1 Serpentis

1 Serpentis
Location of 1 Serpentis (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Virgo
Right ascension 14h 57m 33.251s [1]
Declination −00° 10′ 03.40″ [1]
Apparent magnitude (V) 5.5[2]
Characteristics
Evolutionary stage Red clump[3]
Spectral type K1III[4]
Astrometry
Radial velocity (Rv)20.12[5] km/s
Proper motion (μ) RA: +59.929[1] mas/yr
Dec.: −26.500[1] mas/yr
Parallax (π)10.1280 ± 0.1010 mas[1]
Distance322 ± 3 ly
(98.7 ± 1.0 pc)
Absolute magnitude (MV)+0.76[6]
Details
Mass1.37[2] M☉
Radius13.6[1] R☉
Luminosity75[1] L☉
Surface gravity (log g)2.5[5] cgs
Temperature4,581[5] K
Metallicity [Fe/H]−0.07[5] dex
Rotational velocity (v sin i)3.4[5] km/s
Age4.58[3] Gyr
Other designations
1 Ser, BD+00°3277, GJ 3881, HD 132132, HIP 73193, HR 5573, SAO 120758
Database references
SIMBADdata

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.[3] 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.

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]

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