The Great Debate, also called the Shapley–Curtis Debate, was held on 26 April 1920 at the U.S. National Museum in Washington, D.C. between the astronomers Harlow Shapley and Heber Curtis. It concerned
Harlow Shapley (1885 –1972)
Heber Doust Curtis (1872–1942)
The Pinwheel Galaxy is a face-on, counterclockwise intermediate spiral galaxy located 21 million light-years from Earth in the constellation Ursa Major. It was discovered by Pierre Méchain in 1781 and
Great Debate (astronomy)
…van Maanen, a well-respected astronomer of the time, as providing evidence supporting Shapley's argument. Van Maanen had claimed he had observed the Pinwheel Galaxy rotating, and that if the Pinwheel Galaxy were in fact a distinct galaxy and could be observed to be rotating on a timescale of years, its orbital…
The Pinwheel Galaxy, as taken by Hubble Space Telescope
M101 – combined infrared, visible, and X-ray images
Dark sky image with some objects around Pinwheel Galaxy (M 101). The quarter in the lower right shows the tail of Ursa Major with the stars Mizar, Alcor and Alkaid.
Type Ia supernova SN 2011fe from August 2011