NGC 604 – Nebula in M33 Triangulum Galaxy

NGC 604 is an enormous star-forming nebula in one of M33’s spiral arms. Spanning almost 1,500 light-years, NGC 604 is nearly 100 times larger than the Orion Nebula in our own galaxy and contains more than 200 hot, massive, young stars (versus the Orion Nebula’s four). Most of the brightest and hottest stars form a loose cluster located within a cavity near the center of the nebula. Stellar winds from these hot blue stars, along with supernova explosions, are responsible for carving out the hole at the center. The most massive stars in NGC 604 exceed 120 times the mass of our Sun, and their surface temperatures are as hot as 72,000 degrees Fahrenheit (40,000 Kelvin). Ultraviolet radiation floods out from these hot stars, making the surrounding nebular gas fluorescent. This image of NGC 604 is constructed from observations taken with Hubble’s Wide Field and Planetary Camera 2 in 1994, 1995 and 2001.