A molecular cloud, sometimes called a stellar nursery if star formation is occurring within, is a type of interstellar cloud whose density and size permits the formation of molecules, most commonly molecular hydrogen (H2).
Molecular hydrogen is difficult to detect by infrared and radio observations, so the molecule most often used to determine the presence of H2 is CO (carbon monoxide). 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.
Read more about Molecular Cloud: Occurrence
Famous quotes containing the word cloud:
“Perhaps I stand now on the eve of a new life, shall watch the sun rise and disappear behind a black cloud extending out into a grey sky cover. I shall not be deceived by its glory. If it is to be so, there is work and the influence that work brings, but not happiness. Am I strong enough to face that?”
—Beatrice Potter Webb (1858–1943)