HD 222925
Chemically peculiar star
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HD 222925 is a horizontal branch star about 1,470 light years away in the southern constellation Tucana. It is magnitude 9, far below naked-eye visibility. It is an Ap star, a type of chemically peculiar star with an over-abundance of certain metals in its spectrum.
Elements detected in HD 222925 totalling 65 with 42 coming from the r-process (31 ≤ Z ≤ 92) . Elements with no long-lived isotopes are indicated using the light gray font.[1] | |
| Observation data Epoch J2000.00 Equinox J2000.00 | |
|---|---|
| Constellation | Tucana |
| Right ascension | 23h 45m 17.607s[2] |
| Declination | −61° 54′ 42.84″[2] |
| Apparent magnitude (V) | 9.03[3] |
| Characteristics | |
| Evolutionary stage | horizontal branch |
| Spectral type | F8 Sr Eu[4] (ApSrEu)[5] |
| Astrometry | |
| Radial velocity (Rv) | −38.9±0.6[6] km/s |
| Proper motion (μ) | RA: 143.803[2] mas/yr Dec.: −99.109[2] mas/yr |
| Parallax (π) | 2.2202±0.0117 mas[2] |
| Distance | 1,469 ± 8 ly (450 ± 2 pc) |
| Details | |
| Mass | 0.75±0.20[6] M☉ |
| Radius | 6[7] R☉ |
| Luminosity | 43[4] L☉ |
| Surface gravity (log g) | 2.54±0.17[1] cgs |
| Temperature | 5,636±103[1] K |
| Metallicity [Fe/H] | −1.47±0.08[6] dex |
| Other designations | |
| CD−62°1462, HD 222925, HIP 117168 | |
| Database references | |
| SIMBAD | data |
HD 222925 has been referred to as the 'gold standard star' by the media.[8] In 2022, astronomers from the University of Michigan identified 65 elements in the star (including gold), a turning point to help the scientific community understand the rapid neutron capture process.[9] The elements were produced in a massive supernova or a merger of neutron stars early in the universe, and it was ejected into space where it later reformed into the current star.[10]
