Galactic Dust and Nebulae

Are molecules in the interstellar medium only found in molecular clouds?

No. They exist in the interstellar environments surrounding stars, too. Gas molecules in space, however, are much more fragile than atomic gas. Ultraviolet radiation from stars, for example, readily destroys molecules, breaking them up into atoms again. So the density of dust in molecular clouds helps to shield the molecules floating inside them, and allows them to stay together for long periods of time.


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