molecular cloud
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AI overview
A molecular cloud is a massive collection of gas and dust floating in space between stars, where molecules like hydrogen can form in the cold, dark environment. These clouds matter because they are the birthplaces of new stars and planets, making them essential to understanding how our universe creates and evolves.
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Article
A molecular cloud—sometimes called a stellar nursery if star formation is occurring within—is a type of interstellar cloud of which the density and size permit absorption nebulae, the formation of molecules (most commonly molecular hydrogen, H2), and the formation of H II regions. This is in contrast to other areas of the interstellar medium that contain predominantly ionized gas.
Molecular hydrogen is difficult to detect by infrared and radio observations, so the molecule most often used to determine the presence of H2 is carbon monoxide (CO). The ratio between CO luminosity and H2 mass is thought to be constant, although there are reasons to doubt this assumption in observations of some other galaxies.