78 Pegasi
Binary star system in the Pegasus constellation
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78 Pegasi is a binary star system in the northern constellation of Pegasus. It is visible to the naked eye as a faint, orange-hued point of light with an apparent visual magnitude of 4.93.[2] The system is located approximately 224 light years from the Sun based on parallax,[1] but is drifting closer with a radial velocity of −8 km/s.[6] The double-star nature of this system was discovered by A. G. Clark in 1862. The components of this system orbit each other over a 630-year period with an eccentricity of 0.11.[10]
(5.07 / 8.10)[3]
 | |
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Pegasus |
| Right ascension | 23h 43m 59.48560s[1] |
| Declination | +29° 21′ 41.2342″[1] |
| Apparent magnitude (V) | 4.93[2] (5.07 / 8.10)[3] |
| Characteristics | |
| Spectral type | K0III[4] |
| U−B color index | +0.63[5] |
| B−V color index | +0.96[5] |
| Astrometry | |
| Radial velocity (Rv) | −8.33[6] km/s |
| Proper motion (μ) | RA: +71.10[1] mas/yr Dec.: -40.58[1] mas/yr |
| Parallax (π) | 14.54±0.56 mas[1] |
| Distance | 224 ± 9 ly (69 ± 3 pc) |
| Absolute magnitude (MV) | 0.75[2] |
| Orbit[3] | |
| Period (P) | 630.15 yr |
| Semi-major axis (a) | 1.614″ |
| Eccentricity (e) | 0.112 |
| Inclination (i) | 60.64° |
| Longitude of the node (Ω) | 172.55° |
| Periastron epoch (T) | B 2247.71 |
| Argument of periastron (ω) (secondary) | 241.27° |
| Details | |
| 78 Peg A | |
| Mass | 1.50[7] M☉ |
| Radius | 10[7] R☉ |
| Luminosity | 57.35[2] L☉ |
| Surface gravity (log g) | 2.62[7] cgs |
| Temperature | 4,898[7] K |
| Metallicity [Fe/H] | +0.01[2] dex |
| Rotational velocity (v sin i) | 1.1[8] km/s |
| Other designations | |
| 78 Peg, BD+28°4627, GC 32954, HD 222842, HIP 117073, HR 8997, SAO 91457, CCDM J23440+2922AB, WDS J23440+2922AB[9] | |
| Database references | |
| SIMBAD | data |
The primary member, designated component A, is a magnitude 5.07[3] giant star with a stellar classification of K0III,[4] having exhausted the supply of hydrogen at its core and expanded to 10[7] times the Sun's radius. It is a red clump giant,[11] which indicates it is on the horizontal branch and is generating energy through core helium fusion. It has 1.5[7] times the mass of the Sun and is radiating 57[2] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,898 K.[7] The secondary companion, component B, is magnitude 8.10.[3]
It is the 78th star numbered by Flamsteed in order of right ascension. In the 1795 French-language Fortin-Flamsteed edition of the Atlas Coelestis, 56 Pegasi is labelled with the letter "i".[12]