Following the creation of the deepest and largest panorama of a galaxy, made by the Canada-France-Hawaii telescope of M31, the galaxy also known as Andromeda has been snapped again – this time in the ultraviolet.
24 hours worth of observing time were used on the Gamma Ray Burst searching telescope to create 85 gigabytes of data. This was stitched together into a single image by Erin Grand, an undergraduate student at the University of Maryland at College Park who worked with Stefan Immler, a research scientist on the Swift team at NASA’s Goddard Space Flight Center in Greenbelt, Md, as an intern this summer.
Andromeda is visible to the naked eye in clear dark skies (like this place). It lies 2.5 million light years away and closing. It and the Milky Way are the largest galaxies in the Local Group of gravitationally bound galaxies and M31 is 220,000 light years in diameter. In 1885, a supernova in the bulge became visible to the naked eye. It is expected that supernovae happen around once a century in Andromeda, suggesting another could soon happen.
In the ultraviolet, the galaxy takes on some new features. The central bulge is smoother and redder due to the older, cooler stars. There is a ‘ring of fire’ 150,000 light years in diameter in the disc, where new stars and clusters are prominent. This is thought to be related to the issue explored in the optical image – interactions with satellite galaxies have sparked off new star formation in the outer part of Andromeda.
Swift studied M31 as part of a program to understand star formation in nearby galaxies. This is to help inform scientists on the likely condition of star formation in early galaxies, within with gamma ray bursters occur. These enormous daily flashes of highly energetic photons are believed to be the result of black hole formation at the end of the lives of giant stars. Swift has so far detected more than 400 of these mysterious objects since its launch in November 2005.