Title： How was neutral hydrogen in our Galaxy discovered?

Time：10:00 a.m., Dec.3, Friday

Location：Report Room 510, Institute for the History of Natural Science, Chinese Academy of Sciences, 55 Zhong Guan Cun East Road, Haidian, Beijing 100190, P. R. China 

About the speaker:

Richard Strom was born and raised in New York City. He gained entrance to the selective Bronx High School of Science, and pursued studies at Tufts University in Medford, Massachusetts, where he earned a B.A. in physics. Switching to radio astronomy, he obtained M.Sc. and Ph.D. degrees from the University of Manchester (Jodrell Bank) in 1972, followed by postdoctoral research at Leiden Observatory. Since 1975 he has been a research astronomer at Dwingeloo Radio Observatory, and adjunct professor at the University of Amsterdam (1996). He has also been adjunct or visiting professor in Singapore, Australia and China. He does research in many areas of radio astronomy (supernova remnants, giant radio galaxies, gamma-ray bursts, pulsars, Jupiter, cosmic rays) including its history. He is also interested in Chinese astronomical records, and holds a CAS Visiting Professorship for Senior International Scientists in 2010.

Abstract: 

How was neutral hydrogen in our Galaxy discovered?

Richard Strom

NAOC, Beijing

ASTRON, Dwingeloo

University of Amsterdam

James Cook University, Townsville

In April 1944, at a meeting of the Netherlands Astronomy Club organized by Jan Oort, H.C. van de Hulst suggested that the hyperfine splitting of the ground state of atomic hydrogen at a wavelength of 21 cm might be observable as line radiation from interstellar gas. Oort had realized that radio waves would be able to penetrate dust in the galactic disk, which prevented observation of light from the nuclear region. Within days of the April meeting, Oort was looking into the possibility of building an antenna capable of observing the hoped-for line, though no concrete steps could be taken before the end of the war. Using material from the extensive Oort Archive, I have been able to fill in many details concerning the build up to Van de Hulst’s prediction, and the subsequent effort to actually detect the line, which was first achieved by Ewen and Purcell at Harvard, to be followed within weeks by Muller and Oort. One is struck by the wide circle of top scientists and engineers that Oort was able to call upon in his pursuit of 21 cm HI, which required technology that astronomers like himself had very little knowledge of. Van de Hulst would later remark that through Oort’s effort, all of the ability and ideas in the Netherlands were brought together. Some of the key figures, their contributions and interactions, as well as the sequence of events, will be discussed.

You are welcome！

Center of Ancient Chinese Astronomy, IHNS