Editing Elliptical galaxy (section)

{{Short description|Spherical or ovoid mass of stars}}
{{More footnotes needed|date=March 2015}}
{{Use dmy dates|date=October 2019}}

[[Image:Abell S740, cropped to ESO 325-G004.jpg|thumb|The giant elliptical galaxy [[ESO 325-4]]]]

An '''elliptical galaxy''' is a type of [[galaxy]] with an approximately [[ellipsoid]]al shape and a smooth, nearly featureless image. They are one of the three main [[galaxy morphological classification|classes of galaxy]] described by [[Edwin Hubble]] in his [[Hubble sequence#Physical significance|Hubble sequence]] and 1936 work ''The Realm of the Nebulae'',<ref name=Hubble-1936>{{cite book |last=Hubble |first=E.P. |author-link=Edwin Hubble |title=The realm of the nebulae |year=1936 |publisher=[[Yale University Press]] |location=New Haven |isbn=9780300025002 |oclc=611263346 |series=Mrs. Hepsa Ely [[Silliman Memorial Lectures]], 25 |url=https://books.google.com/books?id=kgiXdDGLpFUC }} [https://archive.org/details/TheRealmOfTheNebulae Alt URL](pp.&nbsp;124–151)</ref> along with [[spiral galaxy|spiral]] and [[lenticular galaxy|lenticular]] galaxies. 
Elliptical (E) galaxies are, together with lenticular galaxies (S0) with their large-scale disks, and ES galaxies<ref name="adsabs.harvard.edu">Liller, M.H. (1966), [http://adsabs.harvard.edu/abs/1966ApJ...146...28L The Distribution of Intensity in Elliptical Galaxies of the Virgo Cluster. II]</ref><ref>Nieto, J.-L. et al. (1988), [http://adsabs.harvard.edu/abs/1988A%26A...195L...1N More isotropic oblate rotators in elliptical galaxies]</ref><ref>Graham, A.W. et al. (2016), [http://adsabs.harvard.edu/abs/2016ApJ...831..132G Disky Elliptical Galaxies and the Allegedly Over-massive Black Hole in the Compact “ES“ Galaxy NGC 1271 (see their Fig.7).]</ref> with their intermediate scale disks, a subset of the "early-type" galaxy population.

Most elliptical galaxies are composed of older, [[stellar evolution#Low-mass stars|low-mass stars]], with a sparse [[interstellar medium]], and they tend to be surrounded by large numbers of [[globular cluster]]s. [[Star formation]] activity in elliptical galaxies is typically minimal; they may, however, undergo brief periods of star formation when merging with other galaxies.<ref>{{cite journal |last1=Pearson |first1=W. J. |last2=Wang |first2=L. |last3=Alpaslan |first3=M. |last4=Baldry |first4=I. |last5=Bilicki |first5=M. |last6=Brown |first6=M. J. I. |last7=Grootes |first7=M. W. |last8=Holwerda |first8=B. W. |last9=Kitching |first9=T. D. |last10=Kruk |first10=S. |last11=van der Tak |first11=F. F. S. |title=Effect of galaxy mergers on star-formation rates |journal=Astronomy & Astrophysics |date=November 2019 |volume=631 |pages=A51 |doi=10.1051/0004-6361/201936337|arxiv=1908.10115 |bibcode=2019A&A...631A..51P }}</ref> Elliptical galaxies are believed to make up approximately 10–15% of galaxies in the [[Virgo Supercluster]], and they are not the dominant type of galaxy in the universe overall.<ref>{{cite journal|author=Loveday, J.|date=February 1996|title=The APM Bright Galaxy Catalogue.|journal=[[Monthly Notices of the Royal Astronomical Society]]|volume=278|issue=4|pages=1025–1048|arxiv=astro-ph/9603040|bibcode=1996MNRAS.278.1025L|doi=10.1093/mnras/278.4.1025|doi-access=free }}</ref> They are preferentially found close to the centers of [[galaxy cluster]]s.<ref>{{cite journal|author=Dressler, A.|date=March 1980|title=Galaxy morphology in rich clusters – Implications for the formation and evolution of galaxies.|journal=The Astrophysical Journal|volume=236|pages=351–365|bibcode=1980ApJ...236..351D|doi=10.1086/157753|doi-access=free}}</ref>

Elliptical galaxies range in size from dwarf ellipticals with tens of millions of stars, to [[Type-cD galaxy|supergiants]] of over one hundred trillion [[star]]s that dominate their galaxy clusters. Originally, Edwin Hubble hypothesized that elliptical galaxies evolved into spiral galaxies, which was later discovered to be false,<ref name="author">John, D. (2006). ''Astronomy: The definitive guide to the universe''. Bath, UK: Parragon Publishing., p. 224-225</ref> although the accretion of gas and smaller galaxies may build a disk around a pre-existing ellipsoidal structure.<ref>Dekel, A., et al. (2009), [http://adsabs.harvard.edu/abs/2009Natur.457..451D Cold streams in early massive hot haloes as the main mode of galaxy formation]</ref><ref>Stewart, Kyle R., et al. (2013), [http://adsabs.harvard.edu/abs/2013ApJ...769...74S Angular Momentum Acquisition in Galaxy Halos]</ref>
Stars found inside of elliptical galaxies are on average much older than stars found in spiral galaxies.<ref name="author" />