2MASS J18082002−5104378

2MASS J18082002−5104378 (abbreviated J1808−5104) is an ultra metal-poor (UMP) binary star system, in the constellation Ara, about 1,950 ly (600 pc)[5][6][7] from Earth, and is a single-lined spectroscopic binary (SB1). It is one of the oldest stars in the universe, about 13.53 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.

[1]

2MASS J18082002−5104378

Example of a binary star system (artist concept)
Observation data
Epoch J2000      Equinox J2000
Constellation Ara[2]
Right ascension 18h 08m 20.02s
Declination −51° 04′ 37.8″
Apparent magnitude (V) 11.9[3]
Astrometry
Proper motion (μ) RA: −5.672[4] mas/yr
Dec.: −12.643[4] mas/yr
Parallax (π)1.6775 ± 0.0397[4] mas
Distance1,950[5][6][7] ly
(600 pc)
Details
A
Radius2.44[4] R☉
Luminosity5.311[4] L☉
Surface gravity (log g)3.0[3] cgs
Temperature5,440[3] K
Metallicity [Fe/H]-4.1[3] dex
B
Mass0.14+0.06
−0.01[1] M☉
Age13.535±0.002[1] Gyr
Other designations
Gaia DR2 6702907209758894848[5]
Database references
SIMBADdata

System

J1808−5104 is an ultra metal-poor (UMP) star, one that has a metallicity [Fe/H] less than −4, ​1⁄10,000th of the levels in the sun.[8] It is a single-lined spectroscopic binary, with 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.[1]

J1808−5104 is the brightest UMP star, as a binary system, known,[8] and is part of the "thin disk" of the Milky Way, the part of the galaxy in which the Sun is located, but unusual for such a metal-poor and old star.[9] At 13.53 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.[1]

Primary star

The primary component of the binary star system, 2MASS J18082002−5104378 A, is a subgiant, cooler than the Sun, but larger and more luminous.[3]

Secondary star

The secondary unseen companion, 2MASS J18082002−5104378 B, thought to be a red dwarf,[5] has an orbital period P = 34.757+0.010
−0.010 days and a mass of 0.14 M☉.[1] It is the first low-mass UMP star to be discovered, and one of the oldest stars in the universe, about 13.53 billion years old.[5] It is possibly one of the first stars, a star made almost entirely of materials released from the Big Bang.[1][10][11][9][12][13][14][15]

References
  1. Schlaufman, Kevin C.; Thompson, Ian B.; Casey, Andrew R. (5 November 2018). "An ultra metal-poor star near the hydrogen-burning limit". The Astrophysical Journal. 867 (2): 98. arXiv:1811.00549. Bibcode:2018ApJ...867...98S. doi:10.3847/1538-4357/aadd97. S2CID 54511945.
  2. "Finding the constellation which contains given sky coordinates". DJM.cc. 2018. Retrieved 5 November 2018.
  3. Meléndez, Jorge; Placco, Vinicius M.; Tucci-Maia, Marcelo; Ramírez, Iván; Li, Ting S.; Perez, Gabriel (2016). "2MASS J18082002-5104378: The brightest (V = 11.9) ultra metal-poor star". Astronomy and Astrophysics. 585: L5. arXiv:1601.03462. Bibcode:2016A&A...585L...5M. doi:10.1051/0004-6361/201527456. S2CID 119240055.
  4. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  5. "One of Milky Way's oldest stars discovered". SciNews.com. 6 November 2018. Retrieved 6 November 2018.
  6. Crockett, Christopher (12 November 2018). "Puny star might be [a] specimen from [the] early universe". Sky & Telescope. Retrieved 14 November 2018.
  7. Williams, Matt (9 November 2018). "Ancient star found that's only slightly younger than the universe itself". Universe Today. Retrieved 14 November 2018.
  8. Ezzeddine, Rana; Frevbel, Anna (27 September 2018). "Revisiting the iron abundance in the hyper iron-poor star HE 1327−2326 with UV COS/HST data". The Astrophysical Journal. 863 (2): 168. arXiv:1807.06153. Bibcode:2018ApJ...863..168E. doi:10.3847/1538-4357/aad3cb. S2CID 118918067.
  9. Rosen, Jill (5 November 2018). "Johns Hopkins scientist finds elusive star with origins close to Big Bang - 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" (Press release). Johns Hopkins University. Retrieved 5 November 2018.
  10. Wehner, Mike (5 November 2018). "Astronomers spot one of the oldest stars ever". BGR. Retrieved 5 November 2018.
  11. "A tiny old star has a huge impact". SpaceRef.com. Gemini Observatory. 5 November 2018. Retrieved 6 November 2018.
  12. "Johns Hopkins scientist finds elusive star with origins close to Big Bang" (Press release). Johns Hopkins University. 5 November 2018. Retrieved 5 November 2018 – via EurekAlert!.
  13. Starr, Michelle (5 November 2018). "Astronomers have detected one of the oldest stars in the entire universe". ScienceAlert.com. Retrieved 5 November 2018.
  14. Irving, Michael (5 November 2018). "13.5 billion year old star was born just after the Big Bang - and it's in our neighborhood". NewAtlas.com. Retrieved 5 November 2018.
  15. Malewar, Amit (5 November 2018). "Johns Hopkins scientists may have found one of the universe's oldest stars - One of the universe's oldest stars". TechExplorist.com. Retrieved 5 November 2018.

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