Vera Rubin by Jacqueline Mitton

Author:Jacqueline Mitton
Language: eng
Format: epub
Publisher: Harvard University Press

CHAPTER 8

ADVENTURES IN ANDROMEDA

In 2011, reflecting at the age of eighty-three on a distinguished professional career spanning more than fifty years, Vera described the years between 1960 and 1970 as being “a remarkable period in our lives.” In that decade, she and Bob completed their family and she made a momentous move from Georgetown to Carnegie. The same years saw the flowering of her exceptional talent for observing, reducing, and analyzing her own data on the dynamics of galaxies.1 At the end of the decade, she and Kent Ford published a landmark paper on the Andromeda Galaxy, M31.

For astronomy more generally, it was a period of groundbreaking change. There was palpable excitement at international meetings and symposia about the latest discoveries. To go to these gatherings was to be confronted with mind-bending questions: Do you think active galaxies are powered by supermassive black holes? Do you know how the missing mass problem might be resolved? Do you believe in dark matter?

Tackling such challenges had become a priority for theoretical and observational cosmologists alike. Vera Rubin, as an observer, was a pioneer in making high-precision measurements of motion in the extragalactic universe. Her data on the rotation of galaxies would in due course both stimulate and constrain theorists. To begin with, though, somewhat against the trend, she had set her sights no farther than the large spiral galaxy in Andromeda, M31, just “next door” in astronomical terms. Our own Milky Way, by then understood to be a large spiral galaxy, too, was often compared with M31 in which many stars and glowing nebulae could be picked out individually. For a whole host of reasons, it represented a tempting target for the capabilities of the DTM image tube spectrograph.

One thing that would have drawn Vera to M31 was her long-standing interest in comparing radio and optical studies to understand the dynamics of galaxies. The prospect of research along these lines had attracted her to DTM in the first place, even before she knew about the new opportunities the image tube spectrograph would open up. Vera was still at Georgetown in 1963, when DTM radio astronomer Bernie Burke, together with Kenneth Turner and Merle Tuve, observed radio emission from the neutral hydrogen gas in M31 and in several other nearby galaxies, with the newly commissioned 300-foot transit telescope of the National Radio Astronomy Observatory (NRAO) at Green Bank, West Virginia. The fledgling radio astronomy group at DTM had designed a spectrometer to use with the new telescope for observing the velocity and density of neutral hydrogen in the Milky Way and the nearest spiral galaxies. For seven weeks (from December 5, 1962, to January 24, 1963) the Green Bank big dish was devoted exclusively to observations with the Carnegie spectrograph. More observations followed in the summer of 1964. Burke and his collaborators presented their results on M31 at length, including a rotation curve, in the Carnegie Year Book for 1963–1964. They conceded, however, that the resolution of their observations was not good enough to plot a rotation curve directly.

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