Editing Molecular cloud (section)

== Star formation ==
{{main|Star formation}}

[[File:Herschel’s_view_of_the_Taurus_molecular_cloud_ESA384012.jpg|thumb|left|Taurus Molecular Cloud. Located about 430 light-years from us, this vast complex of interstellar clouds is where a large amount of stars are being born, and is the closest large region of star formation.]]Star formation involves the collapse of the densest part of the molecular cloud, fragmenting the collapsed region in smaller clumps. These clumps aggregate more interstellar material, increasing in density by gravitational contraction. This process continues until the temperature reaches a point where the fusion of hydrogen can occur.<ref name=":maurizio">{{Cite book |last1=Salaris |first1=Maurizio |title=Evolution of stars and stellar populations |last2=Cassisi |first2=Santi |date=2005 |publisher=Wiley |isbn=978-0-470-09220-0 |location=Chichester}}</ref> The burning of hydrogen then generates enough heat to push against gravity, creating [[hydrostatic equilibrium]]. At this stage, a [[protostar]] is formed and it will continue to aggregate gas and dust from the cloud around it.

One of the most studied star formation regions is the [[Taurus molecular cloud]] due to its close proximity to earth (140 [[Parsec|pc]] or 430 [[Light-year|ly]] away), making it an excellent object to collect data about the relationship between molecular clouds and star formation. Embedded in the Taurus molecular cloud there are [[T Tauri star]]s. These are a class of [[variable star]]s in an early stage of stellar development and still gathering gas and dust from the cloud around them. Observation of star forming regions have helped astronomers develop theories about [[stellar evolution]]. Many [[O-type star|O]] and [[Stellar classification|B]] type stars have been observed in or very near molecular clouds. Since these star types belong to [[Stellar population|population I]] (some are less than 1 million years old), they cannot have moved far from their birth place. Many of these young stars are found embedded in cloud clusters, suggesting stars are formed inside it.<ref name=":maurizio" />