Editing Globular cluster (section)

{{short description|Spherical collection of stars}}
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{{Use mdy dates|date=December 2021}}
{{Infobox astronomical formation
|name=Globular cluster
|image=File:Globular Cluster M2.jpg
|caption= [[Messier 2]]
|thing= [[Star cluster]]
|qid=Q11276
|commonscat=Globular Clusters
|discover=Abraham Ihle, 1665
|Mass= 1{{abbr|K|thousand}} {{solar mass}} - >1{{abbr|M|million}} {{solar mass}}<ref name=britannica>{{Cite web |title=Globular cluster - Colour-magnitude diagrams {{!}} Britannica |url=https://www.britannica.com/science/globular-cluster/Colour-magnitude-diagrams |access-date=2023-03-11 |website=www.britannica.com |language=en}}</ref>
|density= ~2 stars/cubic {{abbr|ly|light year}} <ref name=britannica/>
|size=10-300 ly across<ref name=britannica/>
|luminosity = ~25 000 {{Solar luminosity}}<ref name=britannica/>
}}
A '''globular cluster''' is a [[spheroid]]al conglomeration of [[star]]s that is bound together by [[gravity]], with a higher concentration of stars towards its center. It can contain anywhere from tens of thousands to many millions of member stars,<ref>{{cite web | title=Globular cluster | website=ESA/Hubble | url=https://esahubble.org/wordbank/globular-cluster/ | access-date=2022-07-04}}</ref> all orbiting in a stable, compact formation. Globular clusters are similar in form to [[dwarf spheroidal galaxy|dwarf spheroidal galaxies]], and though globular clusters were long held to be the more luminous of the two, discoveries of outliers had made the distinction between the two less clear by the early 21st century.<ref>{{cite journal
 | title=Globular clusters and dwarf spheroidal galaxies
 | first=Sidney | last=Van Den Bergh
 | journal=Monthly Notices of the Royal Astronomical Society: Letters
 | volume=385 | issue=1 | date=March 2008 | pages=L20–L22
 | doi=10.1111/j.1745-3933.2008.00424.x
 | doi-access=free | arxiv=0711.4795 | bibcode=2008MNRAS.385L..20V }}</ref> Their name is derived from [[Latin]] {{lang|la|globulus}} (small sphere). Globular clusters are occasionally known simply as "globulars".

Although one globular cluster, [[Omega Centauri]], was observed in antiquity and long thought to be a star, recognition of the clusters' true nature came with the advent of telescopes in the 17th century. In early telescopic observations, globular clusters appeared as fuzzy blobs, leading French astronomer [[Charles Messier]] to include many of them in [[Messier catalog|his catalog]] of astronomical objects that he thought could be mistaken for [[comet]]s. Using larger telescopes, 18th-century astronomers recognized that globular clusters are groups of many individual stars. Early in the 20th century the distribution of globular clusters in the sky was some of the first evidence that the [[Sun]] is far from the center of the [[Milky Way]].

Globular clusters are found in nearly all [[Galaxy|galaxies]]. In [[Spiral galaxy|spiral galaxies]] like the Milky Way, they are mostly found in the outer spheroidal part of the galaxy{{snd}}the [[galactic halo]]. They are the largest and most massive type of [[star cluster]], tending to be older, denser, and composed of lower abundances of [[Metallicity|heavy element]]s than [[open cluster]]s, which are generally found in the [[Galactic disk|disk]]s of spiral galaxies. The Milky Way has more than 150 [[List of globular clusters|known globular]]s, and there may be many more.

Both the origin of globular clusters and their role in [[Galaxy formation and evolution|galactic evolution]] are unclear. Some are among the oldest objects in their galaxies and even the [[universe]], constraining estimates of the [[Age of the universe|universe's age]]. Star clusters were formerly thought to consist of stars that all [[Star formation|form]]ed at the same time from one [[Giant molecular cloud|star-forming nebula]], but nearly all globular clusters contain stars that formed at different times, or that have differing compositions. Some clusters may have had multiple episodes of star formation, and some may be remnants of smaller galaxies captured by larger galaxies.