Molecular cloud

type of interstellar cloud

A molecular cloud is a kind of cloud in space. It has enough density and size so that molecules can form, usually molecules of hydrogen (H2). Molecular hydrogen is not easy to find. Instead astronomers use infrared telescopes and radio telescopes to look for CO (carbon monoxide). This lets them find the hydrogen molecules that are also there.

Young stars surrounded by a giant molecular cloud in the Ophiuchus constellation