February 29: Lewis A. Swift

Lewis A. Swift

February 29, 1820 – January 5, 1913

Lewis Swift was an American astronomer. He discovered or co-discovered a number of comets, including periodic comets 11P/Tempel-Swift-LINEAR, 64P/Swift-Gehrels, and 109P/Swift-Tuttle (parent body of the Perseids meteor shower). He also discovered comet D/1895 Q1 (a.k.a. D/Swift) whose debris stream Mariner 4 probably encountered on September 15, 1967. Note, however, comet 54P/de Vico-Swift-NEAT was discovered by his son Edward D. Swift rather than by him. Apart from comets, he also discovered hundreds of nebulae.

In 1878 he believed he had observed two Vulcan-type planets (planets within the orbit of Mercury), but he was mistaken. He discovered his last comet at the age of 79. He was one of the few people to see Comet Halley at two of its appearances, 76 years apart.

Dr. Swift or “Professor” Swift, as he became known, was handicapped by a childhood accident, and devoted his time to the study of astronomy. It appears that his titles were honorary and not the result of the award of any advanced degrees. Indeed, he was an astronomer by avocation only and the operator of a hardware store vocationally. However, his sightings of previously undiscovered comets elevated his reputation and enabled him to give lectures. His notoriety allowed him to begin the process of raising money for an observatory in Rochester.

His patron was the Rochester patent medicine businessman Hulbert Harrington Warner, who financed the building of an observatory for Swift. Warner assured the “famous comet finder” that if Swift could raise the money to purchase a large telescope, Warner would furnish a place to put it. The original estimate for construction of the Observatory was $20,000. Dr. Swift was able to fulfill his part of the bargain and a 16-inch refractor telescope was ordered from Alvan Clark & Son in Massachusetts. Ultimately, the Observatory cost Warner $100,000. The plans for the Observatory also called for an astronomical library, astronomical equipment and a residential space for Dr. Swift and his family.

Warner went bankrupt in the Panic of 1893, which ended his financial support, and Swift then went to California to become director of Mount Lowe Observatory.

The asteroid 5035 Swift is named in his honour, as is the lunar crater Swift. In 1897 he was awarded the Jackson-Gwilt Medal of the Royal Astronomical Society.

February 28: Camille Guillaume Bigourdan

Camille Guillaume Bigourdan

April 6, 1851 – February 28, 1932

Guillaume Bigourdan was a French astronomer. In 1877 he was appointed by Félix Tisserand as assistant astronomer at the Toulouse Observatory, and in 1879 followed Tisserand to the Paris Observatory when the latter became director there.

He spent many years verifying the positions of 6,380 nebulas. He hoped to set a basis for future studies of the proper motion of nebulas; this turned out to be more or less in vain, since distant nebulas will not show any proper motion. However, he did discover approximately 500 new objects, including asteroid 390 Alma (on March 24, 1894).

In 1902 he participated in an effort to redetermine with greater precision the longitude difference between London and Paris. He became a member of the Bureau des Longitudes in 1903, and a member of the French Academy of Sciences in 1904.

He described a method for adjusting equatorial mount telescopes, which was known as "Bigourdan's method".

Bigourdan won the Gold Medal of the Royal Astronomical Society in 1919 for his observations of nebulae for over 25 years. He was director of the Bureau International de l'Heure from 1919 to 1928.

February 27: Bernard Lyot

Bernard Ferdinand Lyot

February 27, 1897 – April 2, 1952

Bernard Lyot was a French astronomer. His interest in astronomy started in 1914. He acquired a 4-inch (100 mm) telescope and soon upgraded to a 6-inch (150 mm). From graduation in 1918 until 1929, he worked as a demonstrator at the Ecole Polytechnique. He studied engineering, physics, and chemistry at the University of Paris, and from 1920 until his death he worked for the Meudon Observatory. 

In 1930 he earned the title of Joint Astronomer of the Observatory. After gaining the title, he earned a reputation of being an expert of polarized and monochromatic light. Throughout the 1930s, he labored to perfect the coronagraph, which he invented to observe the corona without having to wait for a solar eclipse. In 1938, he showed a movie of the corona in action to the International Astronomical Union. 

In 1939, he was elected to the French Academy of Sciences. He became Chief Astronomer at the Meudon Observatory in 1943 and received the Bruce Medal in 1947. Tragically, he suffered a heart attack while returning from an eclipse expedition in Sudan and died on 2 April 1952, at the age of 55.

Lyot's observations and achievements on Pic du Midi include: determination that lunar soil behaves like volanic dust, that Mars has sandstorms, improvment of his coronagraph, made motion pictures of solar prominences and the corona and found spectral lines in the corona.

Lyot was awarded the Gold Medal of the Royal Astronomical Society in 1939, the Bruce Medal in 1947 and the Henry Draper Medal in 1951. The Lunar crater Lyot, the Lyot crater on Mars and the minor planet 2452 Lyot are named in his honor.

February 26: Camille Flammarion

Nicolas Camille Flammarion

February 26, 1842 – June 3, 1925

Nicolas Camille Flammarion was a French astronomer and author. He is commonly referred to as Camille Flammarion.

Camille Flammarion was a prolific author of more than fifty titles, including popular science works about astronomy, several notable early science fiction novels, and several works about Spiritualism and related topics. He also published the magazine L'Astronomie, starting in 1882. He maintained a private observatory at Juvisy-sur-Orge, France.

He was a founder and the first president of the Société Astronomique de France, which originally had its own independent journal, BSAF (Bulletin de la Société astronomique de France), first published in 1887. In January 1895, after 13 volumes of L'Astronomie and 8 of BSAF, the two merged, making L'Astronomie the Bulletin of the Societé. 

He was the first to suggest the names Triton and Amalthea for moons of Neptune and Jupiter, respectively, although these names were not officially adopted until many decades later.

Because of his scientific background, he approached spiritualism and reincarnation from the viewpoint of the scientific method, writing, "It is by the scientific method alone that we may make progress in the search for truth. Religious belief must not take the place of impartial analysis. We must be constantly on our guard against illusions." He was chosen to speak at the funerals of Allan Kardec, founder of Spiritism, on 2 April 1869, when he re-affirmed that "spiritism is not a religion but a science".

His spiritualism studies also influenced some of his science fiction. In "Lumen", a human character meets the soul of a an alien, able to cross the universe faster than light, that has been reincarnated on many different worlds, each with their own gallery of organsims and their evolutionary history. Other than that, his writing about other worlds adhered fairly closely to then current ideas in evolutionary theory and astronomy.

The enigmatic "Flammarion Woodcut" first appeared in an 1888 Flammarion publication. His second wife was Gabrielle Renaudot Flammarion, also a noted astronomer.

The Lunar crater Flammarion is named in his honor.

February 25: Lev Andreevich Artsimovich

Lev Andreevich Artsimovich

February 25, 1909 – March 1, 1973

Lev Artsimovich was a Soviet physicist, academician of the Soviet Academy of Sciences (1953), member of the Presidium of the Soviet Academy of Sciences (since 1957), and Hero of Socialist Labor (1969). Artsimovich worked on the field of nuclear fusion and plasma physics. He was known as "the father of the Tokamak", a special concept for a fusion reactor.

Director of the Kurchatov Institute of Atomic Energy, member of the Presidium of the USSR Academy of Sciences and Academician-Secretary of its Division of General Physics and Astronomy, President of the National Committee of the International Union of Pure and Applied Physics, delegate on the Council of the European Physical Society, President of the National Committee of Soviet Physicists, member of the Commission on disarmament problems of the Presidium of the USSR Academy of Sciences, and member of the International Continuing Committee of the Pugwash Conferences on Science and World Affairs - Artsimovich had for more than a decade played a pivotal role in the internal development of Soviet science and its growing international involvement.

Artsimovich's interests spanned many branches of physics including x-rays, slow neutron physics, interactions of fast electrons, positron annihilation, magnetic bremsstrahlung, ion and electron optics, electromagnetic isotope separation and gas discharges. For the last 20 years of his life, his main scientific interest was in the physics of high temperature plasmas. He invented the tokamak, the device that has come closest to demonstrating the feasibility of controlled thermonuclear (fusion) energy production. In 1955 an international collaboration started constructing the first Tokamak, but by 1970 only the Soviets were actively researching the concept. Nevertheless, although he often stated publicly that he was certain that the conditions for controlled thermonuclear reactions could be attained in the laboratory, he was equally certain that this would not happen in his lifetime - that it was still 10 to 20 years away - because the solution of a problem of such great technological difficulty could not be achieved without a better understanding of the basic physics of the processes involved.

But his interests in science far transcended the field of plasma physics. He was a major driving force in the Soviet Academy in support of research in high energy nuclear and particle physics and in various branches of modern astronomy and astro-physics, believing that only through deep and effective involvement in these frontier fields would Soviet science be able to achieve a position in the forefront of modern world science. He was a conscientious and devoted teacher, as proud of the popularity of his courses in plasma physics and ion optics as of his scientific achievements. As a science administrator, he fought a vigorous and continuing battle to break down the traditional system of control over science by the authoritarian "herr professor," insisting on mandatory early retirement of laboratory heads and the establishment of direct mechanisms for bringing young scientists into positions of authority as early as possible. Although still at the peak of his intellectual powers, he was preparing to step down as the director of his Institute when he died. In this respect he was scrupulously consistent with his own principles.

Lev Artsimovich was a kind and gentle man, but with a sharp, acerbic wit that could not tolerate fools, let alone knaves. He believed in the future, despite a short-range pessimism that was easily mistaken for cynicism on first encounter. He distrusted most politicians but believed that, in the long run, men of intelligence and good will everywhere would converge to bring sanity into the affairs of states. He was a loyal citizen of his country, but believed that it could learn a great deal from observing the rest of the world. He advocated open international contacts of all kinds as a basic good, not only because of the positive effect on international understanding and relations, but also because he could not conceive that others would not enjoy travel and variety as much as he did.

He is perhaps most famous in the field of fusion research for his quote responding to the question of when commercial fusion power would become available; he said "Fusion will be ready when society needs it."

The crater Artsimovich on the Moon is named after him.

February 23: Jean-Baptiste Morin

Jean-Baptiste Morin

February 23, 1583 — November 6, 1656

Jean-Baptiste Morin, also known by his Latin pseudonym as Morinus, was a French mathematician, astrologer, and astronomer.

In 1630, Morin was appointed professor of mathematics at the Collège Royal, a post he held until his death.

A firm believer of the idea that the Earth remained fixed in space, Morin is best known for being opponent of Galileo and the latter's ideas. He continued his attacks after the Trial of Galileo. Morin seems to have been a rather contentious figure, as he also attacked Descartes' ideas after meeting the philosopher in 1638. These disputes isolated Morin from the scientific community at large.

Morin believed that improved methods of solving spherical triangles had to be found and that better lunar tables were needed.

Morin attempted to solve the longitude problem. In 1634, he proposed his solution: it was based on measuring absolute time by the position of the Moon relative to the stars. It was a variation of the lunar distance method. Morin added some improvements to this method, such as better scientific instruments and taking lunar parallax into account. Morin did not believe that Gemma Frisius' transporting clock method for calculating out longitude would work. Morin, unfailingly irascible, remarked, "I do not know if the Devil will succeed in making a longitude timekeeper but it is folly for man to try."

A prize was to be awarded, so a committee was set up by Richelieu to evaluate Morin's proposal. Serving on this committee were Étienne Pascal, Claude Mydorge, and Pierre Hérigone. The committee remained in dispute with Morin for the five years after he made his proposal. Morin refused to listen to objections to his proposal, which was considered impractical. In his attempts to convince the committee members, Morin proposed that an observatory be set up in order to provide accurate lunar data.

In 1645, Cardinal Mazarin, Richelieu's successor, awarded Morin a pension of 2,000 livres for his work on the longitude problem.

Morin’s life has been that of trial and tribulation by his own testament.

February 22: Pierre Janssen

Pierre Jules César Janssen

February 22, 1824 – December 23, 1907

Pierre Janssen was a French astronomer who, along with the English scientist Joseph Norman Lockyer, is credited with discovering the gas helium.

Janssen was born in Paris and studied mathematics and physics at the faculty of sciences. He taught at the lycée Charlemagne in 1853, and in the school of architecture 1865 – 1871, but his energies were mainly devoted to various scientific missions entrusted to him. Thus in 1857 he went to Peru in order to determine the magnetic equator; in 1861 – 1862 and 1864, he studied telluric absorption in the solar spectrum in Italy and Switzerland; in 1867 he carried out optical and magnetic experiments at the Azores; he successfully observed both transits of Venus, that of 1874 in Japan, that of 1882 at Oran in Algeria; and he took part in a long series of solar eclipse-expeditions, e.g. to Trani (1867), Guntur (1868), Algiers (1870), Siam (1875), the Caroline Islands (1883), and to Alcosebre in Spain (1905). To see the eclipse of 1870 he escaped from besieged Paris in a balloon (that eclipse was obscured by cloud cover, however).

In 1868 Janssen discovered how to observe solar prominences without an eclipse. On 18 August of that year, while observing an eclipse of the Sun in India, he noticed a bright yellow line with a wavelength of 587.49 nm in the spectrum of the chromosphere of the Sun. This was the first observation of this particular spectral line, and one possible source for it was an element not yet discovered on the earth. Janssen was at first ridiculed since no element had ever been detected in space before being found on Earth.

On 20 October of the same year, Joseph Norman Lockyer also observed the same yellow line in the solar spectrum and concluded that it was caused by an unknown element, after unsuccessfully testing to see if it were some new type of hydrogen. This was the first time a chemical element was discovered on an extraterrestrial world before being found on the earth. Lockyer and the English chemist Edward Frankland named the element with the Greek word for the Sun, helios.

At the great Indian eclipse of 1868, Janssen also demonstrated the gaseous nature of the red prominences, and devised a method of observing them under ordinary daylight conditions. One main purpose of his spectroscopic inquiries was to answer the question whether the Sun contains oxygen or not. An indispensable preliminary was the virtual elimination of oxygen-absorption in the Earth's atmosphere, and his bold project of establishing an observatory on the top of Mont Blanc was prompted by a perception of the advantages to be gained by reducing the thickness of air through which observations have to be made. This observatory, the foundations of which were fixed in the snow that appears to cover the summit to a depth of ten metres, was built in September 1893, and Janssen, in spite of his sixty-nine years, made the ascent and spent four days taking observations.

In 1875, Janssen was appointed director of the new astrophysical observatory established by the French government at Meudon, and set on foot there in 1876 the remarkable series of solar photographs collected in his great Atlas de photographies solaires (1904). The first volume of the Annales de l'observatoire de Meudon was published by him in 1896.

The Lunar crater Janssen and a crater on Mars are named in his honor.

February 21: Karl Gunnar Malmquist

Karl Gunnar Malmquist

February 21, 1893 – June 27, 1982

Gunnar Malmquist was a Swedish astronomer and Professor of Astronomy at the Uppsala University.

Malmquist was born in Ystad, where he completed his secondary school education before matriculating at the Lund University in 1911. He received his Ph.D. in 1921, was an amanuensis at the Lund Observatory 1915-1920 and a docent from 1920. He continued to work at the observatory in Lund until 1929, was observator at the Stockholm Observatory and taught at the Stockholm University College 1930-1939, and was Professor of Astronomy at the Uppsala University from 1939 until his retirement in 1959.

Malmquist was a student of Carl Charlier at Lund and became one of the best known members of the so-called "Lund school" in statistical astronomy. His work in that field led, among other things, to his observation of the Malmquist bias which is today one of the standard methods in statistical astronomy.

In 1939 he was installed as professor in Uppsala where he continued his theoretical works using the observational data from the large research on the Milky Way which had been in progress in Uppsala since the beginning of the century.

As professor at the Uppsala Astronomical Observatory he got interested in Schmidt telescopes and took the initiative, together with Åke Wallenquist, to get a large Schmidt telescope installed at Uppsala University's Kvistabergs Observatorium (Kvistaberg Observatory, 1964), at the time one of the largest Schmidt telescopes in the world with a mirror of 135 cm and a corrector plate of 100 cm. He also arranged for the university to get an observatory at Mount Stromlo in Australia. The Southern Station gave swedish astronomers the opportunity, on a more regular basis, to carry out observations in the southern hemisphere which was of significant importance before the creation of the European Southern Observatory (ESO).

The asteroid 1527 Malmquista was named in his honor.

February 20: Ranger 8 reached the Moon

Ranger 8 reached the Moon

February 20, 1965

On February 20, 1965, Ranger 8 swept an oblique course over the south of Oceanus Procellarum and Mare Nubium, to crash in Mare Tranquillitatis where Apollo 11 would land 4½ years later. It garnered more than 7,000 images, covering a wider area and reinforcing the conclusions from Ranger 7.

Ranger 8 was a spacecraft designed to achieve a lunar impact trajectory and to transmit high-resolution photographs of the lunar surface during the final minutes of flight up to impact. The spacecraft carried six television vidicon cameras, two wide angle (channel F, cameras A and B) and four narrow angle (channel P) to accomplish these objectives. The cameras were arranged in two separate chains, or channels, each self-contained with separate power supplies, timers, and transmitters so as to afford the greatest reliability and probability of obtaining high-quality video pictures. No other experiments were carried on the spacecraft.

Ranger 8 was launched on February 17, 1965 and reached the Moon on February 20, 1965. The first image was taken at 9:34:32 UT at an altitude of 2510 km. Transmission of 7,137 photographs of good quality occurred over the final 23 minutes of flight. The final image taken before impact has a resolution of 1.5 meters. The spacecraft encountered the lunar surface in a direct hyperbolic trajectory, with incoming asymptotic direction at an angle of -13.6 degrees from the lunar equator. The orbit plane was inclined 16.5 degrees to the lunar equator. After 64.9 hours of flight, impact occurred at 09:57:36.756 UT on February 20, 1965 in Mare Tranquillitatis at approximately 2.67 degrees N, 24.65 degrees E. (The impact site is listed as about 2.72° N, 24.61° E in the initial report "Ranger 8 Photographs of the Moon".) Impact velocity was slightly less than 2.68 km/s. The spacecraft performance was excellent.

The Ranger program was a series of unmanned space missions by the United States in the 1960s whose objective was to obtain the first close-up images of the surface of the Moon. The Ranger spacecraft were designed to collide with the lunar surface, returning imagery until they were destroyed upon impact.

Ranger was originally designed, beginning in 1959, in three distinct phases, called "blocks". Each block had different mission objectives and progressively more advanced system design. The JPL mission designers planned multiple launches in each block, to maximize the engineering experience and scientific value of the mission and to assure at least one successful flight. Total research, development, launch, and support costs for the Ranger series of spacecraft (Rangers 1 through 9) was approximately $170 million.

February 19: Nicolaus Copernicus

Nicolaus Copernicus

February 19, 1473 – May 24, 1543

Nicolaus Copernicus was the first astronomer to formulate a scientifically-based heliocentric cosmology that displaced the Earth from the center of the universe. His epochal book, De revolutionibus orbium coelestium (On the Revolutions of the Celestial Spheres), is often regarded as the starting point of modern astronomy and the defining epiphany that began the Scientific Revolution.

Although Greek, Indian and Muslim savants had published heliocentric hypotheses centuries before Copernicus, his publication of a scientific theory of heliocentrism, demonstrating that the motions of celestial objects can be explained without putting the Earth at rest in the center of the universe, stimulated further scientific investigations and became a landmark in the history of modern science that is known as the Copernican Revolution.

Among the great polymaths of the Renaissance, Copernicus was a mathematician, astronomer, physician, classical scholar, translator, artist, Catholic cleric, jurist, governor, military leader, diplomat and economist. Among his many responsibilities, astronomy figured as little more than an avocation — yet it was in that field that he made his mark upon the world.

Early traces of a heliocentric model are found in several anonymous Vedic Sanskrit texts composed in ancient India before the 7th century BCE. Additionally, in the sixth century the Indian astronomer and mathematician Aryabhata anticipated elements of Copernicus's work, although he did not maintain heliocentrism.

Aristarchus of Samos in the 3rd century BCE elaborated some theories of Heraclides Ponticus (the daily rotation of the Earth on its axis, the revolution of Venus and Mercury around the Sun) to propose what was the first scientific model of a heliocentric solar system: the Earth and all other planets revolving around the Sun, the Earth rotating around its axis daily, the Moon in turn revolving around the Earth once a month. His heliocentric work has not survived, so we can only speculate about what led him to his conclusions. It is notable that, according to Plutarch, a contemporary of Aristarchus accused him of impiety for "putting the Earth in motion".

Copernicus cited Aristarchus and Philolaus in a surviving early manuscript of his book, stating: "Philolaus believed in the mobility of the earth, and some even say that Aristarchus of Samos was of that opinion." For reasons unknown (possibly from reluctance to quote pre-Christian sources), he did not include this passage in the published book. It has been argued that in developing the mathematics of heliocentrism Copernicus drew on not just the Greek, but also the work of Muslim astronomers, especially the works of Nasir al-Din Tusi (Tusi-couple), Mo'ayyeduddin Urdi (Urdi lemma) and Ibn al-Shatir. In his major work, Copernicus also discussed the theories of Ibn Battuta and Averroes.

The Lunar crater Copernicus is named in his honor.

February 18: Nasir al-Din al-Tusi

Nasir al-Din al-Tusi

February 18, 1201 - June 26, 1274

Nasir al-Din al-Tusi, also known as Nasireddin, was a Persian polymath and prolific writer: an astronomer, biologist, chemist, mathematician, philosopher, physician, physicist, scientist, theologian and Marja Taqleed. His works include the definitive Arabic versions of the works of Euclid, Archimedes, Ptolemy, Autolycus, and Theodosius of Bithynia.

Tusi convinced Hulegu Khan to construct an observatory for establishing accurate astronomical tables for better astrological predictions. Beginning in 1259, the Rasad Khaneh observatory was constructed west of Maragheh, the capital of the Ilkhanate Empire.

Based on the observations in this, for the time being, most advanced observatory, Tusi made very accurate tables of planetary movements as depicted in his book Zij-i ilkhani (Ilkhanic Tables). This book contains astronomical tables for calculating the positions of the planets and the names of the stars. His model for the planetary system is believed to be the most advanced of his time, and was used extensively until the development of the heliocentric model in the time of Nicolaus Copernicus. Between Ptolemy and Copernicus, he is considered by many to be one of the most eminent astronomers of his time, and his work and theory in astronomy can also be compared to that of the Chinese scientist Shen Kuo (1031-1095 AD).

For his planetary models, he invented a geometrical technique called a Tusi-couple, which generates linear motion from the sum of two circular motions. He used this technique to replace Ptolemy's problematic equant, and it was later employed in Ibn al-Shatir's geocentric model and Nicolaus Copernicus' heliocentric Copernican model. He also calculated the value for the annual precession of the equinoxes and contributed to the construction and usage of some astronomical instruments including the astrolabe.

Tusi was also the first to present empirical observational evidence of the Earth's rotation, using the location of comets relevant to the Earth as evidence, which Ali al-Qushji elaborated on with further empirical observations. The arguments of Tusi were similar to the arguments later used by Copernicus in 1543 to explain the Earth's rotation.

The Lunar crater Nasireddin, a minor planet 10269 Tusi, discovered by Soviet astronomer Nikolai Stepanovich Chernykh in 1979 and the K. N. Toosi University of Technology in Iran are named in his honor.

February 17: Tobias Mayer

Tobias Mayer

February 17, 1723 – February 20, 1762

Tobias Mayer was a German astronomer famous for his studies of the Moon.

His first important astronomical work was a careful investigation of the libration of the moon (Kosmographische Nachrichten, Nuremberg, 1750), and his chart of the full moon, published in 1775, was unsurpassed for half a century. But his fame rests chiefly on his lunar tables, communicated in 1752, with new solar tables to the Königliche Gesellschaft der Wissenschaften zu Göttingen (Royal Society of Sciences and Humanities at Gottingen), and published in their transactions.

In 1755 he submitted to the British government an amended body of manuscript tables, which James Bradley compared with the Greenwich observations. He found these to be sufficiently accurate to determine the moon's position to 5", and consequently the longitude at sea to about half a degree. An improved set was later published in London (1770), as also the theory (Theoria lunae juxta systema Newtonianum, 1767) upon which the tables are based. His widow, with whom they were sent to England, received in consideration from the British government a grant of £3,000. Appended to the London edition of the solar and lunar tables are two short tracts, one on determining longitude by lunar distances, together with a description of the reflecting circle (invented by Mayer in 1752), the other on a formula for atmospheric refraction, which applies a remarkably accurate correction for temperature.

Mayer left behind him a considerable quantity of manuscript material, part of which was collected by G. C. Lichtenberg and published in one volume (Opera inedita, Göttingen, 1775). It contains an easy and accurate method for calculating eclipses, an essay on colour, in which three primary colours are recognized, a catalogue of 998 zodiacal stars, and a memoir, the earliest of any real value, on the proper motion of eighty stars, originally communicated to the Göttingen Royal Society in 1760.

The remaining manuscripts included papers on atmospheric refraction from 1755, on the motion of Mars as affected by the perturbations of Jupiter and the Earth (1756), and on terrestrial magnetism (1760 and 1762). In these last Mayer sought to explain the magnetic action of the earth by a modification of Euler's hypothesis, and made the first really definite attempt to establish a mathematical theory of magnetic action (C. Hansteen, Magnetismus der Erde, I, 283). In 1881 Ernst Klinkerfues published photo-lithographic reproductions of Mayer's local charts and general map of the moon. His star catalogue was re-edited by Francis Baily in 1830 (Memoirs of the Royal Astronomical Society IV, 391) and by Arthur Auwers in 1894.

The Lunar crater T. Mayer is named in his honor.

February 16: Georg Joachim Rheticus

Georg Joachim Rheticus

February 16, 1514 – December 4 1574

Georg Joachim von Lauchen, also known as Rheticus, was a mathematician, cartographer, navigational and other instrument maker, medical practitioner, and teacher. He is perhaps best known for his trigonometric tables, and for being the only pupil of Nicolaus Copernicus, facilitating the major publication of his De revolutionibus orbium coelestium (On the Revolutions of the Heavenly Spheres).

In 1536 Rheticus was aided by Philipp Melanchthon in obtaining appointment to a teaching position in astronomy and mathematics at Wittenberg University. Two years later, Melanchthon arranged a two year leave for Rheticus in order to study with noted astronomers of the day. Rheticus took this opportunity to visit Copernicus in Frombork (Frauenburg). Leaving Wittenberg in October 1538, he first went to Nuremberg to visit the publisher Johannes Schöner and the printer Petreius. Here, Rheticus was given works of Regiomontanus and others, intended as presents to Copernicus. He proceeded on to Peter Apian in Ingolstadt and Joachim Camerarius in Tübingen, then to Achilles Gasser in his hometown.

In May 1539 he arrived in Frombork (Frauenburg) and spent two years there with Copernicus. It is unknown whether he had prior direct access to Copernicus' Commentariolus, and if so, since when. Copernicus had outlined his revolutionary heliocentric theory of the solar system three decades earlier, but handed out only few copies to friends.

In September 1539 Rheticus went to Danzig (Gdańsk) to visited the mayor who gave Rheticus some financial assistance to publish the First Report or Narratio Prima. This Narratio Prima, published by Rhode in Danzig in 1540, is still considered to be the best introduction to Copernicus' De revolutionibus orbium coelestium. 

In August 1541 Rheticus presented a copy of his work Tabula chorographica auff Preussen und etliche umbliegende lender (Map of Prussia and Neighboring Lands) to Duke Albrecht of Prussia who had been trying to compute the exact time of sunrise. Rheticus made an instrument for him that determined the length of the day. Rheticus asked and received the permission of the duke for the publication of the Copernicus De revolutionibus. Albrecht requested of Rheticus that he return to his teaching position. He returned to the University of Wittenberg in October 1541, after earlier publishing the trigonometrical sections of the Copernicus De revolutionibus. In 1542 he traveled to Nürnberg to supervise the printing of the Copernicus material by Johannes Petreius, published upon Copernicus' death in 1543.

The crater Rhaeticus was named in his honor.

February 15: William Henry Pickering

William Henry Pickering

February 15, 1858 – January 17, 1938

William Pickering was an American astronomer, brother of Edward Charles Pickering.

He discovered Saturn's ninth moon Phoebe in 1899 from plates taken in 1898. He also believed he had discovered a tenth moon in 1905 from plates taken in 1904, which he called "Themis". Unfortunately "Themis" does not exist.

Following George Darwin, he speculated in 1907 that the moon was once a part of the earth and that it broke away where now the Pacific Ocean lies. He also proposed some sort of continental drift (even before Alfred Wegener) and speculated that America, Asia, Africa, and Europe once formed a single continent, which broke up because of the separation of the moon.

He led solar eclipse expeditions and studied craters on the Moon, and hypothesized that changes in the appearance of the crater Eratosthenes were due to "lunar insects". He claimed to have found vegetation on the moon.

In 1919, he predicted the existence and position of a Planet X based on anomalies in the positions of Uranus and Neptune but a search of Mount Wilson Observatory photographs failed to find the predicted planet. Pluto was later discovered at Flagstaff by Clyde Tombaugh in 1930, but in any case it is now known that Pluto's mass is far too small to have appreciable gravitational effects on Uranus or Neptune, and the anomalies are accounted for when today's much more accurate values of planetary masses are used in calculating orbits. When the planet was named, he interpreted its symbol as a monogram referring to himself and Lowell by the phrase "Pickering-Lowell". 

Pickering constructed and established several observatories or astronomical observation stations, notably including Percival Lowell's Flagstaff Observatory. He spent much of the later part of his life at his private observatory in Jamaica. He produced a photographic atlas of the Moon: The Moon: A Summary of the Existing Knowledge of our Satellite in 1903.

The craters Pickering on the Moon and Pickering on Mars are jointly named after him and his brother Edward Charles Pickering.

February 14: Édouard Benjamin Baillaud

Édouard Benjamin Baillaud

February 14, 1848 – July 8, 1934

Benjamin Baillaud was a French astronomer. He worked as an assistant at the Paris Observatory beginning in 1872. Later he was director of the Toulouse Observatory from 1878 to 1907, during much of this time serving as Dean of the University of Toulouse Faculty of Science.

He greatly expanded the observatory and enthusiastically supported the Carte du Ciel project. He specialized in celestial mechanics, in particular the motions of the satellites of Saturn.

In 1903, the observatory took over a facility on the Pic du Midi in the Pyrenees that had been founded by amateurs in the 1850s with the goal of putting a telescope there. However, the height of 2,865 metres (9,400 feet) posed formidable logistical challenges and the ambition had remained unrealised though a meteorological observatory had operated from 1873 to 1880. Baillaud organised a team of soldiers to erect a 0.5 metre (20 inch) reflecting telescope, and 0.25 metre refracting telescope on the summit.

In 1907, he became director of the Paris Observatory where he immediately set to work to relaunch the stalled Carte du Ciel project with a conference held at the observatory, entertained by singers from the Paris Opera and refreshed by wine provided by the director of the Bordeaux Observatory. Though the French government agreed to fund the project, it was becoming increasingly clear that its objectives were hopelessly unrealistic.

Baillaud was active in time standardisation, becoming the founding president of the International Time Bureau and initiating the transmission of a time signal from the Eiffel Tower. Baillaud maintained the observatory and the time signal throughout World War I, even though the German howitzer Big Bertha was targeted on the nominal co-ordinates of Paris, the location of the observatory! Baillaud's concern for the astronomical time standard led him to be an outspoken opponent of daylight saving time.

Baillaud became founding president of the International Astronomical Union in 1919. He retired as director of the Paris Observatory in 1926.

He won the Bruce Medal in 1923. The Lunar crater Baillaud and the asteroid 11764 Benbaillaud are named in his honor. 

February 13: Guido Horn D'Arturo

Guido Horn D'Arturo

February 13, 1879 - April 1, 1967

Guido Horn D'Arturo was an Austrian astronomer who spent much of his career working in Italy. In 1920 he became director of the Bologna University Observatory. His research included positional astronomy, moving clusters, comets, solar eclipses, and history of astronomy; optics including geometric, instrumental, physiologic, & unusual optical instruments. 

Guido Horn d’Arturo designed and built the first “multi mirror” telescope, and the resulting 1.2-m transit instrument was operational at the University of Bologna for almost a decade.

Horn maintained a large number of connections with astronomers throughout the world and intense activity in order to enhance the international role of Bologna Observatory . Between 1912 and 1939 Horn studied the "Black drop" phenomenon and the flying shadows. 

The black drop effect is an optical phenomenon visible during a transit of Venus and, to a lesser extent, a transit of Mercury. Just after second contact, and again just before third contact during the transit, a small black "teardrop" appears to connect Venus' disk to the limb of the Sun, making it impossible to accurately time the exact moment of second or third contact. This led to the failure of the attempts during the 18th century transits of Venus to establish a truly precise value for the astronomical unit.

The black drop effect was long thought to be due to Venus' thick atmosphere, and indeed it was held to be the first real evidence that Venus had an atmosphere. However, it is now thought by many to be an optical effect.

In 1926 D'Arturo made an expedition to Somalia, to observe a solar eclipse. In 1931 he founded the magazine "Coelum" and started the project for setting up a telescope in Loiano. He also devised a method of measuring the density of stellar tracks on photographic plates using diffraction.

February 12: Christopher Clavius

Christopher Clavius

March 25, 1538 – February 12, 1612

Christopher Clavius was a German Jesuit mathematician and astronomer who was the main architect of the modern Gregorian calendar. In his last years he was probably the most respected astronomer in Europe and his textbooks were used for astronomical education for over fifty years in Europe and even in more remote lands (on account of being used by missionaries).

Very little is known about Clavius' early life other than the fact that he was born in Bamberg in either 1538 or 1537 (the exact year is somewhat unknown and depends on when one assumes a new year begins). His given name is not known to any great degree of certainty — it is thought by scholars to be perhaps Christoph Clau or Klau. There are also some who think that his taken name, "Clavius", may be a pun on his original German name, suggesting that his name may have been "Schlüssel" (German for "key", which is "clavis" in Latin).

Clavius joined the Jesuit order in 1555. He attended the University of Coimbra in Portugal, where it is possible that he had some kind of contact with the famous mathematician Pedro Nunes. Following this he went to Italy and studied theology at the Jesuit Collegio Romano in Rome. In 1579 he was assigned to compute the basis for a reformed calendar that would stop the slow process in which the Church's holidays were drifting relative to the seasons of the year. Using the Prussian Tables of Erasmus Reinhold, he proposed a calendar reform that was adopted in 1582 in Catholic countries by order of Pope Gregory XIII and is now the Gregorian calendar used worldwide.

Within the Jesuit order, Clavius was almost single-handedly responsible for the adoption of a rigorous mathematics curriculum in an age where mathematics was often ridiculed by philosophers and theologians.

As an astronomer Clavius held strictly to the geocentric model of the solar system, in which all the heavens rotate about the Earth. Though he opposed the heliocentric model of Copernicus, he recognized problems with the orthodox model. He was treated with great respect by Galileo, who visited him in 1611 and discussed the new observations being made with the telescope; Clavius had by that time accepted the new discoveries as genuine, though he retained doubts about the reality of the mountains on the Moon. Later, a large crater on the Moon, Clavius, was named in his honour.