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{{Infobox Galaxy
| image = [[Image:Galaxy arp 220.jpg|250px|]]
| name = [[Atlas of Peculiar Galaxies|Arp]] 220
| epoch = [[J2000]]
| type = S?<ref name="ned">{{cite web
| title=NASA/IPAC Extragalactic Database
| work=Results for Arp 220
| url=http://nedwww.ipac.caltech.edu/
| accessdate=2006-12-07}}</ref>
| ra = {{RA|15|34|57.1}}<ref name="ned" />
| dec = {{DEC|+23|30|11}}<ref name="ned" />
| dist_ly =
| z = 5434 ± 7 km/[[second|s]]<ref name="ned" />
| appmag_v = 13.9<ref name="ned" />
| size_v = 1′.5 x 1′.2<ref name="ned" />
| constellation name = [[Serpens]]
| notes =
| names = [[Index Catalogue|IC]] 1127,<ref name="ned" /> [[Index Catalogue|IC]] 4553,<ref name="ned" /><br>
[[Uppsala General Catalogue|UGC]] 9913,<ref name="ned" /> [[Principal Galaxies Catalogue|PGC]] 55497<ref name="ned" />
}}
'''Arp 220''' is the result of a collision between two galaxies which are now in the process of merging. It is the 220th object in [[Halton Arp]]'s ''[[Atlas of Peculiar Galaxies]]''.

==Features==
[[Image:Apr220 Hubble WikiSky.jpg|thumb|left|200px|Wider angle (2.4′ ) view by [[Hubble Space Telescope]]]]
[[File:The merging galaxy system Arp 220 from ALMA and Hubble.jpg|thumb|Compound view shows a [[Atacama Large Millimeter Array|ALMA]] Band 5 image of the colliding galaxy system Arp 220.<ref>{{cite web|title=First Light for Band 5 at ALMA - New receivers improve ALMA’s ability to search for water in the Universe|url=https://www.eso.org/public/news/eso1645/|website=www.eso.org|accessdate=22 December 2016}}</ref>]]
Arp 220 is the closest [[Ultraluminous Infrared Galaxy]] (ULIRG) to Earth. Its energy output was discovered by [[IRAS]] to be dominated by the [[far-infrared]] part of the spectrum.<ref>''IRAS exposes a remarkable infrared galaxy'' , Physics Today, 37, part no 8, 18-20 (1984)</ref>
It is often regarded as the prototypical ULIRG and has been the subject of much study as a result.
Most of its energy output is thought to be the result of a massive burst of star formation, or [[Starburst (astronomy)|starburst]], probably triggered by the merging of two smaller galaxies.
Recent (2002 and 1997) [[Hubble Space Telescope|HST]] observations of Arp 220, taken in visible light with the [[Advanced Camera for Surveys|ACS]], and in infrared light with [[Near Infrared Camera and Multi-Object Spectrometer|NICMOS]], revealed more than 200 huge [[star cluster]]s in the central part of the galaxy.
The most massive of these clusters contains enough material to equal about 10 million suns.<ref name="HST">{{cite web
| title=Hubble Eyes Star Birth in the Extreme
| url=http://hubblesite.org/newscenter/newsdesk/archive/releases/2006/26/full
| accessdate=2006-10-16}}</ref>
X-ray observations by the [[Chandra X-ray Observatory|Chandra]] and [[XMM-Newton]] satellites have shown that Arp 220 probably includes an [[active galactic nucleus]] (AGN) at its core, which raises interesting questions about the link between galaxy mergers and AGN, since it is believed that galactic mergers often trigger starbursts, and may also give rise to the supermassive black holes that appear to power AGN.

Luminous far-infrared objects like Arp 220 have been found in surprisingly large numbers by sky surveys of [[Submillimetre astronomy|submillimetre wavelengths]] using instruments such as the Submillimetre Common-User Bolometer Array (SCUBA) at the [[James Clerk Maxwell Telescope]] (JCMT).
Arp 220 and other relatively local [[ULIRG]]s are being studied as equivalents of this kind of object.

Astronomers from the [[Arecibo Observatory]] have detected organic molecules in the galaxy.<ref>{{cite news | title=Arecibo telescope finds critical ingredients for the soup of life in a galaxy far, far away | date=2008-01-14 | publisher=[[Cornell University]] | url =http://www.news.cornell.edu/stories/Jan08/Arecibo.methanimine.html | work =Cornell Chronicle | pages = | accessdate = 2008-04-01 | archiveurl= https://web.archive.org/web/20080512090327/http://www.news.cornell.edu/stories/Jan08/Arecibo.methanimine.html| archivedate= 12 May 2008 | deadurl= no}}</ref>

Arp 220 contains at least two bright maser sources, an OH [[megamaser]], and a [[Astrophysical maser|water maser]].<ref name="simbad">{{cite web
| title=SIMBAD Astronomical Database
| work=Results for Arp 220
| url=http://simbad.u-strasbg.fr/Simbad
| accessdate=2006-12-07}}</ref>

In October 2011, astronomers spotted a record-breaking seven [[supernova]] all found at the same time in Arp 220.<ref>{{cite press release
| publisher = [http://www.chalmers.se/rss/EN/research/research-groups/radio-astronomy/staff/phd-students/batejat-fabien Fabien Batejat] from [[Chalmers University of Technology#Departments|Radio Astronomy and Astrophysics Group]], [[National Geographic Society]]
| date = October 6, 2011
| format =
| language =
| title =Seven Supernovae Found in Single Galaxy—A First
|trans-title=| url = http://news.nationalgeographic.com/news/2011/10/111006-supernovas-universe-galaxy-evolution-arp-220-space-science/
| accessdate = October 10, 2011
| quote = "we can confirm seven supernovae [in a single galaxy], thanks to a 17-year monitoring of the radio sources in Arp 220"
| ref =
}}</ref><ref>{{cite press release
|publisher=Phương Huyền, [[Science Daily]]
|date=October 3, 2011
|format=
|language=Vietnamese
|title=Phát hiện chưa từng thấy về các siêu tân tinh
|trans-title=|url=http://khoahoc.tv/phat-hien-chua-tung-thay-ve-cac-sieu-tan-tinh-35380
|accessdate=October 10, 2011
|quote="Với tất cả dữ liệu tìm thấy, chúng tôi có thể chắc chắn rằng 7 tín hiệu đó chính là các siêu tân tinh - những ngôi sao đã nổ tung trong 60 năm qua"
|ref=
}}</ref><ref>{{cite press release
| publisher = [[Science Daily]]
| date = Oct 2, 2011
| language =
| title =Astronomers Reveal Supernova Factory
|trans-title=| url = http://www.sciencedaily.com/releases/2011/09/110930071705.htm
| accessdate = Oct 10, 2011
| archiveurl = https://web.archive.org/web/20110930233740/http://www.sciencedaily.com/releases/2011/09/110930071705.htm
| archivedate = 2011-09-30
| quote = "With all the data in place, we can now be certain that all seven of these sources are supernovae: stars that exploded in the last 60 years"
| dead-url = yes
| ref =
}}</ref>

The merging of the two galaxies started around 700 million years ago.<ref>{{Cite web|url=https://www.spacetelescope.org/images/heic0810bf/|title=Arp 220|last=United Space in Europe|first=|date=|website=www.spacetelescope.org|language=en-GB|access-date=2017-04-08}}</ref>

==References==
{{reflist}}

==External links==
{{commons category|Arp 220}}
* [http://www.spacedaily.com/reports/Hubble_Sees_Star_Birth_Gone_Wild.html Hubble Sees Star Birth Gone Wild] (SpaceDaily) Jun 16, 2006
* {{WikiSky}}

{{Sky|15|34|57.1|+|23|30|11|250000000}}

[[Category:Spiral galaxies]]
[[Category:Interacting galaxies]]
[[Category:Starburst galaxies]]
[[Category:IC objects]]
[[Category:UGC objects|09913]]
[[Category:Principal Galaxies Catalogue objects|55497]]
[[Category:Arp objects|220]]
[[Category:Astronomical objects discovered in 1866|18660504]]
[[Category:Astronomical objects discovered in 2011|20111002]]
[[Category:Luminous infrared galaxies]]

Arp 220 - Revision history

CriticalT: 1 revision imported