September 27: Martin Ryle

Martin Ryle

September 27, 1918 - October 14, 1984

Sir Martin Ryle was an English radio astronomer who developed revolutionary radio telescope systems (e.g. aperture synthesis) and used them for accurate location and imaging of weak radio sources. In 1946 Ryle and Vonberg were the first people to publish interferometric astronomical measurements at radio wavelengths, although it is claimed that Joseph Pawsey from the University of Sydney had actually made interferometric measurements earlier in the same year. With improved equipment, Ryle observed the most distant known galaxies in the universe at that time. He was the first Professor of Radio Astronomy at the University of Cambridge, and founding director of the Mullard Radio Astronomy Observatory. He was Astronomer Royal from 1972 to 1982.

Ryle and Antony Hewish shared the Nobel Prize for Physics in 1974, the first Nobel prize awarded in recognition of astronomical research.

The focus of early work in Cambridge was on radio waves from the Sun. Ryle's interest quickly shifted to other areas, however, and to explore those he decided early on that the Cambridge group should develop new observing techniques. As a result, Ryle was the driving force in the creation and improvement of astronomical interferometry and aperture synthesis, which have contributed immensely to upgrading the quality of radio astronomical data. In 1946 he built the first multi-element astronomical radio interferometer.

He guided the Cambridge radio astronomy group in the production of several important radio source catalogues. For example, the Third Cambridge Catalogue of Radio Sources (3C) 1959 helped lead to the discovery of the first quasi-stellar object (quasar).

While serving as university lecturer in physics at Cambridge from 1948 to 1959, Ryle became director of the Mullard Radio Astronomy Observatory 1957, and professor of radio astronomy in 1959. He was elected a fellow of the Royal Society in 1952, was knighted in 1966, and succeeded Sir Richard Woolley as Astronomer Royal (1972-82).

Martin Ryle was undoubtedly one of the great astronomers of the 20th Century. He was sometimes considered difficult to work with - in fact he often worked in an office at the Mullard Radio Astronomy Observatory to avoid disturbances from other members of the Cavendish Laboratory and to avoid getting into heated arguments, as Ryle had a hot temper. Ryle worried that Cambridge would lose its standing in the radio astronomy community as other radio astronomy groups had much better funding, so he encouraged a certain amount of secrecy about his aperture synthesis methods in order to keep an advantage for the Cambridge group.

Ryle received the Hughes Medal (1954), the Gold Medal of the Royal Astronomical Society (1964), the Henry Draper Medal (1965), the Royal Medal (1973), the Bruce Medal (1974), and the Nobel Prize in Physics (1974). The Ryle Telescope at Mullard Radio Astronomy Observatory is named in his honor.

September 21: Arthur Covington

Arthur Edwin Covington

September 21, 1913 – March 17, 2001

Arthur Covington is a Canadian physicist who made the first radio astronomy measurements in Canada. Through these he made the valuable discovery that sunspots generate large amounts of microwaves at the 10.7 cm wavelength, offering a simple all-weather method to measure and predict sunspot activity, and their associated effects on communications. The sunspot detection program has run continuously to this day.

Covington was born in Regina and grew up in Vancouver. He showed an early interest in astronomy, and had built a 5-inch (130 mm) refractor telescope after meeting members of the local chapter of the Royal Astronomical Society of Canada. He was also interested in amateur radio and operated station VE3CC for a time. He started his career as a radio operator on ships operated by the Canadian National Railways. He put himself though school and eventually earned a bachelor's degree from the University of British Columbia in 1938, and obtained his master's degree from the same institution in 1940 after building an electron microscope. He then moved to University of California in Berkeley where he received his doctoral degree in nuclear physics in 1942. He was still at Berkeley when he was invited to join the National Research Council (NRC) in Ottawa in 1942 as a radar technician, working at the NRC's Radio Field Station.

Immediately after the war Covington became interested in radio astronomy, and built a small telescope out of the electronic parts from a surplus SCR-268 radar combined with parts from another receiver originally built to test silicon crystal radio parts for radar applications. These electronics were attached to the 4 ft (1.2 m) parabolic dish from a Type III gun-laying radar. The system operated at a frequency of 2800 MHz, or a wavelength of 10.7 cm. Initially the instrument was pointed in the direction of various celestial objects, including Jupiter, the Milky Way, aurora borealis, and the Sun, but it proved too insensitive to pick up any source other than the Sun. So a solar study program was started. As time passed, Covington and his colleagues realized that the Sun's emission at 10.7 cm wavelength was varying, which was unexpected. Thinking at that time was that the solar emission at centimeter wavelengths would be simply black body emission from a ball of hot gas.

Covington became convinced that the effect was due to sunspots, as the flux appeared to vary with the number of visible spots. The resolution of the device, about seven degrees, made it impossible to "pick out" a spot on the sun's surface for study, making a demonstration of the claim difficult. An opportunity to directly measure this possibility presented itself on November 23, 1946 when a partial solar eclipse passed over the Ottawa area, and Covington was able to conclusively demonstrate that the microwave emissions dropped off precipitously when the Moon covered a particularly large sunspot. This also demonstrated that magnetic fields were instrumental in sunspot activity.

Covington remained the director of the ARO until he retired in 1978. One of the buildings at the Dominion Astrophysical Observatory was named in his honour in 2003.

July 15: Jocelyn Bell Burnell

Dame Susan Jocelyn Bell Burnell, DBE, FRS, FRAS

July 15, 1943

Jocelyn Bell Burnell, DBE, FRS, FRAS, known as Jocelyn Bell Burnell, is a British astrophysicist who, as a postgraduate student, discovered the first radio pulsars with her thesis supervisor Antony Hewish, for which Hewish was awarded a Nobel Prize.

The paper announcing the discovery had five authors, Hewish's name being listed first, Bell's second. Hewish was awarded the Nobel Prize, along with Martin Ryle, without the inclusion of Bell as a co-recipient, which was controversial, and was roundly condemned by Hewish's fellow astronomer Fred Hoyle. The Royal Swedish Academy of Sciences, in their press release announcing the 1974 Nobel Prize in Physics, cited Ryle and Hewish for their pioneering work in radio-astrophysics, with particular mention of Ryle's work on aperture-synthesis technique, and Hewish's decisive role in the discovery of pulsars. Iosif Shklovsky, recipient of the 1972 Bruce Medal, had sought out Bell at the 1970 IAU General Assembly, to tell her:

"Miss Bell, you have made the greatest astronomical discovery of the twentieth century."

Born in Belfast, Northern Ireland, where her father was an architect for the nearby Armagh Planetarium, she enjoyed a large library and was encouraged to read. She was especially drawn to the books on astronomy. She attended Lurgan College and lived in Lurgan as a child. She was one of the first girls at the college permitted to study science. Previously, the girls' curriculum had included cross-stitch and cookery. At eleven, she failed the 11+ exam and her parents sent her to the Mount School, York, a Quaker girls' boarding school. There she was impressed by a physics teacher who taught her:

"You don't have to learn lots and lots...of facts; you just learn a few key things, and...then you can apply and build and develop from those... He was a really good teacher and showed me, actually, how easy physics was."

She graduated from the University of Glasgow with a B.Sc. physics in 1965 and received her Ph.D. from New Hall (renamed Murray Edwards College) of the University of Cambridge in 1969. At Cambridge, she worked with Hewish and others to construct a radio telescope for using interplanetary scintillation to study quasars, which had recently been discovered (interplanetary scintillation allows compact sources to be distinguished from extended ones). In July 1967, detecting a bit of "scruff" on her chart recorder papers that tracked across the sky with the stars, Bell Burnell found that the signal was regularly pulsing, about once each second. Temporarily dubbed "Little Green Man 1" the source (now known as PSR B1919+21) was eventually identified as a rapidly rotating neutron star.

After finishing her PhD, Bell Burnell worked at the University of Southampton (1968-73), University College London (1974-82) and the Royal Observatory, Edinburgh (1982-91). In addition, from 1973 to 1987 she was also a tutor, consultant, examiner and lecturer for the Open University. In 1991 she was appointed Professor of Physics at the Open University, a position she held for ten years. She was also a visiting professor at Princeton University. Before retiring Bell Burnell was Dean of Science at the University of Bath between 2001 and 2004, and was President of the Royal Astronomical Society between 2002 and 2004. She is currently Visiting Professor of Astrophysics at the University of Oxford and a Fellow of Mansfield College. She is the current President of the Institute of Physics.

Although she didn't share the 1974 Nobel Prize for Physics with Hewish for her discovery, she has been honoured by many other organisations:

• Michelson Medal of the Franklin Institute (1973, jointly with Hewish).
• J. Robert Oppenheimer Memorial Prize from the Center for Theoretical Studies in Miami (1978).
• Beatrice M. Tinsley Prize of the American Astronomical Society (1987).
• Herschel Medal of the Royal Astronomical Society (1989).
• Karl G. Jansky Lectureship of the National Radio Astronomy Observatory(1995).
• Magellanic Premium of the American Philosophical Society (2000).
• Fellow of the Royal Society (March 2003).

She has been awarded numerous honorary degrees, for instance, recently:

• In 2007 she was awarded an honorary doctorate by Harvard University.
• On 23 June 2007, Bell Burnell was awarded an Honorary Doctorate of Science from the University of Durham.
• She also holds important awards in the British honours system. In 1999 Bell Burnell received a CBE from Queen Elizabeth II. In June 2007 she was awarded a DBE (equivalent to a male knighthood).

June 5: John Gatenby Bolton

John Gatenby Bolton
June 5, 1922 – July 6, 1993

John Bolton was a British-Australian astronomer from Sheffield, England. He attended King Edward VII School (Sheffield), followed by Trinity College, Cambridge from 1940 to 1942, during which time he met C. P. Snow. After graduation he joined the navy, serving on HMS Unicorn during World War II. His ship went to Australia; he remained there after the war. In September 1946 he began working at the CSIRO Division of Radiophysics. At that time the field of radio astronomy was quite new and Bolton took the opportunity to become a pioneer in the field with experimentation at Dover Heights. His group found a number of radio sources in the sky, and realized that certain "radio stars" were actually located outside our galaxy and worked on mapping the structure of our galaxy.

He held a fellowship at Caltech beginning in 1955. In 1956, he resigned his position at CSIRO to become Professor of Radio Astronomy at Caltech, but he returned to Australia just a few years later to help build the Parkes radio telescope. This telescope found some distant radio sources now known to be quasars. It also helped transmit the video of the first Moon landing by Neil Armstrong.

He won the Henry Norris Russell Lectureship in 1968, the Gold Medal of the Royal Astronomical Society in 1977 and the Bruce Medal in 1988.