Next to hydrogen, carbon monoxide is the most common form of molecular gas. This image shows molecular carbon monoxide gas to be concentrated in Maffei 2ΓÇÖs nucleus, at the site of the starburst. Strong carbon monoxide emission is almost always found in regions of star formation, since stars are born from the centers of very dense molecular gas clouds that have collapsed under the influence of their own gravity. The densest of these clouds have about 10,000 molecules per cubic centimeter, or about one hundredth of one trillionth the density of air on Earth. Even so, carbon monoxide clouds are about 10,000 times denser than clouds of H I found elsewhere in the galaxy.
