Key parameters at a glance

A radius of 3.00 Earth radii
A mass of 18.10 Earth masses
Surface gravity around 2.01 g
An orbital period of 17.307 days
Semi-major axis 0.1185 AU
Equilibrium temperature 470 K (197 °C)
Distance from Earth 193.24 light-years
Earth Similarity Index 0.529
Travel time at Voyager 1 speed 3,407,769 years
Almost certainly tidally locked to its host star given the close orbit

Context from the literature

K2-136 is a K-type main-sequence star located in the zodiac constellation Taurus. It is a member of the Hyades open cluster, which provides a well-constrained young age on the system. The star is known to host three transiting exoplanets, discovered in 2017 from lightcurves gathered by the Kepler space telescope during the K2 extension mission. The innermost planet is approximately Earth-sized, the first such planet found in a young open cluster.

Excerpted from Wikipedia · full article

2 siblings around K2-136

K2-136 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
K2-136 b	Rocky Terrestrial	1.01	4.30	7.975	610	2017
K2-136 c this	Sub-Neptune	3.00	18.10	17.307	470	2017
K2-136 d	Super-Earth	1.57	3.00	25.575	420	2017

K2-136 c Planet Profile

Physical Specs

Radius

3.00 R⊕

Radius (Jupiter)

0.268 R♃

Mass

18.10 M⊕

Mass (Jupiter)

0.057 M♃

Density

3.69 g/cm³

Surface Gravity

2.01 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.529

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

#521of 1978

top 26.3%

This planet

3.00R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

Kepler-338 d 3.00 R⊕ HD 3167 c 3.00 R⊕ HIP 94235 b 3.00 R⊕

Metric	Earth	K2-136 c	Jupiter
Radius (R⊕)	1.00	3.00	11.21
Mass (M⊕)	1.00	18.10	317.83
Density (g/cm³)	5.51	3.69	1.33
Surface Gravity (g)	1.00	2.01	2.53
Insolation (S⊕)	1.00	11.91	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	18.100 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

TIC

TIC 18310799

Gaia DR2

Gaia DR2 145916050683920128

Gaia DR3

Gaia DR3 145916050683920128

System

K2-136

Percentile among Sub-Neptune cohort

Radius 3.000 R⊕ · percentile 73 / cohort 1978

Mass 18.100 M⊕ · percentile 94 / cohort 1978

Orbital period 17.31 d · percentile 57 / cohort 1946

Distance 59.25 pc · percentile 13 / cohort 1975

ESI 0.529 · percentile 74 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

17.307 days

Semi-major axis

0.1185 AU

Eccentricity

0.047

Inclination

89.70 °

Year Length

A year here lasts approximately 17.31 Earth days (4.7% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.1185 AU.

Transit Fingerprint

Depth

0.191 %

Duration

3.449 h

Impact parameter b

0.310

Rp / R★

0.040640

Transit midpoint (BJD)

2,457,812.7177

Photometric dip

Transit produces a flux drop of 1,909 ppm lasting ≈ 3.45 h.

Extended Orbital Architecture

Planet / star radius ratio

0.040640

Semi-major axis / stellar radius

39.400

Impact parameter (b)

0.310

RV semi-amplitude (K)

5.490 m/s

Occultation depth

0.024 ppm

Transit mid-time (BJD)

2,457,812.7177

Long. of periastron (ω)

124.00°

Angular separation (arcsec)

2.00000

Eq. Temperature

470K

(197 °C)

Insolation (S⊕)

11.91

Earth = 1.00

Earth Similarity (ESI)

0.529

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

Mann et al. 2018

Instrument

Kepler CCD Array

Publication

2018-01

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 K2-124 b · Sub-Neptune K2-117 c · Sub-Neptune

Host System: K2-136

Spectral Class

K-type orange

Effective Temperature

4,500 K — cooler than the Sun (5,778 K)

Estimated Age

0.65 Gyr — younger than the Sun (4.6 Gyr)

Stellar Radius

0.677 R☉

Stellar Mass

0.742 M☉

Metallicity [Fe/H]

-0.02

Extended Stellar Properties

Surface gravity (log g)

4.680 dex

Stellar density

3.384 g/cm³

Systemic radial velocity

39.20 km/s

Rotational v·sin i

2.00 km/s

Rotation period

15.00 days

Metallicity ratio

[M/H]

Distance

59.25 parsec

Light-years 193.24 ly

V-band magnitude

11.10 mag

Voyager-speed travel 3,407,769 yr

Multi-band Host Photometry — 17 bands

Astrometric Data

Parallax

16.850 mas

Total Proper Motion

90.204 mas/yr

PM Right Ascension

82.87 mas/yr

PM Declination

-35.62 mas/yr

Galactic Cartesian (pc)

x = 0.354 · y = 0.851 · z = 0.389

Equatorial (J2000)

RA 67.41286° · Dec 22.88257°

Galactic ℓ, b

174.775° · -17.351°

Ecliptic λ, β

69.269° · 1.054°

HTM-20 index

-1285742176

Wikipedia →

Similar Worlds

HD 3167 c

Sub-Neptune · K-type orange

Radius 3.00 R⊕ · 154.2 ly

TOI-1246 b

Sub-Neptune · K-type orange

Radius 3.01 R⊕ · 552.6 ly

Kepler-1341 b

Sub-Neptune · K-type orange

Radius 2.99 R⊕ · 1,555.6 ly

TOI-1803 b

Sub-Neptune · K-type orange

Radius 2.99 R⊕ · 388.9 ly

Kepler-1881 b

Sub-Neptune · K-type orange

Radius 2.98 R⊕ · 3,448.2 ly

Kepler-248 b

Sub-Neptune · K-type orange

Radius 3.02 R⊕ · 2,409.6 ly

Explore Related Categories

Sub-Neptune Planets Transit Discoveries K2 Mission K-type orange Hosts