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) 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.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ara |
| Right ascension | 18h 08m 20.02s |
| Declination | −51° 04′ 37.8″ |
| Apparent magnitude (V) | 11.9 |
| Characteristics | |
| Evolutionary stage | Subgiant / Red dwarf |
| Astrometry | |
| Proper motion (μ) | RA: −5.672 mas/yr Dec.: −12.643 mas/yr |
| Parallax (π) | 1.6775 ± 0.0397 mas |
| Distance | 1,950 ly (600 pc) |
| Details | |
| A | |
| Mass | 0.7599 ± 0.0001 M☉ |
| Radius | 2.44 R☉ |
| Luminosity | 5.311 L☉ |
| Surface gravity (log g) | 3.0 cgs |
| Temperature | 5,440 ± 100 K |
| Metallicity [Fe/H] | -4.1 dex |
| Age | 13.535±0.002 Gyr |
| B | |
| Mass | 0.14+0.06 −0.01 M☉ |
| Age | 13.535±0.002 Gyr |
| Other designations | |
Gaia DR2 6702907209758894848 | |
| Database references | |
| SIMBAD | data |
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