a dense - on a cosmic scale - cloud of gas and dust, which is cold enough to allow more or less complex molecules to appear
assive clouds of gas in interstellar space composed primarily of hydrogen molecules (two hydrogen atoms bound together), though also containing other molecules observable by radio telescopes. These clouds can contain enough mass to make several million stars like our Sun and are often the sites of star formation.
Huge, cool clouds of dust grains, and gas, much of which is in the form of molecules. GMC's appear to be where most of the stars are formed in galaxies.
Massive clouds of gas in interstellar space composed primarily of hydrogen molecules. These clouds have enough mass to produce thousands of stars and are frequently the sites of new star formation.
Large, cold interstellar clouds, with diameters of dozens of light years and typical masses of 105 solar masses; found in the spiral arms of galaxies, these clouds are where massive stars form.
Very large, cool clouds of dense gas in which stars form.
large, dense gas cloud (with some dust) that is cold enough for molecules to form. A typical giant molecular cloud has a few hundred thousand to a few million solar masses of material. Stars form in them.