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A molecular cloud, sometimes called a stellar nursery if star formation is occurring within, is a type of interstellar cloud of which the density and size permit absorption nebulae, the formation of molecules (most commonly molecular hydrogen, H 2), and the formation of H II regions.
During gravitational collapse density always increases, [12] thus in the second case the Jeans mass will decrease during collapse, allowing smaller overdense regions to collapse, leading to fragmentation of the giant molecular cloud. For an ideal monatomic gas, the adiabatic index is 5/3.
In triggered star formation, one of several events might occur to compress a molecular cloud and initiate its gravitational collapse. Molecular clouds may collide with each other, or a nearby supernova explosion can be a trigger, sending shocked matter into the cloud at very high speeds. [4]
Stellar evolution starts with the gravitational collapse of a giant molecular cloud. Typical giant molecular clouds are roughly 100 light-years (9.5 × 10 14 km) across and contain up to 6,000,000 solar masses (1.2 × 10 37 kg). As it collapses, a giant molecular cloud breaks into smaller and smaller pieces.
Star-forming regions are a class of emission nebula associated with giant molecular clouds. These form as a molecular cloud collapses under its own weight, producing stars. Massive stars may form in the center, and their ultraviolet radiation ionizes the surrounding gas, making it visible at optical wavelengths.
A new study proposes that the dinosaurs were killed off due to severe global cooling caused when the Earth passed through a ‘giant molecular cloud.’
The phase begins when a molecular cloud fragment first collapses under the force of self-gravity and an opaque, pressure-supported core forms inside the collapsing fragment. It ends when the infalling gas is depleted, leaving a pre-main-sequence star , which contracts to later become a main-sequence star at the onset of hydrogen fusion ...
When a portion of a molecular cloud reaches a critical size, mass, or density, it begins to collapse under its own gravity. As this collapsing cloud, called a solar nebula, becomes denser, random gas motions originally present in the cloud average out in favor of the direction of the nebula's net angular momentum.