JOHN F W HERSCHEL MEDAL : MICHAEL WILLIAM FEAST

Professor Michael Feast has had a lengthy and distinguished career in both physics and astronomy and is an outstanding candidate for the Herschel Medal. His contributions to physics have been recognized by the South African Institute of Physics who awarded him their Gold Medal and made him an Honorary Fellow. His contributions to astronomy have been recognized by the South African Astronomical Society, of which he has twice been President, with the award of the Gill Medal. In May this year Michael Feast was the lead author on an astronomy paper entitled Cepheid variables in the flared outer disk of our Galaxy, which appeared in Nature 66 years after his first publication in physics, Emission Schumann-Runge O2 Bands, appeared in the same journal.

Prof Michael Feast FRSSAf

Prof Michael Feast FRSSAf

Feast’s research career started in 1946 when he entered the Physics Department at the Imperial College of Science and Technology in London as a student of R W B Pearse, studying laboratory spectroscopy and his first publications are in this field. After two years he obtained a PhD, and in 1949 moved to Canada as a post-doc in G Herzberg’s laboratory at the National Research Council in Ottawa, where he remained until 1951. This training in fundamental spectroscopy was going to provide a strong grounding for the spectroscopic studies he was to pursue over the following years.

In 1952 Feast moved to the Radcliffe Observatory in Pretoria where he used the 1.9m reflector which was at the time the largest telescope in the southern hemisphere. He remained in Pretoria until 1974, when the 1.9m was moved to Sutherland, at which time he joined the newly formed South African Astronomical Observatory (SAAO), based in Cape Town. In 1976 he was made Director of SAAO, a position that he held until his formal retirement in 1992, at that stage he returned to full time research as an Honorary Professor at the University of Cape Town.

Feast’s research is characterized by accurate measurements of observational phenomena, using the best techniques available at the time, combined with a careful statistical analysis of the results and their errors. His early work (Feast & Thackeray 1958; Feast 1965) on kinematics and radial velocities provided the first comparison of young stars with the 21 cm HI data and a derivation of the Oort A constant as well as the first kinematic estimate of the distance to the Galactic center. More recently he combined Hipparcos proper motion data with ground-based photometry of Cepheids to obtain, among other things, definitive values for the Oort A and B constants, and a new estimate of the distance to the Galactic Centre (Feast & Whitelock 1997). Extensive studies of Mira variables in the Galaxy (Feast 1963, 1973) showed that their kinematics is a function of their pulsation periods. These stars were also shown to obey a periodluminosity relation and to be very useful as Galactic Structure probes (Glass & Feast 1982, Feast & Whitelock 2000).  In the 1950s, when Feast started work on the Magellanic Clouds, almost nothing was known about their stellar content or structure. Amongst other things he demonstrated that mass loss set the upper limit to stellar luminosity (Feast, Thackeray & Wesselink 1960). Radial velocities for LMC stars enabled a derivation of the LMC’s mass and demonstrated differential rotation. He showed that young objects have a significantly lower velocity dispersion (Feast 1964) than that of old stars (Feast 1968), suggesting that the LMC evolved by collapse. In contrast, data on SMC stars indicated a much more complex structure (Feast 1970). He continued work on the LMC took over the following years, including a recent study of the metallicity gradient (Feast, Abedigamba & Whitelock 2010). Feast has worked extensively on the extragalactic distance scale and encouraged others at SAAO to do the same. Classical Cepheids are particularly important (Feast & Walker 1987, Feast 1999) and his demonstration that the width of the periodluminosity relation in the LMC was intrinsic and not primarily an effect of differential reddening was a major step forward.   As a consequence the period-luminosity-color relation (Martin, Warren & Feast 1979) became the relation of choice for distance determination. Hipparcos data allowed a comparison with parallaxes (Feast & Catchpole 1997, van Leeuwen et al. 2007) and a derivation of the Hubble constant. Some refinements of this were made using data from HST (Benedict et al. 2007). Feast’s work on Mira variables as distance indicators covers many years (from Feast & Clayton 1969 to Feast & Whitelock 2013) and includes major studies of the period-luminosity relation (Feast et al. 1989). This will become increasingly important as the emphasis of new observations shifts to the infrared.

As Director of SAAO from 1976 to 1992, Feast led the only astronomical organization in sub-Saharan Africa with a critical mass (~12) of astronomers. He strongly emphasized the importance of research and, while allowing the staff a great deal of freedom in their research directions, always insisted that their work was published in the top international journals. An international panel review during the 1980s described SAAO as “… producing the most cost effective astronomical research in the world”. Feast was very largely responsible for the strength of South African astronomy at the time when the new democratic government decided to invest heavily in the area. He was strongly aware of the growing need for a large telescope to keep South African research competitive and set the groundwork that eventually led to construction of the Southern African Large Telescope (SALT). In addition to continuing to publish and attend international meetings he is, and has been since 1992, an editor of Monthly Notices of the Royal Astronomical Society.

He has an Honorary DSc from the University of Cape Town and is an Honorary Fellow of the Royal Astronomical Society (UK). He was the first Blaauw Visiting Professor at the University of Groningen (Netherlands) and he was a member of the first time allocation committee for the Hubble Space Telescope. He has also been a Vice President of the International Astronomical Union. NRF Rating A2; h-index (from ADS): 57