Key parameters at a glance

A radius of 8.47 Earth radii
A mass of 54.03 Earth masses
Surface gravity around 0.75 g
An orbital period of 20.813 days
Semi-major axis 0.1500 AU
Distance from Earth 129.09 light-years
Earth Similarity Index 0.341
Travel time at Voyager 1 speed 2,276,501 years

HD 102117 b Planet Profile

Physical Specs

Radius

8.47 R⊕

Radius (Jupiter)

0.756 R♃

Mass

54.03 M⊕

Mass (Jupiter)

0.170 M♃

Density

0.49 g/cm³

Surface Gravity

0.75 g (Earth)

Classification

Planet Type

Neptune-like

ESI Score 0.341

HZ Position Unknown

Controversial No

Discovery

Year 2005

Method Radial Velocity

Facility La Silla Observatory

Telescope 3.6 m ESO Telescope

Size rank in cohort

Rank by radius

#125of 574

top 21.6%

This planet

8.47R⊕

Neptune-like median

6.39R⊕

Nearest-size peers

TOI-6448 b 8.47 R⊕ WASP-148 b 8.47 R⊕ Kepler-16 b 8.45 R⊕

Metric	Earth	HD 102117 b	Jupiter
Radius (R⊕)	1.00	8.47	11.21
Mass (M⊕)	1.00	54.03	317.83
Density (g/cm³)	5.51	0.49	1.33
Surface Gravity (g)	1.00	0.75	2.53
Insolation (S⊕)	1.00	—	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Minimum mass (M sin i)	54.031 M⊕	Lower bound from radial-velocity fitting.

Star Catalogue Identifiers

HD 102117

HIP

HIP 57291

TIC

TIC 267519701

Gaia DR2

Gaia DR2 5341673851394297600

Gaia DR3

Gaia DR3 5341673851394297600

System

HD 102117

Percentile among Neptune-like cohort

Radius 8.470 R⊕ · percentile 78 / cohort 574

Mass 54.031 M⊕ · percentile 74 / cohort 574

Orbital period 20.81 d · percentile 52 / cohort 524

Distance 39.58 pc · percentile 12 / cohort 572

ESI 0.341 · percentile 61 / cohort 574

Orbit & Habitability

Orbital Dynamics

Period

20.813 days

Semi-major axis

0.1500 AU

Eccentricity

0.120

Inclination

— °

Year Length

A year here lasts approximately 20.81 Earth days (5.7% of a terrestrial year) on a mildly elliptical path at a mean orbital distance of 0.1500 AU.

Eq. Temperature

—

Insolation (S⊕)

—

Earth = 1.00

Earth Similarity (ESI)

0.341

0 = alien, 1 = Earth-identical

Discovery Paper

Primary reference

Lovis et al. 2005

Instrument

HARPS Spectrograph

Publication

2005-07

Observation locale

Ground

Discovery cohort

Planets confirmed in 2005 at La Silla Observatory (10 shown).

HD 4308 b · Neptune-like GJ 581 b · Neptune-like HD 11977 b · Gas Giant HD 142022 A b · Gas Giant HD 101930 b · Gas Giant HD 27894 b · Gas Giant HD 212301 b · Gas Giant HD 93083 b · Gas Giant HD 63454 b · Gas Giant HD 2638 b · Gas Giant

Host System: HD 102117

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

5,655 K — cooler than the Sun (5,778 K)

Estimated Age

10.00 Gyr — older than the Sun (4.6 Gyr)

Stellar Radius

1.230 R☉

Stellar Mass

1.060 M☉

Metallicity [Fe/H]

0.28

Extended Stellar Properties

Surface gravity (log g)

4.290 dex

Stellar density

0.741 g/cm³

Systemic radial velocity

49.64 km/s

Rotational v·sin i

0.88 km/s

Metallicity ratio

[Fe/H]

Distance

39.58 parsec

Light-years 129.09 ly

V-band magnitude

7.47 mag

Voyager-speed travel 2,276,501 yr

Multi-band Host Photometry — 11 bands

Astrometric Data

Parallax

25.237 mas

Total Proper Motion

94.873 mas/yr

PM Right Ascension

-63.55 mas/yr

PM Declination

-70.44 mas/yr

Galactic Cartesian (pc)

x = -0.518 · y = 0.034 · z = -0.854

Equatorial (J2000)

RA 176.20973° · Dec -58.70401°

Galactic ℓ, b

294.360° · 3.055°

Ecliptic λ, β

210.748° · -52.906°

HTM-20 index

-376650517

Observation Record

Photometric series

RV measurements

Archive notes