编辑“︁N6946-BH1”︁

{{Starbox begin
| name = N6946-BH1
}}
{{Starbox image
 | image=[[File:Giant star N6946-BH1 before and after it vanished out of sight by imploding to form a black hole.jpg|280px]]
|caption=這對[[哈伯太空望遠鏡]]拍攝的N6946-BH1可見光和近紅外線影像分別拍攝於該恆星疑似內爆形成黑洞之前和之後。
}}
{{Starbox observe 
| epoch = J2000.0
| constell = [[天鵝座]]
| ra = {{RA|20|35|27.56}}<ref name=adams/>
| dec = {{DEC|+60|08|08.29}}<ref name=adams/>
| appmag_v = 18.17 (max)<ref name=gerke>{{cite journal|bibcode=2015MNRAS.450.3289G|arxiv=1411.1761|title=The search for failed supernovae with the Large Binocular Telescope: First candidates|journal=Monthly Notices of the Royal Astronomical Society|volume=450|issue=3|pages=3289|author1=Gerke|first1=J. R.|last2=Kochanek|first2=C. S.|last3=Stanek|first3=K. Z.|year=2015|doi=10.1093/mnras/stv776}}</ref>
}} 
{{Starbox character 
| class =
| b-v =
| u-b =
| variable=疑似[[失敗超新星]]<ref name=gerke/>
}} 
{{Starbox astrometry
| radial_v = 
| prop_mo_ra =
| prop_mo_dec =
| parallax =
| p_error =
| parallax_footnote =
| dist_pc = 5,960,000<ref name=gerke/>
| absmag_v =
}} 
{{Starbox detail 
| mass = 25<ref name=adams/>
| radius =
| luminosity = 200,000 - ~1,000,000<ref name=adams/>
| temperature =
| metallicity_fe =
| gravity =
| rotational_velocity =
| age =
}} 
{{Starbox catalog
| names = N6946-BH1
}}
{{Starbox end}}


'''N6946-BH1'''是一個位於星系[[NGC 6946]]內已消失的[[紅超巨星]]，該恆星質量為太陽的25倍，距離地球約2000萬光年。

== 觀測歷史 ==
2009年3至5月期間，N6946-BH1的光度增加為太陽的數百萬倍，但在2015年時已無法在可見光波段觀測到它。目前在近紅外與中[[紅外線]]波段仍可看到該恆星，但它的亮度正與時間成 t<sup>−4/3</sup> 的比例下降<ref name=adams>{{cite journal|last1=Adams|first1=S. M.|last2=Kochanek|first2=C. S|last3=Gerke|first3=J. R.|last4=Stanek|first4=K. Z.|last5=Dai|first5=X.|title=The search for failed supernovae with the Large Binocular Telescope: conformation of a disappearing star|date=9 September 2016|arxiv=1609.01283v1}}</ref>。N6946-BH1的亮度並不足以被視為[[超新星]]，而被認為是[[失敗超新星]]<ref name=adams/>。

N6946-BH1在天球上的座標是RA 20:35:27.56, Dec +60:08:08.29。2015年7月2日時它的亮度在不同波長分別為 R = 21, V = 21, B =  22, U =  23<ref name=adams/>。N6946-BH1在光學爆發之前的亮度大約是太陽的10萬倍，光學爆發後它的可見光波段亮度下降到無法被觀測，但在紅外線部分則減退為太陽的5千倍<ref name=adams/>。

對此現象的其中一個解釋是N6946-BH1的核心已經塌縮形成[[黑洞]]。塌縮中的物質產生[[微中子]]爆發現象使恆星質量有一定比例的下降，微中子爆發產生衝擊波衝破恆星外層使其亮度更高<ref>{{cite web|last1=Williams|first1=Matt|title=Have we really just seen the birth of a black hole?|url=http://phys.org/news/2016-09-birth-black-hole.html|publisher=PhysOrg|accessdate=16 September 2016|date=16 September 2016|archive-date=2020-11-08|archive-url=https://web.archive.org/web/20201108102946/https://phys.org/news/2016-09-birth-black-hole.html|dead-url=no}}</ref>。

[[File:N6946-BH1 failed supernova (artist's impression).jpg|thumb|left|upright=1.2|N6946-BH1失敗超新星 (藝術家的印象)]]

恆星以超新星形式死亡似乎不是以太陽質量18倍為下限，並且大質量恆星的形成率似乎高於超新星的發生率。因此天文學家懷疑這些大質量恆星在死亡時有其他現象發生，而失敗超新星和黑洞的形成是其中一項解釋<ref name=adams/>。如果N6946-BH1的現象反映了黑洞的形成，這可能就是首次觀測到黑洞的形成<ref name="ns">{{cite web|last1=Nowogrodzki|first1=Anna|title=First glimpse of a black hole being born from a star’s remains|url=https://www.newscientist.com/article/2105588-first-glimpse-of-a-black-hole-being-born-from-a-stars-remains/|publisher=New Scientist|accessdate=17 September 2016|date=12 September 2016|archive-date=2020-11-08|archive-url=https://web.archive.org/web/20201108114413/https://www.newscientist.com/article/2105588-first-glimpse-of-a-black-hole-being-born-from-a-stars-remains/|dead-url=no}}</ref>。韋伯拍到其實3個天體 ，新說法是3個恆星天體 其中合併變亮 但後來噴發遮蔽恆星亮度變暗  。

== 參考資料 ==
{{Reflist}}

== 外部連結 ==
* [http://astrobob.areavoices.com/2017/05/26/giant-star-becomes-a-black-hole-right-before-our-eyes N6946-BH1]{{Wayback|url=http://astrobob.areavoices.com/2017/05/26/giant-star-becomes-a-black-hole-right-before-our-eyes |date=20190305085343 }} Giant Star Becomes A Black Hole Right Before Our Eyes!

{{天鹅座恒星}}

[[Category:天鵝座]]
[[Category:M型超巨星]]
[[Category:銀河系外恆星]]
[[Category:2015年发现的天体]]