Key parameters at a glance

A radius of 2.19 Earth radii
A mass of 5.43 Earth masses
Surface gravity around 1.13 g
An orbital period of 8.527 days
Semi-major axis 0.0858 AU
Equilibrium temperature 1,140 K (867 °C)
Distance from Earth 1,555.38 light-years
Earth Similarity Index 0.228
Travel time at Voyager 1 speed 27,429,112 years

1 sibling around K2-166

K2-166 b shares its host star with 1 other confirmed planet. Side-by-side measurements below.

Planet	Type	Radius (R⊕)	Mass (M⊕)	Period (d)	Eq. T (K)	Year
EPIC 201615463 c	Rocky Terrestrial	1.22	1.98	3.805	—	2019
K2-166 b this	Sub-Neptune	2.19	5.43	8.527	1,140	2018

K2-166 b Planet Profile

Physical Specs

Radius

2.19 R⊕

Radius (Jupiter)

0.195 R♃

Mass

5.43 M⊕

Mass (Jupiter)

0.017 M♃

Density

2.84 g/cm³

Surface Gravity

1.13 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.228

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

#1691of 1978

top 85.4%

This planet

2.19R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

TOI-880.02 2.19 R⊕ Kepler-174 d 2.19 R⊕ K2-146 c 2.19 R⊕

Metric	Earth	K2-166 b	Jupiter
Radius (R⊕)	1.00	2.19	11.21
Mass (M⊕)	1.00	5.43	317.83
Density (g/cm³)	5.51	2.84	1.33
Surface Gravity (g)	1.00	1.13	2.53
Insolation (S⊕)	1.00	—	0.037

Star Catalogue Identifiers

TIC

TIC 377171980

Gaia DR2

Gaia DR2 3701015375282968064

Gaia DR3

Gaia DR3 3701015375282968064

System

K2-166

Percentile among Sub-Neptune cohort

Radius 2.190 R⊕ · percentile 14 / cohort 1978

Mass 5.430 M⊕ · percentile 15 / cohort 1978

Orbital period 8.53 d · percentile 28 / cohort 1946

Distance 476.88 pc · percentile 46 / cohort 1975

ESI 0.228 · percentile 12 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

8.527 days

Semi-major axis

0.0858 AU

Eccentricity

—

Inclination

87.43 °

Year Length

A year here lasts approximately 8.53 Earth days (2.3% of a terrestrial year) at a mean orbital distance of 0.0858 AU.

Transit Fingerprint

Depth

0.016 %

Duration

3.700 h

Impact parameter b

0.400

Rp / R★

0.012400

Transit midpoint (BJD)

2,457,586.7635

Photometric dip

Transit produces a flux drop of 160 ppm lasting ≈ 3.70 h.

Extended Orbital Architecture

Planet / star radius ratio

0.012400

Semi-major axis / stellar radius

11.100

Impact parameter (b)

0.400

Transit mid-time (BJD)

2,457,586.7635

Angular separation (arcsec)

0.18000

Eq. Temperature

1,140K

(867 °C)

Insolation (S⊕)

—

Earth = 1.00

Earth Similarity (ESI)

0.228

0 = alien, 1 = Earth-identical

Insufficient insolation data — the dayside is scorched.

Discovery Paper

Primary reference

Mayo et al. 2018

Instrument

Kepler CCD Array

Publication

2018-03

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: K2-166

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

5,960 K — hotter than the Sun (5,778 K)

Estimated Age

—

Stellar Radius

1.610 R☉

Stellar Mass

1.160 M☉

Metallicity [Fe/H]

0.09

Extended Stellar Properties

Surface gravity (log g)

4.090 dex

Stellar density

0.423 g/cm³

Metallicity ratio

[Fe/H]

Distance

476.88 parsec

Light-years 1,555.38 ly

V-band magnitude

12.08 mag

Voyager-speed travel 27,429,112 yr

Multi-band Host Photometry — 17 bands

Astrometric Data

Parallax

2.069 mas

Total Proper Motion

49.648 mas/yr

PM Right Ascension

-47.37 mas/yr

PM Declination

-14.88 mas/yr

Galactic Cartesian (pc)

x = -0.995 · y = -0.090 · z = 0.040

Equatorial (J2000)

RA 185.18809° · Dec 2.28238°

Galactic ℓ, b

285.158° · 64.090°

Ecliptic λ, β

183.851° · 4.156°

HTM-20 index

-1616119422