An interstellar cloud consisting predominantly of molecular hydrogen, with trace amounts of other molecules such as carbon monoxide and ammonia.
A cold, dense interstellar cloud which contains a high fraction of molecules. It is widely believed that the relatively high density of dust particles in these clouds plays an important role in the formation and protection of the molecules.
a collection of chemical molecules in the interstellar medium mutually attracted by gravity
A cold, dense collection of interstellar gas where stars can form.
An interstellar gas cloud that enables the formation of molecules. Over 125 molecules have now been discovered in interstellar space through radio wavelength observations.
a self-gravitating interstellar cloud of gas, comprised mainly of H2(g) molecules with a 10% abundance by number of He, and other trace compounds (e.g., one of the next most abundant species is CO, with a relative abundance of 0.0001). They also have a dust component, normally about 1% by mass. Molecular clouds contain most of the mass of the galaxy, while occupying only a fraction of the volume. Star formation takes place in these clouds. Masses range from a few to 1.e6 solar masses, with radii from a pc to hundreds of parsecs. Mean densities are typically in the range of 100 to 1000 particles per cubic cm, and mean temperatures are usually low (10 to 50 K), although there can be denser and hotter regions inside these clouds, especially where star formation is taking place. Variants include 'dark clouds', 'Bok globules' (small, featureless clouds), 'giant molecular clouds or complexes (GMC's)' (larger, more massive clouds and active sites of star formation).
Large, dense, massive clouds in the plane of a spiral galaxy; they contain dust and a large fraction of gas in molecular form.
A relatively dense, cold region of interstellar matter where molecules are found in considerable abundance.
Clouds of interstellar dust and gas in the molecular form. They can be very large - with a diameter of up to a hundred light-years. Most of the gas in these clouds is very cold, only tens of degrees above the absolute zero.
A large region (often more than 100 parsecs in diameter) of molecular hydrogen gas. Molecular clouds are usually detected because of the presence of other heavier molecules such as carbon monoxide. Molecular clouds are the birth places of most of the large star associations and clusters in our Milky Way and form the basis of spiral structures such as arcs, arms and rings.
A molecular cloud is a type of interstellar cloud whose density and size permits the formation of molecules, most commonly molecular hydrogen (H2).
