Key parameters at a glance

A radius of 7.32 Earth radii
A mass of 42.20 Earth masses
Surface gravity around 0.79 g
An orbital period of 28.735 days
Distance from Earth 868.61 light-years
Earth Similarity Index 0.375
Travel time at Voyager 1 speed 15,317,974 years
Almost certainly tidally locked to its host star given the close orbit

K2-387 b Planet Profile

Physical Specs

Radius

7.32 R⊕

Radius (Jupiter)

0.653 R♃

Mass

42.20 M⊕

Mass (Jupiter)

0.133 M♃

Density

0.59 g/cm³

Surface Gravity

0.79 g (Earth)

Classification

Planet Type

Neptune-like

ESI Score 0.375

HZ Position Unknown

Controversial No

Discovery

Year 2022

Method Transit

Facility K2

Telescope 0.95 m Kepler Telescope

Size rank in cohort

Rank by radius

#184of 574

top 31.9%

This planet

7.32R⊕

Neptune-like median

6.39R⊕

Nearest-size peers

TOI-1203 e 7.31 R⊕ TOI-7510 b 7.31 R⊕ KMT-2025-BLG-1616L b 7.34 R⊕

Metric	Earth	K2-387 b	Jupiter
Radius (R⊕)	1.00	7.32	11.21
Mass (M⊕)	1.00	42.20	317.83
Density (g/cm³)	5.51	0.59	1.33
Surface Gravity (g)	1.00	0.79	2.53
Insolation (S⊕)	1.00	—	0.037

Star Catalogue Identifiers

TIC

TIC 376938120

Gaia DR2

Gaia DR2 2580505553613124992

Gaia DR3

Gaia DR3 2580505553613124992

System

K2-387

Percentile among Neptune-like cohort

Radius 7.322 R⊕ · percentile 68 / cohort 574

Mass 42.200 M⊕ · percentile 65 / cohort 574

Orbital period 28.74 d · percentile 59 / cohort 524

Distance 266.32 pc · percentile 45 / cohort 572

ESI 0.375 · percentile 69 / cohort 574

Orbit & Habitability

Orbital Dynamics

Period

28.735 days

Semi-major axis

— AU

Eccentricity

—

Inclination

— °

Year Length

A year here lasts approximately 28.74 Earth days (7.9% of a terrestrial year).

Transit Fingerprint

Depth

1.398 %

Duration

2.990 h

Impact parameter b

0.711

Rp / R★

0.114600

Transit midpoint (BJD)

2,457,401.9787

Photometric dip

Transit produces a flux drop of 13,980 ppm lasting ≈ 2.99 h.

Extended Orbital Architecture

Planet / star radius ratio

0.114600

Semi-major axis / stellar radius

55.420

Impact parameter (b)

0.711

Transit mid-time (BJD)

2,457,401.9787

Eq. Temperature

—

Insolation (S⊕)

—

Earth = 1.00

Earth Similarity (ESI)

0.375

0 = alien, 1 = Earth-identical

Insufficient insolation data. Close-orbiting tidally-locked around a cool host.

Discovery Paper

Primary reference

Christiansen et al. 2022

Instrument

Kepler CCD Array

Publication

2022-03

Observation locale

Space

Discovery cohort

Planets confirmed in 2022 at K2 (12 shown).

K2-411 b · Rocky Terrestrial K2-381 b · Rocky Terrestrial K2-384 b · Rocky Terrestrial K2-400 b · Rocky Terrestrial K2-384 c · Rocky Terrestrial K2-369 b · Super-Earth K2-407 b · Super-Earth K2-414 b · Rocky Terrestrial K2-368 b · Super-Earth K2-413 c · Rocky Terrestrial K2-384 e · Super-Earth K2-407 c · Super-Earth

Host System: K2-387

Spectral Class

M-type red dwarf

Effective Temperature

3,572 K — cooler than the Sun (5,778 K)

Estimated Age

—

Stellar Radius

0.585 R☉

Stellar Mass

0.570 M☉

Metallicity [Fe/H]

0.13

Extended Stellar Properties

Surface gravity (log g)

4.660 dex

Stellar density

4.089 g/cm³

Metallicity ratio

[Fe/H]

Distance

266.32 parsec

Light-years 868.61 ly

V-band magnitude

16.15 mag

Voyager-speed travel 15,317,974 yr

Multi-band Host Photometry — 17 bands

Astrometric Data

Parallax

3.727 mas

Total Proper Motion

20.067 mas/yr

PM Right Ascension

2.09 mas/yr

PM Declination

-19.96 mas/yr

Galactic Cartesian (pc)

x = 0.924 · y = 0.326 · z = 0.197

Equatorial (J2000)

RA 19.44183° · Dec 11.36849°

Galactic ℓ, b

133.214° · -50.977°

Ecliptic λ, β

22.224° · 2.926°

HTM-20 index

1257435290