Spiral galaxy M33 in Triangulum
author: IAC/RGO/David Malin Images/Novapix
reference: a-gax05-98012
Image Size 300 DPI: 22 * 28 cm
M33 is a large, almost face-on spiral galaxy about 2.5 million light years distant in the northern constellation of Triangulum. It is a member of the 'Local Group' of galaxies, which is dominated by the Milky Way and M31. Like M31, M33 is approaching the Milky Way at a velocity of about 180km/s. Though the total light M33 galaxy is that of a star of magnitude 5.3, its large diameter makes it hard to see. However, despite its low surface brightness, this galaxy was among the first to be identified as a 'spiral nebula' by Lord Rosse in the 1840s. In the upper left (north-east) part of this wide field view is the reddish nebula NGC 604, one of the biggest and most active nearby starforming regions. It is about 150 light years in diameter, eqivalent to the distance from the Sun to the Orion nebula.