K2-18

Name	Orbital Separation	Planet Size	Method	Year	Reference	Disposition
K2-18
K2-18 c	8.96 d	> 7.51 M_⨁	Radial Velocity	2017	Cloutier et al. 2017	Confirmed Planet
K2-18 b	32.94 d	2.37 R_⨁	Transit	2015	Montet et al. 2015	Confirmed Planet

Exoplanet Archive Notes (4)

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K2-18

Rotation period uncertainty calculated as average from asymmetric uncertainties. (Cloutier et al. 2017)

K2-18 c

Equilibrium temperature was calculated assuming a Bond albedo of 0.3. (Cloutier et al. 2017)
Planet flagged as controversial. (Sarkis et al. 2018)

K2-18 b

Equilibrium temperature was calculated assuming a Bond albedo of 0.3. Time of inferior conjunction entered under mid-transit time. (Cloutier et al. 2017)

K2-18 Stellar Parameters (13 Solutions)

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RA: 11h30m14.43s

Dec: +07d35m16.19s

Distance: 38.02660±0.07955 pc

Parallax: 26.2686000±0.0545906 mas

Ecliptic Latitude: 4.01942 deg

Ecliptic Longitude: 170.16732 deg

Galactic Latitude: 62.57509 deg

Galactic Longitude: 254.63265 deg

Total Proper Motion: 155.5222618±0.0691090 mas/yr

Proper Motion (RA): -80.3765000±0.0834003 mas/yr

Proper Motion (Dec): -133.142000±0.063101 mas/yr

Photometry: m_V
13.477±0.042; m_TESS
11.2373000±0.0073698; m_J
9.763±0.028; m_H
9.135±0.026; m_Ks
8.899±0.019; m_Kep
12.473; m_W1
8.769±0.023; m_W2
8.668±0.020; m_W3
8.552±0.025; m_W4
8.587±0.379; m_Gaia
12.415400±0.000502; m_B
14.991±0.032; m_g
15.1354000±0.0045191; m_i
11.8579000±0.0008067; m_r
13.0855000±0.0021847; m_u
16.7222000±0.0085568; m_z
11.5166000±0.0043013

Abundances (Hypatia Catalog): [Fe/H] -0.01±0.02 dex; [Mg/H] 0.03±0.07 dex; [Si/H] -0.07±0.05 dex

Mission: K2 : Observed in Campaign 1

Tools: Planetary Systems; ExoFOP Target Overview Page; IRSA Finding Chart; TOI; K2 Names; K2 Planets and Candidates; K2 Targets; Stellar Hosts; K2 Time Series

Source	Howard et al. 2025	Benneke et al. 2019	TICv8	Gaia DR2	Sarkis et al. 2018	Cloutier et al. 2017	Benneke et al. 2017	Crossfield et al. 2016	Montet et al. 2015	Kruse et al. 2019	ExoFOP	Barros et al. 2016	Vanderburg et al. 2016
T_eff (K)	3449.0±70.0	3457±39	3464.0±157.0	3856.180+289.595-245.180	3457±39	3457±39	3457±39	3496±91	3503±60	---	3464±157	---	3440
M_✶ (M_⦿)	0.32±0.06	0.4951±0.0043	0.440668±0.020249	---	0.359±0.047	0.359±0.047	0.359±0.047	0.420±0.070	0.413±0.043	---	---	---	---
R_✶ (R_⦿)	0.468±0.019	0.4445±0.0148	0.4445160±0.0131784	---	0.411±0.038	0.411±0.038	0.411±0.038	0.400±0.060	0.394±0.038	0.249 +0.050-0.027	0.444516003131866±0.013178400000000	---	0.36
log g (log₁₀(cm/s²))	4.6±0.2	---	4.7864000±0.0057881	---	---	---	---	4.858±0.062	---	---	4.78640000±0.00578809	---	---
Metallicity (dex)	0.0±0.1 [Fe/H]	---	---	---	0.12±0.16 [Fe/H]	---	0.123±0.157 [Fe/H]	---	0.090±0.090 [Fe/H]	---	---	---	---
ρ_✶ (g/cm³)	---	---	7.0731831±0.3041996	---	---	---	7.87±1.26	---	---	---	---	---	---
Sp. T	---	---	---	---	---	---	M2.5 V	---	---	---	---	---	---
γ (km/s)	---	---	---	---	---	0.6537±0.0009	---	---	---	---	---	---	---
P_rot (days)	---	---	---	---	39.63±0.50	38.6±0.5	---	---	---	---	---	---	---
L_✶ (log₁₀(L_⦿))	---	-1.60+0.03-0.04	-1.59122+0.09407-0.12025	---	---	---	---	---	---	---	---	---	---
S Index	0.5806	---	---	---	---	---	---	---	---	---	---	---	---
CAII LOG RHK	-5.183	---	---	---	---	---	---	---	---	---	---	---	---

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K2-18 c Planetary Parameters (1 Solution)

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Status: Confirmed Planet; Controversial

Detected By: Radial Velocity

Tools: Planetary Systems; K2 Names; K2 Planets and Candidates

Source	Cloutier et al. 2017
T_eq (K)	363±14
M_p sin i (M_⨁)	7.51±1.33
M_p sin i (M_Jup)	0.0236±0.0042
e	<0.47
P (days)	8.962±0.008
K (m/s)	4.63±0.72
a (au)	0.060±0.003

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K2-18 b Planetary Parameters (11 Solutions)

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Status: Confirmed Planet

Detected By: Radial Velocity, Transit

Tools: Planetary Systems; Transit Prediction Service; TOI; K2 Names; K2 Planets and Candidates; Transit; Atmospheric Spectroscopy

Source	Sarkis et al. 2018	Howard et al. 2025	Benneke et al. 2019	Cloutier et al. 2017	Benneke et al. 2017	Crossfield et al. 2016	Montet et al. 2015	Kruse et al. 2019	ExoFOP	Barros et al. 2016	Vanderburg et al. 2016
a/R_✶	---	---	---	---	---	---	83.83±9.03	94.3 +14.6-6.6	---	---	---
P (days)	32.939623+0.000095-0.000100	32.94112±0.00081	32.940045±0.000010	32.93963±0.00010	32.939614+0.000101-0.000084	32.9418±0.0021	32.94488±0.00281	32.94171 +0.00080-0.00084	32.9373716794679±0.0035861705000	32.92801934	32.947328
R_p (R_⨁)	2.37±0.22	2.461+0.079-0.045	2.610±0.087	2.38±0.22	2.279+0.026-0.025	2.28±0.36	2.24±0.23	1.40 +0.29-0.18	2.53362938949389±1.22969880000000	---	2.17
R_p (R_Jup)	0.211±0.020	0.2196+0.0070-0.0040	0.2328±0.0078	0.212±0.020	0.2033+0.0023-0.0022	0.203±0.032	0.200±0.021	0.12 +0.026-0.016	0.226035663483111±0.109706567698881	---	0.194
R_p/R_✶	---	---	0.05375±0.00012	---	0.05295+0.00061-0.00059	0.0517±0.0021	---	0.0517 +0.0017-0.0038	---	---	0.05389
δ (%)	---	---	---	---	---	---	0.285	0.3098 +0.0062-0.0065	0.319214294388034±0.025673434000000	0.354±0.021	0.311
T₁₄ (hours)	---	---	---	---	2.663+0.023-0.027	2.682±0.000	---	2.62800+0.05520-0.06720	2.30595891350263±0.63494870000000	3.77600+0.25600-0.25600	2.97000
T_C (days)	2457264.39144±0.00065 (BJD)	2456836.17187±0.00057 (BJD)	2457725.551189+0.000067-0.000068 (BJD-UTC)	2457264.39157±0.00059 (BJD)	2457264.39144+0.00059-0.00066 (BJD)	2456836.1719±0.0011 (BJD-TDB)	2456836.1849±0.0027 (BJD)	2456836.17194 +0.00059-0.00064 (BJD)	2459537.25009600±0.00227222 (BJD)	2456836.179795 (BJD)	2456836.171 (BJD)
b	---	---	0.641±0.015	---	0.601+0.013-0.011	---	---	---	---	---	0.68
S (S_⨁)	---	1.48+0.31-0.24	1.005+0.084-0.079	---	1.05+0.22-0.20	0.950±0.320	---	---	1.08733356166729	---	---
e	0.20±0.08	---	---	<0.43	0	---	---	---	---	---	---
i (deg)	---	---	---	89.5785+0.0079-0.0088	89.5785+0.0079-0.0088	---	---	---	---	---	---
a (au)	0.1429+0.0060-0.0065	---	0.15910+0.00046-0.00047	0.143±0.006	0.1429+0.0060-0.0065	0.1506±0.0084	0.1491±0.0055	---	---	---	---
T_eq (K)	284±15	281.0+14.0-12.0	254.9±3.9	235±9	---	---	272±15	---	260.441655848903	---	---
M_p (M_⨁)	8.920+1.700-1.600	7.2+1.5-1.4	8.63±1.35	7.96±1.91	---	---	---	---	---	---	---
M_p (M_Jup)	0.02807+0.00535-0.00503	0.023+0.005-0.004	0.0272±0.0042	0.0250±0.0060	---	---	---	---	---	---	---
ρ (g/cm³)	4.11+1.72-1.18	2.28+0.63-0.51	2.67+0.52-0.47	3.3±1.2	---	---	---	---	---	---	---
ω (deg)	-5.70+46.40-33.80	---	---	---	---	---	---	---	---	---	---
K (m/s)	3.55+0.57-0.58	---	---	3.18±0.71	---	---	---	---	---	---	---

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Nearby Data (within 30 arcseconds) Browse Nearby Data

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Known Objects: 2 Confirmed Planets; 1 K2 Targets; 2 2MASS Point Source Catalog

Data Files: 1 K2 Time Series; 2 Associated Literature Data

Bibliography (18 References)

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Planet Masses, Radii, and Orbits from NASA's K2 Mission
Howard et al. 2025 Reference Overview
New Constraints on DMS and DMDS in the Atmosphere of K2-18 b from JWST MIRI
Madhusudhan et al. 2025 Reference Overview
Carbon-bearing Molecules in a Possible Hycean Atmosphere
Madhusudhan et al. 2023 Reference Overview
Water Vapor and Clouds on the Habitable-zone Sub-Neptune Exoplanet K2-18b
Benneke et al. 2019 Reference Overview
The Revised TESS Input Catalog and Candidate Target List
TICv8 Reference Overview
Detection of Hundreds of New Planet Candidates and Eclipsing Binaries in K2 Campaigns 0-8
Kruse et al. 2019 Reference Overview
Water vapour in the atmosphere of the habitable-zone eight-Earth-mass planet K2-18 b
Tsiaras et al. 2019 Reference Overview
Gaia Data Release 2
Gaia DR2 Reference Overview
The CARMENES Search for Exoplanets around M Dwarfs: A Low-mass Planet in the Temperate Zone of the Nearby K2-18
Sarkis et al. 2018 Reference Overview
Characterization of the K2-18 multi-planetary system with HARPS. A habitable zone super-Earth and discovery of a second, warm super-Earth on a non-coplanar orbit
Cloutier et al. 2017 Reference Overview
ExoFOP TOI Table
ExoFOP
Spitzer Observations Confirm and Rescue the Habitable-zone Super-Earth K2-18b for Future Characterization
Benneke et al. 2017 Reference Overview
New planetary and eclipsing binary candidates from campaigns 1-6 of the K2 mission
Barros et al. 2016 Reference Overview
197 Candidates and 104 Validated Planets in K2’s First Five Fields
Crossfield et al. 2016 Reference Overview
The K2 Ecliptic Plane Input Catalog (EPIC) and Stellar Classifications of 138,600 Targets in Campaigns 1-8
EPIC Catalog Reference Overview
Planetary Candidates from the First Year of the K2 Mission
Vanderburg et al. 2016 Reference Overview
Stellar and Planetary Properties of K2 Campaign 1 Candidates and Validation of 17 Planets, Including a Planet Receiving Earth-like Insolation
Montet et al. 2015 Reference Overview
2MASS All-Sky Catalog of Point Sources
2MASS Point Source Catalog Reference Overview

Legend

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System
Star
Confirmed
Candidate
False Positive Planet
Controversial
False Positive

Aliases
Data Access
Transit Prediction Service
Time Series
Kepler | K2

External Link
Search
Browse
Download

Debug Info

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https://vmexoweb2.ipac.caltech.edu/data/Overviews_2.0/7/K2-18.json

Catalog Parameters

RA

ra

11h30m14.43s

Dec

dec

+07d35m16.19s

β

elat

4.01942

λ

elon

170.16732

b

glat

62.57509

l

glon

254.63265

m_V

sy_vmag

13.477±0.042

m_TESS

sy_tmag

11.2373000±0.0073698

m_J

sy_jmag

9.763±0.028

m_H

sy_hmag

9.135±0.026

m_Ks

sy_kmag

8.899±0.019

m_Kep

sy_kepmag

12.473

m_W1

sy_w1mag

8.769±0.023

m_W2

sy_w2mag

8.668±0.020

m_W3

sy_w3mag

8.552±0.025

m_W4

sy_w4mag

8.587±0.379

sy_icmag

no_data

m_Gaia

sy_gaiamag

12.415400±0.000502

m_B

sy_bmag

14.991±0.032

m_g

sy_gmag

15.1354000±0.0045191

m_i

sy_imag

11.8579000±0.0008067

m_r

sy_rmag

13.0855000±0.0021847

m_u

sy_umag

16.7222000±0.0085568

m_z

sy_zmag

11.5166000±0.0043013

μ

sy_pm

155.5222618±0.0691090

μ_δ

sy_pmdec

-133.142000±0.063101

μ_α

sy_pmra

-80.3765000±0.0834003

π

sy_plx

26.2686000±0.0545906

Distance

sy_dist

38.02660±0.07955

Set Parameters

R_✶

st_rad

0.400±0.060

T_eff

st_teff

3496±91

K2-18 Overview

K2-18 Architecture & Discovery Information

K2-18