Key parameters at a glance

A radius of 2.27 Earth radii
A mass of 5.79 Earth masses
Surface gravity around 1.12 g
An orbital period of 6.393 days
Distance from Earth 1,979.74 light-years
Earth Similarity Index 0.739
Travel time at Voyager 1 speed 34,912,728 years

1 sibling around K2-398

K2-398 b 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
K2-398 b this	Sub-Neptune	2.27	5.79	6.393	—	2022
K2-398 c	Neptune-like	5.10	22.80	18.788	—	2022

K2-398 b Planet Profile

Physical Specs

Radius

2.27 R⊕

Radius (Jupiter)

0.203 R♃

Mass

5.79 M⊕

Mass (Jupiter)

0.018 M♃

Density

2.71 g/cm³

Surface Gravity

1.12 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.739

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

#1551of 1978

top 78.4%

This planet

2.27R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

Kepler-1817 b 2.27 R⊕ K2-222 b 2.28 R⊕ TOI-5788 c 2.27 R⊕

Metric	Earth	K2-398 b	Jupiter
Radius (R⊕)	1.00	2.27	11.21
Mass (M⊕)	1.00	5.79	317.83
Density (g/cm³)	5.51	2.71	1.33
Surface Gravity (g)	1.00	1.12	2.53
Insolation (S⊕)	1.00	—	0.037

Star Catalogue Identifiers

TIC

TIC 281660552

Gaia DR2

Gaia DR2 3809028584392561408

Gaia DR3

Gaia DR3 3809028584392561408

System

K2-398

Percentile among Sub-Neptune cohort

Radius 2.274 R⊕ · percentile 22 / cohort 1978

Mass 5.790 M⊕ · percentile 21 / cohort 1978

Orbital period 6.39 d · percentile 19 / cohort 1946

Distance 606.99 pc · percentile 53 / cohort 1975

ESI 0.739 · percentile 96 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

6.393 days

Semi-major axis

— AU

Eccentricity

—

Inclination

— °

Year Length

A year here lasts approximately 6.39 Earth days (1.8% of a terrestrial year).

Transit Fingerprint

Duration

3.700 h

Impact parameter b

0.523

Rp / R★

0.016800

Transit midpoint (BJD)

2,457,909.0449

Extended Orbital Architecture

Planet / star radius ratio

0.016800

Semi-major axis / stellar radius

11.590

Impact parameter (b)

0.523

Transit mid-time (BJD)

2,457,909.0449

Eq. Temperature

—

Insolation (S⊕)

—

Earth = 1.00

Earth Similarity (ESI)

0.739

0 = alien, 1 = Earth-identical

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: K2-398

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

5,946 K — hotter than the Sun (5,778 K)

Estimated Age

—

Stellar Radius

1.239 R☉

Stellar Mass

0.945 M☉

Metallicity [Fe/H]

-0.26

Extended Stellar Properties

Surface gravity (log g)

4.227 dex

Stellar density

0.749 g/cm³

Metallicity ratio

[Fe/H]

Distance

606.99 parsec

Light-years 1,979.74 ly

V-band magnitude

13.29 mag

Voyager-speed travel 34,912,728 yr

Multi-band Host Photometry — 17 bands

Astrometric Data

Parallax

1.619 mas

Total Proper Motion

22.935 mas/yr

PM Right Ascension

-22.94 mas/yr

PM Declination

-0.03 mas/yr

Galactic Cartesian (pc)

x = -0.949 · y = 0.313 · z = 0.034

Equatorial (J2000)

RA 161.73497° · Dec 1.93670°

Galactic ℓ, b

247.806° · 50.973°

Ecliptic λ, β

162.409° · -5.370°

HTM-20 index

-899841411