31 Pegasi
Star in the constellation Pegasus
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31 Pegasi is a single[11] star in the northern constellation of Pegasus. It is visible to the naked eye as a dim, blue-white hued point of light with an apparent visual magnitude of about 5. It is located approximately 1,600 light years away from the Sun based on parallax,[1] but is drifting closer with a radial velocity of −5.3 km/s.[6]
  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Pegasus |
| Right ascension | 22h 21m 31.07511s[1] |
| Declination | 12° 12′ 18.6628″[1] |
| Apparent magnitude (V) | 4.85 - 5.05[2] |
| Characteristics | |
| Evolutionary stage | main sequence[3] |
| Spectral type | B2IV-Ve[4] |
| U−B color index | -0.81[5] |
| B−V color index | -0.10[5] |
| Variable type | γ Cas[2] |
| Astrometry | |
| Radial velocity (Rv) | −5.30[6] km/s |
| Proper motion (μ) | RA: +6.32[1] mas/yr Dec.: +4.80[1] mas/yr |
| Parallax (π) | 2.01±0.28 mas[1] |
| Distance | approx. 1,600 ly (approx. 500 pc) |
| Absolute magnitude (MV) | −3.61[7] |
| Details | |
| Mass | 12.5±0.7[3] M☉ |
| Radius | 11.6[8] R☉ |
| Luminosity (bolometric) | 27,925+4,360 −3,770[3] L☉ |
| Surface gravity (log g) | 3.71±0.15[3] cgs |
| Temperature | 23,890±740[3] K |
| Rotational velocity (v sin i) | 98±8[3] km/s |
| Age | 15.4±1.3[9] Myr |
| Other designations | |
| 31 Peg, IN Peg, BD+11°4784, FK5 843, GC 31255, HD 212076, HIP 110386, HR 8520, SAO 107854[10] | |
| Database references | |
| SIMBAD | data |
This is a massive Be star with a stellar classification of B2IV-V.[13] It is a γ Cas variable; a type of shell star with a circumstellar disc of gas surrounding the star at the equator, and ranges from 5.05 up to 4.85 in visual magnitude.[2] It is spinning with a projected rotational velocity of 98 km/s, with the pole being inclined by an estimated angle of 26°±9° to the line of sight from the Earth.[3] The star is 15.4[9] million years old with 12.5[3] times the mass of the Sun. It is radiating around 28,000 times the luminosity of the Sun from its photosphere at an effective temperature of 23,890 K.[3]