Astronomy
The Formation of Molecular Clouds from Interstellar Gas
Quick fact
Molecular clouds are so cold (about 10 K) and dense that they block out most background starlight, appearing as dark silhouettes against the Milky Way's bright starfields.
Why this is interesting
You've seen pictures of dark, cloudy patches against the starry sky—those are molecular clouds, the coldest, densest places in space. But how does ordinary, invisible gas between the stars turn into these colossal stellar nurseries?