Editing Hubble sequence (section)

{{Short description|Galaxy morphological classification scheme advocated by Edwin Hubble}}
The '''Hubble sequence''' is a [[galaxy morphological classification|morphological classification scheme]] for [[Galaxy|galaxies]] published by [[Edwin Hubble]] in 1926.<ref name="hubble26a">{{cite journal |last=Hubble |first=E.P. |author-link=Edwin Hubble |year=1926 |title=Extra-galactic nebulae |journal=Contributions from the Mount Wilson Observatory / Carnegie Institution of Washington |volume=324 |pages=1–49 |bibcode = 1926CMWCI.324....1H }}</ref><ref name="hubble26">{{cite journal |last=Hubble |first=E.P. |author-link=Edwin Hubble |year=1926 |title=Extra-galactic nebulae |journal=Astrophysical Journal |volume=64 |pages=321–369 |bibcode=1926ApJ....64..321H |doi = 10.1086/143018 |doi-access= }}</ref><ref name="hubble27" /><ref name=Hubble-1936>{{cite book |last=Hubble |first=E.P. |author-link=Edwin Hubble |year=1936 |title=The realm of the nebulae |publisher=Yale University Press |location=New Haven |isbn=9780300025002 |lccn=36018182 |oclc=611263346 |series=Mrs. Hepsa Ely Silliman memorial lectures |volume=25 |url=https://archive.org/details/TheRealmOfTheNebulae |via=Internet Archive (archive.org) }} {{cite book |title=Alt source |isbn=0300025009 |via=Google Books |url=https://books.google.com/books?id=kgiXdDGLpFUC |last1=Hubble |first1=Edwin Powell |date=January 1982 |publisher=Yale University Press }}</ref> It is often colloquially known as the '''Hubble tuning-fork diagram''' because the shape in which it is traditionally represented resembles a [[tuning fork]].
It was invented by John Henry Reynolds and Sir James Jeans.<ref>{{cite conference |first1=David L. |last1=Block |first2=Ken C. |last2=Freeman |orig-date=14 November 2014 |year=2015 |chapter=A walk with Dr.&nbsp;Allan Sandage – changing the history of galaxy morphology, forever |editor1=Freeman, Kenneth |editor2=Elmegreen, Bruce |editor3=Block, David |editor4=Woolway, Matthew |conference=2014 International conference honoring David Block and Bruce Elmegreen, focusing on the Local Group as an example of galactic-scale processes |book-title=Lessons from the Local Group |pages=1–20 |publisher=Springer Cham / Springer International Publishing |publication-place=Switzerland |isbn=978-3-319-37812-1 |edition=softcover |publication-date=10 September 2016 |doi=10.1007/978-3-319-10614-4_1 |bibcode=2015llg..book....1B }} (hardcover ed.) {{ISBN|978-3-319-10613-7}} (published 3&nbsp;December 2014); <br/> {{cite journal |title=ADS abstract |journal=NASA / Astrophysics Data System |date=2015 |publisher=[[Harvard University]] |bibcode=2015llg..book....1B }}</ref>

[[Image:Hubble Tuning Fork diagram.svg|thumb|350px|Tuning-fork style diagram of the Hubble sequence]]

The tuning fork scheme divided regular galaxies into three broad classes – [[elliptical galaxy|ellipticals]], [[lenticular galaxy|lenticulars]] and [[spiral galaxy|spirals]] – based on their visual appearance (originally on [[photographic plate]]s). A fourth class contains galaxies with an [[irregular galaxy|irregular]] appearance. The Hubble sequence is the most commonly used system for classifying galaxies, both in professional astronomical research and in [[amateur astronomy]].