Registry · exoplanet

K2-18 b

Exoplanet 349 papers

harvesting The full record is being pulled from the archives right now — measurement tables, the Gaia row, catalogue photometry. This page will fill itself in.

Right ascension: 11h 30m 14.43s
Declination: +07° 35′ 16.2″
Galactic l, b: 254.63, 62.58
Magnitude V: 13.48
Distance: 38.027 pc

Also known as

1 identifiers

K2-18b

Planet

NASA Exoplanet Archive, composite parameters

Host star	K2-18 · dM2.5
Discovery	Transit, 2015 · K2
Orbital period	32.9396 d
Semi-major axis	0.1429 au
Eccentricity	0.2
Radius	2.37 R⊕ · 0.2114 R♃
Mass	8.92 M⊕ · 0.02807 M♃
Density	4.11 g/cm³
Equilibrium temperature	284 K
System distance	38.027 pc

Published measurements

6 quantities measured more than once

One object can carry a dozen published estimates of the same quantity. The register keeps them side by side rather than picking a winner — the citation is part of the value.

Mass 4 values

Value	Unit	Uncertainty	Band / method	Source	Reference	Year
7.2	M_earth	± 1.5	Transit	NASA Exoplanet Archive	Howard et al. 2025	2025
8.63	M_earth	± 1.35	Transit	NASA Exoplanet Archive	Benneke et al. 2019	2019
8.92	M_earth	± 1.7	Transit	NASA Exoplanet Archive	Sarkis et al. 2018	2018
7.96	M_earth	± 1.91	Transit	NASA Exoplanet Archive	Cloutier et al. 2017	2017

Radius 10 values

Value	Unit	Uncertainty	Band / method	Source	Reference	Year
2.461	R_earth	± 0.079	Transit	NASA Exoplanet Archive	Howard et al. 2025	2025
2.61	R_earth	± 0.087	Transit	NASA Exoplanet Archive	Benneke et al. 2019	2019
1.4	R_earth	± 0.29	Transit	NASA Exoplanet Archive	Kruse et al. 2019	2019
2.37	R_earth	± 0.22	Transit	NASA Exoplanet Archive	Sarkis et al. 2018	2018
2.38	R_earth	± 0.22	Transit	NASA Exoplanet Archive	Cloutier et al. 2017	2017
2.279	R_earth	± 0.026	Transit	NASA Exoplanet Archive	Benneke et al. 2017	2017
2.17	R_earth		Transit	NASA Exoplanet Archive	Vanderburg et al. 2016	2016
2.28	R_earth	± 0.36	Transit	NASA Exoplanet Archive	Crossfield et al. 2016	2016
2.533629	R_earth	± 1.23	Transit	NASA Exoplanet Archive	ExoFOP	2015
2.24	R_earth	± 0.23	Transit	NASA Exoplanet Archive	Montet et al. 2015	2015

Orbital period 11 values

Value	Unit	Uncertainty	Band / method	Source	Reference	Year
32.94112	d	± 0.00081	Transit	NASA Exoplanet Archive	Howard et al. 2025	2025
32.94004	d	± 1.00e-05	Transit	NASA Exoplanet Archive	Benneke et al. 2019	2019
32.94171	d	± 0.0008	Transit	NASA Exoplanet Archive	Kruse et al. 2019	2019
32.93962	d	± 9.50e-05	Transit	NASA Exoplanet Archive	Sarkis et al. 2018	2018
32.93963	d	± 0.0001	Transit	NASA Exoplanet Archive	Cloutier et al. 2017	2017
32.93961	d	± 0.000101	Transit	NASA Exoplanet Archive	Benneke et al. 2017	2017
32.94733	d		Transit	NASA Exoplanet Archive	Vanderburg et al. 2016	2016
32.9418	d	± 0.0021	Transit	NASA Exoplanet Archive	Crossfield et al. 2016	2016
32.92802	d		Transit	NASA Exoplanet Archive	Barros et al. 2016	2016
32.93737	d	± 0.003586	Transit	NASA Exoplanet Archive	ExoFOP	2015
32.94488	d	± 0.00281	Transit	NASA Exoplanet Archive	Montet et al. 2015	2015

Semi-major axis 6 values

Value	Unit	Uncertainty	Band / method	Source	Reference	Year
0.1591	au	± 0.00046	Transit	NASA Exoplanet Archive	Benneke et al. 2019	2019
0.1429	au	± 0.006	Transit	NASA Exoplanet Archive	Sarkis et al. 2018	2018
0.143	au	± 0.006	Transit	NASA Exoplanet Archive	Cloutier et al. 2017	2017
0.1429	au	± 0.006	Transit	NASA Exoplanet Archive	Benneke et al. 2017	2017
0.1506	au	± 0.0084	Transit	NASA Exoplanet Archive	Crossfield et al. 2016	2016
0.1491	au	± 0.0055	Transit	NASA Exoplanet Archive	Montet et al. 2015	2015

Eccentricity 3 values

Value	Uncertainty	Band / method	Source	Reference	Year
0.2	± 0.08	Transit	NASA Exoplanet Archive	Sarkis et al. 2018	2018
0.43		Transit	NASA Exoplanet Archive	Cloutier et al. 2017	2017
0		Transit	NASA Exoplanet Archive	Benneke et al. 2017	2017

Equilibrium temperature 6 values

Value	Unit	Uncertainty	Band / method	Source	Reference	Year
281	K	± 14	Transit	NASA Exoplanet Archive	Howard et al. 2025	2025
254.9	K	± 3.9	Transit	NASA Exoplanet Archive	Benneke et al. 2019	2019
284	K	± 15	Transit	NASA Exoplanet Archive	Sarkis et al. 2018	2018
235	K	± 9	Transit	NASA Exoplanet Archive	Cloutier et al. 2017	2017
260.44	K		Transit	NASA Exoplanet Archive	ExoFOP	2015
272	K	± 15	Transit	NASA Exoplanet Archive	Montet et al. 2015	2015

In the same field

within 9 arcmin · wider search

Object	Type	Separation	V
K2-18 c	Exoplanet	0.003074″	13.48
K2-18	HighPM*	2.41″	13.5
QSO B1127+078	QSO	188.3″	17.7
SDSS J112959.82+073817.0	QSO	282.6″	—
SDSS J112956.44+073712.4	QSO	291.6″	—
LEDA 4282403	AGN Candidate	333″	—
HD 99904	Star	513.7″	6.73

Provenance

where this card came from

Archive	Read at (UTC)	Record
Seeded from the bulk archive load; no per-object fetch yet.

Machine-readable: /api/v1/object/k2-18-b · Registry entry updated 2026-08-14.