编辑“︁UDFy-38135539”︁

{{Infobox Galaxy
| name = UDFy-38135539
| image = [[File:UDFy-38135539.jpg|250px|]]
| caption= [[哈勃太空望遠鏡]]拍攝的UDFy-38135539圖像
| credit =
| constellation name = [[天爐座]]
| epoch =
| type =
| ra =
| dec =
| dist_ly = 超過13[[吉咖|G]][[光年|ly]]
| z = 8.55<ref name="NS"/>
| appmag_v =
| size_v =
| names = HUDF.YD3
}}

'''UDFy-38135539'''（又名為："HUDF.YD3"）是人類觀測到的經[[光譜學|光譜確認]]的最遙遠的[[天體]]（截至2010年10月），也是當前[[宇宙]]中已知存在的第三遙遠的天體（排在[[UDFj-39546284]]之後）。經計算它的光行距離超過40億[[秒差距]]<ref name="Nature">{{cite journal|last=Trenti|first=Michele|title=Astronomy: Galaxy sets distance mark|url=https://archive.org/details/sim_nature-uk_2010-10-21_467_7318/page/924|journal=Nature|volume=467|pages=924–925|year=2010|doi=10.1038/467924a}}</ref>，同移距離為91億秒差距<ref name="Calculator">{{cite web |title=Cosmology Calculator I |publisher=Astronomy @ UCLA |author=Edward L.（Ned）Wright |url=http://www.astro.ucla.edu/~wright/CosmoCalc.html |accessdate=2010-10-22 |archive-date=2018-09-29 |archive-url=https://web.archive.org/web/20180929102855/http://www.astro.ucla.edu/~wright/CosmoCalc.html |dead-url=no }}</ref>。UDFy-38135539（[[哈勃超深空]]（UDF）的[[星系]]分類）最初於2009年9月由三個科學小組從[[哈勃太空望遠鏡]]紅外線圖像中發現<ref name="Bouwens">{{cite web|author=R.J. Bouwens, G.D.Illingworth, P.A. Oesch, M. Stiavelli, P. van Dokkum, M. Trenti,D. Magee, I. Labbe, M. Franx, M. Carollo and V. Gonzalez|url=http://arxiv.org/abs/0909.1803|title=Discovery of z~8 Galaxies in the HUDF from ultra-deep WFC3/IR Observations|publisher=Astrophysical Journal|accessdate=2010-10-22|archive-date=2017-05-10|archive-url=https://web.archive.org/web/20170510132255/https://arxiv.org/abs/0909.1803|dead-url=no}}</ref><ref name="Bunker">{{cite web|author=Andrew Bunker, Stephen Wilkins, Richard Ellis, Daniel Stark, Silvio Lorenzoni, Kuenley Chiu, Mark Lacy, Matt Jarvis and Samantha Hickey|url=http://arxiv.org/abs/0909.2255|title=The Contribution of High Redshift Galaxies to Cosmic Reionization: New Results from Deep WFC3 Imaging of the Hubble Ultra Deep Field|publisher=Monthly Notices of the Royal Astronomical Society|accessdate=2010-10-22|archive-date=2018-04-02|archive-url=https://web.archive.org/web/20180402225654/https://arxiv.org/abs/0909.2255|dead-url=no}}</ref><ref name="McLure">{{cite web|author=R.J. McLure, J.S. Dunlop, M. Cirasuolo, A.M. Koekemoer, E. Sabbi, D.P. Stark, T.A. Targett and R.S. Ellis|url=http://arxiv.org/abs/0909.2437|title=Galaxies at z = 6 - 9 from the WFC3/IR imaging of the HUDF|publisher=Monthly Notices of the Royal Astronomical Society|accessdate=2010-10-22|archive-date=2018-04-03|archive-url=https://web.archive.org/web/20180403173529/https://arxiv.org/abs/0909.2437|dead-url=no}}</ref>。

== 發現 ==
2009年8月至9月，UDFy-38135539星系的景象由[[哈勃太空望遠鏡]]於近期配置的[[第三代廣域照相機]]所拍攝的[[哈勃超深空]]捕捉到<ref name="NS">{{cite web |url=http://www.newscientist.com/article/dn19603-dim-galaxy-is-most-distant-object-yet-found.html |title=Dim galaxy is most distant object yet found |publisher=New Scientist |date= |accessdate=2010-10-21 |archive-date=2013-06-23 |archive-url=https://www.webcitation.org/6HaIk1XY7?url=http://www.newscientist.com/article/dn19603-dim-galaxy-is-most-distant-object-yet-found.html |dead-url=no }}</ref><ref name="SciAm">{{cite web |last=Matson |first=John |url=http://www.scientificamerican.com/article.cfm?id=farthest-galaxy |title=Early Bloomer: Faraway Galaxy Pushes Cosmic View Closer to the Dawn of the Universe |doi=10.1111/j.1365-2966.2009.16176.x |publisher=Scientific American |date= |accessdate=2010-10-21 |archive-date=2012-10-16 |archive-url=https://web.archive.org/web/20121016042907/http://www.scientificamerican.com/article.cfm?id=farthest-galaxy |dead-url=no }}</ref>。之後圖像數據被傳至科學界，最終由Bouwens<ref name="Bouwens"/>、Bunker<ref name="Bunker"/>和McLure<ref name="McLure"/>等小組發現，隨後Lehnert等人的小組進行了[[光譜學|光譜]]證實。這項成果被公佈在2010年的《[[自然 (期刊)|自然]]》雜誌上的一篇題為"紅移為z=8.6的星系光譜證實"（英文標題：Spectroscopic Confirmation of a Galaxy at Redshift z=8.6）的文章中<ref name="MSNBC">{{cite web |author=Alan Boyle |url=http://cosmiclog.msnbc.msn.com/_news/2010/10/20/5322427-scientists-pinpoint-the-farthest-galaxy |title=Scientists pinpoint the farthest galaxy |publisher=MSNBC |date=2010-10-15 |accessdate=2010-10-21 |deadurl=yes |archiveurl=https://web.archive.org/web/20101022163657/http://cosmiclog.msnbc.msn.com/_news/2010/10/20/5322427-scientists-pinpoint-the-farthest-galaxy |archivedate=2010-10-22 }}</ref><ref name="DMUK">{{cite web |author=David Derbyshire |url=http://www.dailymail.co.uk/sciencetech/article-1322166/UDFy-38135539-galaxy-13-billion-light-years-away-astronomers.html |title=Astronomers find most remote galaxy ever seen... 13 BILLION light years away |publisher=DailyMail.co.uk |date= |accessdate=2010-10-21 |archive-date=2017-01-01 |archive-url=https://web.archive.org/web/20170101141550/http://www.dailymail.co.uk/sciencetech/article-1322166/UDFy-38135539-galaxy-13-billion-light-years-away-astronomers.html |dead-url=no }}</ref>。Lehnert的小組在成果發表於自然雜誌以前曾對星系進行了16小時的觀測以及對結果展開為期2個月以上的分析<ref name="DMUK"/>。

== 特徵 ==
UDFy-38135539位於[[天爐座]]，距離地球40多億[[秒差距]]<ref name="Nature"/>，超過130億[[光年]]。星系的光線[[紅移]]達到了8.55。相比之下之前最遙遠的天體紀錄保持者[[伽瑪射線暴]][[GRB 090423]]的光線紅移為8.2<ref name="MSNBC"/>。據估計，UDFy-38135539大概擁有10億顆[[恆星]]<ref name="Fox">{{cite web |title=Long Ago and Far, Far, Away: The Oldest Thing Ever Seen in the Universe |publisher=Fox News |date=2010-10-20 |url=http://www.foxnews.com/scitech/2010/10/20/scientists-discover-oldest-thing-universe/ |accessdate=2010-10-23 |archive-date=2011-01-31 |archive-url=https://web.archive.org/web/20110131193101/http://www.foxnews.com/scitech/2010/10/20/scientists-discover-oldest-thing-universe/ |dead-url=no }}</ref>，它的直徑只有[[銀河系]]的十分之一，不到銀河系恆星質量總和的百分之一。從地球上看到的來自星系的光線是從130億年以前發出的，距[[大爆炸]]僅有6億年<ref name="ABCNews">{{cite web |title=Astronomers Find Oldest Galaxy Yet |publisher=ABCNews |date=2010-10-20 |url=http://abcnews.go.com/Technology/wireStory?id=11927711 |accessdate=2010-10-23 |archive-date=2019-12-07 |archive-url=https://web.archive.org/web/20191207205039/http://abcnews.go.com/Technology/wireStory?id=11927711 |dead-url=no }}</ref>，那時宇宙只有當前年齡的4%<ref name="DMUK"/>。

UDFy-38135539的[[光度距離]]為860.9億秒差距，大約是2830億光年。在[[宇宙學]]中有數種不同的距離測量方法，光行距離和光度距離有别於用來定義[[可觀測宇宙]]大小的同移距離<ref>{{cite journal | last = Davis | first = Tamara M. | coauthors = Charles H. Lineweaver | title = [http://arxiv.org/pdf/astro-ph/0310808v2 Expanding Confusion: common misconceptions of cosmological horizons and the superluminal expansion of the Universe] | journal = Publications of the Astronomical Society of Australia | volume = 21 | issue = 1 | date = 2004 | doi = 10.1071/AS03040 }}{{arxiv | archive = astro-ph | id = 0310808}}</ref><ref>{{cite journal | last = Gott III | first = J. Richard | coauthors = Mario Jurić, David Schlegel, Fiona Hoyle, Michael Vogeley, Max Tegmark, Neta Bahcall, Jon Brinkmann | title = [http://www.astro.princeton.edu/universe/ms.pdf A Map of the Universe] | journal = The Astrophysics Journal | volume = 624 | number = 2 | date = 2005 | doi = 10.1086/428890 }} {{arxiv | archive = astro-ph | id = 0310571}}</ref>。光度距離<math>D_L</math>和一種叫橫向同移距離（comoving transverse distance)<math>D_M</math>的因素相關，用等式表示就是：<math> D_L =(1 + z) D_M</math>，其中''z''是紅移，而在平坦宇宙中橫向同移距離本身等於徑向同移距離（radial comoving distance）<ref>Gabrielli, Andrea. ''Statistical Physics for Cosmic Structures'', [http://books.google.com/books?id=nYHRdjxKOEMC&lpg=PP1&pg=PA377#v=onepage&q&f=false p. 377] {{Wayback|url=http://books.google.com/books?id=nYHRdjxKOEMC&lpg=PP1&pg=PA377#v=onepage&q&f=false |date=20121115023818 }}.</ref><ref>{{cite web |url=http://www.mpifr-bonn.mpg.de/staff/hvoss/DiplWeb/DiplWebap1.html |title=A Cosmology and Cosmography |publisher=Mpifr-bonn.mpg.de |date=2005-09-21 |accessdate=2010-10-22 |deadurl=yes |archiveurl=https://web.archive.org/web/20110102134709/http://www.mpifr-bonn.mpg.de/staff/hvoss/DiplWeb/DiplWebap1.html |archivedate=2011-01-02 }}</ref>。所以由<math>D_L</math> = 860.9億秒差距及''z''=8.55可得知同移距離之值為91億秒差距（大約是300億光年）<ref name="Calculator"/>。

== 後續發現 ==
科學家們希望能夠發現更古老的星系。但每當星系的年齡越接近[[大爆炸]]的時間點時，星系的數量就會相應地减少，它們發出的光線也就越灰暗。畢竟普遍上這些擁有更少可觀測恆星數量的星系發出的光芒相當的微弱，隨著距離的增加，在尋找上的難度上也會大幅度提昇<ref name="Discovery">{{cite web |url=http://news.discovery.com/space/oldest-galaxy-universe-hubble.html |title=Oldest Object in Universe Found |publisher=Discovery News |date= |accessdate=2010-10-21 |archive-date=2010-10-22 |archive-url=https://web.archive.org/web/20101022081824/http://news.discovery.com/space/oldest-galaxy-universe-hubble.html |dead-url=yes }}</ref>。將於2014年投入使用的[[詹姆斯·韋伯太空望遠鏡]]有能力觀測到134億光年以外，誕生時間早於宇宙大爆炸3億年之後的星系。預定於2018年完成的[[歐洲極大望遠鏡]]的鏡片直徑比[[甚大望遠鏡]]（Yepun）的大五倍<ref name="BBC">{{cite web |url=http://www.bbc.co.uk/news/science-environment-11580789 |title=Galaxy is most distant object yet |publisher=BBC News |date= |accessdate=2010-10-21 |archive-date=2019-04-17 |archive-url=https://web.archive.org/web/20190417092318/https://www.bbc.co.uk/news/science-environment-11580789 |dead-url=no }}</ref>，可以使人類對134億光年以外的星系作更詳細的研究<ref name="telegraph">{{cite web |url=http://www.telegraph.co.uk/science/space/8075703/Most-distant-galaxy-identified.html |title=Most distant galaxy identified |publisher=Telegraph.co.uk |date= |accessdate=2010-10-21 |archive-date=2014-08-10 |archive-url=https://web.archive.org/web/20140810124938/http://www.telegraph.co.uk/science/space/8075703/Most-distant-galaxy-identified.html |dead-url=no }}</ref>。

== 參見 ==
* [[IOK-1]]
* [[UDFj-39546284]]

== 參考資料 ==
{{Commons category}}
{{Reflist|colwidth=30em}}

{{start box}}
{{s-records}}
{{Succession record holder box|[[IOK-1]]|[[UDFj-39546284]]|[[星系列表|最遙遠星系]]|2009年－2011年}}  
{{end}}

[[Category:遥远星系]]
[[Category:天爐座]]