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NGC 604 in M33

How were the colors assigned in this image?

This image of NGC 604 was taken in several different wide-band (W) and narrow-band (N) filters with the Wide Field Planetary Camera 2 onboard Hubble. Ten filters were used in conjunction to create this Hubble Heritage color composite. The key on the image at right shows the relative color assignments of the seven narrow-band and three broad-band filters.

How does NGC 604 compare with other nearby star-forming regions?

NGC 604 contains more than 200 hot, bright stars within a cloud that is nearly 1,300 light-years across. By contrast, the Orion Nebula contains just four bright central stars and is 100 times smaller than NGC 604. Within our Local Group, only the Tarantula Nebula in the Large Magellanic Cloud exceeds NGC 604 in the number of young stars even though the Tarantula Nebula is slightly smaller in size.

What does the image look like if only some of the filters are used?

With 10 different filters, there are many permutations on what the image may look like if only a few of the filters are used to produce a color image. The Original Images page shows what each individual filter looks like. A press release image of NGC 604 was released in 1996 (STScI PRC96-27) which included only a few of the narrow-band filters.

NGC 604 in narrow bands
H. Yang (U. Illinois) and NASA

How was the central cavity in NGC 604 created?

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 bright stars in NGC 604 are extremely young by astronomical standards, having formed a mere 3 million years ago.

How hot are the bright blue stars in the center of NGC 604?

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 fluoresce.

Ground-based image of NGC 604 (left) and its host galaxy, M33 (right). Visit the NOAO website for larger images.

Where is NGC 604 located?

NGC 604 lies in a spiral arm of the nearby galaxy M33, located about 2.7 million light-years away in the direction of the constellation Triangulum. M33, a member of the Local Group of galaxies that also includes the Milky Way and the Andromeda Galaxy, can be seen easily with binoculars. NGC 604 itself can be seen with a small telescope, and was first noted by the English astronomer William Herschel in 1784.