Key parameters at a glance

A radius of 9.92 Earth radii
A mass of 70.60 Earth masses
Surface gravity around 0.72 g
An orbital period of 3.386 days
Equilibrium temperature 1,214 K (941 °C)
Distance from Earth 4,287.42 light-years
Earth Similarity Index 0.109
Travel time at Voyager 1 speed 75,608,620 years

K2-308 b Planet Profile

Physical Specs

Radius

9.92 R⊕

Radius (Jupiter)

0.884 R♃

Mass

70.60 M⊕

Mass (Jupiter)

0.222 M♃

Density

0.40 g/cm³

Surface Gravity

0.72 g (Earth)

Classification

Planet Type

Neptune-like

ESI Score 0.109

HZ Position Inner

Controversial No

Discovery

Year 2019

Method Transit

Facility K2

Telescope 0.95 m Kepler Telescope

Size rank in cohort

Rank by radius

#9of 574

top 1.4%

This planet

9.92R⊕

Neptune-like median

6.39R⊕

Nearest-size peers

TOI-1135 b 9.92 R⊕ CoRoT-13 b 9.92 R⊕ HATS-75 b 9.91 R⊕

Metric	Earth	K2-308 b	Jupiter
Radius (R⊕)	1.00	9.92	11.21
Mass (M⊕)	1.00	70.60	317.83
Density (g/cm³)	5.51	0.40	1.33
Surface Gravity (g)	1.00	0.72	2.53
Insolation (S⊕)	1.00	512.92	0.037

Star Catalogue Identifiers

TIC

TIC 411697517

Gaia DR2

Gaia DR2 3393982701757444352

Gaia DR3

Gaia DR3 3393982701757444352

System

K2-308

Percentile among Neptune-like cohort

Radius 9.916 R⊕ · percentile 98 / cohort 574

Mass 70.600 M⊕ · percentile 86 / cohort 574

Orbital period 3.39 d · percentile 7 / cohort 524

Distance 1,314.53 pc · percentile 81 / cohort 572

ESI 0.109 · percentile 4 / cohort 574

Orbit & Habitability

Orbital Dynamics

Period

3.386 days

Semi-major axis

— AU

Eccentricity

—

Inclination

88.44 °

Year Length

A year here lasts approximately 3.39 Earth days (0.9% of a terrestrial year).

Transit Fingerprint

Depth

0.626 %

Duration

3.090 h

Impact parameter b

0.210

Rp / R★

0.074200

Transit midpoint (BJD)

2,457,823.2233

Photometric dip

Transit produces a flux drop of 6,260 ppm lasting ≈ 3.09 h.

Extended Orbital Architecture

Planet / star radius ratio

0.074200

Semi-major axis / stellar radius

7.940

Impact parameter (b)

0.210

Transit mid-time (BJD)

2,457,823.2233

Eq. Temperature

1,214K

(941 °C)

Insolation (S⊕)

512.92

Earth = 1.00

Earth Similarity (ESI)

0.109

0 = alien, 1 = Earth-identical

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

Discovery Paper

Primary reference

Rampalli et al. 2019

Instrument

Kepler CCD Array

Publication

2019-08

Observation locale

Space

Discovery cohort

Planets confirmed in 2019 at K2 (12 shown).

EPIC 206032309 b · Rocky Terrestrial EPIC 201833600 c · Rocky Terrestrial EPIC 206215704 b · Rocky Terrestrial EPIC 201754305 d · Rocky Terrestrial EPIC 201841433 b · Rocky Terrestrial EPIC 206317286 b · Rocky Terrestrial EPIC 201615463 c · Rocky Terrestrial EPIC 212499991 b · Super-Earth EPIC 220554210 c · Super-Earth EPIC 201497682 b · Rocky Terrestrial K2-133 e · Super-Earth EPIC 206024342 b · Super-Earth

Host System: K2-308

Spectral Class

F-type yellow-white

Effective Temperature

6,100 K — hotter than the Sun (5,778 K)

Estimated Age

—

Stellar Radius

1.240 R☉

Stellar Mass

1.090 M☉

Metallicity [Fe/H]

-0.10

Extended Stellar Properties

Surface gravity (log g)

3.940 dex

Systemic radial velocity

8.97 km/s

Rotational v·sin i

29.00 km/s

Metallicity ratio

[Fe/H]

Distance

1,314.53 parsec

Light-years 4,287.42 ly

V-band magnitude

15.07 mag

Voyager-speed travel 75,608,620 yr

Multi-band Host Photometry — 12 bands

Astrometric Data

Total Proper Motion

2.078 mas/yr

PM Right Ascension

1.48 mas/yr

PM Declination

1.46 mas/yr

Galactic Cartesian (pc)

x = 0.194 · y = 0.939 · z = 0.283

Equatorial (J2000)

RA 78.33912° · Dec 16.41420°

Galactic ℓ, b

186.543° · -13.030°

Ecliptic λ, β

78.742° · -6.571°

HTM-20 index

-1155637556