroughly acquainted with the periods of the full moon when it is subject to eclipse, and, knowing beforehand the time when the moon was due to be overtaken by the earth's shadow, imposed upon the women, and made them all believe that she was drawing down the moon."
In the majority of lunar eclipses with which we are now familiar the moon does not seem completely to disappear - merely changing colour and assuming a tawny or coppery shade - yet in the descriptions of Aglaonice's eclipses there is no reference to any failures in which the moon was 'partially consumed' - rather the moon was 'completely devoured'. As Bicknell points out, had Aglaonice made her extravagant claim on occasions when the moon still remained partly visible, she would have excited in her (admittedly credulous) audience nothing but ridicule. Bicknell is extremely cautious in offering what is nonetheless a plausible explanation. He notes that, while an increase in particulate matter in the atmosphere as a result of major volcanic eruptions can result in short-term anomalous darkening of lunar eclipses, the dominant factor in regular, cyclical darkening is a combination of the influence of the 11-year solar cycle discovered by Danjon and expressed in the Danjon scale and 'long-term excursions (cycles) of solar activity' measurable over millennia. Study of the second (greater) cycle undertaken by J.A. Eddy reveals a 'Roman maximum', contributing to unusually dark lunar eclipses (Danjon number: 0) in the last two centuries before the Christian era - encompassing both the temporal 'window' during which Aglaonice could have been active and the time at which Plutarch wrote his accounts of her seeming sorcery.
Cultural influence.
Practitioners of the Wiccan religion reference indirectly the feats of Aglaonice in their ritual entitled "Drawing down the Moon", whereby a priestess invokes the Triple Goddess. They claim that the source for this ritual is to be found in the body of lore entitled "Vangelo" recorded in Leland's "Aradia".
And thus it came to pass one night, at the meeting of all the sorceresses and fairies, she (Aradia/Herodias) declared that she would darken the heavens and turn all the mice into stars
The phrase was also used as part of the title of the influential Wiccan text "Drawing Down the Moon: Witches, Druids, Goddess-Worshippers, and Other Pagans in America Today" by Wiccan priestess Margot Adler published in 1979.
One of the craters on Venus is named after Aglaonice. As "Aglaonice", she is a character in the Jean Cocteau film "Orpheus", where she is a friend of Eurydice and leader of the League of Women. Aglaonice is a featured figure on Judy Chicago's installation piece "The Dinner Party", being represented as one of the 999 names on the "Heritage Floor."


Edward Bernard

Edward Bernard (1638 – 12 January 1697) was an English scholar and Savilian professor of astronomy at the University of Oxford, from 1673 to 1691.
Life.
He was born at Paulerspury, Northamptonshire. He was educated at Merchant Taylors' School and St John's College, Oxford, where he was a scholar in 1655; he became a Fellow in 1658, and graduated M.A. in 1662.
He began to teach astronomy as deputy to Christopher Wren, then Savilian professor. This was from 1669, the year in which Wren became Surveyor-General of the King's Works. Eventually Wren was too busy, and resigned the chair.
In 1673 he became Savilian professor, Fellow of the Royal Society, and chaplain to Peter Mews. In 1676 he went to Paris, as tutor to Henry FitzRoy, 1st Duke of Grafton and George FitzRoy, 1st Duke of Northumberland. From the 1670s he built up good contacts with European scholars. He corresponded with Hiob Ludolf, and met his nephew Heinrich Wilhelm Ludolf in Oxford. He visited Pierre-Daniel Huet, and corresponded with Jean Mabillon and Pasquier Quesnel.
He observed the comet of 1680 and corresponded about it with John Flamsteed. In 1691 he became rector of Brightwell in Oxfordshire.
His biography was written by his friend Thomas Smith.
He died in Oxford on 12 January 1697, and was buried four days later in St John's College chapel.
Works.
He spent much time on manuscripts of Apollonius of Perga, travelling to Leiden to look at the manuscript legacies of Joseph Scaliger and Levinus Warner in 1669, and working on Arabic texts in the Bodleian Library. He returned to the Netherlands more than two decades later, to purchase at auction items from the library of Jacobus Golius, on behalf of Narcissus Marsh. In parallel, he began to edit the works of Josephus in the 1680s. The geometrical work remained fragmentary, while the Josephus edition was heavily annotated but incomplete. Clement Barksdale circulated some doggerel about it: "Savilian Bernard's a right learned man;/Josephus he will finish when he can." His transcriptions and translations were later used by Edmund Halley in his translation of Apollonius.
Much of Bernard's scholarly work remained as book annotations, and came back to the Bodleian when it purchased those books from his library after his death.
"De mensuris et ponderibus antiquis" (1688), on ancient weights and measures, first was an appendix to a work of Edward Pococke, and then published separately in an expanded version. With Humphrey Hody and Henry Aldrich he issued an edition of Aristeas. The "Orbis Eruditi" was a table of many alphabets.
His "Catalogi librorum manuscriptorum Angliae et Hiberniae in unum collecti cum indice alphabetico" (Oxford, 1697), colloquially "Bernard's Catalogue", was a catalogue of manuscripts in British and Irish libraries, and served as a major tool for scholars. Humfrey Wanley assisted him with this compilation.
Recent sources claim that his assertion that tenth-century Egyptian astronomer Ibn Yunis used a pendulum for time measurement, predating Galileo, has no basis in fact.


Solar flare classification


Something Ricked This Way Comes

"Something Ricked This Way Comes" is the ninth episode of the first season of the American science fiction comedy television series "Rick and Morty". Aired on March 24, 2014, the episode was directed by John Rice and written by Mike McMahan. The episode aired on March 6, 2016 in Canada. It stars Justin Roiland as Rick Sanchez and Morty Smith.
Plot.
Summer works in an antique shop run by the Devil, which gives away items that come with harmful curses. Rick sets up a competitor shop where he uses science to remove the curses, and the Devil is put out of business. Summer helps him to relaunch a successful dot-com company, but he betrays her and keeps the company for himself. Summer and Rick build muscle mass and publicly beat up the Devil to get revenge. Meanwhile, Jerry, helping Morty with his homework, insists that Pluto is a planet.
They are abducted by Plutonians to their planet, where Jerry is mistaken for a scientist. His statements about Pluto being a planet make him instantly popular, but it is later revealed to him that Pluto is shrinking due to corporate plutonium mining, and the Plutonian leadership keeps the population distracted by assuring them Pluto is still a planet. Jerry tells the Pluto citizens the truth on a public speech, causing him to be hated and deported back to Earth with Morty.
Reception.
Corey Plante of "Inverse" praised the unusual Morty-Jerry storyline in the episode, but criticized other parts of it, saying "So the surface level plots of “Something Ricked This Way Comes” feel pretty boring, with one being more derivative than it is subversive and the other being a long-winded joke." Zack Handlen of "The A.V. Club" said: "It’s a riff on climate change deniers: when the truth is that unsettling, people would much rather pretend they can make it go away by listening to an idiot."


June 2002 lunar eclipse

A penumbral lunar eclipse took place on June 24, 2002, the second of three lunar eclipses in 2002. This penumbral eclipse was visibly imperceptible due to the small entry into the southern penumbral shadow. This lunar eclipse was during the 2002 FIFA World Cup, occurring only 6 days before the 2002 FIFA World Cup Final, which was won by Brazil. The result was Brazil 2-0 Germany in 2002 FIFA World Cup Final, occurring 6 days after the penumbral lunar eclipse.
Related lunar eclipses.
Half-Saros cycle.
A lunar eclipse will be preceded and followed by solar eclipses by 9 years and 5.5 days (a half saros). This lunar eclipse is related to one partial solar eclipse of Solar Saros 156.


101P/Chernykh

101P/Chernykh is a periodic comet which was first discovered on August 19, 1977, by Nikolaj Stepanovich Chernykh.
In 1991, 101P/Chernykh was observed to split. JPL concluded that the comet split in April 1991, when 3.3 AU from the Sun.
The primary nucleus is in diameter and was last observed in 2020. Fragment B has not been observed since 1996.


Wimborne Minster astronomical clock

Wimborne Minster astronomical clock is a fourteenth-century astronomical clock in Wimborne Minster in Dorset, regarded as "one of the most ancient working clocks in Europe."
History and description.
The clock dates back to the early fourteenth century, possibly around 1320. It is suggested that it was built by Peter Lightfoot, a Glastonbury monk. The clock's case was built in the Elizabethan era, but the face and dial are of a much greater age; the first documents relating to the clock concern repairs carried out in 1409. In early church records the clock is referred to as the "oryall".
In 1593, the clock was removed from the central tower, and moved to its current location in the minster's west tower. The clock's mechanism was replaced in 1695 and the present works were installed in 1792. The gilded angels and cherubim which adorn the case were transplanted from the original organ case during church renovations undertaken in the Victorian era. In 1979 restorations were carried out upon the clock which reproduced the simple designs discovered under the ancient layers of paint.
The display on the clock is based upon the geocentric model, which was not superseded until the advent of heliocentrism in the late 16th century. The earth is represented by a blue-green sphere positioned in the centre of the clock face. The sun rotates in the outer blue ring and points to the hour of day. The gold/black orb in the inner starred ring represents the moon, and shows the lunar phases. At full moon it is golden, and at new moon it is black. For intermediate phases it is partially black and gold in proportion to the phase.
The casing on the wall contains cogs which move the sun and moon models around the face of the clock. The movement is in the belfry. On the outside north wall of the minster is a full-size Grenadier, called the Quarterjack, which strikes the quarter hours. The original figure of a monk was replaced during the Napoleonic Wars.


Olin Observatory

Olin Observatory is an astronomical observatory in New London, Connecticut (USA), owned and operated by Connecticut College. It is part of the F.W. Olin Science Center. The observatory hosts public stargazing events, and is also used for undergraduate instruction.


Harold Knox-Shaw

Harold Knox-Shaw (12 October 1885 – 11 April 1970) was an English astronomer.
He was born in St Leonards-on-Sea, Sussex. He was the oldest of four siblings. During his youth he earned scholarships to Wellington College in Berkshire and to Trinity, Cambridge, from which he graduated in 1907 ranked as Sixth Wrangler. A year following his graduation he became an assistant at the Khedivial Astronomical Observatory in Helwan, Egypt. He was elected Fellow of the Society in 1908. In 1910 he became the first to photograph Halley's comet from this site.
In 1913 he became superintendent of the Khedivial Observatory, and remained at that post until 1924. From 1918 until 1924 he also served as the Director of Meteorological Services in Egypt and Sudan. He performed welfare work for the British army during World War I, and was awarded the Order of the Nile, Class 4. (In 1926 he was awarded Order of the Nile, class 3.)
He returned to England in 1924 to become Radcliffe Observer at the Radcliffe Observatory. Much of his labor during the following years was then spent in production of the "Radcliffe Catalogue of Proper Motions", published in 1934. From 1926–30 he was Secretary of the Royal Astronomical Society, then served as President 1931–32.
His dissatisfaction with the observing conditions in England led him to lobby funds for a site in South Africa. This observatory would not be completed until 1939, however, when Knox-Shaw took up residence. The pouring of the blank for the main telescope was then held up until after World War II. From 1941–42 he was president of the Astronomical Society of Southern Africa (ASSA). The mirror finally arrived in 1948, followed by a Cassegrain spectrograph in 1951. Two years later Knox-Shaw retired.
He married Maisie (née Weir of Pretoria) and the couple had one son, Peter, who was born in 1944. His twenty-year retirement was spent at Elgin, Western Cape. He died from a stroke, and his ashes were scattered on Radcliffe Observatory grounds.


GRB 030329

GRB 030329 was a gamma-ray burst (GRB) that was detected on 29 March 2003 at 11:37 UTC. A gamma-ray burst is a highly luminous flash associated with an explosion in a distant galaxy and producing gamma rays, the most energetic form of electromagnetic radiation, and often followed by a longer-lived "afterglow" emitted at longer wavelengths (X-ray, ultraviolet, optical, infrared, and radio). GRB 030329 was the first burst whose afterglow definitively exhibited characteristics of a supernova, confirming the existence of a relationship between the two phenomena.
Observations.
GRB 030329 was one of three gamma-ray bursts detected on 29 March 2003. The other two were labeled GRB 030329a and GRB 030329b. GRB 030329 was detected by multiple instruments onboard HETE at 11:37 UTC and lasted approximately 25 seconds. The burst's optical afterglow was first observed from Siding Spring Observatory less than two hours after the burst had been detected. The X-ray afterglow was first detected by RXTE approximately five hours after the burst. The radio afterglow was first detected by the Very Large Array and, at the time of its discovery, was the brightest radio afterglow ever observed. The burst was located at a sky position of R.A. = , Dec. = and had a redshift of z = 0.1685, corresponding to a distance of 587 Mpc.
Supernova relation.
GRB 030329's proximity to Earth enabled its afterglow to be studied in great detail. A spectrum taken of the burst's optical afterglow on 6 April 2003 showed peaks at approximately 570 nm and 470 nm. This spectrum was reproduced by combining a power-law distribution with the spectrum from SN 1998bw. These supernova-like features continued to develop in the weeks after the initial burst. Optical observations taken at Kitt Peak National Observatory on indicated that the burst's optical afterglow was brighter than a power-law decay would have predicted, a deviation that could have been explained by additional light from a supernova. On 10 April 2003, NASA announced that GRB 030329 had provided the definitive link between gamma-ray bursts and supernovae. The supernova was later referred to as SN 2003dh.


Rosina Dafter

Rosina Dafter (née Fitton), FRAS (15 March 1875 - 9 June 1959) was an astronomer and the first Australian woman to be made a fellow of the Royal Astronomical Society. She re-discovered the Pons-Winnecke comet in 1927 and was responsible for the discovery of previously unobserved variable stars in the Carina constellation.
Life.
Dafter was born in London to Margaret and Richard Fitton, a pianoforte maker. She was educated at Holy Trinity Church School in London and started work as a dress designer before her marriage to John Albert Dafter on 20 November 1898. The couple arrived in Australia in 1910 and settled in Northgate with their two foster sons who were merchant mariners.
While she had an interest in stars from childhood and studied mathematics as a hobby, it was not until her arrival in Australia that Dafter sought advice and began teaching herself astronomy.
In 1923, Dafter was elected a member of the British Astronomical Association which had a branch in New South Wales. She was the southern observer for the Association for three decades, and was also a member of the New Zealand Astronomical Association and the American Association of Variable Star Observers.
Dafter gathered the data for Brisbane as part of a larger research project involving Broken Hill and Japan that aimed to obtain simultaneous photometric data across the three sites.
She also provided details of astronomical events to local newspapers, held public talks on Astronomy and was published in numerous journals.
Dafter died in 1959.


Bernard of Verdun

Little is known of the life of Bernard of Verdun, except that he was a Franciscan friar who may have been born in Verdun and lived in the second half of the thirteenth century. His most significant work was the Treatise on the Whole of Astronomy ("Tractatus super totam astrologiam"), in which he defended Ptolemy's theory of epicycles and eccentrics against al-Bitruji's system of homocentric spheres. Contrary to the criticisms of Averroes and al-Bitruji, Bernard maintained that Ptolemy's theory was consistent with Aristotle's physics. He further pointed out many technical inadequacies of al-Bitruji's model, and considered it to be insufficiently developed to challenge Ptolemy's system.


HD 33564

HD 33564 is a 5th magnitude star located approximately 68 light-years away in the constellation of Camelopardalis. It is an F-type main sequence, indicating that the star is hotter and more massive than our Sun. The age of the star is only 3 Ga; despite of this, the star is only 76% the solar abundance of iron. HD 33564 is a naked eye planetary host star.
Planetary system.
In September 2005, a massive planet was found orbiting the star surrounded by a disk. However, by next month, the disk was disproved because the infrared radiation is actually coming from the background galaxy passing very close to its star in apparent distance.