Key parameters at a glance

A radius of 0.71 Earth radii
A mass of 0.29 Earth masses
Surface gravity around 0.58 g
An orbital period of 7.814 days
Semi-major axis 0.0679 AU
Equilibrium temperature 665 K (391 °C)
Distance from Earth 252.96 light-years
Earth Similarity Index 0.450
Travel time at Voyager 1 speed 4,460,985 years
Almost certainly tidally locked to its host star given the close orbit

3 siblings around K2-266

K2-266 c 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
K2-266 b	Sub-Neptune	3.30	11.27	0.659	1,515	2018
K2-266 c this	Rocky Terrestrial	0.71	0.29	7.814	665	2018
K2-266 d	Sub-Neptune	2.93	8.90	14.697	538	2018
K2-266 e	Sub-Neptune	2.73	14.30	19.482	490	2018

K2-266 c Planet Profile

Physical Specs

Radius

0.71 R⊕

Radius (Jupiter)

0.063 R♃

Mass

0.29 M⊕

Mass (Jupiter)

0.001 M♃

Density

4.55 g/cm³

Surface Gravity

0.58 g (Earth)

Classification

Planet Type

Rocky Terrestrial

ESI Score 0.450

HZ Position Inner

Controversial No

Discovery

Year 2018

Method Transit

Facility K2

Telescope 0.95 m Kepler Telescope

Size rank in cohort

Rank by radius

#525of 570

top 91.9%

This planet

0.71R⊕

Rocky Terrestrial median

1.01R⊕

Nearest-size peers

Kepler-378 c 0.70 R⊕ KOI-4978 b 0.70 R⊕ Kepler-1349 b 0.70 R⊕

Metric	Earth	K2-266 c	Jupiter
Radius (R⊕)	1.00	0.71	11.21
Mass (M⊕)	1.00	0.29	317.83
Density (g/cm³)	5.51	4.55	1.33
Surface Gravity (g)	1.00	0.58	2.53
Insolation (S⊕)	1.00	32.40	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Computed mass	0.290 M⊕	Model-computed mass (e.g. from mass-radius relation).

Star Catalogue Identifiers

TIC

TIC 374180079

Gaia DR2

Gaia DR2 3855246074629979264

Gaia DR3

Gaia DR3 3855246074629979264

System

K2-266

Percentile among Rocky Terrestrial cohort

Radius 0.705 R⊕ · percentile 8 / cohort 570

Mass 0.290 M⊕ · percentile 6 / cohort 570

Orbital period 7.81 d · percentile 72 / cohort 567

Distance 77.56 pc · percentile 22 / cohort 566

ESI 0.450 · percentile 66 / cohort 570

Orbit & Habitability

Orbital Dynamics

Period

7.814 days

Semi-major axis

0.0679 AU

Eccentricity

0.042

Inclination

88.28 °

Year Length

A year here lasts approximately 7.81 Earth days (2.1% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0679 AU.

Transit Fingerprint

Depth

0.009 %

Duration

2.256 h

Impact parameter b

0.600

Rp / R★

0.009200

Transit midpoint (BJD)

2,457,946.6510

Photometric dip

Transit produces a flux drop of 85 ppm lasting ≈ 2.26 h.

Extended Orbital Architecture

Planet / star radius ratio

0.009200

Semi-major axis / stellar radius

20.800

Impact parameter (b)

0.600

Transit mid-time (BJD)

2,457,946.6510

Long. of periastron (ω)

87.00°

Angular separation (arcsec)

0.87500

Eq. Temperature

665K

(391 °C)

Insolation (S⊕)

32.40

Earth = 1.00

Earth Similarity (ESI)

0.450

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

Rodriguez et al. 2018

Instrument

Kepler CCD Array

Publication

2018-11

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: K2-266

Spectral Class

K-type orange

Effective Temperature

4,285 K — cooler than the Sun (5,778 K)

Estimated Age

—

Stellar Radius

0.703 R☉

Stellar Mass

0.686 M☉

Metallicity [Fe/H]

-0.12

Extended Stellar Properties

Surface gravity (log g)

4.581 dex

Stellar density

2.790 g/cm³

Systemic radial velocity

10.85 km/s

Metallicity ratio

[Fe/H]

Distance

77.56 parsec

Light-years 252.96 ly

V-band magnitude

11.63 mag

Voyager-speed travel 4,460,985 yr

Multi-band Host Photometry — 17 bands

Astrometric Data

Parallax

12.865 mas

Total Proper Motion

89.284 mas/yr

PM Right Ascension

56.87 mas/yr

PM Declination

-68.83 mas/yr

Galactic Cartesian (pc)

x = -0.927 · y = 0.376 · z = 0.016

Equatorial (J2000)

RA 157.93569° · Dec 0.93728°

Galactic ℓ, b

245.045° · 47.483°

Ecliptic λ, β

159.244° · -7.724°

HTM-20 index

266358226