The Great Galaxy in Andromeda

Here's another scan of a vintage PR shot from Palomar. This is of M31, the Andromeda Galaxy. The image was captured by the 48-inch Schmidt telescope at Palomar (now known as the Samuel Oschin Telescope) and was copyrighted by Caltech in 1959. Believe it or not, we still have a limited quantity of this poster for sale in the observatory's gift shop.

M31 has been an important galaxy in the history of astronomy. As the closest spiral galaxy to the Milky Way it has served as an important stepping stone out into the universe. In the 1920s Edwin Hubble used the 100-inch Hooker Telescope on Mt. Wilson to determine that the Andromeda Galaxy is a separate system from the Milky Way. His determination of its distance was off by a factor of two - a measurement that was later corrected by Walter Baade, using the 200-inch on Palomar. Modern estimates place the distance at 2.9 million light years.

M31 was photographed using the Samuel Oschin Telescope as a part of the Second Palomar Sky Survey. The photographic plates from that survey have been digitized and the images are available online. Davide De Martin of SkyFactory.org has used that data to produce a beautiful image of the galaxy.