Key parameters at a glance

A radius of 2.06 Earth radii
A mass of 4.90 Earth masses
Surface gravity around 1.15 g
An orbital period of 5.444 days
Semi-major axis 0.0492 AU
Equilibrium temperature 537 K (264 °C)
Distance from Earth 331.48 light-years
Earth Similarity Index 0.500
Travel time at Voyager 1 speed 5,845,629 years
Almost certainly tidally locked to its host star given the close orbit

1 sibling around K2-117

K2-117 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
K2-117 b	Sub-Neptune	2.03	4.78	1.292	868	2017
K2-117 c this	Sub-Neptune	2.06	4.90	5.444	537	2017

K2-117 c Planet Profile

Physical Specs

Radius

2.06 R⊕

Radius (Jupiter)

0.184 R♃

Mass

4.90 M⊕

Mass (Jupiter)

0.015 M♃

Density

3.08 g/cm³

Surface Gravity

1.15 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.500

HZ Position Inner

Controversial No

Discovery

Year 2017

Method Transit

Facility K2

Telescope 0.95 m Kepler Telescope

Size rank in cohort

Rank by radius

#1875of 1978

top 94.7%

This planet

2.06R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

Kepler-377 c 2.06 R⊕ TOI-1670 b 2.06 R⊕ Kepler-1615 b 2.06 R⊕

Metric	Earth	K2-117 c	Jupiter
Radius (R⊕)	1.00	2.06	11.21
Mass (M⊕)	1.00	4.90	317.83
Density (g/cm³)	5.51	3.08	1.33
Surface Gravity (g)	1.00	1.15	2.53
Insolation (S⊕)	1.00	21.40	0.037

Star Catalogue Identifiers

TIC

TIC 458686847

Gaia DR2

Gaia DR2 597829077890316928

Gaia DR3

Gaia DR3 597829077890316928

System

K2-117

Percentile among Sub-Neptune cohort

Radius 2.060 R⊕ · percentile 5 / cohort 1978

Mass 4.900 M⊕ · percentile 6 / cohort 1978

Orbital period 5.44 d · percentile 14 / cohort 1946

Distance 101.63 pc · percentile 20 / cohort 1975

ESI 0.500 · percentile 70 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

5.444 days

Semi-major axis

0.0492 AU

Eccentricity

0.150

Inclination

89.49 °

Year Length

A year here lasts approximately 5.44 Earth days (1.5% of a terrestrial year) on a mildly elliptical path at a mean orbital distance of 0.0492 AU.

Transit Fingerprint

Depth

0.169 %

Duration

2.110 h

Impact parameter b

0.400

Rp / R★

0.036800

Transit midpoint (BJD)

2,457,143.5663

Photometric dip

Transit produces a flux drop of 1,686 ppm lasting ≈ 2.11 h.

Extended Orbital Architecture

Planet / star radius ratio

0.036800

Semi-major axis / stellar radius

18.520

Impact parameter (b)

0.400

Transit mid-time (BJD)

2,457,143.5663

Long. of periastron (ω)

-77.06°

Angular separation (arcsec)

0.48400

Eq. Temperature

537K

(264 °C)

Insolation (S⊕)

21.40

Earth = 1.00

Earth Similarity (ESI)

0.500

0 = alien, 1 = Earth-identical

Inside the inner HZ boundary (too hot for liquid water) — the surface is too hot to retain surface water. Close-orbiting tidally-locked around a cool host.

Discovery Paper

Primary reference

Dressing et al. 2017

Instrument

Kepler CCD Array

Publication

2017-11

Observation locale

Space

Discovery cohort

Planets confirmed in 2017 at K2 (12 shown).

K2-129 b · Rocky Terrestrial K2-130 b · Super-Earth K2-133 b · Super-Earth K2-128 b · Super-Earth K2-133 c · Super-Earth K2-116 b · Rocky Terrestrial K2-125 b · Sub-Neptune K2-118 b · Sub-Neptune K2-136 d · Super-Earth K2-123 b · Sub-Neptune K2-136 c · Sub-Neptune K2-124 b · Sub-Neptune

Host System: K2-117

Spectral Class

M-type red dwarf

Effective Temperature

3,778 K — cooler than the Sun (5,778 K)

Estimated Age

—

Stellar Radius

0.510 R☉

Stellar Mass

0.540 M☉

Metallicity [Fe/H]

-0.05

Extended Stellar Properties

Surface gravity (log g)

4.750 dex

Stellar density

5.297 g/cm³

Metallicity ratio

[Fe/H]

Distance

101.63 parsec

Light-years 331.48 ly

V-band magnitude

14.64 mag

Voyager-speed travel 5,845,629 yr

Multi-band Host Photometry — 17 bands

Astrometric Data

Parallax

9.811 mas

Total Proper Motion

21.435 mas/yr

PM Right Ascension

11.55 mas/yr

PM Declination

18.06 mas/yr

Galactic Cartesian (pc)

x = -0.681 · y = 0.709 · z = 0.182

Equatorial (J2000)

RA 133.85573° · Dec 10.46922°

Galactic ℓ, b

217.625° · 32.246°

Ecliptic λ, β

133.302° · -6.623°

HTM-20 index

415865403