Key parameters at a glance

A radius of 3.21 Earth radii
A mass of 10.40 Earth masses
Surface gravity around 1.01 g
An orbital period of 29.627 days
Distance from Earth 814.55 light-years
Earth Similarity Index 0.617
Travel time at Voyager 1 speed 14,364,562 years

1 sibling around K2-172

K2-172 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
K2-172 b	Super-Earth	1.67	3.42	14.317	—	2018
K2-172 c this	Sub-Neptune	3.21	10.40	29.627	—	2018

K2-172 c Planet Profile

Physical Specs

Radius

3.21 R⊕

Radius (Jupiter)

0.286 R♃

Mass

10.40 M⊕

Mass (Jupiter)

0.033 M♃

Density

1.73 g/cm³

Surface Gravity

1.01 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.617

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

#347of 1978

top 17.5%

This planet

3.21R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

Kepler-1674 b 3.21 R⊕ K2-370 b 3.21 R⊕ MOA-2009-BLG-266L b 3.21 R⊕

Metric	Earth	K2-172 c	Jupiter
Radius (R⊕)	1.00	3.21	11.21
Mass (M⊕)	1.00	10.40	317.83
Density (g/cm³)	5.51	1.73	1.33
Surface Gravity (g)	1.00	1.01	2.53
Insolation (S⊕)	1.00	—	0.037

Star Catalogue Identifiers

TIC

TIC 188507501

Gaia DR2

Gaia DR2 2602237602799035008

Gaia DR3

Gaia DR3 2602237602799035008

System

K2-172

Percentile among Sub-Neptune cohort

Radius 3.206 R⊕ · percentile 82 / cohort 1978

Mass 10.400 M⊕ · percentile 76 / cohort 1978

Orbital period 29.63 d · percentile 73 / cohort 1946

Distance 249.74 pc · percentile 32 / cohort 1975

ESI 0.617 · percentile 84 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

29.627 days

Semi-major axis

— AU

Eccentricity

—

Inclination

89.50 °

Year Length

A year here lasts approximately 29.63 Earth days (8.1% of a terrestrial year).

Transit Fingerprint

Depth

0.130 %

Duration

4.992 h

Impact parameter b

0.090

Rp / R★

0.033824

Transit midpoint (BJD)

2,456,993.5398

Photometric dip

Transit produces a flux drop of 1,302 ppm lasting ≈ 4.99 h.

Extended Orbital Architecture

Planet / star radius ratio

0.033824

Semi-major axis / stellar radius

44.209

Impact parameter (b)

0.090

Transit mid-time (BJD)

2,456,993.5398

Eq. Temperature

—

Insolation (S⊕)

—

Earth = 1.00

Earth Similarity (ESI)

0.617

0 = alien, 1 = Earth-identical

Discovery Paper

Primary reference

Mayo 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: K2-172

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

5,569 K — cooler than the Sun (5,778 K)

Estimated Age

—

Stellar Radius

0.869 R☉

Stellar Mass

0.934 M☉

Metallicity [Fe/H]

-0.06

Extended Stellar Properties

Surface gravity (log g)

4.610 dex

Stellar density

2.181 g/cm³

Systemic radial velocity

22.44 km/s

Metallicity ratio

[Fe/H]

Distance

249.74 parsec

Light-years 814.55 ly

V-band magnitude

12.50 mag

Voyager-speed travel 14,364,562 yr

Multi-band Host Photometry — 12 bands

Astrometric Data

Parallax

3.976 mas

Total Proper Motion

56.091 mas/yr

PM Right Ascension

-52.93 mas/yr

PM Declination

-18.56 mas/yr

Galactic Cartesian (pc)

x = 0.887 · y = -0.408 · z = -0.217

Equatorial (J2000)

RA 335.30814° · Dec -12.55698°

Galactic ℓ, b

47.929° · -51.985°

Ecliptic λ, β

332.551° · -2.136°

HTM-20 index

47931094