Triangulum galaxy (M33), ultraviolet image. This spiral galaxy, also known as the Pinwheel galaxy, is a member of the Local Group of galaxies, which also includes Andromeda and our galaxy the Milky Way. It has a diameter of around 50-60,000 light years, around half that of the Milky Way. Its spiral arms contain mainly hot young blue stars, while its central nucleus is home to older, yellower stars, and more obscuring dust. The galaxy lies around 2.4 million light years from Earth in the constellation Triangulum. Image taken by the Galaxy Evolution Explorer (GALEX) space telescope.