查看“︁蓋亞香腸”︁的源代码

{{Infobox galaxy
| name               = 蓋亞香腸<br/>或蓋亞-恩克拉多斯<br/>或恩克拉多斯星系
| image              = [[File:Simulated Gaia-Enceladus debris.jpg|400px|藝術家對蓋亞-恩克拉多斯星系碎片的印象。]]
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| caption            = 藝術家對蓋亞-恩克拉多斯星系碎片的印象。黃色箭頭表示起源於矮星系的恆星位置和速度，這些數據來自於與銀河系的模擬合併，據信其性質與已經發生的合併相似。
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| dist_pc            = <!-- {{cvt|000|+/-|00|kpc|kly|order=flip|lk=on}}{{hub|0.73}} <!-- comoving distance -->
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| mass               = <!-- In solar masses {{Val|0|e=0}} -->
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}}

[[File:Gaia Milky Way star density map 2015-07-03.png|thumb|400px|蓋亞跨越夜空的恆星密度圖。蓋亞香腸是看不見的，但是它的位置比[[隱帶]]更低。]]

'''蓋亞香腸'''或'''蓋亞-恩克拉多斯'''是大約80-110億年前與[[銀河系]]合併的[[矮星系]]（'''Sausage Galaxy'''、'''Gaia-Enceladus-Sausage'''、或'''Gaia-Sausage-Enceladus'''）的遺跡。銀河系中至少有8個[[球狀星團]]以及500億[[太陽質量]]的恆星、氣體和[[暗物質]]來自這個矮星系<ref name=Myeong_etal>{{cite journal |last1=Myeong |first1=G.C.
 |last2=Evans |first2=N.W.
 |last3=Belokurov |first3=V.
 |last4=Sanders |first4=J.L.
 |last5=Koposov |first5=S.
 |title=The Sausage globular clusters
 |journal=The Astrophysical Journal |volume=863 |issue=2 |pages=L28
 |date=2018|bibcode=2018ApJ...863L..28M |arxiv=1805.00453 |doi=10.3847/2041-8213/aad7f7|s2cid=67791285
 }}</ref>。它代表著銀河系最後一次重大的合併<ref name=ESA-GAIA-60892>{{cite web |url= https://sci.esa.int/web/gaia/-/60892-galactic-ghosts-gaia-uncovers-major-event-in-the-formation-of-the-milky-way |title= Galactic Ghosts: Gaia Uncovers Major Event in the Formation of the Milky Way Galaxy |date= 31 October 2018 |work= Gaia |publisher= ESA |access-date= 2022-06-08 |archive-date= 2022-03-14 |archive-url= https://web.archive.org/web/20220314113825/https://sci.esa.int/web/gaia/-/60892-galactic-ghosts-gaia-uncovers-major-event-in-the-formation-of-the-milky-way }}</ref>。

== 詞源 ==
其所以被稱為'''蓋亞香腸'''，是因為在速度空間圖中，成員分布的特徵像香腸的形狀，特別是使用[[蓋亞任務]]的數據繪製的徑向（<math>\boldsymbol{v}_r</math>）與恆星（見[[球面坐標系]]）的方位角速度（<math>\boldsymbol{v}_\theta</math>）的曲線圖<ref name=Myeong_etal/>。與銀河系合併的恆星有高度細長的軌道。它們軌道的最外側點距離[[銀心|銀河系中心]]約20,000[[秒差距]]，這就是所謂的"暈斷裂"<ref name=Deason>{{cite journal |last1=Deason |first1=Alis |last2=Belokurov |first2=Vasily |last3=Koposov |first3=Sergey |last4=Lancaster |first4=Lachlan |title=Apocenter Pile-Up: Origin of the stellar halo density break |journal=The Astrophysical Journal |volume=862 |issue=1 |pages=L1 |date=2018|bibcode=2018ApJ...862L...1D |arxiv=1805.10288 |doi=10.3847/2041-8213/aad0ee|s2cid=118936735 }}</ref>。這些恆星以前在依巴谷數據中見過<ref>{{cite journal |last1=Chiba |first1=Masashi |last2=Beers |first2=Timothy C. |title=Kinematics of Metal-poor Stars in the Galaxy. III. Formation of the Stellar Halo and Thick Disk as Revealed from a Large Sample of Nonkinematically Selected Stars |url=https://archive.org/details/sim_astronomical-journal_2000-06_119_6/page/2843 |journal=The Astronomical Journal |date=June 2000 |volume=119 |issue=6 |pages=2843–2865 |doi=10.1086/301409|bibcode=2000AJ....119.2843C |arxiv=astro-ph/0003087 |s2cid=16620828 }}</ref>，並被確認為起源於一個吸積星系<ref>{{cite journal |last1=Brook |first1=Chris B. |last2=Kawata |first2=Daisuke |last3=Gibson |first3=Brad K. |last4=Flynn |first4=Chris |title=Galactic Halo Stars in Phase Space: A Hint of Satellite Accretion? |journal=The Astrophysical Journal |date=10 March 2003 |volume=585 |issue=2 |pages=L125–L129 |doi=10.1086/374306|bibcode=2003ApJ...585L.125B |arxiv=astro-ph/0301596 |s2cid=16936195 }}</ref>。

"恩克拉多斯"這個名字是指神話中的巨人[[恩克拉多斯]]，他被埋葬在[[埃特納火山]]下，並引發了地震。因此，這個前星系被掩埋在銀河系中，並導致膨脹的厚圓盤<ref name=ESA-GAIA-60892/>。

== 成員 ==
=== 球狀星團 ===
確定為前蓋亞香腸成員的球狀星團有[[M2 (球狀星團)|M2]]、[[M56]]、[[M75 (球狀星團)|M75]]、[[M79 (球狀星團)|M79]]、[[NGC 1851]]、[[NGC 2298]]、[[NGC 5286]]<ref name=Myeong_etal/>。

=== NGC 2808: 球狀星團還是舊核心？ ===
[[File:NGC 2808 HST.jpg|thumb|250px|[[NGC 2808]]可能是蓋亞香腸的舊核心。]] 

[[NGC 2808]]是蓋亞香腸類似球狀星團的成員。這個星團的成員全部都是在星團形成後2億年內誕生的三代恆星組成<ref>{{cite journal
 | author=Piotto, G. |display-authors=etal  | title=A Triple Main Sequence in the Globular Cluster NGC 2808
 | journal=The Astrophysical Journal | volume=661| issue=1
 | pages=L53–L56 |date=May 2007
 | doi=10.1086/518503 | bibcode=2007ApJ...661L..53P |arxiv = astro-ph/0703767 |s2cid=119376556 }}</ref>。

解釋三代恆星的一種理論是NGC 2808是蓋亞香腸的前核心<ref name=Myeong_etal/>。這也可以解釋超過一百萬顆恆星的異常，因為對於球狀星團來說，這樣的恆星數量是異常大的。

=== 恆星 ===
來自這個矮星系的恆星圍繞銀河系核心運行，其極端的[[軌道離心率|離心率]]約為0.9。它們的[[金屬量]]通常也比其它暈星高，大多數恆星的[Fe/H]>為 -1.7dex，即至少為太陽值的2%<ref name=Deason/><ref>{{cite journal|last1=Iorio|first1=Giuliano|date=2021|title=Chemo-kinematcs of the Gaia RR Lyrae: the halo and the disc|journal=Monthly Notices of the Royal Astronomical Society|volume=502|issue=4|pages=5686–5710|doi=10.1093/mnras/stab005|bibcode=2021MNRAS.502.5686I|last2=Belokurov|first2=Vasily}}</ref>。

"蓋亞香腸"重建了銀河系，它帶入銀河系的氣體觸發了新一輪的恆星誕生，補充了銀河盤面的恆星，使[[薄盤]]膨脹成為[[厚盤]]。來自矮星系的碎片提供了[[銀暈]]中大部分富含金屬的部分<ref name=Myeong_etal/>。

== 相關條目 ==
* {{link-en|流場|Field of Streams}}
* [[麒麟座環]]
* [[半人馬座ω]]
* {{link-en|M32p|M32p}}：合併進仙女座星系的大星系，為仙女座提供了厚的星系盤和許多的星系暈星。
* {{link-en|J1124+4535}}

== 參考資料 ==
{{Reflist}}

== 進階讀物 ==
* {{cite journal |title=Co-formation of the disc and the stellar halo |journal=Monthly Notices of the Royal Astronomical Society |volume=478 |number=1 |pages= 611–619 |date=July 2018 |arxiv=1802.03414 |doi=10.1093/mnras/sty982 |bibcode= 2018MNRAS.478..611B |last1=Belokurov |first1=V. |last2=Erkal |first2=D. |last3=Evans |first3=N.W. |last4=Koposov |first4=S.E. |last5=Deason |first5=A.J.}}
* {{cite journal |title=The Milky Way halo in action space |date=April 2018 |arxiv=1802.03351 |doi=10.3847/2041-8213/aab613 |bibcode=2018ApJ...856L..26M |journal=The Astrophysical Journal Letters |volume=856 |issue=2 |page=L26 |last1=Myeong |first1=G.C. |last2=Evans |first2=N.W. |last3=Belokurov |first3=V. |last4=Sanders |first4=J.L. |last5=Koposov |first5=S.E.|s2cid=73518200 }}
* {{cite arXiv  |title= The Shards of ω&nbsp;Centauri |eprint=1804.07050 |class=astro-ph.GA |date=April 2018 |last1=Myeong |first1=G.C. |last2=Evans |first2=N.W. |last3=Belokurov |first3=V. |last4= Sanders |first4=J.L. |last5=Koposov |first5=S.E.}}
* {{Cite journal|last1=Chaplin|first1=William J.|last2=Serenelli|first2=Aldo M.|last3=Miglio|first3=Andrea|last4=Morel|first4=Thierry|last5=Mackereth|first5=J. Ted|last6=Vincenzo|first6=Fiorenzo|last7=Kjeldsen|first7=Hans|last8=Basu|first8=Sarbani|last9=Ball|first9=Warrick H.|last10=Stokholm|first10=Amalie|last11=Verma|first11=Kuldeep|date=Jan 13, 2020|title=Age dating of an early Milky Way merger via asteroseismology of the naked-eye star ν Indi|url=https://www.nature.com/articles/s41550-019-0975-9.epdf?referrer_access_token=Ca7nRnyr3C49uBgmsm-4sdRgN0jAjWel9jnR3ZoTv0Odljv0OfEChFx0q4V7_rzUC-EEaxJWxx7dsC-D_gi7hRCWTw5MofCSJ5jynvhYK7dc8srNhZu5QWmnxu9pK7Wd9goIIrhLQCkOzCIuFTJica29pOpMKI2x4uL5ht7W5hv1Bafba_TKip_1JvofCVnF-hZgcMZgxvazegSCaC9HJEJneYq0RAtNGpbryR6_upe0exooqN00Lm-0ZdMcLO_5t3DUlbzw7Sgq-SvBmEw7eUkW9MM08ogPyuQfhF3h7hpS3EeI6QixsOpEIpw3gIfZ&tracking_referrer=www.newscientist.com|journal=Nature Astronomy|volume=4|issue=4|language=en|pages=382–389|doi=10.1038/s41550-019-0975-9|issn=2397-3366|arxiv=2001.04653|bibcode=2020NatAs...4..382C|hdl=1721.1/128912|s2cid=210166431|access-date=2022-06-08|archive-date=2022-03-21|archive-url=https://web.archive.org/web/20220321110346/https://www.nature.com/articles/s41550-019-0975-9.epdf?referrer_access_token=Ca7nRnyr3C49uBgmsm-4sdRgN0jAjWel9jnR3ZoTv0Odljv0OfEChFx0q4V7_rzUC-EEaxJWxx7dsC-D_gi7hRCWTw5MofCSJ5jynvhYK7dc8srNhZu5QWmnxu9pK7Wd9goIIrhLQCkOzCIuFTJica29pOpMKI2x4uL5ht7W5hv1Bafba_TKip_1JvofCVnF-hZgcMZgxvazegSCaC9HJEJneYq0RAtNGpbryR6_upe0exooqN00Lm-0ZdMcLO_5t3DUlbzw7Sgq-SvBmEw7eUkW9MM08ogPyuQfhF3h7hpS3EeI6QixsOpEIpw3gIfZ&tracking_referrer=www.newscientist.com}}

== 外部連結 ==
* {{youtube |8T2EdRZ_iE4 |Gaia Sausage Simulation}} YouTube
* {{cite news |url=https://www.cmu.edu/news/stories/archives/2018/july/gaia-sausage.html |title=The Gaia Sausage: The major collision that changed the Milky Way galaxy |date=4 July 2018 |author=Jocelyn Duffy |publisher=Carnegie Mellon University |accessdate=2019-12-06 |archive-date=2020-08-21 |archive-url=https://web.archive.org/web/20200821231453/https://www.cmu.edu/news/stories/archives/2018/july/gaia-sausage.html }}
* {{cite news |url=https://www.cam.ac.uk/research/news/the-gaia-sausage-the-major-collision-that-changed-the-milky-way |title=The Gaia Sausage: The major collision that changed the Milky Way |publisher=University of Cambridge |author=Sarah Collins |date=4 July 2018 |accessdate=2019-12-06 |archive-date=2021-03-09 |archive-url=https://web.archive.org/web/20210309173516/http://www.cam.ac.uk/research/news/the-gaia-sausage-the-major-collision-that-changed-the-milky-way }}

{{銀河}}

[[Category:蓋亞-恩克拉多斯| ]]
[[Category:銀河系]]
[[Category:矮星系]]