70 Pegasi
Binary star system in the constellation Pegasus
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70 Pegasi is a binary star[6] system in the northern constellation Pegasus. It is a faint star, visible to the naked eye under good seeing conditions, with an apparent visual magnitude of 4.56.[2] The measured annual parallax shift measured from Earth's orbit is 18.65 mas,[1] yielding a distance estimate of around 175 light years. The visual magnitude of the star is diminished by an extinction of 0.07±0.02 due to interstellar dust. It is moving closer to the Sun with a radial velocity of −17 km/s.[4]
 | |
| Observation data Epoch J2000.0 Equinox ICRS | |
|---|---|
| Constellation | Pegasus |
| Right ascension | 23h 29m 09.29698s[1] |
| Declination | +12° 45′ 37.9918″[1] |
| Apparent magnitude (V) | 4.56[2] |
| Characteristics | |
| Spectral type | G8 IIIa[3] |
| B−V color index | 0.940[2] |
| Astrometry | |
| Radial velocity (Rv) | −16.88±0.43[4] km/s |
| Proper motion (μ) | RA: +61.40[1] mas/yr Dec.: +24.82[1] mas/yr |
| Parallax (π) | 18.65±0.78 mas[1] |
| Distance | 175 ± 7 ly (54 ± 2 pc) |
| Absolute magnitude (MV) | 0.90[5] |
| Orbit[6] | |
| Period (P) | 941.03±0.12 d |
| Eccentricity (e) | 0.713±0.006 |
| Argument of periastron (ω) (secondary) | 57.0±1.2° |
| Semi-amplitude (K1) (primary) | 3.16±0.04 km/s |
| Details[4] | |
| 70 Peg A | |
| Mass | 2.49±0.06 M☉ |
| Radius | 8.95±0.69[7] R☉ |
| Luminosity | 49.2±2.4[7] L☉ |
| Surface gravity (log g) | 2.92±0.05 cgs |
| Temperature | 5,108±185[7] K |
| Metallicity [Fe/H] | 0.05±0.03 dex |
| Rotational velocity (v sin i) | 3.6[8] km/s |
| Age | 590±40 Myr |
| Other designations | |
| 70 Peg, BD+11°5009, FK5 885, HD 221115, HIP 115919, HR 8923, SAO 108638[9] | |
| Database references | |
| SIMBAD | data |
This is a single-lined spectroscopic binary with an orbital period of 2.58 years (941 days) and a high eccentricity of 0.713.[6] The visible component has a stellar classification of G8 IIIa,[3] indicating it is an evolved G-type giant star. It is a probable red clump star, which would mean it is generating energy through helium fusion at its core.[10] The star has 2.5 times the mass of the Sun[4] and has expanded to nine times the Sun's radius. It is radiating about 49 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 5,108 K.[7]
The secondary is most likely a low mass main sequence star with no more than 0.4 times the mass of the Sun.[6]