The NGC 604 is a colorful, cavernous nebula situated in the Triangulum Galaxy M33, three million light years away. The NGC 604 is a site in which new stars are being born in a spiral arm of the galaxy. The nebula NGC 604 is so vast it is easily seen in ground-based telescopic images. The bright stars in NGC 604 are quite young by astronomical standards, having formed only 3 million years ago.
Discovered by William Herschel on September 11, 1784, the NGC 604 is a gigantic star-forming region which contains more than 200 brilliant blue stars within a cloud of glowing gases some 1,500 light-years across, and is nearly 100 times the size of the Orion Nebula. By contrast, the Orion Nebula contains just four bright central stars.
At the heart of NGC 604 there are over 200 hot stars, much more massive than our Sun (15 to 60 solar masses). They heat the gaseous walls of the nebula making the gas flouresce. Their light also highlights the nebula's three-dimensional shape, like a lantern in a cavern. By studying the physical structure of a giant nebula, astronomers may determine how clusters of massive stars affect the evolution of the interstellar medium of the galaxy.