Sigma Pegasi
Star in the constellation Pegasus
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σ Pegasi, Latinised as Sigma Pegasi, is a binary star[3] system in the northern constellation of Pegasus. With a combined apparent visual magnitude of 5.16,[2] it is faintly visible to the naked eye. Based upon an annual parallax shift of 36.66 mas as seen from Earth,[1] the system is located 89 light years distant from the Sun. It has a relatively high proper motion, advancing across the celestial sphere at the rate of 0.524 arcseconds per year.[11]
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Pegasus |
| Right ascension | 22h 52m 24.07496s[1] |
| Declination | +09° 50′ 08.3791″[1] |
| Apparent magnitude (V) | 5.16[2] + 13.5[3] |
| Characteristics | |
| Spectral type | F6 V[4] or F7 IV[5] + M4 V[3] |
| U−B color index | −0.016[2] |
| B−V color index | +0.486[2] |
| Astrometry | |
| Radial velocity (Rv) | +11.4[6] km/s |
| Proper motion (μ) | RA: +521.04[1] mas/yr Dec.: +42.65[1] mas/yr |
| Parallax (π) | 36.66±0.29 mas[1] |
| Distance | 89.0 ± 0.7 ly (27.3 ± 0.2 pc) |
| Absolute magnitude (MV) | 3.01[7] |
| Details | |
| σ Peg A | |
| Mass | 1.275[6] M☉ |
| Surface gravity (log g) | 3.69[4] cgs |
| Temperature | 6,250[4] K |
| Metallicity [Fe/H] | −0.32[4] dex |
| Rotational velocity (v sin i) | 3[8] km/s |
| Age | 2.71±0.61[9] Gyr |
| Other designations | |
| σ Peg, 49 Peg, BD+09°5122, FK5 3828, HD 216385, HIP 112935, HR 8697, SAO 127810[10] | |
| Database references | |
| SIMBAD | data |
The primary, component A, is a yellow-white hued F-type main-sequence star with a stellar classification of F6 V.[4] However, Frasca et al. (2009) lists it as a somewhat more evolved F-type subgiant star with a class of F7 IV.[5] At the age of 2.7[9] billion years, it has an inactive chromosphere[4] and is spinning with a leisurely projected rotational velocity of 3 km/s.[8] It has a faint, magnitude 13.23[12] red dwarf companion, designated component B, at an angular separation of 248 arc seconds.[3] The system is most likely (96% chance) a member of the thin disk population of the Milky Way.[6]