The Triangulum Galaxy, designated as M33, is the third largest spiral in the local group of galaxies, after our home galaxy, the Milky Way, and the Andromeda Galaxy, which is the largest. The Triangulum Galaxy lies some 3 million light years away, which means that the light recorded in this image terminated an intergalactic journey that began long before the first human even walked on Earth. Although small by galactic standards, M33 is home to an estimated 40 billion stars, as well as being a galaxy with a relatively high rate of star formation. This high star forming activity is evidenced by the numerous reddish regions of ionised hydrogen. Unlike many other spiral galaxies, however, M33 lacks a distinct core despite having well-defined spiral arms.