  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Scorpius |
| Right ascension | 17h 52m 13.662s[1] |
| Declination | −34° 47′ 57.11″[1] |
| Apparent magnitude (V) | 5.87[2] |
| Characteristics | |
| Spectral type | B5 IIIp[3] |
| U−Bcolor index | −0.64[4] |
| B−Vcolor index | −0.10[4] |
| Variable type | SX Ari[2] |
| Astrometry | |
| Radial velocity (Rv) | −9.70[5] km/s |
| Proper motion (μ) | RA: 3.148[1]mas/yr Dec.: −5.604[1]mas/yr |
| Parallax (π) | 3.6766±0.1521 mas[1] |
| Distance | 890 ± 40 ly (270 ± 10 pc) |
| Absolute magnitude (MV) | −1.441[6] |
| Details | |
| Mass | 5.13[7] M☉ |
| Radius | 4.00[7] R☉ |
| Luminosity | 1,148[7] L☉ |
| Surface gravity (log g) | 3.94[7] cgs |
| Temperature | 16,600[7] K |
| Metallicity [Fe/H] | +0.01[8] dex |
| Rotational velocity (v sin i) | 30[9] km/s |
| Age | 50[7] Myr |
| Other designations | |
| V957 Sco,HR 6647,HD 162374,CD−34°12165,SAO 209383,HIP 87460 | |
| Database references | |
| SIMBAD | data |
V957 Scorpii is avariable star in the constellation ofScorpius. It is ablue straggler in the open clusterMessier 7, a star that is unexpectedly hot compared to other members of the cluster. A 6thmagnitude star, it is faintly visible to thenaked eye under very good observing conditions.
V957 Scorpii shows a peculiar B5 or B6 spectrum. Its luminosity class has been given asmain sequence (V),subgiant (IV),giant (III), andsupergiant (Ib).[10] From its position in theH-R diagram, it is actually thought to be a main sequence star.[11] With a helium abundance 25 times lower than that of the sun,[12] it is classified ashelium-weak. It also has a low carbon abundance and a strong magnetic field.[7]
Messier 7 is a naked eyeopen cluster. Except for one obvious orange giant star, its brightest members are mostly early A and late B main sequence stars and giants. Several of them are alsochemically peculiar stars. However, two stars are hotter than the others and lie to the left of theisochrone for the cluster. These are theblue stragglersHD 162586 and V957 Scorpii. V957 Scorpii is considered 92% likely to be a member of M7. M7 has an age around 220 million years, but the apparent age of V957 Scorpii is less than 100 million years.[12]
V957 Scorpii varies in brightness by about 0.05 magnitudes. This is thought to be due to its rotation and variations in its surface brightness. It is classified as anSX Arietis variable, also known as helium variables. Theirspectral lines also vary as the stars rotate.[2]
