Editing Stephan's Quintet

{{Short description|Visual grouping of five galaxies}}
{{Galaxy cluster
| name = Stephan's Quintet 
| image = [[File:Stephan's Quintet Hubble 2009.full denoise.jpg|300px]]
| caption = Clockwise from upper left: [[NGC 7320]], [[NGC 7319]], [[NGC 7318]] (a and b), [[NGC 7317]]
| credit= [[Hubble Space Telescope]]
| epoch = [[J2000]]
| ra = {{RA|22|35|57.5}}<ref name="ned">{{cite web|title=NASA/IPAC Extragalactic Database|work=Results for HCG 92| url=http://nedwww.ipac.caltech.edu/|access-date=2006-09-18}}</ref>
| dec = {{DEC|+33|57|36}}<ref name="ned"/>
| constellation = [[Pegasus (constellation)|Pegasus]]
| member_no = 5<ref name="ned"/>
| brightest_member = [[NGC 7318B]]<ref name="ned"/>
| other_names = [[Hickson Compact Group|HCG]] 92, [[Atlas of Peculiar Galaxies|Arp]] 319, VV 288,<ref name="ned"/> SQ<ref name="Molesetal1998">{{cite journal| author=Moles, M.| author2=Marquez, I.| author3=Sulentic, J. W.
| title=The observational status of Stephan's Quintet | journal=Astronomy and Astrophysics|date=1998|volume=334|pages=473–481|bibcode=1998A&A...334..473M |arxiv = astro-ph/9802328 }}</ref>
}}

'''Stephan's Quintet''' is a visual grouping of five [[galaxies]] of which four form the first [[Galaxy group#Compact Groups|compact galaxy group]] ever discovered.<ref name="Molesetal1998"/> The group, visible in the constellation [[Pegasus (constellation)|Pegasus]], was discovered by [[Édouard Stephan]] in 1877 at the [[Marseille Observatory]].<ref name="Stephan1877">{{cite journal
 | author=Stephan, M. E.
 | title=Nebulæ (new) discovered and observed at the observatory of Marseille, 1876 and 1877, M. Stephan
 | journal=[[Monthly Notices of the Royal Astronomical Society]]
 | date=1877
 | volume=37
 | pages=334–339
 | bibcode=1877MNRAS..37..334S 
 | doi = 10.1093/mnras/37.6.334 | doi-access=free
 }}</ref>
The group is the most studied of all the compact galaxy groups.<ref name="Molesetal1998"/> The brightest member of the visual grouping (and the only non-member of the true group) is [[NGC 7320]], which has extensive [[H II region]]s, identified as red blobs, where active star formation is occurring.

Four of the five galaxies in Stephan's Quintet form a physical association, a true [[galaxy group]], [[Hickson Compact Group]] 92, and will likely merge with each other. Radio observations in the early 1970s revealed a filament of emission between the galaxies in the group. This same region is also detected in the faint glow of ionized atoms seen in the visible part of the spectrum as a green arc.

Space telescopes have provided new insight into the nature of the filament, which is now believed to be a [[shock-wave]] in the [[intergalactic gas]], caused by one galaxy (NGC 7318B) falling into the center of the group at several million kilometres per hour.

Stephan's Quintet was selected as one of the five cosmic objects observed by the [[James Webb Space Telescope]] as part of the release of its first official science images.<ref>{{Cite web |last=Garner |first=Rob |date=2022-07-08 |title=NASA Shares List of Cosmic Targets for Webb Telescope's 1st Images |url=http://www.nasa.gov/feature/goddard/2022/nasa-shares-list-of-cosmic-targets-for-webb-telescope-s-first-images |access-date=2022-07-08 |website=NASA}}</ref>

== Emissions ==

=== X-rays ===
[[Image:Stephan's Quintet X-ray + Optical.jpg|thumb|300px|right|Stephan's Quintet. The blue arc across the top center is a shock caused by colliding intergalactic gas. Image Credits: X-ray (blue): NASA/CXC/CfA/E. O'Sullivan Optical (brown): Canada-France-Hawaii-Telescope/Coelum]]

As [[NGC 7318|NGC 7318B]] collides with gas in the group, a huge shock wave bigger than the Milky Way spreads throughout the medium between the galaxies, heating some of the gas to temperatures of millions of degrees where they emit X-rays detectable with the [[NASA]] [[Chandra X-ray Observatory]].<ref>{{Cite web|url=https://chandra.harvard.edu/photo/2003/stephan/|title=Chandra :: Photo Album :: Stephan's Quintet :: 08 May 03|website=chandra.harvard.edu|access-date=2019-12-24}}</ref><ref>{{Cite web|url=https://www.space.com/2125-shock-galaxies-caught-colliding.html|title=What a Shock! Galaxies Caught Colliding|last=Than 2006-03-07T11:18:00Z|first=Ker|website=Space.com|date=7 March 2006 |language=en|access-date=2019-12-24}}</ref><ref>{{Cite web|url=https://phys.org/news/2006-03-gigantic-cosmic-cataclysm-stephan-quintet.html|title=Gigantic cosmic cataclysm in Stephan's Quintet of galaxies|website=phys.org|language=en-us|access-date=2019-12-24}}</ref>

===Molecular hydrogen emission===

The [[NASA]] [[Spitzer Space Telescope]], which detects infrared radiation, discovered a very powerful molecular hydrogen signal from the shock wave between the galaxies. This emission is one of the most turbulent formations of molecular hydrogen ever seen, and the strongest emission originates near the center of the green area in the visible light picture discussed earlier. This phenomenon was discovered by an international team led by scientists at the [[California Institute of Technology]] and including scientists from Australia, Germany and China. The detection of molecular hydrogen from the collision was initially unexpected because the hydrogen molecule is very fragile and is easily destroyed in shock waves of the kind expected in Stephan's Quintet. However, one solution is that when a shock front moves through a cloudy medium like the center of the group, millions of smaller shocks are produced in a turbulent layer, and this can allow molecular hydrogen to survive.
[[File:Stephans Quintet sdss-g Goran Nilsson & The Liverpool Telescope.jpg|thumb|Earthbound monochrome (sdss-g filtered) image of Stephan's Quintet from the [[Liverpool Telescope]]]]

===Redshift===

NGC 7320 indicates a small [[redshift]] (790&nbsp;km/s) while the other four exhibit large redshifts (near 6,600&nbsp;km/s). Since galactic redshift is proportional to distance, NGC 7320 is only a foreground projection<ref name="Molesetal1998"/> and is ~39 million light-years<ref name="Molesetal1998"/> from [[Earth]], making it a possible member of the [[NGC 7331]] group, versus the 210–340 million light-years of the other four.<ref>{{Cite web|url=http://pages.astronomy.ua.edu/gifimages/stephan.html|title=Stephan's Quintet|website=pages.astronomy.ua.edu|access-date=2019-12-24}}</ref>

[[NGC 7319]] has a type 2 [[Seyfert galaxy|Seyfert]] nucleus.

[[File:StephansQuintettIlustrated2.gif|500px|thumb|center|alt=Photo of the area of the Hubble photo, with the various galaxies labeled by NGC number|The galaxies in the vicinity of Stephan's Quintet. The rectangle indicates the area covered by the 1998–99 [[:File:StephansQuintet3.jpg|Hubble Space Telescope image]] below.]]

A sixth galaxy, NGC&nbsp;7320C, probably belongs to the Hickson association: it has a redshift similar to the Hickson galaxies, and a tidal tail appears to connect it with NGC&nbsp;7319.<ref>{{Cite web|url=https://www.noao.edu/image_gallery/html/im0414.html|title=National Optical Astronomy Observatory: Stephan's Quintet|website=www.noao.edu|access-date=2019-12-24|archive-date=2019-12-24|archive-url=https://web.archive.org/web/20191224142658/https://www.noao.edu/image_gallery/html/im0414.html|url-status=dead}}</ref>

[[File:StephansQuintet3.jpg|thumb|Detail of the quintet in a photo by [[Hubble Space Telescope]], 1998–99. Credits: [[NASA]]/[[ESA]]]]

===Infrared===
Using its Mid Infrared Instrument (MIRI), the [[James Webb Space Telescope]] shows details shrouded by dust in visible light including large shock waves and tidal tails in four of the five galaxies, and previously hidden areas of star formation. These new details will contribute to insights on galaxy evolution. <ref>{{Cite web|date=2022-07-12|title=Stephan's Quintet (MIRI Image) |url=https://webbtelescope.org/contents/media/images/2022/034/01G7DBCJA1M1SSGKDMH7F5XMBE |access-date=2022-07-12 |website=James Webb Space Telescope}}</ref>

[[File:Stephan's Quintet (MIRI Image) (2022-034-01G7DBCJA1M1SSGKDMH7F5XMBE).png|thumb|center|Four galaxies (Missing is NGC 7317) of Stephan's Quintet using MIRI by [[James Webb Space Telescope]]]]

==Members==
{| class="wikitable" style="text-align:center;border-collapse:collapse" cellpadding="2"
|+'''Members of the Hickson Compact Group 92'''
|-
! style="background:#efefef;" | Name
! style="background:#efefef;" | [[Galaxy morphological classification|Type]]<ref name="ned2">{{cite web
 | title=NASA/IPAC Extragalactic Database
 | work=Results for various galaxies
 | url=http://nedwww.ipac.caltech.edu/
 | access-date=2006-10-20}}</ref>
! style="background:#efefef;" | [[Right Ascension|R.A.]] ([[J2000]])<ref name="ned2"/>
! style="background:#efefef;" | [[Declination|Dec.]] ([[J2000]])<ref name="ned2"/>
! style="background:#efefef;" | [[Redshift]] (km/s)<ref name="ned2"/>
! style="background:#efefef;" | [[Apparent Magnitude]]<ref name="ned2"/>
|- 
| [[NGC 7317]]
| E4
| {{RA|22|35|51.9}}
| {{DEC|+33|56|42}}
| 6,599 ± 26
| +14.6
|-
| [[NGC 7318a]]<br>(UGC 12099)
| E2 pec
| {{RA|22|35|56.7}}
| {{DEC|+33|57|56}}
| 6,630 ± 23
| +14.3
|-
| [[NGC 7318b]]<br>(UGC 12100)
| SB(s)bc pec
| {{RA|22|35|58.4}}
| {{DEC|+33|57|57}}
| 5,774 ± 24
| +13.9
|-
| [[NGC 7319]]
| SB(s)bc pec
| {{RA|22|36|03.5}}
| {{DEC|+33|58|33}}
| 6,747 ± 7
| +14.1
|-
| [[NGC 7320c]]
| (R)SAB(s)0/a
| {{RA|22|36|20.4}}
| {{DEC|+33|59|06}}
| 5,985 ± 9
| +16.7
|-
|}

== In popular culture ==
The angelic figures at the beginning of the 1946 holiday film ''[[It's a Wonderful Life]]'' are based on images of Stephan's Quintet.<ref>{{Cite web|url=https://www.spacetelescope.org/images/opo0122h/|title=Stephan's Quintet|website=ESA/Hubble Space Telescope|language=en|access-date=2019-12-22}}</ref><ref>{{Cite web|url=https://www.wral.com/Classic-film-Its-a-Wonderful-Life-features-angelic-galaxies/18849527/|title=Classic film 'It's a Wonderful Life' features angelic galaxies|last=Rice|first=Tony|date=2019-12-22|website=WRAL|language=en|access-date=2019-12-24}}</ref>

== Gallery ==
<gallery>
File:NGC7317 CDK Large04.jpg|Stephan's Quintet acquired with 17" PlaneWave CDK scope by W4SM in Louisa, VA
File:Stephan's Quintet taken by James Webb Space Telescope.jpg|alt=Image mosaic of Stephan's Quintet|Near-to-mid-infrared composite of [[NIRCam]] and MIRI imagery from the [[James Webb Space Telescope]].
</gallery>

== See also ==
* [[Wild's Triplet]]
* [[Zwicky's Triplet]]
* [[NGC 7331 Group]] (''Deer Lick Group'', about half a degree northeast of Stephan's Quintet)
* [[Robert's Quartet]]
* [[Seyfert's Sextet]]
* [[Copeland Septet]]

==References==
{{reflist}}

==External links==
{{commons category|Stephan's Quintet}}
* [http://www.galex.caltech.edu/media/glx2005-02r_img06.html GALEX: Stephan's Quintet and NGC 7331]
* [http://hubblesite.org/newscenter/newsdesk/archive/releases/2001/22/text/ Star Clusters Born in the Wreckage of Cosmic Collisions]
* [http://www.spacetelescope.org/news/html/heic0007.html News Release at ESA/Hubble]
* [http://www.dsi-astronomie.de/NGC7320.html Stephan's Quintet]
* [http://www.nightskyinfo.com/archive/stephans_quintet/ NightSkyInfo.com : Stephan's Quintet]
* [http://chandra.harvard.edu/blog/node/150 What's Behind Stephan's Quintet?] Peter Edmonds, Chandra Blog, 21 July 2009
* Astronomy Picture of the Day on Stephan's Quintet: [http://antwrp.gsfc.nasa.gov/apod/ap001113.html 13 Nov 2000] &nbsp; [http://antwrp.gsfc.nasa.gov/apod/ap030812.html 12 Aug 2003] &nbsp; [http://antwrp.gsfc.nasa.gov/apod/ap090911.html 11 Sep 2009]
* [https://webbtelescope.org/contents/news-releases/2022/news-2022-034 NASA’s James Webb Space Telescope reveals never-before-seen details of the galaxy group called “Stephan’s Quintet.”]
* {{WikiSky}}
{{Sky|22|35|57.5|+|33|57|36|300000000}}
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[[Category:Stephan's Quintet| ]]
[[Category:Hickson Compact Groups|92]]
[[Category:Pegasus (constellation)]]
[[Category:Astronomical objects discovered in 1877]]
[[Category:Discoveries by Édouard Stephan]]