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.

February 11: Carl Seyfert

Carl Keenan Seyfert

February 11, 1911 – June 13, 1960

Carl Seyfert was an American astronomer. He is best known for his 1943 research paper on high-excitation line emission from the centers of some spiral galaxies, which are named Seyfert galaxies after him. Seyfert's Sextet, a group of galaxies, is also named after him.

In 1936 he received his Ph.D. in astronomy. His thesis was "Studies of the External Galaxies", supervised by Harlow Shapley. The thesis dealt with colors and magnitudes of galaxies. In 1936 he joined the staff of the new McDonald Observatory in Texas, where he helped get the observatory started. He stayed until 1940, working with Daniel M. Popper on the properties of faint B stars and continuing his work on colors in spiral galaxies.

In 1940 he went to Mt. Wilson Observatory as a fellow with the National Research Council. He stayed until 1942, studying a class of active galaxies now called Seyfert galaxies. In 1942 he returned to Cleveland, at the Case Institute, where he taught navigation to military personnel and participated in secret military research. He also carried out some astronomical research at the Warner and Swasey Observatory of the Case Institute.

In 1946 he joined the faculty of Vanderbilt University in Nashville, Tennessee. The astronomy program at Vanderbilt was very small at the time. The university had only a small observatory, equipped with a 6-inch (150 mm) refractor, and only a modest teaching program. Seyfert worked diligently to improve the teaching program and to raise funds to build a new observatory. Within a few years, he had obtained significant public support from the Nashville community. As the result, the Arthur J. Dyer Observatory with its 24-inch (610 mm) reflector was completed in December 1953. Seyfert became director of the new observatory, a position he held until his death.

Carl Seyfert published many papers in the astronomical literature, on a wide variety of topics in stellar and galactic astronomy, as well as on observing methods and instrumentation.

In 1943 he published a paper on galaxies with bright nuclei that emit light with emission line spectra with characteristically broadened emission lines. The prototype example is Messier 77 (NGC 1068). It is this class of galaxies that is now known as Seyfert galaxies, in his honor.

During his time at the Case Institute, he and Nassau obtained the first good color images of nebulae and stellar spectra. In 1951 he observed and described a group of galaxies around NGC 6027, now known as Seyfert's Sextet. He was an active innovator in instrumentation, being involved in new techniques such as the astronomical use of photomultiplier tubes and television techniques, and electronically controlled telescope drives.

The Lunar crater Seyfert is named in his honor. The 24-inch (610 mm) telescope at Dyer Observatory was renamed for him.

February 10: Eugène Michel Antoniadi

Eugène Michel Antoniadi

March 1, 1870 – February 10, 1944

Eugène Michel Antoniadi was a Greek astronomer who spent most of his life in France. His first publications date from the late 1880s, and his last ones from 1941 or 1942. He is best known for his work concerning the planets Mars and Mercury, and drew the best pre-Space Age maps of them, despite the fact that his first attempts to draw a map of Mercury were flawed by his incorrect assumption that Mercury had synchronous rotation with the Sun.

He became a highly reputed observer of Mars, and at first supported the notion of Martian canals. In 1909, using the great 83-cm aperture refracting telescope of the Meudon Observatory near Paris under ideal observing conditions, he demonstrated that the so-called “canals” of Mars were optical illusions.

He is also famed for creating the Antoniadi scale of seeing, which is commonly used by amateur astronomers. Now the scale is seen as the metric system of astronomy, being used as a default measurement all over the world.

The scale is on a 5 point system, with one being the best seeing conditions and 5 being worst. The actual definitions are as follows:

I.   Perfect seeing, without a quiver.

II.  Slight quivering of the image with moments of calm lasting several seconds.

III. Moderate seeing with larger air tremors that blur the image.

IV. Poor seeing, constant troublesome undulations of the image.

V.  Very bad seeing, hardly stable enough to allow a rough sketch to be made.

Note: the scale is usually indicated by use of a Roman numeral.

Antoniadi was also a noted historian, as well as a superb artist, writing about the pyramids and Egyptian astronomy. In the early twentieth century he further demonstrated his skills as an architect by compiling a great three-volume work on the mosque of St Sophia in Constantinople (now Istanbul). He was also a strong chess player. His best result was equal first with Frank Marshall in a tournament in Paris in 1907, a point ahead of Savielly Tartakower.

A crater on Mars and the crater Antoniadi on the Moon were named in his honor, as well as Antoniadi Dorsum on Mercury itself. 

February 9: Nevil Maskelyne

Dr Nevil Maskelyne

October 6, 1732 – February 9, 1811

The Reverend Dr Nevil Maskelyne was the fifth English Astronomer Royal. He held the office from 1765 to 1811.

In 1758 Maskelyne was admitted to the Royal Society, which in 1761 despatched him to the island of St. Helena to observe the transit of Venus. This was an important observation since accurate measurements would allow the accurate calculation of Earth's distance from the Sun, which would in turn allow the scale of the solar system to be calculated.

Bad weather prevented any useful observations, however Maskelyne used his journey to develop a method of determining longitude using the position of the moon, the lunar distance method. He returned to England, resuming his position as curate at Chipping Barnet in 1761, and began work on a book, publishing the lunar distance method of longitude calculation in 1763 in The British Mariner's Guide, which included the suggestion that to facilitate the finding of longitude at sea, lunar distances should be calculated beforehand for each year and published in a form accessible to navigators. This proposal, the germ of the Nautical Almanac, was approved by the government, and under the care of Maskelyne the Nautical Almanac for 1767 was published in 1766. He further induced the government to print his observations annually.

The lunar distance method was the predominant method used well into the 19th century. Since Maskelyne's observations and calculations were made at the Royal Greenwich Observatory, the Greenwich meridian eventually became a common base for longitude worldwide and was adopted internationally as the Prime Meridian in 1884.

Maskelyne’s first contribution to astronomical literature was A Proposal for Discovering the Annual Parallax of Sirius, published in 1760. Subsequent contributions to the Transactions contained his observations of the transits of Venus (1761 and 1769), on the tides at Saint Helena (1762), and on various astronomical phenomena at Saint Helena (1764) and at Barbados (1764).

Maskelyne also introduced several practical improvements, such as the measurement of time to tenths of a second; and prevailed upon the government to replace Bird’s mural quadrant by a repeating circle 6 feet (1.8 m) in diameter. The new instrument was constructed by Edward Troughton but Maskelyne did not live to see it completed.

In 1775 he was awarded the Royal Society's Copley medal. The Lunar crater Maskelyne is named in his honor.

February 8: Fritz Zwicky

Fritz Zwicky

February 14, 1898 – February 8, 1974

Fritz Zwicky was a Bulgarian born, America-based Swiss astronomer. He was an original thinker, with many important contributions in theoretical and observational astronomy. His amazing scientific career is relatively unknown to the general public, but he remains a giant in the astronomical community.

He was responsible for positing numerous cosmological theories that have a profound impact on understanding of our universe today. He was appointed Professor of Astronomy at Caltech in 1942 and also worked as a research director/consultant for Aerojet Engineering Corporation (1943-1961) and staff member of Mount Wilson Observatory and Palomar Observatory for most of his career.

In an article titled “Idea Man” published in 2001 Stephen M. Maurer wrote that Zwicky will be “remembered as a gifted observational astronomer who had discovered more supernovae than everyone else in human history combined. Today, Zwicky’s reputation is bigger than ever, except that now astronomers think of him as a theorist. When researchers talk about neutron stars, dark matter, and gravitational lenses, they all start the same way: ‘Zwicky noticed this problem in the 1930s. Back then, nobody listened . . .’”

Together with colleague Walter Baade, Zwicky pioneered and promoted the use of the first Schmidt telescopes used in a mountain-top observatory in 1935. He hand-carried the Schmidt lens from Germany, which had been polished by the optician, Bernard Schmidt. In 1934 he and Baade coined the term "supernova" and hypothesized that they were the transition of normal stars into neutron stars, as well as the origin of cosmic rays. It was a prescient insight that had tremendous impact in determining the size and age of the universe in subsequent decades.

In support of this hypothesis, Zwicky started hunting for supernovae, and found a total of 120 by himself over a stretch of 52 years, a record which still stands as of 2006 (the current runner-up is Jean Mueller, with 98 discoveries and 9 co-discoveries).

While examining the Coma galaxy cluster in 1933, Zwicky was the first to use the virial theorem to infer the existence of unseen matter, what is now called dark matter. He was able to infer the average mass of galaxies within the cluster, and obtained a value about 160 times greater than expected from their luminosity, and proposed that most of the matter was dark. The same calculation today shows a smaller factor, based on greater values for the mass of luminous material; but it is still clear that the great majority of matter is dark.

Zwicky devoted considerable time to the search for galaxies and the production of catalogs. From 1961 to 1968 he and his colleagues published a comprehensive six volume Catalogue of galaxies and of clusters of galaxies. They were all published in Pasadena, by the California Institute of Techology.

In 1949, Truman awarded Zwicky the Presidential Medal of Freedom, for work on rocket propulsion during World War II. In 1968, Zwicky was made professor emeritus at California Institute of Technology. In 1972, Zwicky was awarded the Gold Medal of the Royal Astronomical Society, their most prestigious award, for "distinguished contributions to astronomy and cosmology". This award noted in particular his work on neutron stars, dark matter, and cataloging of galaxies. The asteroid 1803 Zwicky and the Lunar crater Zwicky are both named in his honour.

February 7: Johann Friedrich Julius Schmidt

Johann Friedrich Julius Schmidt

October 25, 1825 – February 7, 1884

Johann Schmidt was a German astronomer. When he was 14, he came into the possession of a copy of Selenotopographische Fragmente by Johann Hieronymus Schröter, and this influenced a lifelong interest in selenography, the study of the Moon. He went to school in Hamburg and visited Altona Observatory, where he became acquainted with the well-known map of the Moon made by Wilhelm Beer and Johann Heinrich Mädler.

In 1845 he obtained a position as an assistant at an observatory in Düsseldorf, but a year later joined the Bonn Observatory under Friedrich Wilhelm Argelander. In 1853 he became director of Baron von Unkrechtsberg's private observatory at Olmütz (today Olomouc, Czech Republic). In 1858 he became director of Athens Observatory, where he spent the rest of his career.

He spent most of his career since his youth making drawings of the Moon, preparing a map of it. In 1866 he made the astonishing claim that Linné crater had considerably changed its appearance, which began a controversy that continued for many decades. Coming from such a careful lifelong observer, the claim carried some weight; however, the claim is generally considered unproven.

By 1868 his map of the Moon was almost ready, although he did not put the finishing touches to it until 1874. This was the first map of the Moon to surpass the celebrated map of Beer and Mädler.

In 1878, Schmidt also edited and published all 25 sections of a moon map by Wilhelm Gotthelf Lohrmann. Lohrmann had completed his map in 1836 but had died in 1840; only the first four sections of the map had been published in 1824.

In addition to his study of the Moon, he also made many other observations of all kinds. He also discovered Nova Cygni 1876, also known as Q Cygni, on November 24, 1876.

When he died, the King and Queen of Greece attended the funeral oration at his observatory. The crater Schmidt on the Moon is jointly named for him and two other people of the same last name.

February 6: Edward Emerson Barnard

Edward Emerson Barnard

December 16, 1857 – February 6, 1923

Edward Emerson Barnard was an American astronomer. He was commonly known as E. E. Barnard, and was recognized as a gifted observational astronomer. He is best known for his discovery of Barnard's star in 1916, which is named in his honor.

His first interest was in the field of photography, and he became a photographer's assistant at the age of nine. He later developed an interest in astronomy. In 1876 he purchased a 5-inch (130 mm) refractor telescope, and in 1881 he discovered his first comet. (But he failed to announce his discovery). He found his second comet later the same year and a third in 1882. While he was still working at a photography studio he was married to the English-born woman Rhoda Calvert in 1881. In the 1880s a Hulbert Harrington Warner offered US$200 per discovery of a new comet. Edward discovered a total of eight, and used the money to build a house for himself and his bride.

With his name being brought to the attention of amateur astronomers in Nashville, they collectively raised enough money to give Edward a fellowship to Vanderbilt University. Barnard never graduated from the school, but he did receive the only honorary degree Vanderbilt has ever awarded. He joined the staff of the Lick Observatory in 1887, though he later clashed with the director, Edward S. Holden, over access to observing time on the larger instruments and other issues of research and management.

In 1892 he made observations of a nova and was the first to notice the gaseous emissions, thus deducing that it was a stellar explosion. The same year he also discovered Amalthea, the fifth moon of Jupiter. He was the first to discover a new moon of Jupiter since Galileo Galilei in 1609. This was the last satellite discovered by visual observation (rather than by examining photographic plates or other recorded images).

In 1895 he joined the University of Chicago as professor of astronomy. There he was able to use the 40-inch (1,000 mm) telescope at Yerkes Observatory. Much of his work during this period was taking photographs of the Milky Way. Together with Max Wolf, he discovered that certain dark regions of the galaxy were actually clouds of gas and dust that obscured the more distant stars in the background. From 1905, his niece Mary R. Calvert worked as his assistant and computer. 

The faint Barnard's Star is named for Edward Barnard after he discovered in 1916 that it had a very large proper motion, relative to other stars. This is the second nearest star system to the Sun, second only to the Alpha Centauri system.

He was also a pioneering astrophotographer. He cataloged a series of dark nebula giving them numerical designation akin to the Messier catalog. They begin with Barnard 1 and end with Barnard 366. He published his initial list with the 1919 paper in the Astrophysical Journal, "On the Dark Markings of the Sky with a Catalogue of 182 such Objects".

The Lunar crater Barnard is named in his honor.

February 5: Mariner 10 flyby of Venus

Mariner 10 passed Venus on February 5, 1974, 

at a closest range of 5,768 km at 17:01 UT

Mariner 10 was a robotic space probe launched on November 3, 1973 to fly by the planets Mercury and Venus. It was launched approximately 2 years after Mariner 9 and was the last spacecraft in the Mariner program (Mariner 11 and 12 were re-purposed to the Voyager program and redesignated Voyager 1 and Voyager 2). 

Mariner 10 was the seventh successful launch in the Mariner series and the first spacecraft to visit Mercury. It was also the first spacecraft to use the gravitational pull of one planet (Venus) to reach another (Mercury), and the first spacecraft mission to visit two planets. The spacecraft flew by Mercury three times in a retrograde heliocentric orbit and returned images and data on the planet. Mariner 10 returned the first-ever close-up images of Venus and Mercury. The primary scientific objectives of the mission were to measure Mercury's environment, atmosphere, surface, and body characteristics and to make similar investigations of Venus. Secondary objectives were to perform experiments in the interplanetary medium and to obtain experience with a dual-planet gravity-assist mission.

Mariner 10 was the first spacecraft to make use of an interplanetary "gravitational slingshot" maneuver, using Venus to bend its flight path and bring its perihelion down to the level of Mercury's orbit. This maneuver, inspired by the orbital mechanics calculations of the Italian scientist Giuseppe Colombo, put the spacecraft into an orbit that repeatedly brought it back to Mercury. Mariner 10 used the solar radiation pressure on its solar panels and its high-gain antenna as a means of attitude control during flight, the first spacecraft to use active solar pressure control.

The spacecraft passed Venus on February 5, 1974, at a closest range of 5768 km at 17:01 UT. Using a near-ultraviolet filter, it photographed the Cytherean chevron clouds and performed other atmospheric studies. It was discovered that extensive cloud detail could be seen via Mariner's ultra-violet camera filters. Venus's cloud cover is nearly featureless in visible light. Earth-based ultra-violet observation did reveal some indistinct blotching even before Mariner 10, but the detail seen by Mariner was a surprise to most researchers.

During its flyby of Venus, Mariner 10 discovered evidence of rotating clouds and a very weak magnetic field.

With its maneuvering gas just about exhausted, Mariner 10 started another orbit of the Sun. Engineering tests were continued until March 24, 1975, when the final depletion of the nitrogen supply was signaled by the onset of an un-programmed pitch turn. Commands were immediately sent to the spacecraft to turn off its transmitter, and radio signals to Earth ceased.

Presently, Mariner 10 is still orbiting the sun, although its on-board electronics have probably been damaged by the sun's radiation.

February 4: Satyendra Nath Bose

Satyendra Nath Bose

January 1, 1894 – February 4, 1974

Satyendra Nath Bose, FRS, was an Indian physicist from the state of West Bengal, specializing in mathematical physics. He is best known for his work on quantum mechanics in the early 1920s, providing the foundation for Bose-Einstein statistics and the theory of the Bose-Einstein condensate. He is honored as the namesake of the boson.

In his book, The Scientific Edge, the noted physicist Jayant Narlikar observed:

“S.N.Bose’s work on particle statistics (c. 1922), which clarified the behaviour of photons (the particles of light in an enclosure) and opened the door to new ideas on statistics of Microsystems that obey the rules of quantum theory, was one of the top ten achievements of 20th century Indian science and could be considered in the Nobel Prize class.”

In 1924 Bose wrote a paper deriving Planck's quantum radiation law without any reference to classical physics. After initial setbacks to his efforts to publish, he sent the article directly to Albert Einstein in Germany. Einstein, recognizing the importance of the paper, translated it into German himself and submitted it on Bose's behalf to the prestigious Zeitschrift für Physik. As a result of this recognition, Bose was able to leave India for the first time and spent two years in Europe, during which he worked with Louis de Broglie, Marie Curie, and Einstein.

Einstein adopted the idea and extended it to atoms. This led to the prediction of the existence of phenomena which became known as Bose-Einstein condensate, a dense collection of bosons (which are particles with integer spin, named after Bose), which was proven to exist by experiment in 1995.

February 3: Jean-Baptiste Biot

Jean-Baptiste Biot

April 21, 1774 – February 3, 1862

Jean-Baptiste Biot was a French physicist, astronomer and mathematician. In 1800 he became professor of physics at the Collège de France, through the influence of Pierre-Simon Laplace, from whom he had sought and obtained the favor of reading the proof sheets of the Mécanique céleste. Three years later, at an unusually early age, he was elected a member of the Academy of Sciences.

In the early 1800s, he studied the polarisation of light passing through chemical solutions, as well as the relationship between electrical current and magnetism. The Biot-Savart law, which describes the magnetic field generated by a steady current, is named after him and Félix Savart. Biot was the first to discover the unique optical properties of mica, and therefore the mica-based mineral biotite was named after him.

In 1804 Biot and Joseph Gay-Lussac made a hot-air balloon ascent to a height of five kilometres in an early investigation of the Earth's atmosphere. It was the first balloon ascent undertaken for scientific purposes.

His researches extended to almost every branch of physical science, but his most important work was of an optical character. He was especially interested in questions relating to the polarization of light, and his observations in this field, which gained him the Rumford medal of the Royal Society in 1840, laid the foundations of the polarimetric analysis of sugar.

Late in Biot's life, Pasteur demonstrated to him the opposite optical rotations (equal angle, but opposite direction) of polarized light passing through aqueous solutions of mirror-image crystals.

Biot was an extremely prolific writer, and besides a great number of scientific memoirs, biographies, etc., his published works include: Analyse de la mécanique céleste de M. Laplace (1801); Recueil d'observations géodésiques, astronomiques et physiques exécutées en Espagne et Écosse, with Arago (1821); Traité élémentaire d'astronomie physique (1805).

The Lunar crater Biot is named in his honor.

February 2: Ernst Zinner

Ernst Zinner

February 2, 1886 – August 30, 1970

Ernst Zinner was a German astronomer and noted historian of astronomy. After studies in Munich and Jena he obtained his PhD in 1907 at the University of Jena, followed by stays at the University of Lund, the University of Paris, and the Königstuhl Observatory in Heidelberg. 

On October 23, 1913 he rediscovered the Comet Giacobini-Zinner, which had been previously discovered by Michel Giacobini in 1900. His main work during this time was on variable stars. 

Dr. Ernst Zinner, director of the Remais-Sternwarte in Bamberg (Germany) 1926-1953 and distinguished historian of Renaissance astronomy, is well known to historians of scientific instruments through his manifold publications on instruments, amongst which his Deutsche und niederländische astronomische Instrumente des 11 – 18 Jahrhunderts (Munich: Beck, 1956), is certainly the most widely known.

Zinner was an untiring traveller, always interested to visit instrument collections or to see sundials on public buildings all over Europe before and after the Second World War. He painstakingly noted what he saw and which pictures he took, thereby accumulating an enormous reference collection on instruments.

His main astronomical work centered on stellar astronomy. His main speciality and interest, however, was Rennaissance Astronomy and the history of astronomical instruments, an area in which he started working in 1925. His obituaries quote a total of 9,000 printed pages on this subject, with the most significant ones focusing on biographies and cataloguing early astronomical works and instruments.

The Lunar crater Zinner is named in his honor.

February 1: Laurel Clark

Laurel Blair Salton Clark

March 10, 1961 – February 1, 2003

Laurel Clark was a medical doctor, United States Navy Captain, NASA astronaut and Space Shuttle mission specialist who was killed in the Space Shuttle Columbia disaster.

Clark underwent six months of aeromedical training at the Naval Aerospace Medical Institute in Pensacola, Florida and was designated as a Naval Flight Surgeon. She was stationed at MCAS Yuma, Arizona and assigned as Flight Surgeon for a Marine Corps AV-8B Night Attack Harrier Squadron (VMA 211). She made several deployments, including one overseas to the Western Pacific, practiced medicine in austere environments, and flew on multiple aircraft. Her squadron won the Marine Attack Squadron of the year for its successful deployment. She was then assigned as the Group Flight Surgeon for the Marine Aircraft Group (MAG 13).

Before her selection as an astronaut candidate she served as a Flight Surgeon for the Naval Flight Officer advanced training squadron (VT-86) in Pensacola, Florida. Clark was Board Certified by the National Board of Medical Examiners and held a Wisconsin Medical License. Her military qualifications included Radiation Health Officer, Undersea Medical Officer, Diving Medical Officer, Submarine Medical Officer, and Naval Flight Surgeon. She was a Basic Life Support Instructor, Advanced Cardiac Life Support Provider, Advanced Trauma Life Support Provider, and Hyperbaric Chamber Advisor.

Selected by NASA in April 1996, Clark reported to the Johnson Space Center in August 1996. After completing two years of training and evaluation, she was qualified for flight assignment as a mission specialist. From July 1997 to August 2000 Clark worked in the Astronaut Office Payloads/Habitability Branch. Clark flew aboard STS-107, logging 15 days, 22 hours, and 20 minutes in space.

STS-107 Columbia – The 16-day flight was a dedicated science and research mission. Working 24 hours a day, in two alternating shifts, the crew successfully conducted approximately 80 experiments. Clark's bioscience experiments included gardening in space, as she discussed only days before her death in an interview with Milwaukee media near her Wisconsin hometown. The STS-107 mission ended abruptly on February 1, 2003, when Columbia and her crew perished during re-entry, 16 minutes before scheduled landing.

Life continues in lots of places -- and life is a magical thing.

—Laurel Clark, in reference to her rose bushes.

Tributes

• Asteroid 51827 Laurelclark was named for Clark.
  
• Clark Hill in the Columbia Hills on Mars was named for Clark
  
• Clark Hall, in the Columbia Village apartments, at the Florida Institute of Technology is named after her.
  
• Dr. Laurel Salton Clark Memorial Fountain, in Racine, WI
  
• Laurel B. Clark and David M. Brown Aerospace Medicine Academic Center, located at the Naval Aerospace Medical Institute