Key parameters at a glance

A radius of 4.19 Earth radii
A mass of 16.30 Earth masses
Surface gravity around 0.93 g
An orbital period of 17.043 days
Equilibrium temperature 716 K (443 °C)
Distance from Earth 360.62 light-years
Earth Similarity Index 0.286
Travel time at Voyager 1 speed 6,359,549 years

2 siblings around K2-198

K2-198 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
K2-198 c	Super-Earth	1.42	2.61	3.360	1,230	2019
K2-198 d	Sub-Neptune	2.44	6.52	7.450	943	2019
K2-198 b this	Neptune-like	4.19	16.30	17.043	716	2018

K2-198 b Planet Profile

Physical Specs

Radius

4.19 R⊕

Radius (Jupiter)

0.374 R♃

Mass

16.30 M⊕

Mass (Jupiter)

0.051 M♃

Density

1.22 g/cm³

Surface Gravity

0.93 g (Earth)

Classification

Planet Type

Neptune-like

ESI Score 0.286

HZ Position Unknown

Controversial No

Discovery

Year 2018

Method Transit

Facility K2

Telescope 0.95 m Kepler Telescope

Size rank in cohort

Rank by radius

#523of 574

top 90.9%

This planet

4.19R⊕

Neptune-like median

6.39R⊕

Nearest-size peers

Kepler-610 b 4.19 R⊕ Kepler-11 e 4.19 R⊕ KMT-2023-BLG-1896L b 4.19 R⊕

Metric	Earth	K2-198 b	Jupiter
Radius (R⊕)	1.00	4.19	11.21
Mass (M⊕)	1.00	16.30	317.83
Density (g/cm³)	5.51	1.22	1.33
Surface Gravity (g)	1.00	0.93	2.53
Insolation (S⊕)	1.00	—	0.037

Star Catalogue Identifiers

TIC

TIC 135043332

Gaia DR2

Gaia DR2 3628687065162340224

Gaia DR3

Gaia DR3 3628687065162340224

System

K2-198

Percentile among Neptune-like cohort

Radius 4.189 R⊕ · percentile 9 / cohort 574

Mass 16.300 M⊕ · percentile 14 / cohort 574

Orbital period 17.04 d · percentile 48 / cohort 524

Distance 110.57 pc · percentile 26 / cohort 572

ESI 0.286 · percentile 47 / cohort 574

Orbit & Habitability

Orbital Dynamics

Period

17.043 days

Semi-major axis

— AU

Eccentricity

—

Inclination

88.90 °

Year Length

A year here lasts approximately 17.04 Earth days (4.7% of a terrestrial year).

Transit Fingerprint

Depth

0.274 %

Duration

2.959 h

Impact parameter b

0.661

Rp / R★

0.039000

Transit midpoint (BJD)

2,457,204.5687

Photometric dip

Transit produces a flux drop of 2,737 ppm lasting ≈ 2.96 h.

Extended Orbital Architecture

Planet / star radius ratio

0.039000

Semi-major axis / stellar radius

25.860

Impact parameter (b)

0.661

Transit mid-time (BJD)

2,457,204.5687

Eq. Temperature

716K

(443 °C)

Insolation (S⊕)

—

Earth = 1.00

Earth Similarity (ESI)

0.286

0 = alien, 1 = Earth-identical

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

Discovery Paper

Primary reference

Mayo et al. 2018

Instrument

Kepler CCD Array

Publication

2018-03

Observation locale

Space

Discovery cohort

Planets confirmed in 2018 at K2 (12 shown).

K2-190 c · Rocky Terrestrial K2-183 b · Rocky Terrestrial K2-209 b · Rocky Terrestrial K2-210 b · Rocky Terrestrial K2-165 b · Super-Earth K2-169 b · Super-Earth K2-148 b · Super-Earth K2-219 b · Super-Earth K2-190 b · Super-Earth K2-200 b · Super-Earth K2-201 b · Super-Earth K2-170 b · Super-Earth

Host System: K2-198

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

5,213 K — cooler than the Sun (5,778 K)

Estimated Age

—

Stellar Radius

0.757 R☉

Stellar Mass

0.799 M☉

Metallicity [Fe/H]

0.09

Extended Stellar Properties

Surface gravity (log g)

4.596 dex

Stellar density

2.596 g/cm³

Systemic radial velocity

2.07 km/s

Metallicity ratio

[M/H]

Distance

110.57 parsec

Light-years 360.62 ly

V-band magnitude

10.97 mag

Voyager-speed travel 6,359,549 yr

Multi-band Host Photometry — 12 bands

Astrometric Data

Parallax

9.016 mas

Total Proper Motion

42.723 mas/yr

PM Right Ascension

-36.69 mas/yr

PM Declination

-21.89 mas/yr

Galactic Cartesian (pc)

x = -0.940 · y = -0.321 · z = -0.113

Equatorial (J2000)

RA 198.84368° · Dec -6.46499°

Galactic ℓ, b

313.583° · 55.911°

Ecliptic λ, β

199.833° · 1.396°

HTM-20 index

-1524105840