Key parameters at a glance

A radius of 2.40 Earth radii
A mass of 6.35 Earth masses
Surface gravity around 1.10 g
An orbital period of 4.499 days
Semi-major axis 0.0542 AU
Equilibrium temperature 1,133 K (860 °C)
Distance from Earth 4,920.75 light-years
Earth Similarity Index 0.221
Travel time at Voyager 1 speed 86,777,389 years

Kepler-666 b Planet Profile

Physical Specs

Radius

2.40 R⊕

Radius (Jupiter)

0.214 R♃

Mass

6.35 M⊕

Mass (Jupiter)

0.020 M♃

Density

2.52 g/cm³

Surface Gravity

1.10 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.221

HZ Position Inner

Controversial No

Discovery

Year 2016

Method Transit

Facility Kepler

Telescope 0.95 m Kepler Telescope

Size rank in cohort

Rank by radius

#1333of 1978

top 67.3%

This planet

2.40R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

Kepler-194 d 2.40 R⊕ KIC 8540376 c 2.40 R⊕ Kepler-112 c 2.40 R⊕

Metric	Earth	Kepler-666 b	Jupiter
Radius (R⊕)	1.00	2.40	11.21
Mass (M⊕)	1.00	6.35	317.83
Density (g/cm³)	5.51	2.52	1.33
Surface Gravity (g)	1.00	1.10	2.53
Insolation (S⊕)	1.00	575.64	0.037

Star Catalogue Identifiers

TIC

TIC 267989336

Gaia DR2

Gaia DR2 2086935024430952960

Gaia DR3

Gaia DR3 2086935024430952960

System

Kepler-666

Percentile among Sub-Neptune cohort

Radius 2.400 R⊕ · percentile 32 / cohort 1978

Mass 6.350 M⊕ · percentile 31 / cohort 1978

Orbital period 4.50 d · percentile 10 / cohort 1946

Distance 1,508.71 pc · percentile 93 / cohort 1975

ESI 0.221 · percentile 10 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

4.499 days

Semi-major axis

0.0542 AU

Eccentricity

0.000

Inclination

88.00 °

Year Length

A year here lasts approximately 4.50 Earth days (1.2% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0542 AU.

Transit Fingerprint

Depth

0.046 %

Duration

3.831 h

Impact parameter b

0.834

Rp / R★

0.020882

Transit midpoint (BJD)

2,455,004.3511

Photometric dip

Transit produces a flux drop of 460 ppm lasting ≈ 3.83 h.

Extended Orbital Architecture

Planet / star radius ratio

0.020882

Semi-major axis / stellar radius

9.168

Impact parameter (b)

0.834

Transit mid-time (BJD)

2,455,004.3511

Angular separation (arcsec)

0.03590

Eq. Temperature

1,133K

(860 °C)

Insolation (S⊕)

575.64

Earth = 1.00

Earth Similarity (ESI)

0.221

0 = alien, 1 = Earth-identical

Inside the inner HZ boundary (too hot for liquid water) — the dayside is scorched.

Discovery Paper

Primary reference

Morton et al. 2016

Instrument

Kepler CCD Array

Publication

2016-05

Observation locale

Space

Discovery cohort

Planets confirmed in 2016 at Kepler (12 shown).

Kepler-1512 b · Rocky Terrestrial Kepler-1410 b · Super-Earth Kepler-560 b · Super-Earth Kepler-1389 b · Super-Earth Kepler-1450 b · Super-Earth Kepler-1544 b · Super-Earth Kepler-1459 b · Super-Earth Kepler-1638 b · Super-Earth Kepler-737 b · Super-Earth Kepler-1185 b · Super-Earth Kepler-1178 b · Rocky Terrestrial Kepler-1040 b · Sub-Neptune

Host System: Kepler-666

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

5,887 K — hotter than the Sun (5,778 K)

Estimated Age

3.80 Gyr — younger than the Sun (4.6 Gyr)

Stellar Radius

1.050 R☉

Stellar Mass

1.030 M☉

Metallicity [Fe/H]

0.01

Extended Stellar Properties

Surface gravity (log g)

4.410 dex

Stellar density

0.720 g/cm³

Metallicity ratio

[Fe/H]

Distance

1,508.71 parsec

Light-years 4,920.75 ly

V-band magnitude

15.42 mag

Voyager-speed travel 86,777,389 yr

Multi-band Host Photometry — 16 bands

Astrometric Data

Parallax

0.635 mas

Total Proper Motion

5.367 mas/yr

PM Right Ascension

3.00 mas/yr

PM Declination

4.45 mas/yr

Galactic Cartesian (pc)

x = 0.314 · y = -0.579 · z = 0.752

Equatorial (J2000)

RA 298.45689° · Dec 48.79159°

Galactic ℓ, b

82.711° · 10.684°

Ecliptic λ, β

323.512° · 67.019°

HTM-20 index

1528249077