Molecular Cloud: Formation of Stars, Interstellar Gas and Dust
Category: General Science — Astronomy
A molecular cloud is a dense region of the interstellar medium containing gas, primarily molecular hydrogen, along with dust and other molecules. These clouds are important sites of star formation.
Key facts
Molecular clouds are composed mainly of molecular hydrogen, with helium and trace amounts of other molecules.
They contain dust grains that affect the absorption and emission of radiation.
Some molecular clouds are cold and dense enough for gravitational collapse to occur in parts of the cloud.
Collapsing regions can form protostars, which may eventually become stars.
The surrounding material may form a rotating disk from which planets can develop.
Star formation process
Dense regions develop within a molecular cloud.
Gravity causes suitable regions to contract.
A protostar forms as matter accumulates.
A circumstellar disk may develop around the protostar.
If conditions permit, nuclear fusion eventually begins in the stellar core.
UPSC key pointers
Molecular clouds are important sites of star formation.
Molecular hydrogen is their principal constituent.
Gravitational collapse is a key process in protostar formation.
A molecular cloud is not the same as a planetary nebula, which is a later-stage phenomenon associated with certain stars.
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