51 Pegasi

51 Pegasi / Helvetios
	; 51 Peg (circled) in the constellation Pegasus.
Observation data; Epoch J2000.0 Equinox J2000.0
Constellation	Pegasus
Right ascension	22h 57m 27.9805s
Declination	+20° 46′ 07.797″
Apparent magnitude (V)	5.49
Characteristics
Spectral type	G2V+
Apparent magnitude (B)	6.16
Apparent magnitude (R)	5.0
Apparent magnitude (I)	4.7
Apparent magnitude (J)	4.66
Apparent magnitude (H)	4.23
Apparent magnitude (K)	3.91
U−B color index	+0.20
B−V color index	+0.67
Astrometry
Radial velocity (Rv)	−33.33 km/s
Proper motion (μ)	RA: +207.328 mas/yr ; Dec.: +61.164 mas/yr
Parallax (π)	64.4048 ± 0.0543 mas
Distance	50.64 ± 0.04 ly ; (15.53 ± 0.01 pc)
Absolute magnitude (MV)	4.48
Details
Mass	1.09±0.02 M☉
Radius	1.152±0.009 R☉
Luminosity	1.398±0.016 L☉
Surface gravity (log g)	4.33 cgs
Temperature	5,768±8 K
Metallicity	= 0.18±0.07
Metallicity [Fe/H]	+0.20 dex
Rotation	21.9±0.4 days
Rotational velocity (v sin i)	5.6 km/s
Age	4.8+0.7; −0.4 Gyr
Other designations
	Helvetios, 51 Peg, GJ 882, HR 8729, BD+19°5036, HD 217014, LTT 16750, GCTP 5568.00, SAO 90896, HIP 113357
Database references
SIMBAD	data
Exoplanet Archive	data
ARICNS	data

51 Pegasi (abbreviated 51 Peg), formally named Helvetios /hɛlˈviːʃiəs/,^[12] is a Sun-like star located 50.6 light-years (15.5 parsecs) from Earth in the constellation of Pegasus. It was the first main-sequence star found to have an exoplanet (designated 51 Pegasi b, officially named Dimidium) orbiting it.^[13]

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Observation data Epoch J2000.0 Equinox J2000.0
51 Peg (circled) in the constellation Pegasus.
Constellation	Pegasus
Right ascension	22^h 57^m 27.9805^s^[1]
Declination	+20° 46′ 07.797″^[1]
Apparent magnitude (V)	5.49^[2]
Characteristics
Spectral type	G2V+^[3]
Apparent magnitude (B)	6.16^[4]
Apparent magnitude (R)	5.0^[4]
Apparent magnitude (I)	4.7^[4]
Apparent magnitude (J)	4.66^[4]
Apparent magnitude (H)	4.23^[4]
Apparent magnitude (K)	3.91^[2]
U−B color index	+0.20^[5]
B−V color index	+0.67^[5]
Astrometry

Radial velocity (R_v)	−33.33^[1] km/s
Proper motion (μ)	RA: +207.328^[1] mas/yr Dec.: +61.164^[1] mas/yr
Parallax (π)	64.4048 ± 0.0543 mas^[1]
Distance	50.64 ± 0.04 ly (15.53 ± 0.01 pc)
Absolute magnitude (M_V)	4.48^[6]

Details^[7]

Mass	1.09±0.02 `M`_☉
Radius	1.152±0.009 `R`_☉
Luminosity	1.398±0.016 `L`_☉
Surface gravity (log g)	4.33^[8] cgs
Temperature	5,768±8^[6] K
Metallicity	${\begin{smallmatrix}\left[{\ce {M}}/{\ce {H}}\right]\end{smallmatrix}}$ = 0.18±0.07
Metallicity [Fe/H]	+0.20^[8] dex
Rotation	21.9±0.4 days^[9]
Rotational velocity (v sin i)	5.6^[10] km/s
Age	4.8+0.7 −0.4 Gyr

Other designations
Helvetios, 51 Peg, GJ 882, HR 8729, BD+19°5036, HD 217014, LTT 16750, GCTP 5568.00, SAO 90896, HIP 113357^[11]
Database references
SIMBAD	data
Exoplanet Archive	data
ARICNS	data