Key parameters at a glance

A radius of 2.63 Earth radii
A mass of 7.87 Earth masses
Surface gravity around 1.14 g
An orbital period of 18.370 days
Semi-major axis 0.1300 AU
Equilibrium temperature 582 K (309 °C)
Distance from Earth 1,256.45 light-years
Earth Similarity Index 0.313
Travel time at Voyager 1 speed 22,157,565 years

3 siblings around Kepler-221

Kepler-221 e 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-221 b	Super-Earth	1.71	5.96	2.796	1,090	2014
Kepler-221 c	Sub-Neptune	2.93	9.30	5.691	860	2014
Kepler-221 d	Sub-Neptune	2.73	3.61	10.042	712	2014
Kepler-221 e this	Sub-Neptune	2.63	7.87	18.370	582	2014

Kepler-221 e Planet Profile

Physical Specs

Radius

2.63 R⊕

Radius (Jupiter)

0.235 R♃

Mass

7.87 M⊕

Mass (Jupiter)

0.025 M♃

Density

0.57 g/cm³

Surface Gravity

1.14 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.313

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

#969of 1978

top 48.9%

This planet

2.63R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

Kepler-1241 b 2.63 R⊕ GJ 3473 c 2.63 R⊕ Kepler-319 c 2.63 R⊕

Metric	Earth	Kepler-221 e	Jupiter
Radius (R⊕)	1.00	2.63	11.21
Mass (M⊕)	1.00	7.87	317.83
Density (g/cm³)	5.51	0.57	1.33
Surface Gravity (g)	1.00	1.14	2.53
Insolation (S⊕)	1.00	25.16	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	7.867 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

TIC

TIC 272601375

Gaia DR2

Gaia DR2 2080344586094498432

Gaia DR3

Gaia DR3 2080344586094498432

System

Kepler-221

Percentile among Sub-Neptune cohort

Radius 2.630 R⊕ · percentile 50 / cohort 1978

Mass 7.867 M⊕ · percentile 53 / cohort 1978

Orbital period 18.37 d · percentile 59 / cohort 1946

Distance 385.23 pc · percentile 40 / cohort 1975

ESI 0.313 · percentile 31 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

18.370 days

Semi-major axis

0.1300 AU

Eccentricity

0.000

Inclination

87.37 °

Year Length

A year here lasts approximately 18.37 Earth days (5.0% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.1300 AU.

Transit Fingerprint

Depth

0.108 %

Duration

2.245 h

Impact parameter b

0.260

Rp / R★

0.029628

Transit midpoint (BJD)

2,454,964.8605

Photometric dip

Transit produces a flux drop of 1,076 ppm lasting ≈ 2.25 h.

Extended Orbital Architecture

Planet / star radius ratio

0.029628

Semi-major axis / stellar radius

64.800

Impact parameter (b)

0.260

Transit mid-time (BJD)

2,454,964.8605

Angular separation (arcsec)

0.33700

Eq. Temperature

582K

(309 °C)

Insolation (S⊕)

25.16

Earth = 1.00

Earth Similarity (ESI)

0.313

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.

Transit timing variations

Gravitational interactions from neighbours have been detected.

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-221

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

5,243 K — cooler than the Sun (5,778 K)

Estimated Age

1.78 Gyr — younger than the Sun (4.6 Gyr)

Stellar Radius

0.821 R☉

Stellar Mass

0.854 M☉

Metallicity [Fe/H]

0.06

Extended Stellar Properties

Surface gravity (log g)

4.543 dex

Stellar density

1.800 g/cm³

Metallicity ratio

[M/H]

Distance

385.23 parsec

Light-years 1,256.45 ly

V-band magnitude

13.97 mag

Voyager-speed travel 22,157,565 yr

Multi-band Host Photometry — 16 bands

Astrometric Data

Parallax

2.567 mas

Total Proper Motion

3.487 mas/yr

PM Right Ascension

-2.71 mas/yr

PM Declination

-2.20 mas/yr

Galactic Cartesian (pc)

x = 0.307 · y = -0.611 · z = 0.729

Equatorial (J2000)

RA 296.65475° · Dec 46.83522°

Galactic ℓ, b

80.373° · 10.802°

Ecliptic λ, β

318.570° · 65.839°

HTM-20 index

-1912311971