S Pegasi
Variable star in the constellation Pegasus
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S Pegasi (S Peg) is a Mira variable star in the constellation Pegasus located about 2,300 light-years away. It varies between apparent magnitude 6.9 and 13.8 with a period of 319 days (10 months),[3][4] representing a nearly 600–fold change in brightness. S Pegasi enters solar conjunction and is hidden by the Sun's glare each year from late February through late March. It reaches opposition in mid-September, when it is visible all night.
Right ascension23h 20m 32.61474s[2]
Declination+08° 55′ 08.1627″[2]
Apparentmagnitude(V)6.9–13.8[3][4]
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Pegasus |
| Right ascension | 23h 20m 32.61474s[2] |
| Declination | +08° 55′ 08.1627″[2] |
| Apparent magnitude (V) | 6.9–13.8[3][4] |
| Characteristics | |
| Spectral type | M5e – M8.5e[4] |
| Variable type | Mira[4] |
| Astrometry | |
| Radial velocity (Rv) | 5.0±4.6[5] km/s |
| Proper motion (μ) | RA: −18.494 mas/yr[2] Dec.: −17.197 mas/yr[2] |
| Parallax (π) | 1.399±0.083 mas[6] |
| Distance | 2,300 ± 100 ly (710 ± 40 pc) |
| Details | |
| Radius | 278–316[6] R☉ |
| Luminosity | 6,545+583 −531[6] L☉ |
| Surface gravity (log g) | −0.45 to −0.39[6] cgs |
| Temperature | 2,910–2,932[6] K |
| Other designations | |
| S Peg, BD+08°5047a, HD 220033, HIP 115242 | |
| Database references | |
| SIMBAD | data |
It is believed to be pulsating in the first overtone. First overtone pulsators have masses less than 1.8 M☉ at a temperature of 2,107 K, and less than 1.4 M☉ at the luminosity of S Pegasi.[7]
