Editing Star cluster (section)

===Embedded cluster===
[[File:Chandra_X-ray_View_of_Orion.jpg|thumb|The [[embedded cluster|embedded]] Trapezium cluster seen in [[X-ray astronomy|X-rays]] which penetrate the surrounding clouds]]
{{main|Embedded cluster}}

Embedded clusters are groups of very young stars that are partially or fully encased in [[Cosmic dust|interstellar dust or gas]] which is often impervious to optical observations. Embedded clusters form in [[molecular clouds]], when the clouds begin to collapse and [[star formation|form stars]]. There is often ongoing star formation in these clusters, so embedded clusters may be home to various types of [[young stellar object]]s including [[protostar]]s and [[pre-main-sequence star]]s. An example of an embedded cluster is the [[Trapezium Cluster]] in the [[Orion Nebula]]. In [[Rho Ophiuchi cloud complex|ρ Ophiuchi cloud]] (L1688) core region there is an embedded cluster.<ref>{{cite journal|bibcode=1995ApJ...450..233G|title=An Infrared Spectroscopic Survey of the rho Ophiuchi Young Stellar Cluster: Masses and Ages from the H-R Diagram|journal=Astrophysical Journal |volume=450|pages=233|last1=Greene|first1=Thomas P|last2=Meyer|first2=Michael R|year=1995|doi=10.1086/176134}}</ref>

The embedded cluster phase may last for several million years, after which gas in the cloud is depleted by star formation or dispersed through [[radiation pressure]], [[stellar wind]]s and [[astrophysical jet|outflows]], or [[supernova explosion]]s. In general less than 30% of cloud mass is converted to stars before the cloud is dispersed, but this fraction may be higher in particularly dense parts of the cloud. With the loss of mass in the cloud, the energy of the system is altered, often leading to the disruption of a star cluster. Most young embedded clusters disperse shortly after the end of star formation.<ref name="Lada Lada 2003 pp. 57–115">{{cite journal | last1=Lada | first1=Charles J. | last2=Lada | first2=Elizabeth A. | title=Embedded Clusters in Molecular Clouds | journal=Annual Review of Astronomy and Astrophysics | volume=41 | issue=1 | year=2003 | issn=0066-4146 | doi=10.1146/annurev.astro.41.011802.094844 | pages=57–115| bibcode=2003ARA&A..41...57L | arxiv=astro-ph/0301540 | s2cid=16752089 }}</ref>

The open clusters found in the Galaxy are former embedded clusters that were able to survive early cluster evolution. However, nearly all freely floating stars, including the [[Sun]],<ref name="Gounelle Meynet p=A4">{{cite journal | last1=Gounelle | first1=M. | last2=Meynet | first2=G. | title=Solar system genealogy revealed by extinct short-lived radionuclides in meteorites | journal=Astronomy & Astrophysics | publisher=EDP Sciences | volume=545 | date=2012-08-27 | issn=0004-6361 | doi=10.1051/0004-6361/201219031 | page=A4| bibcode=2012A&A...545A...4G | arxiv=1208.5879 | s2cid=54970631 }}</ref> were originally born into embedded clusters that disintegrated.<ref name="Lada Lada 2003 pp. 57–115" />