M82 Cigar galaxy

M82 Cigar Galaxy

The M82 galaxy is a small galaxy about a quarter of the size of our own Galaxy. It is thought to be disk shaped and seen edge on. At 12 million light years, it is quite close to us, and is part of a group of galaxies that also includes M81, NGC 3077 and NGC 2976. It has previously been classified as an irregular galaxy, but is now more frequently referred to as a starburst galaxy of type peculiar. Only a few percent of all known galaxies are starburst galaxies, but they are thought to have been much more common in the early universe.

Most if not all peculiar galaxies have been involved in recent interactions with another galaxy. This is certainly the case for M82 which had a close approach with the much larger M81 spiral galaxy about 300 million years ago. It is thought that the gravitational interactions forced much of the galaxy's gas to migrate to the centre of the galaxy. This in turn has led to a massive increase in star production, thought to have started about 10 million years ago.

Red filaments can be seen flowing from the centre of the galaxy, perpendicular to the galaxies disk, at speeds of up to 1000km/s. It used to be thought that this was due to a massive explosion from within the galaxy, but is now thought to be due to the rapid star formation. The most massive stars produced have brilliant but short lives, and end their lives with a supernovae explosion. These galaxy sized outflows are referred to as superwinds.

M82 has what is referred to as an infrared excess - it is much brighter in the infrared compared to the visible. This makes it the brightest galaxy in our skies at infrared wavelengths.

Recently, over 100 young globular clusters have been discovered around M82 by the Hubble Space Telescope. This is also thought to be due to the gravitational tidal forces during the interaction with M81.

In May 2009, a new radiowave object was discovered in M82. It has been suggested that his might be a micro-quasar: http://www.sciencedaily.com/releases/2010/04/100413202858.htm

Hydrogen Alpha image, showing the jets of gas above and below the galaxy.

The two images below were taken with a red and blue filter. They both have the correct relative brightness, and exactly the same processing was applied to both of them.