John Charles Duncan, Photographic studies of Nebulae, Fifth pape

John Charles Duncan’s (8 February 1882 - 10 September 1967) chief contribution to astronomy was his photographic demonstration of expansion in the Crab nebula. He is perhaps better known, however, as the author of Astronomy, a standard college textbook for over thirty years, which was illustrated with many of his own excellent photographs of nebulae and galaxies.

The Crab nebula, located in the constellation of Taurus, is still today a fruitful subject for investigation because of its association with the pulsar NP 0532; it is believed to be the remnant of a supernova observed in Japan and China in A.D. 1054. By comparing a photograph taken with the sixty-inch telescope at Mount Wilson in 1909 by George Willis Ritchey with one he took himself in 1921 with the same instrument, Duncan was able to demonstrate outward motions in the filaments of the Crab. He later confirmed these motions with another photograph taken in 1938, thus showing that it was indeed an expanding envelope such as has been observed around other novae.

Photo ID: 5851