Bright Nebulae of M33
Gorgeous spiral galaxy M33 seems to have more than its fair share of bright emission nebulae. In fact, narrow-band and broad-band image data are combined in this beautifully detailed composite to trace the reddish emission nebulae, star forming HII regions , sprawling along loose spiral arms that wind toward the galaxy's core. Historically of great interest to astronomers, M33's giant HII regions are some of the largest known stellar nurseries - sites of the formation of short-lived but very massive stars . Intense ultraviolet radiation from the luminous, massive stars ionizes the surrounding gas and ultimately produces the characteristic red glow. Spanning over 50,000 light-years and a prominent member of the local group of galaxies , M33 is also known as the Triangulum Galaxy . It lies about 3 million light-years distant.