Key parameters at a glance

A radius of 2.83 Earth radii
A mass of 8.40 Earth masses
Surface gravity around 1.05 g
An orbital period of 7.810 days
Semi-major axis 0.0785 AU
Equilibrium temperature 1,026 K (753 °C)
Distance from Earth 1,457.33 light-years
Earth Similarity Index 0.232
Travel time at Voyager 1 speed 25,700,075 years

1 sibling around K2-188

K2-188 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
K2-188 b	Super-Earth	1.35	2.39	1.742	1,692	2018
K2-188 c this	Sub-Neptune	2.83	8.40	7.810	1,026	2018

K2-188 c Planet Profile

Physical Specs

Radius

2.83 R⊕

Radius (Jupiter)

0.252 R♃

Mass

8.40 M⊕

Mass (Jupiter)

0.026 M♃

Density

2.04 g/cm³

Surface Gravity

1.05 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.232

HZ Position Inner

Controversial No

Discovery

Year 2018

Method Transit

Facility K2

Telescope 0.95 m Kepler Telescope

Size rank in cohort

Rank by radius

#703of 1978

top 35.5%

This planet

2.83R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

HD 3167 e 2.83 R⊕ GJ 3634 b 2.83 R⊕ Kepler-1099 b 2.83 R⊕

Metric	Earth	K2-188 c	Jupiter
Radius (R⊕)	1.00	2.83	11.21
Mass (M⊕)	1.00	8.40	317.83
Density (g/cm³)	5.51	2.04	1.33
Surface Gravity (g)	1.00	1.05	2.53
Insolation (S⊕)	1.00	230.63	0.037

Star Catalogue Identifiers

TIC

TIC 175236511

Gaia DR2

Gaia DR2 666195851913506816

Gaia DR3

Gaia DR3 666195851913506816

System

K2-188

Percentile among Sub-Neptune cohort

Radius 2.830 R⊕ · percentile 64 / cohort 1978

Mass 8.400 M⊕ · percentile 58 / cohort 1978

Orbital period 7.81 d · percentile 25 / cohort 1946

Distance 446.82 pc · percentile 44 / cohort 1975

ESI 0.232 · percentile 12 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

7.810 days

Semi-major axis

0.0785 AU

Eccentricity

—

Inclination

88.10 °

Year Length

A year here lasts approximately 7.81 Earth days (2.1% of a terrestrial year) at a mean orbital distance of 0.0785 AU.

Transit Fingerprint

Depth

0.048 %

Duration

3.581 h

Impact parameter b

0.370

Rp / R★

0.021800

Transit midpoint (BJD)

2,457,144.8545

Photometric dip

Transit produces a flux drop of 480 ppm lasting ≈ 3.58 h.

Extended Orbital Architecture

Planet / star radius ratio

0.021800

Semi-major axis / stellar radius

15.560

Impact parameter (b)

0.370

Transit mid-time (BJD)

2,457,144.8545

Angular separation (arcsec)

0.17600

Eq. Temperature

1,026K

(753 °C)

Insolation (S⊕)

230.63

Earth = 1.00

Earth Similarity (ESI)

0.232

0 = alien, 1 = Earth-identical

Inside the inner HZ boundary (too hot for liquid water) — the dayside is scorched.

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: K2-188

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

5,977 K — hotter than the Sun (5,778 K)

Estimated Age

—

Stellar Radius

1.190 R☉

Stellar Mass

1.060 M☉

Metallicity [Fe/H]

-0.01

Extended Stellar Properties

Surface gravity (log g)

4.310 dex

Stellar density

0.836 g/cm³

Systemic radial velocity

-34.21 km/s

Metallicity ratio

[Fe/H]

Distance

446.82 parsec

Light-years 1,457.33 ly

V-band magnitude

12.66 mag

Voyager-speed travel 25,700,075 yr

Multi-band Host Photometry — 17 bands

Astrometric Data

Parallax

2.210 mas

Total Proper Motion

16.765 mas/yr

PM Right Ascension

13.18 mas/yr

PM Declination

-10.37 mas/yr

Galactic Cartesian (pc)

x = -0.588 · y = 0.705 · z = 0.396

Equatorial (J2000)

RA 129.81370° · Dec 23.35744°

Galactic ℓ, b

201.660° · 33.445°

Ecliptic λ, β

126.144° · 4.775°

HTM-20 index

-143642014