Curtis, Heber Doust (1872–1942)
American astronomer who started out as a student and then a professor of
Latin and Greek, but went on to play an important role in establishing the
nature of external galaxies. Having earned his Ph.D. in astronomy (1902)
from the University of Virginia he joined the staff of the Lick
Observatory where he remained until 1920. He then became director of
the University of Pittsburgh's Allegheny Observatory
and, finally, in 1930, was appointed director of the University of Michigan's
observatory. Curtis's early work involving measuring the radial
velocities of stars. In 1910, however, he began investigating spiral
nebulae and became convinced that they were independent star systems. In
1917 he argued that the observed brightness of novae,
found by him and by George Ritchey on photographs of spiral nebulae, indicated
that the nebulae lay well beyond our Galaxy. He also maintained that extremely
bright novae, later identified as supernovae,
could not be included with the novae as distance indicators. He estimated
the Andromeda Nebula (now known as the Andromeda
Galaxy) to be 500,000 light-years away, a view opposed by many, including
Harlow Shapley who proposed that the Milky
Way Galaxy was 300,000 light-years in diameter – far larger than previously
assumed – and that the spiral nebulae lay within it. In 1920, at a
meeting of the National Academy of Sciences, Curtis engaged in a famous
debate with Shapley over the size of the Galaxy and the distance of the
spiral nebulae. The matter lay unresolved, however, until 1924 when Edwin
Hubble redetermined the distance of the Andromeda
Nebula and demonstrated that it was a galaxy in its own right.
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