imported>Ziv：(GR) Duplicate: File:Hubble's view of dazzling globular cluster NGC 6397.jpg → File:Hubble uncovers concentration of small black holes (50933077132).jpg Exact or scaled-down duplicate: c::File:Hubble uncovers concentration of small black holes (50933077132).jpg

2025-12-21T11:50:09Z

(GR) Duplicate: File:Hubble's view of dazzling globular cluster NGC 6397.jpg → File:Hubble uncovers concentration of small black holes (50933077132).jpg Exact or scaled-down duplicate: c::File:Hubble uncovers concentration of small black holes (50933077132).jpg

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{{Infobox globular cluster
| name = NGC 6397
| image = [[File:P0321a.jpg|250px]]
|caption = [[哈伯太空望遠鏡]](HST)拍攝的NGC 6397。<br/>創建者： HST/[[NASA]]/[[欧洲空间局|ESA]].
| epoch = [[J2000]]
| class = IX<ref name=hcob849_11/>
| constellation = [[天壇座]]
| ra = {{RA|17|40|42.09}}<ref name=aj140_6_1830/>
| dec = {{DEC|–53|40|27.6}}<ref name=aj140_6_1830/>
| dist_ly = {{Convert|7.8|kly|kpc|abbr=on|lk=on}}<ref name="Salazar">{{cite web|last1=Salazar|first1=Doris Elen|title=Cosmic 'Yardstick' Measures Distance to One of Universe's Oldest Objects|url=https://www.space.com/40222-wobbles-ancient-stars-cosmic-yardstick.html|website=Space.com|access-date=5 April 2018|archive-date=2021-07-19|archive-url=https://web.archive.org/web/20210719225122/https://www.space.com/40222-wobbles-ancient-stars-cosmic-yardstick.html}}</ref>
| appmag_v = +6.68<ref name="simbad" />
| size_v = 32′.0
| mass_msol = {{Val|1.2|e=5}}<ref name="VitralMamon21"/>
| radius_ly = 34 ly<ref>distance × sin( diameter_angle / 2 ) = ~34 ly. radius</ref>
| v_hb = 14.2
| metal_fe = –1.76<ref name=mnras404_3_1203/>
| age = 13.4 ± 0.8 Gyr<ref name="eso" />
| notes = 第二接近的[[球狀星團]]
| names = GCl 74,<ref name="simbad" /> Lacaille III.11, Dunlop 366, Bennett 98, [[科德韋爾深空天體表|科德韋爾]] 86
}}

'''NGC 6397'''(也稱為'''科德韋爾86''')是在[[天壇座]]的[[球狀星團]]。它距離[[地球]]大約7,800[[光年]]<ref name="Salazar" />，使它成為離地球最近的兩個球狀星團之一（另一個是[[M4 (球狀星團)| M4]]）。這個星團大約有400,000顆恆星<ref name="eso" />，在良好的觀察條件下可以用[[肉眼]]看到<ref name="nightsky">{{cite book
|last = Dunlop
|first = Storm
|author-link = Storm Dunlop
|title = Atlas of the Night Sky
|url = https://archive.org/details/collinsatlasofni0000dunl
|url-access = registration
|publisher = [[HarperCollins|Collins]]
|year = 2005
|isbn = 978-0-00-717223-8
}}</ref>。

NGC 6397是[[銀河系]]中至少20個經歷了[[球狀星團#質量層化、光度和核心坍縮|核心坍塌]]的球狀星團之一<ref name="eso" />，這意味著核心收縮而有著非常緻密的恒星。 .

== 天文學研究 ==

=== 估計銀河系的年齡 ===
在2004年，一組[[天文學家]]<ref name="eso" />聚焦在星團，用它來估計[[銀河系]]的年齡。這組的成員包括盧卡·帕斯奎尼、皮爾卡洛·博尼法西奧、索菲亞·蘭迪奇、丹尼爾·加利和拉斐爾·G·格拉頓。他們使用[[帕瑞納山]][[甚大望遠鏡]]的紫外-可見光的[[階梯光柵|光柵攝譜儀]]測量星團中兩顆恆星的[[鈹]]含量。這使他們能夠推斷整個銀河系中第一代恆星的誕生到星團中第一代恆星誕生之間所經過的時間。再加上對星團中恆星估計的年齡，就可以估計銀河系的年齡：136億年，這年齡幾乎和宇宙本身一樣老。這一估計假設NGC 6397不會比銀河系古老。

=== 恒星質量的下限 ===
在2006年，發表了使用[[哈伯太空望遠鏡]]對NGC 6397的一項研究，顯示星丸中黯淡恆星的[[絕對星等|亮度]]明顯的有一個下限。作者推斷，這表明恆星的核心要能夠進行[[核融合]]有一個[[質量]]下限：大約是[[太陽質量]]的0.83倍<ref name="HST">{{cite web
|title=HST analysis of faint stars in NGC6397
|work=Results for NGC 6397
|url=http://hubblesite.org/newscenter/newsdesk/archive/releases/2006/37
|access-date=2006-09-26
|archive-date=2008-07-08
|archive-url=https://web.archive.org/web/20080708234723/http://hubblesite.org/newscenter/newsdesk/archive/releases/2006/37/
}}</ref>。

=== 黑洞 ===
在2021年2月據報導，根據哈伯太空望遠鏡和歐洲航天局[[蓋亞任務]]收集的數據得出核心附近恒星的運動：NGC 6397的核心含有相對密集的緻密天體（[[白矮星]]、[[中子星]]和[[黑洞]]）<ref name="VitralMamon21">{{Citation | last1=Vitral | first1=Eduardo | title=Does NGC 6397 contain an intermediate-mass black hole or a more diffuse inner subcluster? | last2=Mamon | first2=Gary A. | doi=10.1051/0004-6361/202039650 | date=2021 | journal=A&A | volume=646 | issue=A63 | pages=A63 |bibcode = 2021A&A...646A..63V | doi-access=free }}</ref><ref>{{cite news|date=11 February 2021|title=Hubble Uncovers Concentration of Small Black Holes|url=https://esahubble.org/news/heic2103/|work=ESA|access-date=21 February 2021|archive-date=2021-04-27|archive-url=https://web.archive.org/web/20210427140754/https://esahubble.org/news/heic2103/}}</ref>。這個中心區域的黑洞總質量上限約為1,000個太陽質量，來自許多顆，估計平均大小為20個太陽質量的較小黑洞<ref name="NYT-20210226">{{cite news |last=Overbye |first=Dennis |authorlink=Dennis Overbye |title=Hunting for a Giant Black Hole, Astronomers Found a Nest of Darkness - No Gargantua dwells at the heart of stellar cluster NGC 6397. Instead, a few dozen smaller black holes seem to be swarming around in there, throwing their considerable masses around. |url=https://www.nytimes.com/2021/02/26/science/astronomy-black-hole-ngc6397.html |date=26 February 2021 |work=[[The New York Times]] |access-date=27 February 2021 |archive-date=2021-07-28 |archive-url=https://web.archive.org/web/20210728112403/https://www.nytimes.com/2021/02/26/science/astronomy-black-hole-ngc6397.html }}</ref>。然而，也有人認為，由於動力相互作用，這些黑洞中的許多都會從星團核心噴出，這導致這種看不見的濃縮物主要由白矮星和中子星組成，只有極少數的黑洞<ref>{{Citation | last1=Weatherford | first1=Newlin C. |title=A Dynamical Survey of Stellar-mass Black Holes in 50 Milky Way Globular Clusters| last2=Sourav | first2=Chatterjee | last3=Kremer | first3=Kyle | last4=Rasio | first4=Frederic A. | doi=10.3847/1538-4357/ab9f98 | date=2020 | journal= The Astrophysical Journal| volume=898 | issue=162 | page=162 | bibcode = 2020ApJ...898..162W | arxiv=1911.09125 | s2cid=208202116 }}</ref>。

== 圖集 ==
<gallery>
Hubble uncovers concentration of small black holes (50933077132).jpg|哈伯觀察所見的球狀星團NGC 6397<ref>{{cite web|title=Hubble's view of dazzling globular cluster NGC 6397|url=https://www.spacetelescope.org/images/opo1824a/|website=www.spacetelescope.org|access-date=13 April 2018|archive-date=2018-08-16|archive-url=https://web.archive.org/web/20180816204048/http://www.spacetelescope.org/images/opo1824a/}}</ref>
</gallery>

== 參考資料 ==
{{Reflist|refs=

<ref name=aj140_6_1830>{{citation | display-authors=1 | last1=Goldsbury | first1=Ryan | last2=Richer | first2=Harvey B. | last3=Anderson | first3=Jay | last4=Dotter | first4=Aaron | last5=Sarajedini | first5=Ata | last6=Woodley | first6=Kristin | title=The ACS Survey of Galactic Globular Clusters. X. New Determinations of Centers for 65 Clusters | journal=The Astronomical Journal | volume=140 | issue=6 | pages=1830–1837 |date=December 2010 | doi=10.1088/0004-6256/140/6/1830 | bibcode=2010AJ....140.1830G | postscript=. |arxiv = 1008.2755 | s2cid=119183070 }}</ref>

<ref name="simbad">{{cite simbad | title=NGC 6397 | access-date=2006-11-16 }}</ref>

<ref name="eso">{{cite web | title=How Old is the Milky Way ? | work=Results for NGC 6397 | url=http://www.eso.org/outreach/press-rel/pr-2004/pr-20-04.html | access-date=2006-09-26 | archive-url=https://web.archive.org/web/20080905233636/http://www.eso.org/outreach/press-rel/pr-2004/pr-20-04.html | archive-date=2008-09-05 | url-status=dead }}</ref>

<ref name=hcob849_11>{{citation | last1=Shapley | first1=Harlow | last2=Sawyer | first2=Helen B. | title=A Classification of Globular Clusters | journal=Harvard College Observatory Bulletin | volume=849 | issue=849 | pages=11–14 |date=August 1927 | bibcode=1927BHarO.849...11S | postscript=. }}</ref>

<ref name=mnras404_3_1203>{{citation | last1=Forbes | first1=Duncan A. | last2=Bridges | first2=Terry | title=Accreted versus in situ Milky Way globular clusters | journal=[[Monthly Notices of the Royal Astronomical Society]] | volume=404 | issue=3 | pages=1203–1214 |date=May 2010 | doi=10.1111/j.1365-2966.2010.16373.x | bibcode=2010MNRAS.404.1203F | postscript=. |arxiv = 1001.4289 | s2cid=51825384 }}</ref>



}}

== 外部連結 ==
{{commons category|NGC 6397}}
* {{wikiSky}}
* {{APOD |date=8 August 2003 |title=Blue Stragglers in NGC 6397}}
* {{APOD |date=20 February 2002 |title=Oddities of Star Cluster NGC 6397}}

{{Ngc65}}
{{科德韦尔天体}}

{{DEFAULTSORT:NGC 6397}}
[[Category:天壇座]]
[[Category:球狀星團]]
[[Category:NGC天體|6397]]
[[Category: 科德韦尔天体|086b]]

NGC 6397 - 版本历史

imported>Ziv：​(GR) Duplicate: File:Hubble's view of dazzling globular cluster NGC 6397.jpg → File:Hubble uncovers concentration of small black holes (50933077132).jpg Exact or scaled-down duplicate: c::File:Hubble uncovers concentration of small black holes (50933077132).jpg

imported>Ziv：(GR) Duplicate: File:Hubble's view of dazzling globular cluster NGC 6397.jpg → File:Hubble uncovers concentration of small black holes (50933077132).jpg Exact or scaled-down duplicate: c::File:Hubble uncovers concentration of small black holes (50933077132).jpg