Key parameters at a glance

A radius of 5.10 Earth radii
A mass of 22.80 Earth masses
Surface gravity around 0.88 g
An orbital period of 18.788 days
Distance from Earth 1,979.74 light-years
Earth Similarity Index 0.471
Travel time at Voyager 1 speed 34,912,728 years

1 sibling around K2-398

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

K2-398 c Planet Profile

Physical Specs

Radius

5.10 R⊕

Radius (Jupiter)

0.455 R♃

Mass

22.80 M⊕

Mass (Jupiter)

0.072 M♃

Density

0.95 g/cm³

Surface Gravity

0.88 g (Earth)

Classification

Planet Type

Neptune-like

ESI Score 0.471

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

#370of 574

top 64.3%

This planet

5.10R⊕

Neptune-like median

6.39R⊕

Nearest-size peers

TOI-6651 b 5.09 R⊕ TOI-421 c 5.09 R⊕ 61 Vir d 5.11 R⊕

Metric	Earth	K2-398 c	Jupiter
Radius (R⊕)	1.00	5.10	11.21
Mass (M⊕)	1.00	22.80	317.83
Density (g/cm³)	5.51	0.95	1.33
Surface Gravity (g)	1.00	0.88	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 Neptune-like cohort

Radius 5.098 R⊕ · percentile 36 / cohort 574

Mass 22.800 M⊕ · percentile 37 / cohort 574

Orbital period 18.79 d · percentile 50 / cohort 524

Distance 606.99 pc · percentile 61 / cohort 572

ESI 0.471 · percentile 85 / cohort 574

Orbit & Habitability

Orbital Dynamics

Period

18.788 days

Semi-major axis

— AU

Eccentricity

—

Inclination

— °

Year Length

A year here lasts approximately 18.79 Earth days (5.1% of a terrestrial year).

Transit Fingerprint

Duration

4.700 h

Impact parameter b

0.701

Rp / R★

0.037700

Transit midpoint (BJD)

2,457,911.6845

Extended Orbital Architecture

Planet / star radius ratio

0.037700

Semi-major axis / stellar radius

23.550

Impact parameter (b)

0.701

Transit mid-time (BJD)

2,457,911.6845

Eq. Temperature

—

Insolation (S⊕)

—

Earth = 1.00

Earth Similarity (ESI)

0.471

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