Key parameters at a glance

A radius of 2.72 Earth radii
A mass of 7.85 Earth masses
Surface gravity around 1.06 g
An orbital period of 22.997 days
Equilibrium temperature 673 K (400 °C)
Distance from Earth 689.59 light-years
Earth Similarity Index 0.364
Travel time at Voyager 1 speed 12,160,948 years

1 sibling around K2-331

K2-331 c shares its host star with 1 other confirmed planet. Side-by-side measurements below.

Planet	Type	Radius (R⊕)	Mass (M⊕)	Period (d)	Eq. T (K)	Year
K2-331 b	Super-Earth	1.79	3.86	9.399	909	2021
K2-331 c this	Sub-Neptune	2.72	7.85	22.997	673	2021

K2-331 c Planet Profile

Physical Specs

Radius

2.72 R⊕

Radius (Jupiter)

0.243 R♃

Mass

7.85 M⊕

Mass (Jupiter)

0.025 M♃

Density

2.14 g/cm³

Surface Gravity

1.06 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.364

HZ Position Unknown

Controversial No

Discovery

Year 2021

Method Transit

Facility K2

Telescope 0.95 m Kepler Telescope

Size rank in cohort

Rank by radius

#838of 1978

top 42.3%

This planet

2.72R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

Kepler-26 c 2.72 R⊕ Kepler-351 d 2.72 R⊕ Kepler-358 b 2.72 R⊕

Metric	Earth	K2-331 c	Jupiter
Radius (R⊕)	1.00	2.72	11.21
Mass (M⊕)	1.00	7.85	317.83
Density (g/cm³)	5.51	2.14	1.33
Surface Gravity (g)	1.00	1.06	2.53
Insolation (S⊕)	1.00	—	0.037

Star Catalogue Identifiers

TIC

TIC 46296576

Gaia DR2

Gaia DR2 608206676654888064

Gaia DR3

Gaia DR3 608206676654888064

System

K2-331

Percentile among Sub-Neptune cohort

Radius 2.720 R⊕ · percentile 57 / cohort 1978

Mass 7.850 M⊕ · percentile 53 / cohort 1978

Orbital period 23.00 d · percentile 67 / cohort 1946

Distance 211.43 pc · percentile 30 / cohort 1975

ESI 0.364 · percentile 44 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

22.997 days

Semi-major axis

— AU

Eccentricity

—

Inclination

— °

Year Length

A year here lasts approximately 23.00 Earth days (6.3% of a terrestrial year).

Transit Fingerprint

Depth

0.047 %

Duration

4.430 h

Impact parameter b

0.370

Rp / R★

0.023500

Transit midpoint (BJD)

2,458,113.3048

Photometric dip

Transit produces a flux drop of 470 ppm lasting ≈ 4.43 h.

Extended Orbital Architecture

Planet / star radius ratio

0.023500

Semi-major axis / stellar radius

37.870

Impact parameter (b)

0.370

Transit mid-time (BJD)

2,458,113.3048

Eq. Temperature

673K

(400 °C)

Insolation (S⊕)

—

Earth = 1.00

Earth Similarity (ESI)

0.364

0 = alien, 1 = Earth-identical

Insufficient insolation data — the surface is too hot to retain surface water.

Discovery Paper

Primary reference

De Leon et al. 2021

Instrument

Kepler CCD Array

Publication

2021-08

Observation locale

Space

Discovery cohort

Planets confirmed in 2021 at K2 (12 shown).

EPIC 220492298 b · Rocky Terrestrial EPIC 206042996 c · Rocky Terrestrial EPIC 212624936 b · Rocky Terrestrial EPIC 206024342 c · Super-Earth EPIC 201427007 b · Super-Earth K2-332 b · Sub-Neptune EPIC 212624936 c · Sub-Neptune EPIC 206024342 d · Sub-Neptune K2-345 b · Sub-Neptune K2-349 b · Super-Earth K2-343 c · Sub-Neptune K2-346 b · Sub-Neptune

Host System: K2-331

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

5,994 K — hotter than the Sun (5,778 K)

Estimated Age

—

Stellar Radius

1.060 R☉

Stellar Mass

1.100 M☉

Metallicity [Fe/H]

0.08

Extended Stellar Properties

Surface gravity (log g)

4.430 dex

Stellar density

1.227 g/cm³

Rotation period

9.98 days

Metallicity ratio

[Fe/H]

Distance

211.43 parsec

Light-years 689.59 ly

V-band magnitude

11.31 mag

Voyager-speed travel 12,160,948 yr

Multi-band Host Photometry — 17 bands

Astrometric Data

Parallax

4.701 mas

Total Proper Motion

20.905 mas/yr

PM Right Ascension

-5.89 mas/yr

PM Declination

-20.06 mas/yr

Galactic Cartesian (pc)

x = -0.661 · y = 0.715 · z = 0.228

Equatorial (J2000)

RA 132.73764° · Dec 13.17027°

Galactic ℓ, b

214.180° · 32.384°

Ecliptic λ, β

131.501° · -4.326°

HTM-20 index

2119077450