Key parameters at a glance

A radius of 1.00 Earth radii
A mass of 0.97 Earth masses
Surface gravity around 0.97 g
An orbital period of 7.775 days
Semi-major axis 0.0576 AU
Equilibrium temperature 427 K (154 °C)
Distance from Earth 101.39 light-years
Earth Similarity Index 0.736
Travel time at Voyager 1 speed 1,787,929 years
Almost certainly tidally locked to its host star given the close orbit

Context from the literature

K2-239 is a small red dwarf star in the constellation Sextans, about 32 parsecs away from Earth. Observed by the Kepler Space Telescope during Campaign 14 of its K2 "Second Light" mission, it was found to have three hot, likely rocky Earth-sized planets in orbit around it.

Excerpted from Wikipedia · full article

2 siblings around K2-239

K2-239 c 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
K2-239 b	Rocky Terrestrial	1.10	1.37	5.240	502	2018
K2-239 c this	Rocky Terrestrial	1.00	0.97	7.775	427	2018
K2-239 d	Rocky Terrestrial	1.10	1.37	10.115	399	2018

K2-239 c Planet Profile

Physical Specs

Radius

1.00 R⊕

Radius (Jupiter)

0.089 R♃

Mass

0.97 M⊕

Mass (Jupiter)

0.003 M♃

Density

5.34 g/cm³

Surface Gravity

0.97 g (Earth)

Classification

Planet Type

Rocky Terrestrial

ESI Score 0.736

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

#335of 570

top 58.6%

This planet

1.00R⊕

Rocky Terrestrial median

1.01R⊕

Nearest-size peers

Kepler-1464 c 1.00 R⊕ Kepler-1417 b 1.00 R⊕ Kepler-392 b 1.00 R⊕

Metric	Earth	K2-239 c	Jupiter
Radius (R⊕)	1.00	1.00	11.21
Mass (M⊕)	1.00	0.97	317.83
Density (g/cm³)	5.51	5.34	1.33
Surface Gravity (g)	1.00	0.97	2.53
Insolation (S⊕)	1.00	—	0.037

Star Catalogue Identifiers

TIC

TIC 374339566

Gaia DR2

Gaia DR2 3857872051994269824

Gaia DR3

Gaia DR3 3857872051994269824

System

K2-239

Percentile among Rocky Terrestrial cohort

Radius 1.000 R⊕ · percentile 40 / cohort 570

Mass 0.972 M⊕ · percentile 36 / cohort 570

Orbital period 7.78 d · percentile 71 / cohort 567

Distance 31.08 pc · percentile 13 / cohort 566

ESI 0.736 · percentile 85 / cohort 570

Orbit & Habitability

Orbital Dynamics

Period

7.775 days

Semi-major axis

0.0576 AU

Eccentricity

—

Inclination

88.77 °

Year Length

A year here lasts approximately 7.78 Earth days (2.1% of a terrestrial year) at a mean orbital distance of 0.0576 AU.

Transit Fingerprint

Depth

0.058 %

Duration

1.248 h

Impact parameter b

0.730

Rp / R★

0.024100

Transit midpoint (BJD)

2,457,916.8600

Photometric dip

Transit produces a flux drop of 580 ppm lasting ≈ 1.25 h.

Extended Orbital Architecture

Planet / star radius ratio

0.024100

Semi-major axis / stellar radius

34.000

Impact parameter (b)

0.730

Transit mid-time (BJD)

2,457,916.8600

Angular separation (arcsec)

1.85000

Eq. Temperature

427K

(154 °C)

Insolation (S⊕)

—

Earth = 1.00

Earth Similarity (ESI)

0.736

0 = alien, 1 = Earth-identical

Insufficient insolation data — the surface is too hot to retain surface water. Close-orbiting tidally-locked around a cool host.

Discovery Paper

Primary reference

D Iacute Ez Alonso et al. 2018

Instrument

Kepler CCD Array

Publication

2018-10

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: K2-239

Spectral Class

M-type red dwarf

Effective Temperature

3,420 K — cooler than the Sun (5,778 K)

Estimated Age

—

Stellar Radius

0.360 R☉

Stellar Mass

0.400 M☉

Metallicity [Fe/H]

-0.10

Extended Stellar Properties

Surface gravity (log g)

4.900 dex

Stellar density

19.151 g/cm³

Metallicity ratio

[Fe/H]

Distance

31.08 parsec

Light-years 101.39 ly

V-band magnitude

14.63 mag

Voyager-speed travel 1,787,929 yr

Multi-band Host Photometry — 18 bands

Astrometric Data

Parallax

32.141 mas

Total Proper Motion

42.452 mas/yr

PM Right Ascension

-42.27 mas/yr

PM Declination

3.98 mas/yr

Galactic Cartesian (pc)

x = -0.940 · y = 0.331 · z = 0.077

Equatorial (J2000)

RA 160.59413° · Dec 4.44138°

Galactic ℓ, b

243.590° · 51.777°

Ecliptic λ, β

160.402° · -3.481°

HTM-20 index

1898505774

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