Key parameters at a glance

A radius of 0.57 Earth radii
A mass of 0.13 Earth masses
Surface gravity around 0.39 g
An orbital period of 1.745 days
Semi-major axis 0.0212 AU
Equilibrium temperature 758 K (485 °C)
Distance from Earth 49.62 light-years
Earth Similarity Index 0.364
Travel time at Voyager 1 speed 875,084 years
Almost certainly tidally locked to its host star given the close orbit

GJ 238 b Planet Profile

Physical Specs

Radius

0.57 R⊕

Radius (Jupiter)

0.051 R♃

Mass

0.13 M⊕

Mass (Jupiter)

0.000 M♃

Density

3.82 g/cm³

Surface Gravity

0.39 g (Earth)

Classification

Planet Type

Rocky Terrestrial

ESI Score 0.364

HZ Position Inner

Controversial No

Discovery

Year 2024

Method Transit

Facility Transiting Exoplanet Survey Satellite (TESS)

Telescope 0.1 m TESS Telescope

Size rank in cohort

Rank by radius

#555of 570

top 97.2%

This planet

0.57R⊕

Rocky Terrestrial median

1.01R⊕

Nearest-size peers

Kepler-102 c 0.57 R⊕ Kepler-42 d 0.57 R⊕ Kepler-444 e 0.55 R⊕

Metric	Earth	GJ 238 b	Jupiter
Radius (R⊕)	1.00	0.57	11.21
Mass (M⊕)	1.00	0.13	317.83
Density (g/cm³)	5.51	3.82	1.33
Surface Gravity (g)	1.00	0.39	2.53
Insolation (S⊕)	1.00	107.26	0.037

Star Catalogue Identifiers

HIP

HIP 31300

TIC

TIC 260708537

Gaia DR2

Gaia DR2 5482827676662168832

Gaia DR3

Gaia DR3 5482827676662168832

System

GJ 238

Percentile among Rocky Terrestrial cohort

Radius 0.566 R⊕ · percentile 3 / cohort 570

Mass 0.126 M⊕ · percentile 2 / cohort 570

Orbital period 1.74 d · percentile 20 / cohort 567

Distance 15.21 pc · percentile 8 / cohort 566

ESI 0.364 · percentile 53 / cohort 570

Orbit & Habitability

Orbital Dynamics

Period

1.745 days

Semi-major axis

0.0212 AU

Eccentricity

—

Inclination

89.99 °

Year Length

A year here lasts approximately 1.74 Earth days (0.5% of a terrestrial year) at a mean orbital distance of 0.0212 AU.

Transit Fingerprint

Depth

0.016 %

Duration

1.239 h

Impact parameter b

0.202

Rp / R★

0.012040

Transit midpoint (BJD)

2,458,326.9822

Photometric dip

Transit produces a flux drop of 163 ppm lasting ≈ 1.24 h.

Extended Orbital Architecture

Planet / star radius ratio

0.012040

Impact parameter (b)

0.202

Transit mid-time (BJD)

2,458,326.9822

Angular separation (arcsec)

1.40000

Eq. Temperature

758K

(485 °C)

Insolation (S⊕)

107.26

Earth = 1.00

Earth Similarity (ESI)

0.364

0 = alien, 1 = Earth-identical

Inside the inner HZ boundary (too hot for liquid water) — the surface is too hot to retain surface water. Close-orbiting tidally-locked around a cool host.

Discovery Paper

Primary reference

Tey et al. 2024

Instrument

TESS CCD Array

Publication

2024-06

Observation locale

Space

Discovery cohort

Planets confirmed in 2024 at Transiting Exoplanet Survey Satellite (TESS) (12 shown).

Gliese 12 b · Rocky Terrestrial TOI-6002 b · Super-Earth TOI-5713 b · Super-Earth TOI-4336 A b · Sub-Neptune TOI-406.01 · Sub-Neptune TOI-1224 c · Sub-Neptune LHS 1678 d · Rocky Terrestrial TOI-2088 b · Sub-Neptune TOI-2120 b · Sub-Neptune TOI-1806.01 · Sub-Neptune TOI-4633 c · Sub-Neptune TOI-260 b · Super-Earth

Host System: GJ 238

Spectral Class

M-type red dwarf

Effective Temperature

3,485 K — cooler than the Sun (5,778 K)

Estimated Age

—

Stellar Radius

0.431 R☉

Stellar Mass

0.419 M☉

Metallicity [Fe/H]

0.15

Extended Stellar Properties

Surface gravity (log g)

4.852 dex

Stellar density

7.645 g/cm³

Rotation period

44.00 days

Metallicity ratio

[Fe/H]

Distance

15.21 parsec

Light-years 49.62 ly

V-band magnitude

11.62 mag

Voyager-speed travel 875,084 yr

Multi-band Host Photometry — 8 bands

Astrometric Data

Parallax

65.699 mas

Total Proper Motion

892.680 mas/yr

PM Right Ascension

-404.35 mas/yr

PM Declination

795.85 mas/yr

Galactic Cartesian (pc)

x = -0.077 · y = 0.516 · z = -0.853

Equatorial (J2000)

RA 98.45488° · Dec -58.52503°

Galactic ℓ, b

267.833° · -25.124°

Ecliptic λ, β

119.697° · -81.087°

HTM-20 index

1792962449