Computer-enhanced optical photograph of the spiral galaxy M33, a major member of the Local Group of galaxies which includes our own Milky Way. Located 2.4 million light years away, in the constellation of Triangulum, it has a diameter of 40,000 light years & a mass of 15,000 million Suns. The image was derived from photographs taken through blue, green & red filters, combined by computer to show the natural, but enhanced, colour of the galaxy. Star formation is occurring in several giant clouds of hydrogen gas, which glow pink. The blue patches that dominate the spiral arms are populations of young, hot, blue stars. Older stars glow yellow & red at the centre of the galaxy.