Key parameters at a glance

A radius of 2.61 Earth radii
A mass of 13.40 Earth masses
Surface gravity around 1.97 g
An orbital period of 77.611 days
Semi-major axis 0.3474 AU
Equilibrium temperature 430 K (157 °C)
Distance from Earth 921.60 light-years
Earth Similarity Index 0.595
Travel time at Voyager 1 speed 16,252,348 years

Context from the literature

Kepler-20d is an exoplanet orbiting Kepler-20. It has a mass and radius similar to Neptune. Despite being the furthest planet from the star, it has an orbit similar to Mercury, meaning that it is a hot Neptune. Along with the other four planets in the system, Kepler-20d was announced on December 20, 2011.

Excerpted from Wikipedia · full article

5 siblings around Kepler-20

Kepler-20 d shares its host star with 5 other confirmed planets. Side-by-side measurements below.

Planet	Type	Radius (R⊕)	Mass (M⊕)	Period (d)	Eq. T (K)	Year
Kepler-20 b	Super-Earth	1.77	9.70	3.696	1,187	2011
Kepler-20 e	Rocky Terrestrial	0.82	0.76	6.098	1,004	2011
Kepler-20 c	Sub-Neptune	2.89	11.10	10.854	828	2011
Kepler-20 f	Rocky Terrestrial	0.95	1.40	19.578	681	2011
Kepler-20 g	Neptune-like	4.71	19.96	34.940	524	2016
Kepler-20 d this	Sub-Neptune	2.61	13.40	77.611	430	2011

Kepler-20 d Planet Profile

Physical Specs

Radius

2.61 R⊕

Radius (Jupiter)

0.232 R♃

Mass

13.40 M⊕

Mass (Jupiter)

0.042 M♃

Density

4.10 g/cm³

Surface Gravity

1.97 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.595

HZ Position Inner

Controversial No

Discovery

Year 2011

Method Transit

Facility Kepler

Telescope 0.95 m Kepler Telescope

Size rank in cohort

Rank by radius

#1014of 1978

top 51.2%

This planet

2.61R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

K2-207 b 2.61 R⊕ HD 110067 g 2.61 R⊕ HD 22946 d 2.61 R⊕

Metric	Earth	Kepler-20 d	Jupiter
Radius (R⊕)	1.00	2.61	11.21
Mass (M⊕)	1.00	13.40	317.83
Density (g/cm³)	5.51	4.10	1.33
Surface Gravity (g)	1.00	1.97	2.53
Insolation (S⊕)	1.00	5.71	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	13.400 M⊕	Direct mass measurement (not derived).
Minimum mass (M sin i)	12.947 M⊕	Lower bound from radial-velocity fitting.

Star Catalogue Identifiers

TIC

TIC 158554588

Gaia DR2

Gaia DR2 2102548708017562112

Gaia DR3

Gaia DR3 2102548708017562112

System

Kepler-20

Percentile among Sub-Neptune cohort

Radius 2.606 R⊕ · percentile 49 / cohort 1978

Mass 13.400 M⊕ · percentile 89 / cohort 1978

Orbital period 77.61 d · percentile 91 / cohort 1946

Distance 282.56 pc · percentile 34 / cohort 1975

ESI 0.595 · percentile 82 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

77.611 days

Semi-major axis

0.3474 AU

Eccentricity

0.082

Inclination

89.71 °

Year Length

A year here lasts approximately 77.61 Earth days (21.2% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.3474 AU.

Transit Fingerprint

Depth

0.083 %

Duration

7.257 h

Impact parameter b

0.588

Rp / R★

0.027680

Transit midpoint (BJD)

2,454,997.7296

Photometric dip

Transit produces a flux drop of 828 ppm lasting ≈ 7.26 h.

Extended Orbital Architecture

Planet / star radius ratio

0.027680

Semi-major axis / stellar radius

78.230

Impact parameter (b)

0.588

RV semi-amplitude (K)

2.120 m/s

Transit mid-time (BJD)

2,454,997.7296

Angular separation (arcsec)

1.23000

Eq. Temperature

430K

(157 °C)

Insolation (S⊕)

5.71

Earth = 1.00

Earth Similarity (ESI)

0.595

0 = alien, 1 = Earth-identical

Inside the inner HZ boundary (too hot for liquid water) — the surface is too hot to retain surface water.

Detection Signatures

Transit photometry

A transit dip has been observed from at least one telescope.

Radial velocity

Stellar wobble has been measured spectroscopically.

Discovery Paper

Primary reference

Gautier et al. 2011

Instrument

Kepler CCD Array

Publication

2012-04

Observation locale

Space

Discovery cohort

Planets confirmed in 2011 at Kepler (12 shown).

Kepler-22 b · Sub-Neptune Kepler-26 c · Sub-Neptune Kepler-19 c · Sub-Neptune Kepler-26 b · Sub-Neptune Kepler-28 c · Super-Earth Kepler-10 c · Sub-Neptune Kepler-20 f · Rocky Terrestrial Kepler-42 d · Rocky Terrestrial Kepler-16 b · Neptune-like Kepler-28 b · Super-Earth Kepler-34 b · Neptune-like Kepler-29 c · Sub-Neptune

Host System: Kepler-20

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

5,495 K — cooler than the Sun (5,778 K)

Estimated Age

5.60 Gyr — older than the Sun (4.6 Gyr)

Stellar Radius

0.916 R☉

Stellar Mass

0.929 M☉

Metallicity [Fe/H]

0.07

Extended Stellar Properties

Surface gravity (log g)

4.446 dex

Stellar density

1.360 g/cm³

Systemic radial velocity

-20.93 km/s

Rotational v·sin i

0.40 km/s

Metallicity ratio

[Fe/H]

Distance

282.56 parsec

Light-years 921.60 ly

V-band magnitude

12.61 mag

Voyager-speed travel 16,252,348 yr

Multi-band Host Photometry — 16 bands

Astrometric Data

Parallax

3.510 mas

Total Proper Motion

27.251 mas/yr

PM Right Ascension

-3.98 mas/yr

PM Declination

-26.96 mas/yr

Galactic Cartesian (pc)

x = 0.225 · y = -0.704 · z = 0.674

Equatorial (J2000)

RA 287.69799° · Dec 42.33858°

Galactic ℓ, b

73.377° · 14.573°

Ecliptic λ, β

300.714° · 63.902°

HTM-20 index

-1933436408

Wikipedia → Image: Wikimedia Commons · NASA/Ames/JPL-Caltech · Public domain