Henrietta Leavitt the Overlooked Pioneer of Distance

Almost exactly 100 years ago (October 1923) Edwin Hubble established that Andromeda was a galaxy in its own right, separate and very distant from our Milky Way. It is incredible to think that prior to that, there had been a vigorous debate about whether separate galaxies existed at all or whether nebulae and other mysterious objects all formed part of our Milky Way.

In making his historic discovery Hubble drew on principles established in the previous two decades by Henrietta Swan Leavitt. She had been employed at Harvard Observatory as a lowly ‘computer’. Not allowed to work as an astronomer she spent her short career examining and recording evidence from thousands of photographic plates. She nevertheless provided one of the great insights of twentieth century astronomy which paved the way to the measurement of the distances of incredibly distant objects. Largely overlooked in her lifetime (and long after) Leavitt, in…