Key parameters at a glance

A radius of 2.98 Earth radii
A mass of 9.17 Earth masses
Surface gravity around 1.03 g
An orbital period of 3.335 days
Semi-major axis 0.0488 AU
Equilibrium temperature 1,711 K (1438 °C)
Distance from Earth 2,565.02 light-years
Earth Similarity Index 0.126
Travel time at Voyager 1 speed 45,234,090 years

K2-278 b Planet Profile

Physical Specs

Radius

2.98 R⊕

Radius (Jupiter)

0.266 R♃

Mass

9.17 M⊕

Mass (Jupiter)

0.029 M♃

Density

1.90 g/cm³

Surface Gravity

1.03 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.126

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

#542of 1978

top 27.4%

This planet

2.98R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

Kepler-985 b 2.98 R⊕ Kepler-1299 b 2.98 R⊕ Kepler-1881 b 2.98 R⊕

Metric	Earth	K2-278 b	Jupiter
Radius (R⊕)	1.00	2.98	11.21
Mass (M⊕)	1.00	9.17	317.83
Density (g/cm³)	5.51	1.90	1.33
Surface Gravity (g)	1.00	1.03	2.53
Insolation (S⊕)	1.00	—	0.037

Star Catalogue Identifiers

TIC

TIC 422334505

Gaia DR2

Gaia DR2 3606596502170799104

Gaia DR3

Gaia DR3 3606596502170799104

System

K2-278

Percentile among Sub-Neptune cohort

Radius 2.980 R⊕ · percentile 72 / cohort 1978

Mass 9.170 M⊕ · percentile 66 / cohort 1978

Orbital period 3.33 d · percentile 6 / cohort 1946

Distance 786.44 pc · percentile 65 / cohort 1975

ESI 0.126 · percentile 1 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

3.335 days

Semi-major axis

0.0488 AU

Eccentricity

—

Inclination

— °

Year Length

A year here lasts approximately 3.33 Earth days (0.9% of a terrestrial year) at a mean orbital distance of 0.0488 AU.

Transit Fingerprint

Depth

0.037 %

Duration

3.936 h

Impact parameter b

0.430

Rp / R★

0.016900

Transit midpoint (BJD)

2,457,219.8229

Photometric dip

Transit produces a flux drop of 374 ppm lasting ≈ 3.94 h.

Extended Orbital Architecture

Planet / star radius ratio

0.016900

Semi-major axis / stellar radius

6.240

Impact parameter (b)

0.430

Transit mid-time (BJD)

2,457,219.8229

Angular separation (arcsec)

0.06210

Eq. Temperature

1,711K

(1438 °C)

Insolation (S⊕)

—

Earth = 1.00

Earth Similarity (ESI)

0.126

0 = alien, 1 = Earth-identical

Insufficient insolation data — the dayside is scorched.

Discovery Paper

Primary reference

Livingston et al. 2018

Instrument

Kepler CCD Array

Publication

2018-12

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: K2-278

Spectral Class

F-type yellow-white

Effective Temperature

6,747 K — hotter than the Sun (5,778 K)

Estimated Age

—

Stellar Radius

1.610 R☉

Stellar Mass

1.400 M☉

Metallicity [Fe/H]

0.00

Extended Stellar Properties

Surface gravity (log g)

4.170 dex

Stellar density

0.413 g/cm³

Metallicity ratio

[Fe/H]

Distance

786.44 parsec

Light-years 2,565.02 ly

V-band magnitude

13.45 mag

Voyager-speed travel 45,234,090 yr

Multi-band Host Photometry — 12 bands

Astrometric Data

Parallax

1.243 mas

Total Proper Motion

21.556 mas/yr

PM Right Ascension

18.26 mas/yr

PM Declination

-11.46 mas/yr

Galactic Cartesian (pc)

x = -0.889 · y = -0.383 · z = -0.250

Equatorial (J2000)

RA 203.30187° · Dec -14.50411°

Galactic ℓ, b

317.885° · 47.151°

Ecliptic λ, β

206.891° · -4.442°

HTM-20 index

853615274