View source for Astronomy:2MASS J18082002−5104378

{{Short description|One of the oldest stars in the universe in the constellation Ara}}
{{starbox begin
|name=2MASS J18082002−5104378}}<ref name="ApJ-20181105">
{{cite journal
 |last1=Schlaufman  |first1=Kevin C.
 |last2=Thompson    |first2=Ian B.
 |last3=Casey       |first3=Andrew R.
 |date=5 November 2018
 |title=An ultra metal-poor star near the hydrogen-burning limit
 |journal=[[Astronomy:The Astrophysical Journal|The Astrophysical Journal]]
 |volume=867  |number=2  |pages=98
 |arxiv=1811.00549  |doi=10.3847/1538-4357/aadd97  |bibcode=2018ApJ...867...98S
|s2cid=54511945
 |doi-access=free
 }}
</ref>
{{starbox observe
| epoch=[[Astronomy:J2000|J2000]]
| constell=[[Astronomy:Ara (constellation)|Ara]]<ref name="DJM-2018">
{{cite web
 |author=
 |title=Finding the constellation which contains given sky coordinates
 |year=2018
 |website=DJM.cc
 |url=http://djm.cc/constellation.html
 |access-date=5 November 2018
}}
</ref>
| ra={{RA|18|08|20.02}}
| dec={{DEC|−51|04|37.8}}
| appmag_v=11.9<ref name=melendez>
{{cite journal
 |last1=Meléndez |first1=Jorge
 |last2=Placco |first2=Vinicius M.
 |last3=Tucci-Maia |first3=Marcelo
 |last4=Ramírez |first4=Iván
 |last5=Li |first5=Ting S.
 |last6=Perez |first6=Gabriel
 |year=2016
 |title=2MASS J18082002-5104378: The brightest (V = 11.9) ultra metal-poor star
 |journal=Astronomy and Astrophysics
 |volume=585 |page=L5
 |doi=10.1051/0004-6361/201527456 |arxiv=1601.03462 |bibcode=2016A&A...585L...5M
|s2cid=119240055
 }}
</ref>
}}
{{starbox character
|type= [[Astronomy:Subgiant|Subgiant]] / [[Astronomy:Red dwarf|Red dwarf]]
|appmag_1_passband=
|appmag_1=
|appmag_2_passband=
|appmag_2=
|appmag_3_passband=
|appmag_3=
}}
{{starbox astrometry
| radial_v = <!--Radial velocity (in km/s)-->
| prop_mo_ra = −5.672<ref name=dr2/>
| prop_mo_dec = −12.643<ref name=dr2/>
| parallax=1.6775
| p_error=0.0397
| parallax_footnote=<ref name=dr2>{{cite Gaia DR2|6702907209758894848}}</ref>
| dist_ly = 1,950<ref name=SCI-20181106/><ref name="S&T-20181112"/><ref name=UT-20181109/>
| dist_pc = 600
| absmag_v = <!--Absolute magnitude ([[Astronomy:UBV photometric system|Johnson-Cousins V system]])-->
}}
{{Starbox detail
| component1 = A
| mass = 0.7599 ± 0.0001<ref name=ApJ-20181105/>
| temperature = 5,440 ± 100<ref name=melendez/>
| luminosity = 5.311<ref name=dr2/>
| radius = 2.44<ref name=dr2/>
| gravity = 3.0<ref name=melendez/>
| metal_fe = -4.1<ref name=melendez/>
| age_gyr  = {{val|13.535|0.002}}<ref name=ApJ-20181105/>
| component2 = B
| mass2 = {{val|0.14|0.06|0.01}}<ref name=ApJ-20181105/>
| age_gyr2 = {{val|13.535|0.002}}<ref name=ApJ-20181105/>
}}
{{starbox catalog
|names= Gaia DR2 6702907209758894848<ref name=SCI-20181106/>
}}
{{starbox reference
|Simbad=2MASS+J18082002-5104378
}}
{{starbox end}}

'''2MASS J18082002−5104378''' (abbreviated '''J1808−5104''') is an ultra metal-poor (UMP) [[Astronomy:Binary star|binary star system]], in the constellation [[Astronomy:Ara (constellation)|Ara]], about {{convert|1950|ly|pc|abbr=on}}<ref name=SCI-20181106/><ref name=S&T-20181112>{{cite news
 |last=Crockett |first=Christopher
 |title=Puny star might be [a] specimen from [the] early universe
 |date=12 November 2018
 |website=Sky & Telescope
 |url=https://www.skyandtelescope.com/astronomy-news/puny-star-might-be-specimen-from-early-universe/
 |access-date=14 November 2018 }}</ref><ref name="UT-20181109">
{{cite web
 |last=Williams |first=Matt
 |date=9 November 2018
 |title=Ancient star found that's only slightly younger than the universe itself
 |website=Universe Today
 |url=https://www.universetoday.com/140468/ancient-star-found-thats-only-slightly-younger-than-the-universe-itself/
 |access-date=14 November 2018
}}
</ref> from [[Astronomy:Earth|Earth]], and is a [[Astronomy:Binary star#Spectroscopic binaries|single-lined spectroscopic binary]] (SB1). It is one of the oldest stars known, about 13.53&nbsp;billion years old, possibly one of the first stars, a star made almost entirely of materials released from the Big Bang. A tiny unseen companion, a low-mass UMP star, is particularly unusual.

==System==
J1808−5104 is an ultra metal-poor (UMP) star, one that has a [[Logarithmic scale|logarithmic]] [[Astronomy:Metallicity|metallicity]] [Fe/H] less than {{val|−4}}, or {{sfrac|1| 10,000 }}th of the levels in the Sun.<ref name=Ezzeddine-Frevbel-2018/> It is a single-lined spectroscopic binary, with [[Astronomy:Radial velocity|radial velocity]] variations in its spectral absorption lines interpreted as orbital motion of the visible star. The companion is invisible, but inferred from the orbit.<ref name=ApJ-20181105/>

J1808−5104 is the brightest UMP star, as a binary system, known,<ref name=Ezzeddine-Frevbel-2018>
{{cite journal
 |last1=Ezzeddine |first1=Rana
 |last2=Frevbel   |first2=Anna
 |date=27 September 2018
 |title=Revisiting the iron abundance in the hyper iron-poor star HE&nbsp;1327−2326 with UV COS/HST data
 |journal=The Astrophysical Journal
 |volume=863  |issue=2  |page=168
 |arxiv=1807.06153 |bibcode=2018ApJ...863..168E
 |doi=10.3847/1538-4357/aad3cb |s2cid=118918067
|doi-access=free
 }}
</ref> and is part of the "[[Astronomy:Milky Way#Age and cosmological history|thin disk]]" of the [[Astronomy:Milky Way|Milky Way]], the part of the [[Astronomy:Galaxy|galaxy]] in which the Sun is located, but unusual for such a metal-poor and old star.<ref name=JHU-20181105/> At {{val|13.53|ul=Gyr}}, the star is the oldest known thin-disk star, and several billion years older than most estimates for the age of the Milky Way's thin disk.<ref name=ApJ-20181105/>

===Primary star===
The primary component of the binary star system, 2MASS&nbsp;J18082002−5104378&nbsp;A, is a [[Astronomy:Subgiant|subgiant]], cooler than the Sun, but larger and more luminous.<ref name=melendez/>

===Secondary star===
The secondary unseen companion, 2MASS&nbsp;J18082002−5104378&nbsp;B, thought to be a [[Astronomy:Red dwarf|red dwarf]],<ref name=SCI-20181106>
{{cite news
 |title=One of Milky Way's oldest stars discovered
 |date=6 November 2018
 |website=SciNews.com
 |url=http://www.sci-news.com/astronomy/ultra-metal-poor-star-06577.html
 |access-date=6 November 2018
}}
</ref> has an [[Astronomy:Orbital period|orbital period]] {{mvar|P}} = {{val|34.757|+0.010|-0.010}} days and a mass of {{solar mass|0.14|link=yes}}.<ref name=ApJ-20181105/> It is the first low-mass UMP star to be discovered, and one of the oldest stars in the universe, about 13.53&nbsp;billion years old.<ref name=SCI-20181106/> It is possibly one of the first stars, a star made almost entirely of materials released from the [[Astronomy:Big Bang|Big Bang]].<ref name=ApJ-20181105/><ref name=BGR-20181105>
{{cite news
 |last=Wehner |first=Mike
 |date=5 November 2018
 |title=Astronomers spot one of the oldest stars ever
 |website=BGR
 |url=https://bgr.com/2018/11/05/oldest-star-ever-astronomy-milky-way/
 |access-date=5 November 2018
}}
</ref><ref name=SR-20181105-go>{{cite press release
 |publisher=Gemini Observatory
 |date=5 November 2018
 |title=A tiny old star has a huge impact
 |website=SpaceRef.com
 |url=http://spaceref.com/astronomy/a-tiny-old-star-has-a-huge-impact.html
 |access-date=6 November 2018
 }} </ref><ref name=JHU-20181105>
{{cite press release
 |last=Rosen  |first=Jill
 |date=5 November 2018
 |title=Johns Hopkins scientist finds elusive star with origins close to Big Bang
 |publisher=[[Organization:Johns Hopkins University|Johns Hopkins University]]
 |url=https://hub.jhu.edu/2018/11/05/scientists-find-star-with-big-bang-origins/
 |access-date=5 November 2018
 |quote=The newly discovered star's composition indicates that, in a cosmic family tree, it could be as little as one generation removed from the Big Bang.
}}
</ref><ref name=EA-20181105>
{{cite press release
 |title=Johns Hopkins scientist finds elusive star with origins close to Big Bang
 |date=5 November 2018
 |via=EurekAlert!
 |publisher=[[Organization:Johns Hopkins University|Johns Hopkins University]]
 |url=https://www.eurekalert.org/pub_releases/2018-11/jhu-jhs110518.php
 |access-date=5 November 2018
}}
</ref><ref name=SA-20181105>
{{cite news
 |last=Starr |first=Michelle
 |date=5 November 2018
 |title=Astronomers have detected one of the oldest stars in the entire universe
 |website=ScienceAlert.com
 |url=https://www.sciencealert.com/tiny-ancient-metal-poor-star-in-the-milky-way-could-be-one-of-the-oldest-in-the-universe
 |access-date=5 November 2018
}}
</ref><ref name=NAtlas-20181105>
{{cite news
 |last=Irving |first=Michael
 |date=5 November 2018
 |title=13.5&nbsp;billion year old star was born just after the Big Bang - and it's in our neighborhood
 |website=NewAtlas.com
 |url=https://newatlas.com/ancient-star-one-generation-big-bang/57089/
 |access-date=5 November 2018
}}
</ref><ref name=TE-20181105>
{{cite news
 |last=Malewar |first=Amit
 |date=5 November 2018
 |title=Johns Hopkins scientists may have found one of the universe's oldest stars - One of the universe's oldest stars
 |website=TechExplorist.com
 |url=https://www.techexplorist.com/johns-hopkins-scientists-may-have-found-one-of-the-universes-oldest-stars/18215/
 |access-date=5 November 2018
}}
</ref>

{{clear}}

== References ==
{{reflist|25em}}

== External links ==
* {{cite simbad|title=2MASS J18082002−5104378}}
* {{cite simbad|title=2MASS J18082002−5104378 B}}
* {{YouTube|O2D1XDHEO-I|Video (00:30) – Orbit of newly found 13.5&nbsp;billion-year-old star }} (5 November 2018; [[Organization:Johns Hopkins University|Johns Hopkins University]])

{{2018 in space}}
{{Ara (constellation)}}
{{Stellar system}}
{{Sky|18|08|20.02|-|51|04|37.8|1950}}

{{DEFAULTSORT:2MASS J18082002-5104378}}
[[Category:2MASS objects|J18082002−5104378]]
[[Category:Ara (constellation)]]
[[Category:Spectroscopic binaries]]

{{Sourceattribution|2MASS J18082002−5104378}}