Frank John Kerr, who made major contributions to our understanding of the structure of the Milky Way, died of cancer on 15 September 2000 at his home in Silver Spring, Maryland.
Frank was born on 8 January 1918 in St. Albans, England, of Australian parents who were in England during World War I. The family returned to Australia after the war, when Frank was 1 year old. Frank received his BSc (1938) and MSc (1940) in physics at the University of Melbourne in Australia. He earned an MA in astronomy from Harvard University in 1951. He then was awarded his DSc in astronomy from Melbourne in 1962.
Frank joined the Commonwealth Scientific and Industrial Research Organization (CSIRO) radiophysics laboratory in Sydney in 1940. Of the 12 staff members at that time, he was one of the few physicists who concentrated on both theoretical and experimental fundamental science. In 1941, he put into use the “Micropup,” a lightweight, air-cooled triode tube for airborne radar with 10-kW peak pulse at 450 MHz. Later, he was a key person in the use of the magnetron, and he spent the mid-1940s studying superrefraction.
Using the Radio Australia 100-kW transmitting antenna pointed at the US and a CSIRO-built receiving antenna in a shielded valley 20 miles north of Sydney, Frank obtained radio echoes of the Moon in 1948. He was the first person to conclude that serious irregularities at the top of the F2 ionospheric layer cause long-term variations in the Moon echo, and he correctly interpreted the strong short-term fluctuations as being due to lunar libration. His Moon-echo work was epoch-making. In the Proceedings of the Institute of Radio Engineers (volume 40, page 660, 1952), he published the classic paper on the possibility that radar echoes are reflected from the planets and the Sun. He was the first person at the radiophysics lab to specifically study astronomy, even though the group was already one of the world’s leading radio astronomy organizations.
While spending a year at Harvard on a research scholarship, Frank witnessed the first detection of the 21-cm spectral line of neutral hydrogen from interstellar space. Back in Australia in late 1951, he set up the Southern Hemisphere 21-cm line program and started mapping the Magellanic Clouds. This was pioneering work—the first detection of a radio spectral line in an external galaxy. According to the conventional wisdom of the time, the clouds, being almost devoid of dust—especially the Small Cloud—were thought to be free of gas. Frank was undeterred by this preconception and found copious neutral hydrogen and an extended envelope around both clouds. He used a specially built 36-foot transit telescope, which at the time was the largest dish of its kind in Australia.
In 1954 and 1955, Frank, Jim Hindman, Brian Robinson, and Gérard de Vaucouleurs determined the rotation of the Magellanic Clouds and their masses—another first. Frank then started mapping the galactic disk, publishing the southern part of the disk shortly after the 1955 publication of the “Dutch map” of the Northern Hemisphere by Gart Westerhout and Maarten Schmidt. He observed that the upswing of the hydrogen layer in the northern part of the Galaxy was mirrored by a downswing in the southern part.
Frank coined the term “galactic warp” to suggest the distorting effect of the Magellanic Clouds’ gravity on the shape of our galaxy. With Dutch astronomer Westerhout, Frank and Colin Gum determined the precise position of the neutral hydrogen plane. The International Astronomical Union (IAU) adopted that determination as the basis for the new galactic coordinate system. By 1960, Frank had become a leading expert in the field of galactic structure. That same year, he became a senior principal research officer at CSIRO.
Frank was heavily involved in conceptual studies for the Parkes 210-foot radio telescope and pushed for an accurate (to 10-cm wavelength) surface for his planned 21-cm line research program. He embarked on an extensive galactic structure program when the telescope became operational in 1962. In 1966, he left Australia to join the University of Maryland, College Park, as a visiting professor of astronomy. He then became a professor of astronomy in 1968, a position he held until his retirement in 1987. But Frank did not lose interest in the Southern Hemisphere. In 1968 and 1970, he traveled to Argentina, where he amazed local astronomers with his tenacious observing. And during the 1970s, Frank and some of his students went to Australia to make a complete 21-cm survey along a 20-degree strip of the Southern Milky Way. Between 1986 and 1990, Frank successfully searched for evidence of galaxies hidden behind the Milky Way dust, and thus opened up a new and active field of research.
Frank served astronomy in many capacities: He was the chairman of the NSF advisory panel on astronomy (1971–72); director of the University of Maryland astronomy program (1973–78); councilor of the American Astronomical Society (AAS; 1972–75); and president of IAU Commission 33 (1976–79). He also was provost of the University of Maryland physical and mathematical sciences and engineering division (1978–85); AAS vice president (1980–82); chair of an IAU working group that recommended new standard values for the size and rotation properties of the Galaxy (1982–86); director of the Universities Space Research Association (USRA) astronomy and space physics division (1983–95); and chairman of the USRA Council of Institutions (1984–85).
Frank was a leader, adviser, innovator, and mentor for his scientific colleagues around the world and an outstanding source of ideas. He was a renaissance man with a pleasant, self-effacing disposition belying his enormous stature.
