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] |
Characteristics | |
Evolutionary stage | Subgiant / Red dwarf |
Astrometry | |
Proper motion (μ) |
RA: −5.672
[4]
mas/
yr Dec.: −12.643 [4] mas/ yr |
Parallax (π) | 1.6775 ± 0.0397 mas [4] |
Distance | 1,950
[5]
[6]
[7]
ly (600 pc) |
Details | |
A | |
Mass | 0.7599 ± 0.0001 [1] M☉ |
Radius | 2.44 [4] R☉ |
Luminosity | 5.311 [4] L☉ |
Surface gravity (log g) | 3.0 [3] cgs |
Temperature | 5,440 ± 100 [3] K |
Metallicity [Fe/H] | -4.1 [3] dex |
Age | 13.535±0.002 [1] Gyr |
B | |
Mass | 0.14+0.06 −0.01 [1] M☉ |
Age | 13.535±0.002 [1] Gyr |
Other designations | |
Gaia DR2 6702907209758894848
[5] | |
Database references | |
SIMBAD | data |
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 known, 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.
J1808−5104 is an ultra metal-poor (UMP) star, one that has a logarithmic metallicity [Fe/H] less than −4, or 1/ 10,000 th 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]
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]
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]
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.