 The ultra-metal-poor star HE0107-5240 | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Phoenix |
| Right ascension | 01h 09m 29.1s |
| Declination | −52° 24′ 20″ |
| Apparent magnitude (V) | 15.86 |
| Astrometry | |
| Proper motion (μ) | RA: +2.357 mas/yr Dec.: −3.826 mas/yr |
| Parallax (π) | 0.1064 ± 0.0195 mas |
| Distance | 36000 ly |
| Details | |
| Mass | 1.789 M☉ |
| Radius | 3.7 R☉ |
| Luminosity | 14 L☉ |
| Temperature | 5,765 K |
| Metallicity [Fe/H] | −5.3 dex |
| Other designations | |
| Database references | |
| SIMBAD | data |
HE0107-5240 is a Population II star that has almost no metal. This kind of star is called a metal-poor star. It is close to 36000 light-years away from Earth. It is one of the most metal-poor stars known in our galaxy, with a metallicity of -5.2; This means it has just 1/160000 of the metal that the Sun has. Because of its very low metallicity, it is believed to be one of the earliest Population II stars to have formed. If so, then it is also very old, with an age of roughly 13 billion years. Because the star still has a bit of metal, it does not belong to the first generation of stars (the hypothetical Population III). These stars changed the pure hydrogen, helium, and lithium formed by the Big Bang into heavier elements, such as carbon, oxygen, and metals.
The star is small for a star that formed in the early universe. This explains why it is so old, as bigger stars die more quickly. To help explain why this star is so small, people think it was once part of a binary system.
