Registry · exoplanet

51 Peg b

Exoplanet

harvesting The full record is being pulled from the archives right now — measurement tables, the Gaia row, catalogue photometry. This page will fill itself in.

Right ascension: 22h 57m 28.21s
Declination: +20° 46′ 08.7″
Galactic l, b: 90.064, -34.73
Magnitude V: 5.453
Distance: 15.461 pc

Planet

NASA Exoplanet Archive, composite parameters

Host star	51 Peg · G5V
Discovery	Radial Velocity, 1995 · Haute-Provence Observatory
Orbital period	4.2308 d
Semi-major axis	0.052 au
Eccentricity	0.0063
Radius	14.1 R⊕ · 1.26 R♃
Mass	193.88 M⊕ · 0.61 M♃
Density	0.38 g/cm³
Equilibrium temperature	1,328.9 K
System distance	15.461 pc

Published measurements

4 quantities measured more than once

One object can carry a dozen published estimates of the same quantity. The register keeps them side by side rather than picking a winner — the citation is part of the value.

Mass 6 values

Value	Unit	Uncertainty	Band / method	Source	Reference	Year
193.8753	M_earth	± 19.07	Radial Velocity	NASA Exoplanet Archive	Cont et al. 2026	2026
147.4724	M_earth	± 4.45	Radial Velocity	NASA Exoplanet Archive	Rosenthal et al. 2021	2021
146.2018	M_earth	± 19.07	Radial Velocity	NASA Exoplanet Archive	Martins et al. 2015	2015
150.009	M_earth	± 12.39	Radial Velocity	NASA Exoplanet Archive	Butler et al. 2006	2006
148.738	M_earth	± 2.225	Radial Velocity	NASA Exoplanet Archive	Naef et al. 2004	2004
149.3801	M_earth	± 6.357	Radial Velocity	NASA Exoplanet Archive	Mayor & Queloz 1995	1995

Orbital period 6 values

Value	Unit	Uncertainty	Band / method	Source	Reference	Year
4.230797	d	± 2.70e-06	Radial Velocity	NASA Exoplanet Archive	Cont et al. 2026	2026
4.230797	d	± 7.30e-06	Radial Velocity	NASA Exoplanet Archive	Rosenthal et al. 2021	2021
4.231	d		Radial Velocity	NASA Exoplanet Archive	Martins et al. 2015	2015
4.230785	d	± 3.60e-05	Radial Velocity	NASA Exoplanet Archive	Butler et al. 2006	2006
4.23077	d	± 4.00e-05	Radial Velocity	NASA Exoplanet Archive	Naef et al. 2004	2004
4.2293	d	± 0.0011	Radial Velocity	NASA Exoplanet Archive	Mayor & Queloz 1995	1995

Semi-major axis 5 values

Value	Unit	Uncertainty	Band / method	Source	Reference	Year
0.052	au		Radial Velocity	NASA Exoplanet Archive	Cont et al. 2026	2026
0.05235	au	± 0.00076	Radial Velocity	NASA Exoplanet Archive	Rosenthal et al. 2021	2021
0.052	au		Radial Velocity	NASA Exoplanet Archive	Martins et al. 2015	2015
0.0527	au	± 0.003	Radial Velocity	NASA Exoplanet Archive	Butler et al. 2006	2006
0.052	au		Radial Velocity	NASA Exoplanet Archive	Naef et al. 2004	2004

Eccentricity 6 values

Value	Uncertainty	Band / method	Source	Reference	Year
0.0063		Radial Velocity	NASA Exoplanet Archive	Cont et al. 2026	2026
0.0042	± 0.0046	Radial Velocity	NASA Exoplanet Archive	Rosenthal et al. 2021	2021
0		Radial Velocity	NASA Exoplanet Archive	Martins et al. 2015	2015
0.013	± 0.012	Radial Velocity	NASA Exoplanet Archive	Butler et al. 2006	2006
0	± 0	Radial Velocity	NASA Exoplanet Archive	Naef et al. 2004	2004
0		Radial Velocity	NASA Exoplanet Archive	Mayor & Queloz 1995	1995

In the same field

within 9 arcmin · wider search

Object	Type	Separation	V
51 Peg	Star	0″	—
* 51 Peg	HighPM*	3.35″	5.46
* 51 Peg b	Planet	3.35″	—
SDSS J225738.50+204223.4	QSO	267.7″	—
SDSS J225735.26+205048.7	QSO	297″	—
G 128-23	HighPM*	427.3″	—
SDSS J225717.43+203926.4	QSO	429.8″	—
SDSS J225720.31+203855.3	QSO	447.4″	—
SDSS J225750.80+204044.5	QSO	453.5″	—
SDSS J225707.83+205214.8	QSO	464.4″	—

Provenance

where this card came from

Archive	Read at (UTC)	Record
Seeded from the bulk archive load; no per-object fetch yet.

Machine-readable: /api/v1/object/51-peg-b · Registry entry updated 2026-08-14.