Key parameters at a glance

A radius of 1.40 Earth radii
A mass of 2.54 Earth masses
Surface gravity around 1.30 g
An orbital period of 13.343 days
Semi-major axis 0.0781 AU
Equilibrium temperature 379 K (106 °C)
Distance from Earth 579.23 light-years
Earth Similarity Index 0.764
Travel time at Voyager 1 speed 10,214,782 years
Almost certainly tidally locked to its host star given the close orbit

Context from the literature

Kepler-186 is a main-sequence M1-type dwarf star, located 177.5 parsecs away in the constellation of Cygnus. The star is slightly cooler than the sun, with roughly half its metallicity. It is known to have five planets, including the first Earth-sized world discovered in the habitable zone: Kepler-186f. The star hosts four other planets discovered so far, though they all orbit interior to the habitable zone.

Excerpted from Wikipedia · full article

3 siblings around Kepler-186

Kepler-186 d shares its host star with 3 other confirmed planets. Side-by-side measurements below.

Planet	Type	Radius (R⊕)	Mass (M⊕)	Period (d)	Eq. T (K)	Year
Kepler-186 b	Rocky Terrestrial	1.07	1.24	3.887	571	2014
Kepler-186 c	Super-Earth	1.25	2.10	7.267	464	2014
Kepler-186 d this	Super-Earth	1.40	2.54	13.343	379	2014
Kepler-186 e	Super-Earth	1.27	2.15	22.408	319	2014

Kepler-186 d Planet Profile

Physical Specs

Radius

1.40 R⊕

Radius (Jupiter)

0.125 R♃

Mass

2.54 M⊕

Mass (Jupiter)

0.008 M♃

Density

5.09 g/cm³

Surface Gravity

1.30 g (Earth)

Classification

Planet Type

Super-Earth

ESI Score 0.764

HZ Position Inner

Controversial No

Discovery

Year 2014

Method Transit

Facility Kepler

Telescope 0.95 m Kepler Telescope

Size rank in cohort

Rank by radius

#923of 1176

top 78.4%

This planet

1.40R⊕

Super-Earth median

1.60R⊕

Nearest-size peers

K2-85 b 1.40 R⊕ Kepler-1301 b 1.40 R⊕ TOI-5489 b 1.40 R⊕

Metric	Earth	Kepler-186 d	Jupiter
Radius (R⊕)	1.00	1.40	11.21
Mass (M⊕)	1.00	2.54	317.83
Density (g/cm³)	5.51	5.09	1.33
Surface Gravity (g)	1.00	1.30	2.53
Insolation (S⊕)	1.00	7.20	0.037

Star Catalogue Identifiers

TIC

TIC 268159861

Gaia DR2

Gaia DR2 2079000330051813504

Gaia DR3

Gaia DR3 2079000330051813504

System

Kepler-186

Percentile among Super-Earth cohort

Radius 1.400 R⊕ · percentile 21 / cohort 1176

Mass 2.540 M⊕ · percentile 20 / cohort 1176

Orbital period 13.34 d · percentile 74 / cohort 1164

Distance 177.59 pc · percentile 22 / cohort 1171

ESI 0.764 · percentile 88 / cohort 1176

Orbit & Habitability

Orbital Dynamics

Period

13.343 days

Semi-major axis

0.0781 AU

Eccentricity

0.000

Inclination

89.10 °

Year Length

A year here lasts approximately 13.34 Earth days (3.7% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0781 AU.

Transit Fingerprint

Depth

0.087 %

Duration

2.900 h

Impact parameter b

0.360

Rp / R★

0.027150

Transit midpoint (BJD)

2,455,009.9045

Photometric dip

Transit produces a flux drop of 873 ppm lasting ≈ 2.90 h.

Extended Orbital Architecture

Planet / star radius ratio

0.027150

Semi-major axis / stellar radius

17.800

Impact parameter (b)

0.360

Transit mid-time (BJD)

2,455,009.9045

Angular separation (arcsec)

0.44000

Eq. Temperature

379K

(106 °C)

Insolation (S⊕)

7.20

Earth = 1.00

Earth Similarity (ESI)

0.764

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

Rowe et al. 2014

Instrument

Kepler CCD Array

Publication

2014-03

Observation locale

Space

Discovery cohort

Planets confirmed in 2014 at Kepler (12 shown).

Kepler-186 e · Super-Earth Kepler-395 c · Super-Earth Kepler-220 e · Super-Earth Kepler-249 d · Super-Earth Kepler-296 f · Super-Earth Kepler-367 c · Rocky Terrestrial Kepler-296 e · Super-Earth Kepler-155 c · Sub-Neptune Kepler-138 d · Super-Earth Kepler-333 c · Rocky Terrestrial Kepler-331 d · Super-Earth Kepler-267 d · Sub-Neptune

Host System: Kepler-186

Spectral Class

M-type red dwarf

Effective Temperature

3,788 K — cooler than the Sun (5,778 K)

Estimated Age

4.00 Gyr — younger than the Sun (4.6 Gyr)

Stellar Radius

0.472 R☉

Stellar Mass

0.478 M☉

Metallicity [Fe/H]

-0.28

Extended Stellar Properties

Surface gravity (log g)

4.770 dex

Stellar density

6.400 g/cm³

Metallicity ratio

[M/H]

Distance

177.59 parsec

Light-years 579.23 ly

V-band magnitude

15.14 mag

Voyager-speed travel 10,214,782 yr

Multi-band Host Photometry — 16 bands

Astrometric Data

Parallax

5.602 mas

Total Proper Motion

4.839 mas/yr

PM Right Ascension

2.10 mas/yr

PM Declination

-4.36 mas/yr

Galactic Cartesian (pc)

x = 0.345 · y = -0.632 · z = 0.694

Equatorial (J2000)

RA 298.65274° · Dec 43.95499°

Galactic ℓ, b

78.520° · 8.171°

Ecliptic λ, β

318.672° · 62.636°

HTM-20 index

1990400524

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