Key parameters at a glance

A radius of 2.44 Earth radii
A mass of 6.52 Earth masses
Surface gravity around 1.10 g
An orbital period of 7.450 days
Equilibrium temperature 943 K (670 °C)
Distance from Earth 360.62 light-years
Earth Similarity Index 0.269
Travel time at Voyager 1 speed 6,359,549 years

2 siblings around K2-198

K2-198 d 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 this	Sub-Neptune	2.44	6.52	7.450	943	2019
K2-198 b	Neptune-like	4.19	16.30	17.043	716	2018

K2-198 d Planet Profile

Physical Specs

Radius

2.44 R⊕

Radius (Jupiter)

0.218 R♃

Mass

6.52 M⊕

Mass (Jupiter)

0.021 M♃

Density

2.47 g/cm³

Surface Gravity

1.10 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.269

HZ Position Unknown

Controversial No

Discovery

Year 2019

Method Transit

Facility K2

Telescope 0.95 m Kepler Telescope

Size rank in cohort

Rank by radius

#1277of 1978

top 64.5%

This planet

2.44R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

Kepler-1845 b 2.44 R⊕ Kepler-1754 b 2.44 R⊕ Kepler-338 b 2.44 R⊕

Metric	Earth	K2-198 d	Jupiter
Radius (R⊕)	1.00	2.44	11.21
Mass (M⊕)	1.00	6.52	317.83
Density (g/cm³)	5.51	2.47	1.33
Surface Gravity (g)	1.00	1.10	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 Sub-Neptune cohort

Radius 2.438 R⊕ · percentile 35 / cohort 1978

Mass 6.520 M⊕ · percentile 34 / cohort 1978

Orbital period 7.45 d · percentile 24 / cohort 1946

Distance 110.57 pc · percentile 22 / cohort 1975

ESI 0.269 · percentile 21 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

7.450 days

Semi-major axis

— AU

Eccentricity

—

Inclination

89.86 °

Year Length

A year here lasts approximately 7.45 Earth days (2.0% of a terrestrial year).

Transit Fingerprint

Depth

0.108 %

Duration

3.002 h

Impact parameter b

0.047

Rp / R★

0.022000

Transit midpoint (BJD)

2,457,213.5759

Photometric dip

Transit produces a flux drop of 1,082 ppm lasting ≈ 3.00 h.

Extended Orbital Architecture

Planet / star radius ratio

0.022000

Semi-major axis / stellar radius

14.900

Impact parameter (b)

0.047

Transit mid-time (BJD)

2,457,213.5759

Eq. Temperature

943K

(670 °C)

Insolation (S⊕)

—

Earth = 1.00

Earth Similarity (ESI)

0.269

0 = alien, 1 = Earth-identical

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

Discovery Paper

Primary reference

Hedges et al. 2019

Instrument

Kepler CCD Array

Publication

2019-07

Observation locale

Space

Discovery cohort

Planets confirmed in 2019 at K2 (12 shown).

EPIC 206032309 b · Rocky Terrestrial EPIC 201833600 c · Rocky Terrestrial EPIC 206215704 b · Rocky Terrestrial EPIC 201754305 d · Rocky Terrestrial EPIC 201841433 b · Rocky Terrestrial EPIC 206317286 b · Rocky Terrestrial EPIC 201615463 c · Rocky Terrestrial EPIC 212499991 b · Super-Earth EPIC 220554210 c · Super-Earth EPIC 201497682 b · Rocky Terrestrial K2-133 e · Super-Earth EPIC 206024342 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