View source for Astronomy:SN 185

{{Short description|Possible supernova event}}
{{Infobox supernova
|name    = Supernova SN 185
|image   =Image:RCW 86.jpg
|caption = [[Physics:Infrared|Infrared]] images from NASA's [[Astronomy:Spitzer Space Telescope|Spitzer Space Telescope]] and [[Astronomy:Wide-field Infrared Survey Explorer|WISE]] are combined with X-ray data from the [[Astronomy:Chandra X-ray Observatory|Chandra X-ray Observatory]] and ESA's [[Astronomy:XMM-Newton|XMM-Newton]] Observatory in this image of RCW 86.
|epoch   = J2000
|type    = [[Astronomy:Supernova#Type I|Type Ia]]?
|SNRtype = Shell
|host    = [[Astronomy:Milky Way|Milky Way]]
|constellation = [[Astronomy:Circinus|Circinus]] and [[Astronomy:Centaurus|Centaurus]]
|ra          = {{RA|14|43}}
|dec         = {{DEC|−62|30}}
|gal         = G315.4−2.3
|discovery   = 7 December  185
|iauc        =
|mag_v       = "as much as -8"<ref name=stothers/>
|distance    = {{convert|2800|parsec|abbr=on|lk=off}}<ref name=Volk/>
|predecessor = None known
|successor   = [[Astronomy:SN 386|SN 386]]
|notes       = Ancient records of SN 185 may be the earliest written description of a supernova.
}}

'''SN 185''' was a [[Astronomy:Transient astronomical event|transient astronomical event]] observed in the year AD 185, likely a [[Astronomy:Supernova|supernova]]. The transient occurred in the direction of [[Astronomy:Alpha Centauri|Alpha Centauri]], between the constellations Circinus and [[Astronomy:Centaurus|Centaurus]], centered at [[Right ascension|RA]] {{RA|14|43}} [[Declination|Dec]] {{Dec|-62|30}}, in Circinus. This "[[Astronomy:Guest star|guest star]]" was observed by [[Astronomy:Chinese astronomy|Chinese astronomers]] in the ''Book of Later Han'' (后汉书),<ref>{{Cite journal
 |author=Zhao FY|author2= Strom RG|author3=Jiang SY 
 |title=The Guest Star of AD185 Must Have Been a Supernova 
 |journal=Chinese Journal of Astronomy and Astrophysics  
 |date=2006 
 |volume=6 
 |issue=5 
 |pages=635&ndash;40 
 |doi=10.1088/1009-9271/6/5/17 
 |bibcode = 2006ChJAA...6..635Z 
|doi-access=free 
 }}</ref> and might have been recorded in Roman literature.<ref name=stothers
>{{Cite journal|last = Stothers 
 |first = Richard 
 |title=Is the Supernova of A.D. 185 Recorded in Ancient Roman Literature? 
 |journal=Isis 
 |date=1977 
 |volume=68 
 |issue=3 
 |pages=443&ndash;447 
 |jstor=231322 
 |doi=10.1086/351822 
|s2cid = 145250371 
 }}</ref> It remained visible in the night sky for eight months. This is believed to be the first supernova for which records exist.

==History==
''The Book of Later Han'' gives the following description:

<blockquote>In the 2nd year of the epoch Zhongping [中平], the 10th month, on the day Guihai [癸亥] [December 7, Year 185], a '[[Astronomy:Guest star|guest star]]' appeared in the middle of the [[Astronomy:Horn (Chinese constellation)|Southern Gate]] [南門] [an asterism consisting of [[Astronomy:Epsilon Centauri|ε Centauri]] and [[Astronomy:Alpha Centauri|α Centauri]]], The size was half a bamboo mat. It displayed various colors, both pleasing and otherwise.<ref>{{Cite book |last=Ye |first=Fan |url=http://chinesenotes.com/houhanshu/houhanshu113.html |title=Book of the Later Han}}</ref> It gradually lessened. In the 6th month of the succeeding year it disappeared.<ref>《後漢書·卷十二·天文下》："中平二年十月癸亥，客星出南門中，大如半筵，五色喜怒稍小，至後年六月消。占曰：‘為兵。’至六年，司隸校尉袁紹 誅滅中官，大將軍 部曲將 吳匡 攻殺 車騎將軍 何苗，死者數千人。"</ref></blockquote>

The gaseous shell [[Astronomy:RCW Catalogue|RCW]] 86 is probably the [[Astronomy:Supernova remnant|supernova remnant]] of this event and has a relatively large angular size of roughly 45 arc minutes<ref name=Volk
>{{Cite journal
 |author=Völk HJ|author2=Berezhko EG|author3=Ksenofontov LT 
 |title=Magnetic field amplification in Tycho and other shell-type supernova remnants 
 |journal=Astron. Astrophys. 
 |date=2005 
 |volume=433 
 |issue= 1
 |pages=229&ndash;40 
 |doi=10.1051/0004-6361:20042015 
 |url=http://www.aanda.org/index.php?option=article&url=/articles/aa/full/2005/13/aa2015/aa2015.right.html&access=standard 
 |bibcode=2005A&A...433..229V
 |arxiv = astro-ph/0409453 
|s2cid=16726273}}</ref> (larger than the apparent size of the full moon, which varies from 29 to 34 arc minutes). The distance to RCW 86 is estimated to be {{convert|2800|parsec|abbr=off|lk=on}}.<ref name=Volk/> Recent X-ray studies show a good match for the expected age.<ref>{{Cite news
 |title=New evidence links stellar remains to oldest recorded supernova 
 |publisher=ESA News 
 |date=2006-09-18 
 |url=http://www.esa.int/esaCP/SEMGE58LURE_index_0.html 
 |access-date=2006-05-24}}</ref>

Infrared observations from NASA's [[Astronomy:Spitzer Space Telescope|Spitzer Space Telescope]] and [[Astronomy:Wide-field Infrared Survey Explorer|Wide-field Infrared Survey Explorer]] (WISE) reveal how the supernova occurred and how its shattered remains ultimately spread out to great distances. The findings show that the stellar explosion took place in a hollowed-out cavity, allowing material expelled by the star to travel much faster and farther than it would have otherwise.<ref name="nasa-2011-10-24"
>{{Cite news 
 |title=NASA Telescopes Help Solve Ancient Supernova Mystery 
 |publisher=NASA 
 |date=2011-10-24 
 |url=http://www.nasa.gov/mission_pages/spitzer/news/spitzer20111024.html 
 |access-date=2011-10-25 
 |archive-date=2019-06-17 
 |archive-url=https://web.archive.org/web/20190617105712/https://www.nasa.gov/mission_pages/spitzer/news/spitzer20111024.html 
 |url-status=dead 
 }}</ref>

Differing modern interpretations of the Chinese records of the guest star have led to quite different suggestions for the astronomical mechanism behind the event, from a core-collapse supernova<ref name="nasa-2011-10-24" /> to a distant, slow-moving comet<ref name=Chin>{{cite journal
 |author1=Y.-N. Chin |author2=Y.-L. Huang
 |date=29 September 1994
 |title=Identification of the Guest Star of AD 185 as a comet rather than a supernova
 |journal=Nature
 |doi=10.1038/371398a0
 |volume=371
 |issue=6496
 |pages=398–399
 |url=http://mail.tku.edu.tw/einmann/papers/SN185.ps |format=PS
|bibcode = 1994Natur.371..398C |s2cid=4240119
 }}</ref> &ndash; with correspondingly wide-ranging estimates of its apparent visual magnitude (&minus;8 to +4). The recent [[Astronomy:Chandra X-ray Observatory|Chandra]] results suggest that it was most likely a [[Astronomy:Type Ia supernova|Type Ia]] supernova (a type with consistent absolute magnitude),<ref name="nasa-2011-10-24" /><ref name="ApJ-2011-10-21">{{Cite journal
 |last=Williams |first=Brian J. |display-authors=0 
 |title=RCW 86: A Type Ia Supernova in a Wind-blown Bubble 
 |journal=The Astrophysical Journal 
 |date=October 2011 
 |volume=741 
 |issue= 2
 |page=96
 |doi=10.1088/0004-637X/741/2/96
 |arxiv=1108.1207 |bibcode=2011ApJ...741...96W |s2cid=118523755 }}</ref> and therefore similar to Tycho's Supernova (SN 1572), which had apparent magnitude &minus;4 at a similar distance.

==Gallery==
<gallery heights="200px" mode="packed">
File:Iotw2236a - RCW 86.jpg|{{center|The SMARTS 0.9-meter Telescope has captured an echo of the past in this image. RCW 86 is a literal shell of its former self, the gaseous remnant of a supernova. }}<ref>{{cite news|title=Dynastic Vibes|url=https://noirlab.edu/public/images/iotw2236a/|access-date=26 December 2022}}</ref>
</gallery>


==See also==
* [[Astronomy:List of supernovae|List of supernovae]]
* [[Astronomy:History of supernova observation|History of supernova observation]]
* [[Astronomy:List of supernova remnants|List of supernova remnants]]
* [[Astronomy:List of supernova candidates|List of supernova candidates]]

==References==
{{Reflist}}

== External links ==
* {{APOD |date=28 September 2006 |title=RCW 86: Historical Supernova Remnant}}
* {{APOD |date=10 November 2011 |title=RCW 86: Historical Supernova Remnant}}
* [https://www.bbc.co.uk/news/science-environment-15445688 BBC News] &ndash; Ancient supernova mystery solved (25 October 2011)

{{supernovae}}
{{Centaurus}}{{Circinus}}
{{DEFAULTSORT:Sn 185}}
[[Category:Supernova remnants]]
[[Category:Supernovae]]
[[Category:Astronomical objects known since antiquity|85]]

{{Sourceattribution|SN 185}}