Mini-Neptune · GJ 3138

GJ 3138 d

ExoplanetsDiscovered 2017

Scientific overview

GJ 3138 d is a mini-neptune orbiting GJ 3138, completing an orbit every 258 days, about 93 light-years from Earth. It was discovered in 2017 using the radial velocity method.

Host star

GJ 3138

Spectral type

Temperature

3,717 K

Mass

0.681 M☉

Planetary system — GJ 3138 system

View the GJ 3138 system (3 known planets).

Planet	Class	Radius (R⊕)	Period (d)	Distance (ly)
GJ 3138 bRadial Velocity · 2017	Terrestrial planet	1.18	1.22	93
GJ 3138 cRadial Velocity · 2017	Super-Earth	1.88	5.974	93
GJ 3138 dRadial Velocity · 2017	Mini-Neptune	3.23	258	93

Discovery and detection

Detection method

Radial Velocity Method

Discovery year

2017

Discovered at

La Silla Observatory

Knowledge connections

OrbitsGJ 3138
Member of systemGJ 3138 system
Discovered by methodRadial Velocity Method
Discovered atLa Silla Observatory
Catalogued inNASA Exoplanet Archive

Quick facts

Class: Mini-Neptune
Host star: GJ 3138
Discovery method: Radial Velocity Method
Discovery year: 2017
Orbital period: 257.8 d
Semi-major axis: 0.698 AU
Eccentricity: 0.32
Radius: 3.23 R⊕
Mass: 10.5 M⊕
Density: 1.72 g/cm³ · derived
Equilibrium temp.: 152 K
Insolation: 0.1 S⊕
Distance: 93 ly

Density is derived from the archive mass and radius via ρ = M / (4⁄3·π·r³); all other values are catalogued measurements.

Derived values

Computed from source-backed inputs via standard formulae — not observations. Every input and constant is traced below.

Bulk density1.72 g/cm³derived
Formula & inputs
Formula: ρ = M / (4⁄3·π·r³) (v1.0.0, impl v1.0.0)
Inputs:
- massEarth = 10.5 M⊕ · NASA
- radiusEarth = 3.23 R⊕ · NASA
Assumptions: M⊕ = 5.972e+24 kg, R⊕ = 6371000 m (IAU 2015 B3 nominal); Assumes a uniform sphere.
Limitations: Withheld above 30 g/cm³ (inconsistent mass/radius inputs).; Archive mass/radius carry no propagated uncertainty here.
Uncertainty: not propagated (inputs carry no catalogued uncertainty)
Computed as of 2026-06-29.

Quality & authority

Partial

Unreviewed

Description: Complete
Source coverage: Partial
Relationship coverage: Complete
Review coverage: None
Citation coverage: None
Image coverage: Not applicable

Data from the NASA Exoplanet Archive. See source quality.