2MASS J18082002-5104378

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2MASS J18082002-5104378[1]
Artist’s impression of the exotic binary star system AR Scorpii.jpg
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]
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)
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
[1] M
Age13.535±0.002[1] Gyr
Other designations
Gaia DR2 6702907209758894848[5]
Database references

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 very 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.


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 are 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][9] 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.[10] 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[edit]

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[edit]

The secondary unseen companion, 2MASS J18082002-5104378 B, thought to be a red dwarf,[5] has an orbital period P = 34.757+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] possibly one of the very first stars, a star made almost entirely of materials released from the Big Bang.[17]


  1. ^ a b c d e f g 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. doi:10.3847/1538-4357/aadd97.
  2. ^ Staff (2018). "Finding the constellation which contains given sky coordinates". DJM.cc. Retrieved 5 November 2018.
  3. ^ a b c d e 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. Bibcode:2016A&A...585L...5M. doi:10.1051/0004-6361/201527456.
  4. ^ a b c d e 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. ^ a b c d e News Staff (6 November 2018). "One of Milky Way's Oldest Stars Discovered". SciNews.com. Retrieved 6 November 2018.
  6. ^ a b Crockett, Christopher (12 November 2018). "Puny Star Might Be Specimen from Early Universe". Sky & Telescope. Retrieved 14 November 2018.
  7. ^ a b Williams, Matt (9 November 2018). "Ancient Star Found that's Only Slightly Younger than the Universe Itself". Universe Today. Retrieved 14 November 2018.
  8. ^ a b Ezzeddine, Rana; Frebel, Anna (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. Bibcode:2018ApJ...863..168E. doi:10.3847/1538-4357/aad3cb.
  9. ^ 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" (PDF). arxiv. arXiv:1807.06153v1. Retrieved 8 November 2018.
  10. ^ a b 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". Johns Hopkins University. Retrieved 5 November 2018.
  11. ^ Wehner, Mike (5 November 2018). "Astronomers spot one of the oldest stars ever". BGR. Retrieved 5 November 2018.
  12. ^ Gemini Observatory (5 November 2018). "A Tiny Old Star Has A Huge Impact". SpaceRef.com. Retrieved 6 November 2018.
  13. ^ Johns Hopkins University (5 November 2018). "Johns Hopkins scientist finds elusive star with origins close to Big Bang". EurekAlert!. Retrieved 5 November 2018.
  14. ^ Starr, Michelle (5 November 2018). "Astronomers Have Detected One of The Oldest Stars in The Entire Universe". ScienceAlert.com. Retrieved 5 November 2018.
  15. ^ 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.
  16. ^ 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.
  17. ^ [1][11][12][10][13][14][15][16]

External links[edit]

Coordinates: Sky map 18h 08m 20.02s, −51° 04′ 37.8″