Key parameters at a glance

A radius of 1.20 Earth radii
A mass of 1.84 Earth masses
Surface gravity around 1.28 g
An orbital period of 3.931 days
Semi-major axis 0.0360 AU
Equilibrium temperature 518 K (245 °C)
Distance from Earth 30.80 light-years
Earth Similarity Index 0.604
Travel time at Voyager 1 speed 543,070 years
Almost certainly tidally locked to its host star given the close orbit

2 siblings around GJ 357

GJ 357 b shares its host star with 2 other confirmed planets. Side-by-side measurements below.

Planet	Type	Radius (R⊕)	Mass (M⊕)	Period (d)	Eq. T (K)	Year
GJ 357 b this	Rocky Terrestrial	1.20	1.84	3.931	518	2019
GJ 357 c	Super-Earth	1.66	3.40	9.125	401	2019
GJ 357 d	Sub-Neptune	2.34	6.10	55.661	220	2019

GJ 357 b Planet Profile

Physical Specs

Radius

1.20 R⊕

Radius (Jupiter)

0.107 R♃

Mass

1.84 M⊕

Mass (Jupiter)

0.006 M♃

Density

5.60 g/cm³

Surface Gravity

1.28 g (Earth)

Classification

Planet Type

Rocky Terrestrial

ESI Score 0.604

HZ Position Inner

Controversial No

Discovery

Year 2019

Method Transit

Facility Transiting Exoplanet Survey Satellite (TESS)

Telescope 0.1 m TESS Telescope

Size rank in cohort

Rank by radius

#75of 570

top 13.0%

This planet

1.20R⊕

Rocky Terrestrial median

1.01R⊕

Nearest-size peers

Kepler-225 b 1.20 R⊕ Kepler-282 c 1.20 R⊕ Kepler-367 c 1.20 R⊕

Metric	Earth	GJ 357 b	Jupiter
Radius (R⊕)	1.00	1.20	11.21
Mass (M⊕)	1.00	1.84	317.83
Density (g/cm³)	5.51	5.60	1.33
Surface Gravity (g)	1.00	1.28	2.53
Insolation (S⊕)	1.00	12.60	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	1.840 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

HIP

HIP 47103

TIC

TIC 413248763

Gaia DR2

Gaia DR2 5664814198431308288

Gaia DR3

Gaia DR3 5664814198431308288

System

GJ 357

Percentile among Rocky Terrestrial cohort

Radius 1.200 R⊕ · percentile 84 / cohort 570

Mass 1.840 M⊕ · percentile 76 / cohort 570

Orbital period 3.93 d · percentile 43 / cohort 567

Distance 9.44 pc · percentile 4 / cohort 566

ESI 0.604 · percentile 78 / cohort 570

Orbit & Habitability

Orbital Dynamics

Period

3.931 days

Semi-major axis

0.0360 AU

Eccentricity

—

Inclination

89.23 °

Year Length

A year here lasts approximately 3.93 Earth days (1.1% of a terrestrial year) at a mean orbital distance of 0.0360 AU.

Transit Fingerprint

Depth

0.096 %

Duration

1.291 h

Impact parameter b

0.307

Rp / R★

0.030900

Transit midpoint (BJD)

2,459,272.6757

Photometric dip

Transit produces a flux drop of 955 ppm lasting ≈ 1.29 h.

Extended Orbital Architecture

Planet / star radius ratio

0.030900

Semi-major axis / stellar radius

22.890

Impact parameter (b)

0.307

RV semi-amplitude (K)

1.520 m/s

Transit mid-time (BJD)

2,459,272.6757

Angular separation (arcsec)

3.81000

Eq. Temperature

518K

(245 °C)

Insolation (S⊕)

12.60

Earth = 1.00

Earth Similarity (ESI)

0.604

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.

Detection Signatures

Transit photometry

A transit dip has been observed from at least one telescope.

Radial velocity

Stellar wobble has been measured spectroscopically.

Discovery Paper

Primary reference

Luque et al. 2019

Instrument

TESS CCD Array

Publication

2019-08

Observation locale

Space

Discovery cohort

Planets confirmed in 2019 at Transiting Exoplanet Survey Satellite (TESS) (12 shown).

LP 791-18 c · Sub-Neptune LTT 1445 A b · Super-Earth TOI-270 d · Sub-Neptune L 98-59 d · Super-Earth GJ 143 b · Sub-Neptune HD 23472 c · Super-Earth L 98-59 c · Super-Earth LP 791-18 b · Rocky Terrestrial TOI-270 c · Sub-Neptune HD 23472 b · Sub-Neptune TOI-270 b · Super-Earth L 98-59 b · Rocky Terrestrial

Host System: GJ 357

Spectral Class

M-type red dwarf

Effective Temperature

3,505 K — cooler than the Sun (5,778 K)

Estimated Age

—

Stellar Radius

0.337 R☉

Stellar Mass

0.342 M☉

Metallicity [Fe/H]

-0.12

Extended Stellar Properties

Surface gravity (log g)

4.940 dex

Stellar density

13.600 g/cm³

Systemic radial velocity

-34.60 km/s

Rotational v·sin i

2.00 km/s

Rotation period

77.80 days

Activity index (log R'HK)

-5.370

Metallicity ratio

[Fe/H]

Distance

9.44 parsec

Light-years 30.80 ly

V-band magnitude

10.91 mag

Voyager-speed travel 543,070 yr

Multi-band Host Photometry — 11 bands

Astrometric Data

Parallax

105.883 mas

Total Proper Motion

999.976 mas/yr

PM Right Ascension

138.69 mas/yr

PM Declination

-990.31 mas/yr

Galactic Cartesian (pc)

x = -0.752 · y = 0.546 · z = -0.369

Equatorial (J2000)

RA 144.00746° · Dec -21.66506°

Galactic ℓ, b

253.888° · 22.080°

Ecliptic λ, β

154.771° · -33.777°

HTM-20 index

-465961619

Observation Record

Photometric series

Stellar spectra

Transmission spectra