9 Pegasi

9 Pegasi (9 Peg) is a supergiant star in the constellation Pegasus. Its apparent magnitude is 4.35.

9 Pegasi

Location of 9 Peg (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Pegasus
Right ascension	21h 44m 30.69581s[1]
Declination	+17° 21′ 00.0571″[1]
Apparent magnitude (V)	4.35[2]
Characteristics
Spectral type	G5Ib[3]
U−B color index	+0.96[2]
B−V color index	+1.17[2]
Astrometry
Radial velocity (Rv)	−23.11[4] km/s
Proper motion (μ)	RA: 8.66[1] mas/yr Dec.: −11.33[1] mas/yr
Parallax (π)	3.52±0.22 mas[1]
Distance	900 ly (276[5] pc)
Absolute magnitude (MV)	~−3[6]
Details
Mass	7.1[3] M☉
Radius	61[5] R☉
Luminosity	1,950[7] L☉
Surface gravity (log g)	1.58[3] cgs
Temperature	4,910[3] K
Metallicity [Fe/H]	−0.04[6] dex
Rotational velocity (v sin i)	10[3] km/s
Other designations
9 Peg, HR 8313, BD+16°4582, HD 206859, SAO 107365, HIP 107348
Database references
SIMBAD	data

9 Pegasi is defined and used as an MK standard star for the spectral type G5 Ib.^[8][9] It is a yellow supergiant nearly two thousand times more luminous than the sun and sixty times larger. It has been reported to be slightly variable and is listed in the New Catalogue of Suspected Variable Stars with a magnitude range of 4.20 to 4.35.^[10]

9 Pegasi does not have a Bayer designation although it is brighter than several stars in Pegasus that do such as τ, φ, and σ Pegasi. It is the 9th star numbered by Flamsteed in order of right ascension. In the 1795 French-language Fortin-Flamsteed edition of the Atlas Coelestis, 9 Pegasi is labelled with the letter "g".^[11]