1 Serpentis
Red giant star in the constellation Virgo
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1 Serpentis (1 Ser) is a red giant in the constellation Virgo with an apparent magnitude of 5.5. It is a red clump giant, a cool horizontal branch star that is fusing helium in its core.[4] It has expanded to over 13 times the radius of the Sun and although it is cooler at 4,581 K it is 77 times more luminous. It is 322 light years away.
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Virgo[1] |
| Right ascension | 14h 57m 33.251s [2] |
| Declination | −00° 10′ 03.40″ [2] |
| Apparent magnitude (V) | 5.5[3] |
| Characteristics | |
| Evolutionary stage | Red clump[4] |
| Spectral type | K1III[5] |
| Astrometry | |
| Radial velocity (Rv) | 20.12[6] km/s |
| Proper motion (μ) | RA: +59.929[2] mas/yr Dec.: −26.500[2] mas/yr |
| Parallax (π) | 10.1280±0.1010 mas[2] |
| Distance | 322 ± 3 ly (98.7 ± 1.0 pc) |
| Absolute magnitude (MV) | +0.76[1] |
| Details | |
| Mass | 1.37[3] M☉ |
| Radius | 13.6[2] R☉ |
| Luminosity | 75[2] L☉ |
| Surface gravity (log g) | 2.5[6] cgs |
| Temperature | 4,581[6] K |
| Metallicity [Fe/H] | −0.07[6] dex |
| Rotational velocity (v sin i) | 3.4[6] km/s |
| Age | 4.58[4] Gyr |
| Other designations | |
| 1 Ser, BD+00°3277, GJ 3881, HD 132132, HIP 73193, HR 5573, SAO 120758 | |
| Database references | |
| SIMBAD | data |
The Flamsteed designation 1 Serpentis was given to the star when the constellation Serpens was combined with the constellation Ophiuchus.[7] It was also given the Bayer designation M Serpentis. When Ophiuchus and Serpens were separated into distinct constellations, 1 Serpentis was left over the border in Libra. Since then it has moved slightly and is now in Virgo.[8]
A 10th-magnitude companion star discovered by William Herschel is 86″ away.[9] It is at the same distance as 1 Ser and shares a common proper motion,[10] It is considered likely to be a physical companion,[11] with the two stars separated by 8,600 au.[12] It has a spectral type of G5 IV,[12] and it is slightly smaller and less luminous than the sun.[10]
A much more widely-separated 10th-magnitude star is also listed in multiple star catalogues,[9] but it is an unrelated background object.[13]