December 20: Walter Sydney Adams

Walter Sydney Adams

December 20, 1876 – May 11, 1956

Walter Sydney Adams was an American astronomer.

He was born in Antioch, Syria to missionary parents, and was brought to the U.S. in 1885. He graduated from Dartmouth College in 1898, then continued his education in Germany. After returning to the U.S., he began a career in Astronomy that culminated when he became director of the Mount Wilson Observatory.

His primary interest was the study of stellar spectra. He worked on solar spectroscopy and co-discovered a relationship between the relative intensities of certain spectral lines and the absolute magnitude of a star. He was able to demonstrate that spectra could be used to determine whether a star was a giant or a dwarf.

In 1915 he began a study of the companion of Sirius and found that despite a size only slightly larger than the Earth, the surface of the star was brighter per unit area than the Sun and it was about as massive. Such a star later came to be known as a white dwarf.

Along with Theodore Dunham, he discovered the strong presence of carbon dioxide in the infrared spectrum of Venus.

Adams received the Gold Medal of the Royal Astronomical Society (1917), the Henry Draper Medal (1918), the Bruce Medal (1928) and the Henry Norris Russell Lectureship (1947).

The asteroid 3145 Walter Adams and a crater on Mars are named in his honor. The crater Adams on the Moon is jointly named after him, John Couch Adams and Charles Hitchcock Adams.

December 19: Albert Michelson

Albert Michelson

December 19, 1852 – May 9, 1931

Albert Abraham Michelson was an American physicist known for his work on the measurement of the speed of light and especially for the Michelson-Morley experiment. In 1907 he received the Nobel Prize in Physics. He became the first American to receive the Nobel Prize in sciences.

Michelson was born in Strzelno, Provinz Posen in the Kingdom of Prussia (now Poland). He moved to the United States with his parents in 1855, when he was two years old.

President Ulysses S. Grant awarded Michelson a special appointment to the U.S. Naval Academy in 1869. During his four years as a midshipman at the Academy, Michelson excelled in optics, heat and climatology as well as drawing. After his graduation in 1873 and two years at sea, he returned to the Academy in 1875 to become an instructor in physics and chemistry until 1879. In 1879, he was posted to the Nautical Almanac Office, Washington, to work with Simon Newcomb, but in the following year, he obtained leave of absence to continue his studies in Europe. He visited the Universities of Berlin and Heidelberg, and the Collège de France and École Polytechnique in Paris.

Michelson was fascinated with the sciences and the problem of measuring the speed of light in particular. While at Annapolis, he conducted his first experiments of the speed of light, as part of a class demonstration in 1877. After two years of studies in Europe, he resigned from the Navy in 1881. In 1883 he accepted a position as professor of physics at the Case School of Applied Science in Cleveland, Ohio and concentrated on developing an improved interferometer. In 1887 he and Edward Morley carried out the famous Michelson-Morley experiment which seemed to rule out the existence of the aether. He later moved on to use astronomical interferometers in the measurement of stellar diameters and in measuring the separations of binary stars.

In 1907, Michelson had the honor of being the first American to receive a Nobel Prize in Physics "for his optical precision instruments and the spectroscopic and meteorological investigations carried out with their aid". He also won the Copley Medal in 1907, the Henry Draper Medal in 1916 and the Gold Medal of the Royal Astronomical Society in 1923.

The Lunar crater Michelson is named in his honor.

December 18: Gottfried Kirch

Gottfried Kirch

December 18, 1639 — July 25, 1710

Gottfried Kirch was a German astronomer. He first worked as a calendar-maker in Saxonia and Franconia. He began to learn astronomy in Jena, and studied under Hevelius in Danzig. In Danzig in 1667, Kirch published calendars and built several telescopes and instruments.

In 1686, Kirch went to Leipzig. There, he observed the great comet of 1686, together with Christoph Arnold. At Leipzig, Kirch also met his second wife, Maria Winckelmann (1670-1720), who had learned astronomy from Arnold. In 1688, he invented and charted the now obsolete constellation Sceptrum Brandenburgicum, the Brandenburg Scepter. Later, in 1699, he observed comet 55P/Tempel-Tuttle but this observation was not recognized until later analysis by Joachim Schubart.

In 1700, Kirch was appointed by Frederick I of Prussia as the first astronomer of the Prussian Royal Society of Sciences.

Kirch studied the double star Mizar, and discovered both the Wild Duck Cluster (Messier 11) (1681) and Globular Cluster M5 (May 5, 1702). He also discovered the variability of the Mira variable Chi Cygni in 1686.

The Lunar crater Kirch and the asteroid 6841 Gottfriedkirch are named in his honor.

December 6: Yoshio Nishina

Yoshio Nishina

December 6, 1890 – January 10, 1951

Yoshio Nishina was the founding father of modern physics research in Japan. He co-authored the well-known Klein-Nishina Formula. He was a principal investigator of RIKEN and mentored generations of physicists, including two Novel Laureates: Hideki Yukawa and Sin-Itiro Tomonaga. During World War II he was the head of the Japanese atomic program.

Nishina was born in Satosho, Okayama and graduated from Tokyo Imperial University in 1918. After graduation, he became a staff member at RIKEN. In 1921 he was sent to Europe for research. He visited some European universities and institutions, including Cavendish Laboratory, Georg August University of Göttingen, and University of Copenhagen. In Copenhagen he did research with Niels Bohr and they became good friends. In 1928 he wrote a paper on incoherent or Compton scattering with Oskar Klein in Copenhagen, from which the Klein-Nishina formula derives.

In the same year he returned to Japan, where he endeavored to foster an environment for the study of quantum mechanics. He invited some Western scholars to Japan including Heisenberg, Dirac and Bohr to stimulate Japanese physicists. He detected what turned out to be the muon in cosmic rays, independently of Anderson et al.

His research was concerned with cosmic rays and particle accelerator development.

In 1946 he was awarded the Order of Culture by the Emperor of Japan.

The Lunar crater Nishina is named in his honor.

December 5: Werner Heisenberg

Werner Heisenberg

December 5, 1901 – February 1, 1976

Werner Heisenberg was a German theoretical physicist who made foundational contributions to quantum mechanics and is best known for asserting the uncertainty principle of quantum theory. In addition, he also made important contributions to nuclear physics, quantum field theory, and particle physics.

Heisenberg, along with Max Born and Pascual Jordan, set forth the matrix formulation of quantum mechanics in 1925. Heisenberg was awarded the 1932 Nobel Prize in Physics.

Following the war, he was appointed director of the Kaiser Wilhelm Institute for Physics, which was soon thereafter renamed the Max Planck Institute for Physics. He was director of the institute until it was moved to Munich in 1958, when it was expanded and renamed the Max Planck Institute for Physics and Astrophysics.

Heisenberg was also president of the German Research Council, chairman of the Commission for Atomic Physics, chairman of the Nuclear Physics Working Group, and president of the Alexander von Humboldt Foundation.

Heisenberg studied under Arnold Sommerfeld, who was born on this date in 1868. Sommerfeld was a German theoretical physicist who pioneered developments in atomic and quantum physics, and also educated and groomed a large number of students for the new era of theoretical physics. He introduced the fine-structure constant into quantum mechanics.

December 4: Wilhelm Tempel

Ernst Wilhelm Leberecht Tempel

December 4, 1821 – March 16, 1889

Wilhelm Tempel, was a German astronomer who worked in Marseille until the outbreak of the Franco-Prussian War in 1870, then later moved to Italy.

He was a prolific discoverer of comets, discovering or co-discovering 21 in all, including Comet 55P/Tempel-Tuttle, now known to be the parent body of the Leonid meteor shower, and 9P/Tempel, the target of the NASA probe Deep Impact in 2005.

Other periodic comets that bear his name include 10P/Tempel and 11P/Tempel-Swift-LINEAR.

The asteroid 3808 Tempel and the Lunar crater Tempel are named in his honor.

November 20: Edwin Powell Hubble

Edwin Powell Hubble

November 20, 1889 – September 28, 1953

Edwin Hubble was an American astronomer. He profoundly changed our understanding of the universe by demonstrating the existence of other galaxies besides the Milky Way. He also discovered that the degree of redshift observed in light coming from a galaxy increased in proportion to the distance of that galaxy from the Milky Way. This became known as Hubble's law, and would help establish that the known universe is expanding.

In 1919, Hubble was offered a staff position in California by George Ellery Hale, the founder and director of the Carnegie Institution's Mount Wilson Observatory, near Pasadena, California, where he remained on the staff until his death. Shortly before his death, Mount Palomar's giant 200-inch (5.1 m) reflector Hale Telescope was completed, and Hubble was the first astronomer to use it. Hubble continued his research at the Mount Wilson and Mount Palomar Observatories, where he remained active until his death.

Edwin Hubble's arrival at Mount Wilson, California, in 1919 coincided roughly with the completion of the 100-inch (2.5 m) Hooker Telescope, then the world's largest telescope. At that time, the prevailing view of the cosmos was that the universe consisted entirely of the Milky Way Galaxy. Using the Hooker Telescope at Mt. Wilson, Hubble identified Cepheid variables (a kind of star; see also standard candle) in several spiral nebulae, including the Andromeda Nebula. His observations, made in 1922–1923, proved conclusively that these nebulae were much too distant to be part of the Milky Way and were, in fact, entire galaxies outside our own. This idea had been opposed by many in the astronomy establishment of the time, in particular by the Harvard University-based Harlow Shapley. Hubble's discovery, announced on January 1, 1925, fundamentally changed the view of the universe.

Hubble also devised the most commonly used system for classifying galaxies, grouping them according to their appearance in photographic images. He arranged the different groups of galaxies in what became known as the Hubble sequence.

Hubble was awarder the Bruce Medal (1938) and the Gold Medal of the Royal Astronomical Society (1940).

The Lunar crater Hubble, asteroid 2069 Hubble and the orbiting Hubble Space Telescope are named in his honor.

October 30: Marcin Poczobutt

Marcin Odlanicki Poczobutt

October 30, 1728 – February 7, 1810

Marcin Poczobutt was a Polish-Lithuanian astronomer, jesuit and mathematician.

He became mathematics professor and rector of the Vilnius University where he organized the construction of the university's observatory and the purchase of the equipment. He also made observations of solar and lunar eclipses, comets and asteroids. In addition, he made measurements of Mercury to compute an orbit, and also determined the geographic coordinates of locations in Lithuania, including Vilnius.

He was granted the title of the King's Astronomer and became a member of the British Royal Academy of Science.

The Lunar crater Poczobutt is named in his honor.

October 29: Richard Hawley Tucker

Richard Hawley Tucker

October 29, 1859 – March 31, 1952

Richard Tucker was an American astronomer.

He was born in Wiscasset, Maine to a ship-owning and sea-faring family. After a brief stint at sea starting at age 14, he attended Lehigh University where he studied civil engineering but became interested in the study of astronomy. He graduated in 1879 and became an assistant at Dudley Observatory. He remained there for four years, and briefly worked with the United States Coast and Geodetic Survey.

In 1883 he joined Lehigh as an instructor of mathematics and astronomy. A year later he was offered a position with the Argentine National Observatory, where he would assist in a survey of the southern night sky. He remained there for nine years, then joined the staff of Lick Observatory in 1893. He remained at Lick until 1908, operating the Meridian Circle program to make precise measurements of star positions.

In 1908 he would travel to San Louis, Argentina as part of an expedition to measure the positions of stars in the southern part of the sky. These measurements were to be incorporated into a catalog for Dudley Observatory. During his time there he made 20,800 observations of stars.

After his work in Argentina, he returned to Lick Observatory. In 1914 he married Ruth Standen, a secretary at Lick. He remained at the observatory until he retired in 1926, when he became Astronomer Emeritus. He spent his retirement years in Palo Alto, California.

During his career he published fifty three scientific articles.

The Lunar crater Tucker is named in his honor.

October 27: Thomas Gwyn Elger

Image Credit: C.A. Wood Collection

Thomas Gwyn Empy Elger

October 27, 1836 – January 9, 1897

Thomas Elger was an English lunar mapper and the first director of the Lunar Section of the British Astronomical Association (BAA).

He was born in Bedford, where the family had been established for several generations. His father Thomas Gwyn Elger (1794–April 4, 1841) was an architect and builder. Grandfather, father and son engaged in the town politics, and all held the post of mayor.

He studied at University College London and adopted the profession of a civil engineer. He was engaged in several important works, including the Metropolitan Railway and the Severn Valley Railway. His surveys for railway construction in Holstein were put to a stop by the war with Prussia and Austria in 1864.

Soon afterwards he relinquished the active pursuit of his profession and devoted himself to scientific studies. He had developed a strong taste for astronomy already at an early age and erected his first observatory in Bedford. Elger observed with an 8.5 inch reflector. His sketches from 1884 to 1896 are now in the possession of the BAA. He is best known as a careful and indefatigable selenographer, and for this work his artistic skill eminently qualified him.

He is most remembered for his book The Moon: A full Description and Map of its Principal Physical Features. Published in 1895, its maps are still highly regarded by lunar observers due to their uncluttered nature.

Elger was member of several astronomical associations, as the Royal Astronomical Society, the short-lived Selenographical Society and the British Astronomical Association. Besides his astronomical work, he was an ardent archaeologist and founded the Bedfordshire Natural History Society and Field Club.

The Lunar crater Elger is named in his honor.

October 26: Lewis Boss

Lewis Boss

October 26, 1846 - October 12, 1912

Lewis Boss was an American astronomer. He was born in Providence, Rhode Island. In 1870 he graduated from Dartmouth College, then went to work as a clerk for the U.S. Government. He served as an assistant astronomer for a government expedition to survey the U.S-Canadian border. In 1876 he became the director of the Dudley Observatory in Schenectady, New York.

He became editor of the Astronomical Journal in 1909, but responsibility passed to his son, Benjamin Boss, upon his death in 1912. Benjamin continued to edit the journal until 1941.

Lewis Boss is noted for his work in cataloguing the locations and proper motions of stars. He also led an expedition to Chile in 1882 to observe the transit of Venus, and also catalogued information concerning cometary orbits.

In 1910, he published Preliminary General Catalogue of 6188 Stars for the Epoch 1900, a compilation of the proper motions of stars. This catalog was later expanded after his death by his son Benjamin Boss.

His most significant discovery was the calculation of the convergent point of the Hyades star cluster.

Boss was awarded the Gold Medal of the Royal Astronomical Society in 1905.

The Lunar crater Boss is named in his honor.

October 25: Henry Norris Russell

Henry Norris Russell

October 25, 1877 – February 18, 1957

Henry Norris Russell was an American astronomer who, along with Ejnar Hertzsprung, developed the Hertzsprung-Russell diagram (1910). In 1923, working with Frederick Saunders, he developed Russell-Saunders coupling which is also known as LS coupling.

Russell was born in 1877 in Oyster Bay, New York. He studied astronomy at Princeton University, obtaining his B.A. in 1897 and his doctorate in 1899, studying under Charles Augustus Young. From 1903 to 1905, he worked at the Cambridge Observatory with Arthur Robert Hinks as a research assistant of the Carnegie Institution and came under the strong influence of George Darwin.

He returned to Princeton to become an instructor in astronomy (1905-1908), assistant professor (1908-1911), professor (1911-1927) and research professor (1927-1947). He was also the director of the Princeton University Observatory from 1912 to 1947.

He co-wrote an influential two-volume textbook in 1927 with Raymond Smith Dugan and John Quincy Stewart: Astronomy: A Revision of Young’s Manual of Astronomy (Ginn & Co., Boston, 1926–27, 1938, 1945). This became the standard astronomy textbook for about two decades. There were two volumes: the first was The Solar System and the second was Astrophysics and Stellar Astronomy. The textbook popularized the idea that a star's properties (radius, surface temperature, luminosity, etc.) were largely determined by the star's mass and chemical composition, which became known as the Vogt-Russell theorem (including Hermann Vogt who independently discovered the result). Since a star's chemical composition gradually changes with age (usually in a non-homogeneous fashion), stellar evolution results.

The Lunar crater Russell is named in his honor.

October 24: Wilhelm Eduard Weber

Wilhelm Eduard Weber

October 24, 1804 – June 23, 1891

Wilhelm Weber was a German physicist and, together with Carl Friedrich Gauss, inventor of the first electromagnetic telegraph.

During 1831, on the recommendation of Carl Friedrich Gauss, he was hired by the University of Göttingen as professor of physics, at the age of twenty-seven. His lectures were interesting, instructive, and suggestive. Weber thought that, in order to thoroughly understand physics and apply it to daily life, mere lectures, though illustrated by experiments, were insufficient, and he encouraged his students to experiment themselves, free of charge, in the college laboratory.

As a student of twenty years he, with his brother, Ernst Heinrich Weber, Professor of Anatomy at Leipzig, had written a book on the Wave Theory and Fluidity, which brought its authors a considerable reputation. Acoustics was a favourite science of his, and he published numerous papers upon it in Poggendorffs Annalen, Schweigger's Jahrbücher für Chemie und Physik, and the musical journal Carcilia. The 'mechanism of walking in mankind' was another study, undertaken in conjunction with his younger brother, Eduard Weber. These important investigations were published between the years 1825 and 1838. Gauss and Weber constructed the first electromagnetic telegraph during 1833, which connected the observatory with the institute for physics in Göttingen.

Dismissed by the Hanoverian Government for his liberal political opinions, Weber travelled for a time, visiting England, among other countries, and became professor of physics in Leipzig from 1843 to 1849, when he was reinstalled at Göttingen. One of his most important works was the Atlas des Erdmagnetismus ("atlas of geomagnetism"), a series of magnetic maps, and it was chiefly through his efforts that magnetic observatories were instituted. He studied magnetism with Gauss, and during 1864 published his Electrodynamic Proportional Measures containing a system of absolute measurements for electric currents, which forms the basis of those in use.

He was elected a foreign member of the Royal Swedish Academy of Sciences during 1855.

The Lunar crater Weber and the SI unit of magnetic flux, the weber (symbol: Wb) are named in his honor. He is also known for first use of 'c' for speed of light.

October 23: Gustav Spörer

Friederich Wilhelm Gustav Spörer

October 23, 1822 – July 7, 1895

Gustav Spörer was a German astronomer.

He is noted for his studies of sunspots and sunspot cycles. In this regard he is often mentioned together with Edward Maunder. Spörer was the first to note a prolonged period of low sunspot activity from 1645 to 1715. This period is known as the Maunder Minimum.

Spörer was a contemporary of Richard Christopher Carrington, an English astronomer. Carrington is generally credited with discovering Spörer's law, which governs the variation of sunspot latitudes during the course of a solar cycle. Spörer added to Carrington's observations of sunspot drift and is sometimes credited with the discovery.

The Spörer minimum was a period of low sunspot activity from roughly 1420 to 1570.

The Lunar crater Spörer is named in his honor.

October 22: Albert Whitford

Albert Edward Whitford

October 22, 1905 – March 28, 2002

Albert Whitford was an American astronomer.

Whitford was born in Milton, Wisconsin and attended Milton College. He received his PhD from the University of Wisconsin–Madison. He served as the director of Washburn Observatory from 1948 to 1958. From 1958 to 1968 he was the director of Lick Observatory. Later he served on the faculties of both the University of California, Santa Cruz and the University of Wisconsin–Madison.

Whitford was a pioneer in the field of photoelectric photometry, greatly improving sensitivity. The Whitford reddening curve, quantifying the interstellar absorption of light, was important in the mapping of the distribution of stars in the Milky Way. He also studied the stars in galactic nuclear bulges.

In 1986 Whitford received the Henry Norris Russell Lectureship and in 1996 he was awarded the Bruce Medal.

The asteroid 2301 Whitford is named in his honor.

October 20: Christopher Wren

Sir Christopher Wren

October 20, 1632 – February 25, 1723

Christopher Wren was one of the best known and highest acclaimed English architects in history, responsible for rebuilding 55 churches in the City of London after the Great Fire in 1666, including his masterpiece St Paul's Cathedral, completed in 1710.

Educated in Latin and Aristotelian physics at the University of Oxford, Wren was a notable astronomer, geometer, mathematician-physicist as well as an architect. He was a founder of the Royal Society (president 1680–82), and his scientific work was highly regarded by Sir Isaac Newton and Blaise Pascal.

One of Wren's friends, another great scientist and architect in his time, Robert Hooke said of him "Since the time of Archimedes there scarce ever met in one man in so great perfection such a mechanical hand and so philosophical mind."

When a fellow of All Souls, Wren constructed a transparent beehive for scientific observation; he began observing the moon, which was to lead to the invention of micrometers for the telescope. He experimented on terrestrial magnetism and had taken part in medical experiments, performing the first successful injection of a substance into the bloodstream (of a dog).

In Gresham College, he did experiments involving determining longitude through magnetic variation and through lunar observation to help with navigation, and helped construct a 35-foot (11 m) telescope with Sir Paul Neile. Wren also studied and improved the microscope and telescope at this time. He had also been making observations of the planet Saturn from around 1652 with the aim of explaining its appearance. His hypothesis was written up in De corpore saturni but before the work was published, Huygens presented his theory of the rings of Saturn. Immediately Wren recognized this as a better hypothesis than his own and De corpore saturni was never published. In addition, he constructed an exquisitely detailed lunar model and presented it to the king.

A year into Wren's appointment as a Savilian Professor in Oxford, the Royal Society was created and Wren became an active member. As a Savilian Professor, Wren studied thoroughly in mechanics, especially in elastic collisions and pendulum motions, which he studied extensively. He also directed his far-ranging intelligence to the study of meteorology, and fabricated a "weather-clock" that recorded temperature, humidity, rainfall and barometric pressure, which could be used to predict the weather.

Another topic to which Wren contributed was optics. He published a description of an engine to create perspective drawings and he discussed the grinding of conical lenses and mirrors. Out of this work came another of Wren's important mathematical results, namely that the hyperboloid of revolution is a ruled surface. These results were published in 1669. In subsequent years, Wren continued with his work with the Royal Society, although after the 1680s his scientific interests seem to have waned: no doubt his architectural and official duties absorbed all his time.

Mentioned above are only a few of Wren’s scientific works. He also studied in other areas not mentioned, ranging from agriculture, ballistics, water and freezing, to investigating light and refraction only to name a few. Thomas Birch's History of the Royal Society is one of the most important sources of our knowledge not only of the origins of the Society, but also the day to day running of the Society. It is in these records that the majority of Wren’s scientific works are recorded.

October 19: Subrahmanyan Chandrasekhar

Subrahmanyan Chandrasekhar

October 19, 1910 – August 21, 1995

Subrahmanyan Chandrasekhar was an Indian American astrophysicist. He was a Nobel laureate in physics along with William Alfred Fowler for their work in the theoretical structure and evolution of stars. He was the nephew of Indian Nobel Laureate Sir C. V. Raman.

Chandrasekhar served on the University of Chicago faculty from 1937 until his death in 1995 at the age of 84. He became a naturalized citizen of the United States in 1953.

Chandrasekhar (Chandra) was born in Lahore, India (present day Pakistan). Chandra was awarded a Government of India scholarship to pursue graduate studies at the University of Cambridge, where he was admitted to Trinity College and became a research student of Professor R. H. Fowler. On the advice of Prof. P. A. M. Dirac, as part of his graduate studies, Chandra spent a year at the Institut for Teoretisk Fysik in Copenhagen, where he met Prof. Niels Bohr.

In January 1937, Chandrasekhar was recruited to the University of Chicago faculty as Assistant Professor by Dr. Otto Struve and President Robert Maynard Hutchins. He was to remain at the university for his entire career, becoming Morton D. Hull Distinguished Service Professor of Theoretical Astrophysics in 1952 and attaining emeritus status in 1985.

Chandrasekhar developed a style of working continuously in one specific area of physics for a number of years; consequently, his working life can be divided into distinct periods. He studied stellar structure, including the theory of white dwarfs, during the years 1929 to 1939, and subsequently focused on stellar dynamics from 1939 to 1943. Next, he concentrated on the theory of radiative transfer and the quantum theory of the negative ion of hydrogen from 1943 to 1950. This was followed by sustained work on hydrodynamic and hydromagnetic stability from 1950 to 1961. In the 1960s, he studied the equilibrium and the stability of ellipsoidal figures of equilibrium, but also general relativity. During the period, 1971 to 1983 he studied the mathematical theory of black holes, and, finally, during the late 80s, he worked on the theory of colliding gravitational waves.

From 1952 to 1971 Chandrasekhar was editor of the Astrophysical Journal.

During the years 1990 to 1995, Chandrasekhar worked on a project devoted to explaining the detailed geometric arguments in Sir Isaac Newton's Philosophiae Naturalis Principia Mathematica using the language and methods of ordinary calculus. The effort resulted in the book Newton's Principia for the Common Reader, published in 1995. Chandrasekhar was an honorary member of the International Academy of Science.

Chandrasekhar's most famous success was the astrophysical Chandrasekhar limit. The limit describes the maximum mass of a white dwarf star, ~1.44 solar masses, or equivalently, the minimum mass, above which a star will ultimately collapse into a neutron star or black hole (following a supernova). The limit was first calculated by Chandrasekhar in 1930 during his maiden voyage from India to Cambridge, England for his graduate studies.

In 1999, NASA named the third of its four "Great Observatories'" after Chandrasekhar. The Chandra X-ray Observatory was launched and deployed by Space Shuttle Columbia on July 23, 1999.

The asteroid 1958 Chandra is also named after Chandrasekhar.

Chandrasekhar was the mathematics professor of the renowned American astronomer Carl Sagan at the University of Chicago. In his book The Demon-Haunted World Sagan wrote "I discovered what true mathematical elegance is from Subrahmanyan Chandrasekhar."

October 18: Pascual Jordan

Pascual Jordan

October 18, 1902 - July 31, 1980

Pascual Jordan was a theoretical and mathematical physicist who made significant contributions to quantum mechanics and quantum field theory. He contributed much to the mathematical form of matrix mechanics, and developed canonical anticommutation relations for fermions. While the Jordan algebra he invented is no longer employed in quantum mechanics, it has found other mathematical applications.

Jordan joined the Nazi party and became a brownshirt, a political affiliation which isolated him within the physics community.

Jordan enrolled in the Hanover Technical University in 1921 where he studied an eclectic mix of zoology, mathematics, and physics. As was typical for a German university student of the time, he shifted his studies to another university before obtaining a degree. Göttingen University, his destination in 1923, was then at the very zenith of its prowess and fame in mathematics and the physical sciences. At Göttingen Jordan became an assistant first to mathematician Richard Courant and then to physicist Max Born.

Together with Max Born and Werner Heisenberg he was co-author of an important series of papers on quantum mechanics. He went on to pioneer early quantum field theory before largely switching his focus to cosmology before World War II.

Jordan devised a type of non-associative algebras, now named Jordan algebras in his honor, in an attempt to create an algebra of observables for quantum mechanics and quantum field theory. Today, von Neumann algebras are employed for this purpose. Jordan algebras have since been applied in projective geometry and number theory.

Had Jordan not joined the Nazi party, it is conceivable that he could have shared the 1954 Nobel Prize in Physics awarded to Max Born.

October 17: Peter Nilson

Peter Nilson

October 17, 1937 – March 8, 1998

Peter Nilson was a Swedish astronomer and novelist. Active at Uppsala University, he compiled a catalogue of galaxies. He was appreciated for a number of essay books (primarily about science) and for a number of science fiction novels like "The Space Guardian."

He was born in a Smålandian village and under the early teens a farmer, but science, with its celebrities such as Charles Darwin and Albert Einstein made such an impression on him, as to motivate him to accomplish college studies by letter correspondence.

In the early 1960's he began his studies in Uppsala University, initially in mathematics, and thereafter theoretical physics, aesthetics, history of ideas and astronomy.

He was elected a member of the Royal Swedish Academy of Sciences in 1993.

October 16: Frederick Eugene Wright

Dr. Frederick Eugene Wright

October 16, 1877 – August 25, 1953

Frederick Wright was an American optician and geophysicist. He was the second president of the Optical Society of America from 1918-1919.

He was born in Marquette, Michigan, and his father was a state geologist. In 1895 his mother took Frederick and his two brothers to Germany where he would complete his education. He was awarded his Ph.D. summa cum laude from the University of Heidelberg.

After returning to the United States, he taught at the Michigan College of Mines and became the Assistant State Geologist. He moved to Washington D.C. in 1904, joining the United States Geological Survey. He then spent some time in exploration of Alaska. In 1906 he joined the Carnegie Institution as a member of their Geophysical Laboratory. He remained on the staff until his retirement in 1944.

In 1906 he met Kathleen Finley and in 1909 they were married. Their daughter Helen Wright (1914-1997) who became a pioneer in the study of science history.

Among his contributions were studies in the military uses of optical glass; physical study of lunar features based on the properties of the reflected light, and the precambrian geology of the region near Lake Superior. At the time of his death he was considered the foremost authority on the Moon.

Wright was co-author of a major 1963 summary: "The Lunar Surface: Introduction" in The Moon, Meteorites and Comets (Edited by Middlehurst and GP Kuiper). F.E. Wright also was responsible for creating one of the most remarkable - and rare - lunar globes ever. Photographic emulsions were deposited on globes and then telescopic images were projected onto the globes. Some globes were made of glass and had light bulbs within - apparently, they "beautifully and realistically simulate the Moon."

He served as the home secretary of the National Academy of Sciences for two decades. He was a member of the Optical Society of America, and was president for three years. In 1941 he became president of the Mineralogical Society of America. He was also a member of the London Physical Society, a fellow of the American Academy of Arts and Sciences.

The crater Wright on the Moon is co-named for him and two others.

October 13: Peter Barlow

Peter Barlow

October 13, 1776 – March 1, 1862

Peter Barlow was an English mathematician and physicist.

In 1801, Barlow was appointed assistant mathematics master at the Royal Military Academy, Woolwich, and retained this post until 1847. He contributed articles on mathematics to The Ladies' Diary as well as publishing books such as: An Elementary Investigation of the Theory of Numbers (1811); A New Mathematical and Philosophical Dictionary (1814); and New Mathematical Tables (1814).

The latter became known as Barlow's Tables and gives squares, cubes, square roots, cube roots, and reciprocals of all numbers from 1 to 10,000. These tables were regularly reprinted until 1965, when computers rendered them obsolete. Barlow also contributed largely to the Encyclopaedia Metropolitana.

Barlow made an important contribution to astronomy by inventing the Barlow lens, an achromatic telescope lens in which two glass layers enclosed a colourless liquid (later replaced by a different kind of glass).

In 1823 he was made a fellow of the Royal Society and two years later received its Copley Medal for his work on correcting the deviation in ship compasses caused by the presence of iron in the hull. Some of his magnetic research was done in collaboration with Samuel Hunter Christie. Barlow's Wheel is an early electric motor he invented, while Barlow's law is an (incorrect) law describing electrical conductance.

October 12: Carl August von Steinheil

Carl August von Steinheil

October 12, 1801 – September 14, 1870

Carl August von Steinheil was a German physicist.

Steinheil was born in Ribeauvillé, Alsace. He studied law in Erlangen then astronomy in Göttingen and Königsberg. He continued his studies in astronomy and physics when he started living on his father's manor in Perlachseck near Munich. He was professor for mathematics and physics at the University of Munich from 1832 to 1849.

In 1839, Steinheil used silver chloride and a cardboard camera to make pictures in negative from the Museum of Art and the Munich Frauenkirche, then taking another picture of the negative to get a positive, the actual black and white reproduction of a view on the object. The round pictures were about four cm wide, the way to get these pictures was called Steinheil method.

In 1846 Steinheil was called to Naples to install a new system for weight and measure units. Three years later, he was in the Board of Telegraphy in the Austrian Trade Ministry, designing a telegraph network for the entire empire, and helped to form the "Deutsch-Österreichischer Telegraphenverein" (German-Austrian Telegraph Society). In 1851 he started the Swiss telegraph network, when he returned to Munich as 'Konservator' of the mathematic-physical collections and ministerial secretary in the Trade Ministry of Bavaria.

He founded the optical-astronomical company C.A. Steinheil und Söhne to build telescopes, spectroscopes and photometers (his invention, used to measure brightness). In 1852 he added refractors and reflectors with silver-covered mirrors to the production. The silvering was done in a process developed by his friend Justus Liebig. Since 1862, his sons continued his company.

The Lunar crater Steinheil is named in his honor.

October 11: Heinrich Olbers

Heinrich Wilhelm Matthäus Olbers

October 11, 1758 – March 2, 1840

Heinrich Olbers was a German physician and astronomer.

Olbers was born in Arbergen, near Bremen, and studied to be a physician at Göttingen. After his graduation in 1780, he began practicing medicine in Bremen, Germany. At night he dedicated his time to astronomical observation, making the upper story of his home into an observatory. He also devised the first satisfactory method of calculating cometary orbits.

On March 28, 1802, Olbers discovered and named the asteroid Pallas. Five years later, on March 29, 1807, he discovered the asteroid Vesta, which he allowed Carl Friedrich Gauss to name. As the word "asteroid" was not yet coined, the literature of the time referred to these minor planets as planets in their own right. He proposed that the asteroid belt, where these objects lay, was the remnants of a planet that had been destroyed. The current view of most scientists is that tidal effects from the planet Jupiter disrupt the formation of planets in the asteroid belt.

On March 6, 1815, Olbers also discovered a periodic comet, now named after him (formally designated 13P/Olbers).

Olbers' paradox, described by him in 1823 (and then reformulated in 1826), states that the darkness of the night sky conflicts with the supposition of an infinite and eternal static universe.

In 1827, he was elected a foreign member of the Royal Swedish Academy of Sciences.

The crater Olbers on the Moon, the asteroid 1002 Olbersia and a 200-km-diameter dark albedo feature on Vesta's surface are all named in his honor.