Key parameters at a glance

A radius of 14.30 Earth radii
A mass of 146.20 Earth masses
Surface gravity around 0.71 g
An orbital period of 4.231 days
Semi-major axis 0.0527 AU
Distance from Earth 50.43 light-years
Earth Similarity Index 0.247
Travel time at Voyager 1 speed 889,303 years

51 Peg b Planet Profile

Physical Specs

Radius

14.30 R⊕

Radius (Jupiter)

1.270 R♃

Mass

146.20 M⊕

Mass (Jupiter)

0.460 M♃

Density

0.28 g/cm³

Surface Gravity

0.71 g (Earth)

Classification

Planet Type

Gas Giant

ESI Score 0.247

HZ Position Unknown

Controversial No

Discovery

Year 1995

Method Radial Velocity

Facility Haute-Provence Observatory

Telescope 1.93 m Telescope

Size rank in cohort

Rank by radius

#301of 1771

top 16.9%

This planet

14.30R⊕

Gas Giant median

13.52R⊕

Nearest-size peers

HIP 65407 b 14.30 R⊕ HD 30669 b 14.30 R⊕ HD 45652 b 14.30 R⊕

Metric	Earth	51 Peg b	Jupiter
Radius (R⊕)	1.00	14.30	11.21
Mass (M⊕)	1.00	146.20	317.83
Density (g/cm³)	5.51	0.28	1.33
Surface Gravity (g)	1.00	0.71	2.53
Insolation (S⊕)	1.00	—	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	146.202 M⊕	Direct mass measurement (not derived).
Minimum mass (M sin i)	150.009 M⊕	Lower bound from radial-velocity fitting.
Computed mass	145.000 M⊕	Model-computed mass (e.g. from mass-radius relation).

Star Catalogue Identifiers

HD 217014

HIP

HIP 113357

TIC

TIC 139298196

Gaia DR2

Gaia DR2 2835207319109249920

Gaia DR3

Gaia DR3 2835207319109249920

System

51 Peg

Percentile among Gas Giant cohort

Radius 14.300 R⊕ · percentile 82 / cohort 1771

Mass 146.202 M⊕ · percentile 12 / cohort 1747

Orbital period 4.23 d · percentile 32 / cohort 1533

Distance 15.46 pc · percentile 2 / cohort 1759

ESI 0.247 · percentile 44 / cohort 1771

Orbit & Habitability

Orbital Dynamics

Period

4.231 days

Semi-major axis

0.0527 AU

Eccentricity

0.013

Inclination

80.00 °

Year Length

A year here lasts approximately 4.23 Earth days (1.2% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0527 AU.

Extended Orbital Architecture

RV semi-amplitude (K)

55.940 m/s

Transit mid-time (BJD)

2,455,705.0010

Long. of periastron (ω)

58.00°

Angular separation (arcsec)

3.41000

Eq. Temperature

—

Insolation (S⊕)

—

Earth = 1.00

Earth Similarity (ESI)

0.247

0 = alien, 1 = Earth-identical

Discovery Paper

Primary reference

Mayor Queloz 1995

Instrument

ELODIE Spectrograph

Publication

1995-11

Observation locale

Ground

Host System: 51 Peg

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

5,758 K — cooler than the Sun (5,778 K)

Estimated Age

10.00 Gyr — older than the Sun (4.6 Gyr)

Stellar Radius

1.176 R☉

Stellar Mass

1.030 M☉

Metallicity [Fe/H]

0.18

Extended Stellar Properties

Surface gravity (log g)

4.310 dex

Stellar density

0.894 g/cm³

Systemic radial velocity

-33.25 km/s

Rotational v·sin i

2.20 km/s

Rotation period

30.00 days

Activity index (log R'HK)

-5.080

Metallicity ratio

[M/H]

Distance

15.46 parsec

Light-years 50.43 ly

V-band magnitude

5.45 mag

Voyager-speed travel 889,303 yr

Multi-band Host Photometry — 11 bands

Astrometric Data

Parallax

64.649 mas

Total Proper Motion

216.460 mas/yr

PM Right Ascension

207.36 mas/yr

PM Declination

62.09 mas/yr

Galactic Cartesian (pc)

x = 0.900 · y = -0.252 · z = 0.355

Equatorial (J2000)

RA 344.36754° · Dec 20.76910°

Galactic ℓ, b

90.064° · -34.728°

Ecliptic λ, β

354.281° · 25.186°

HTM-20 index

-490247217

Observation Record

Photometric series

RV measurements

Stellar spectra

Archive notes