Messier 82 (also known as NGC 3034,or Galaxy M82) is the prototype nearby starburst galaxy about 12 million light-years away in the constellation Ursa Major. The starburst galaxy is five times as bright as the whole Milky Way and one hundred times as bright as our galaxy's center.
In 2005, the Hubble revealed 197 young massive clusters in the starburst core. Throughout the galaxy's center, young stars are being born 10 times faster than they are inside our entire Milky Way Galaxy.
M82 was previously believed to be an irregular galaxy. However, in 2005, two symmetric spiral arms were discovered in the near-infrared (NIR) images of M82. The arms were detected by subtracting an axisymmetric exponential disk from the NIR images. These arms emanate from the ends of the NIR bar and can be followed for the length of 3 disc scales. Assuming that the northern part of M82 is nearer to us, which most literature assumes, the observed sense of rotation implies trailing arms. Due to M82's high disk surface brightness, nearly edge-on orientation (~80°) with respect to us, and the presence of a complex network of dusty filaments in optical images, the arms were not previously detected.
Source: en.wikipedia.org/wiki/Messier_82 - 21.09.2010
In spite of such fascinating pictures we still can not imagine the largeness and energy of Galaxy M82.