Key parameters at a glance

A radius of 2.07 Earth radii
A mass of 4.94 Earth masses
Surface gravity around 1.15 g
An orbital period of 7.955 days
Semi-major axis 0.0677 AU
Equilibrium temperature 552 K (279 °C)
Distance from Earth 421.90 light-years
Earth Similarity Index 0.487
Travel time at Voyager 1 speed 7,440,248 years
Almost certainly tidally locked to its host star given the close orbit

1 sibling around K2-154

K2-154 c 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
K2-154 b	Super-Earth	1.99	4.62	3.676	715	2018
K2-154 c this	Sub-Neptune	2.07	4.94	7.955	552	2018

K2-154 c Planet Profile

Physical Specs

Radius

2.07 R⊕

Radius (Jupiter)

0.185 R♃

Mass

4.94 M⊕

Mass (Jupiter)

0.016 M♃

Density

3.06 g/cm³

Surface Gravity

1.15 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.487

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

#1860of 1978

top 94.0%

This planet

2.07R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

TOI-262 b 2.07 R⊕ Kepler-654 b 2.07 R⊕ Kepler-988 b 2.07 R⊕

Metric	Earth	K2-154 c	Jupiter
Radius (R⊕)	1.00	2.07	11.21
Mass (M⊕)	1.00	4.94	317.83
Density (g/cm³)	5.51	3.06	1.33
Surface Gravity (g)	1.00	1.15	2.53
Insolation (S⊕)	1.00	20.50	0.037

Star Catalogue Identifiers

TIC

TIC 175371068

Gaia DR2

Gaia DR2 3683121446312149504

Gaia DR3

Gaia DR3 3683121446312149504

System

K2-154

Percentile among Sub-Neptune cohort

Radius 2.070 R⊕ · percentile 6 / cohort 1978

Mass 4.940 M⊕ · percentile 7 / cohort 1978

Orbital period 7.95 d · percentile 26 / cohort 1946

Distance 129.36 pc · percentile 24 / cohort 1975

ESI 0.487 · percentile 69 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

7.955 days

Semi-major axis

0.0677 AU

Eccentricity

—

Inclination

— °

Year Length

A year here lasts approximately 7.95 Earth days (2.2% of a terrestrial year) at a mean orbital distance of 0.0677 AU.

Transit Fingerprint

Depth

0.110 %

Duration

2.100 h

Impact parameter b

0.420

Rp / R★

0.030000

Transit midpoint (BJD)

2,457,584.3376

Photometric dip

Transit produces a flux drop of 1,100 ppm lasting ≈ 2.10 h.

Extended Orbital Architecture

Planet / star radius ratio

0.030000

Semi-major axis / stellar radius

24.900

Impact parameter (b)

0.420

Transit mid-time (BJD)

2,457,584.3376

Angular separation (arcsec)

0.52300

Eq. Temperature

552K

(279 °C)

Insolation (S⊕)

20.50

Earth = 1.00

Earth Similarity (ESI)

0.487

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

Hirano 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: K2-154

Spectral Class

M-type red dwarf

Effective Temperature

4,097 K — cooler than the Sun (5,778 K)

Estimated Age

—

Stellar Radius

0.630 R☉

Stellar Mass

0.650 M☉

Metallicity [Fe/H]

0.21

Extended Stellar Properties

Surface gravity (log g)

4.650 dex

Stellar density

3.250 g/cm³

Systemic radial velocity

14.30 km/s

Metallicity ratio

[Fe/H]

Distance

129.36 parsec

Light-years 421.90 ly

V-band magnitude

13.86 mag

Voyager-speed travel 7,440,248 yr

Multi-band Host Photometry — 17 bands

Astrometric Data

Parallax

7.702 mas

Total Proper Motion

34.576 mas/yr

PM Right Ascension

0.75 mas/yr

PM Declination

-34.57 mas/yr

Galactic Cartesian (pc)

x = -0.987 · y = -0.156 · z = -0.047

Equatorial (J2000)

RA 189.00152° · Dec -2.66962°

Galactic ℓ, b

295.214° · 59.971°

Ecliptic λ, β

189.316° · 1.114°

HTM-20 index

295760025