Key parameters at a glance

A radius of 3.44 Earth radii
A mass of 24.50 Earth masses
Surface gravity around 2.07 g
An orbital period of 3.485 days
Semi-major axis 0.0287 AU
Equilibrium temperature 494 K (221 °C)
Distance from Earth 146.63 light-years
Earth Similarity Index 0.485
Travel time at Voyager 1 speed 2,585,790 years
Almost certainly tidally locked to its host star given the close orbit

Context from the literature

K2-25 is a young red dwarf star located in the Hyades cluster. There is a single known Neptune-sized planet in a 3.5 day orbit.

Excerpted from Wikipedia · full article

K2-25 b Planet Profile

Physical Specs

Radius

3.44 R⊕

Radius (Jupiter)

0.306 R♃

Mass

24.50 M⊕

Mass (Jupiter)

0.077 M♃

Density

3.31 g/cm³

Surface Gravity

2.07 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.485

HZ Position Inner

Controversial No

Discovery

Year 2015

Method Transit

Facility K2

Telescope 0.95 m Kepler Telescope

Size rank in cohort

Rank by radius

#200of 1978

top 10.1%

This planet

3.44R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

Kepler-223 c 3.44 R⊕ KOI-142 b 3.44 R⊕ TOI-1723 b 3.44 R⊕

Metric	Earth	K2-25 b	Jupiter
Radius (R⊕)	1.00	3.44	11.21
Mass (M⊕)	1.00	24.50	317.83
Density (g/cm³)	5.51	3.31	1.33
Surface Gravity (g)	1.00	2.07	2.53
Insolation (S⊕)	1.00	9.91	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	24.500 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

TIC

TIC 434226736

Gaia DR2

Gaia DR2 3311804515502788352

Gaia DR3

Gaia DR3 3311804515502788352

System

K2-25

Percentile among Sub-Neptune cohort

Radius 3.440 R⊕ · percentile 90 / cohort 1978

Mass 24.500 M⊕ · percentile 96 / cohort 1978

Orbital period 3.48 d · percentile 6 / cohort 1946

Distance 44.96 pc · percentile 11 / cohort 1975

ESI 0.485 · percentile 69 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

3.485 days

Semi-major axis

0.0287 AU

Eccentricity

0.428

Inclination

87.16 °

Year Length

A year here lasts approximately 3.48 Earth days (1.0% of a terrestrial year) on a highly eccentric trajectory at a mean orbital distance of 0.0287 AU.

Transit Fingerprint

Depth

1.155 %

Duration

0.764 h

Impact parameter b

0.628

Rp / R★

0.107500

Transit midpoint (BJD)

2,458,515.6421

Photometric dip

Transit produces a flux drop of 11,550 ppm lasting ≈ 0.76 h.

Extended Orbital Architecture

Planet / star radius ratio

0.107500

Semi-major axis / stellar radius

21.090

Impact parameter (b)

0.628

RV semi-amplitude (K)

27.900 m/s

Transit mid-time (BJD)

2,458,515.6421

Long. of periastron (ω)

120.00°

Sky-projected obliquity (λ)

3.00°

True obliquity (ψ)

17.00°

Angular separation (arcsec)

0.63800

Eq. Temperature

494K

(221 °C)

Insolation (S⊕)

9.91

Earth = 1.00

Earth Similarity (ESI)

0.485

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.

Detection Signatures

Transit photometry

A transit dip has been observed from at least one telescope.

Radial velocity

Stellar wobble has been measured spectroscopically.

Discovery Paper

Primary reference

Mann et al. 2016

Instrument

Kepler CCD Array

Publication

2016-02

Observation locale

Space

Discovery cohort

Planets confirmed in 2015 at K2 (12 shown).

K2-18 b · Sub-Neptune K2-9 b · Sub-Neptune K2-3 d · Super-Earth K2-3 c · Super-Earth K2-21 c · Sub-Neptune K2-5 c · Sub-Neptune K2-13 b · Super-Earth K2-3 b · Sub-Neptune K2-17 b · Sub-Neptune K2-21 b · Super-Earth K2-16 c · Sub-Neptune K2-5 b · Super-Earth

Host System: K2-25

Spectral Class

M-type red dwarf

Effective Temperature

3,207 K — cooler than the Sun (5,778 K)

Estimated Age

0.73 Gyr — younger than the Sun (4.6 Gyr)

Stellar Radius

0.293 R☉

Stellar Mass

0.263 M☉

Metallicity [Fe/H]

0.15

Extended Stellar Properties

Surface gravity (log g)

4.944 dex

Stellar density

14.600 g/cm³

Systemic radial velocity

38.64 km/s

Rotational v·sin i

8.80 km/s

Rotation period

1.88 days

Metallicity ratio

[Fe/H]

Distance

44.96 parsec

Light-years 146.63 ly

V-band magnitude

16.21 mag

Voyager-speed travel 2,585,790 yr

Multi-band Host Photometry — 17 bands

Astrometric Data

Parallax

22.215 mas

Total Proper Motion

123.517 mas/yr

PM Right Ascension

122.15 mas/yr

PM Declination

-18.34 mas/yr

Galactic Cartesian (pc)

x = 0.434 · y = 0.862 · z = 0.263

Equatorial (J2000)

RA 63.27393° · Dec 15.24770°

Galactic ℓ, b

178.256° · -25.293°

Ecliptic λ, β

64.138° · -5.825°

HTM-20 index

1465639053

Wikipedia → Image: Wikimedia Commons · NOIRLab/NSF/AURA/Digitized Sky Survey 2 · CC BY 4.0