Example of a binary star system (artist concept)
Epoch J2000 Equinox J2000
|Right ascension||18h 08m 20.02s|
|Declination||−51° 04′ 37.8″|
|Apparent magnitude (V)||11.9|
|Proper motion (μ)|| RA: -5.672 mas/yr |
Dec.: -12.643 mas/yr
|Parallax (π)||1.6775 ± 0.0397 mas|
|Distance||1,950 ly |
|Surface gravity (log g)||3.0 cgs|
|Metallicity [Fe/H]||-4.1 dex|
Gaia DR2 6702907209758894848
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) 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 , 1/10,000th of the levels in the sun. −4 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.
J1808-5104 is the brightest UMP star, as a binary system, known, 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. At 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. 13.53 
The secondary unseen companion, 2MASS J18082002-5104378 B, thought to be a red dwarf, has an orbital period P = +0.010
−0.010 days and a mass of 0.14 34.757M☉. 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, possibly one of the very first stars, a star made almost entirely of materials released from the Big Bang.
- 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.
- Staff (2018). "Finding the constellation which contains given sky coordinates". DJM.cc. Retrieved 5 November 2018.
- 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.
- 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.
- News Staff (6 November 2018). "One of Milky Way's Oldest Stars Discovered". SciNews.com. Retrieved 6 November 2018.
- Crockett, Christopher (12 November 2018). "Puny Star Might Be Specimen from Early Universe". Sky & Telescope. Retrieved 14 November 2018.
- Williams, Matt (9 November 2018). "Ancient Star Found that's Only Slightly Younger than the Universe Itself". Universe Today. Retrieved 14 November 2018.
- 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.
- 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.
- 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.
- Wehner, Mike (5 November 2018). "Astronomers spot one of the oldest stars ever". BGR. Retrieved 5 November 2018.
- Gemini Observatory (5 November 2018). "A Tiny Old Star Has A Huge Impact". SpaceRef.com. Retrieved 6 November 2018.
- Johns Hopkins University (5 November 2018). "Johns Hopkins scientist finds elusive star with origins close to Big Bang". EurekAlert!. Retrieved 5 November 2018.
- Starr, Michelle (5 November 2018). "Astronomers Have Detected One of The Oldest Stars in The Entire Universe". ScienceAlert.com. Retrieved 5 November 2018.
- 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.
- 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.
- "2MASS J18082002-5104378". SIMBAD. Centre de données astronomiques de Strasbourg.
- "2MASS J18082002-5104378 B". SIMBAD. Centre de données astronomiques de Strasbourg.
- on YouTube (5 November 2018; Johns Hopkins University)