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K2-18 Overview

  • Star: K2-18
    • Stellar Radius: 0.44 Solar Radius
    • Stellar Effective Temperature: 3464.00 K
    • Planet: K2-18 c
      • Disposition Confirmed Controversial
    • Planet: K2-18 b
      • Disposition Confirmed
      • Planet Radius 0.211 Jupiter Radius

K2-18 Architecture & Discovery Information

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
K2-18 K2-18 c 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)
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
mV 13.477±0.042
mTESS 11.2373000±0.0073698
mJ 9.763±0.028
mH 9.135±0.026
mKs 8.899±0.019
mKep 12.473
mW1 8.769±0.023
mW2 8.668±0.020
mW3 8.552±0.025
mW4 8.587±0.379
mGaia 12.415400±0.000502
mB 14.991±0.032
mg 15.1354000±0.0045191
mi 11.8579000±0.0008067
mr 13.0855000±0.0021847
mu 16.7222000±0.0085568
mz 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
Teff
(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
L✶
(log10(L⦿))
---
-1.60+0.03-0.04
-1.59122+0.09407-0.12025
 --- --- --- --- --- --- --- --- --- ---
ρ✶
(g/cm3)
--- --- 7.0731831±0.3041996 --- --- --- 7.87±1.26 --- --- --- --- --- ---
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] --- --- --- ---
S Index
0.5806 --- --- --- --- --- --- --- --- --- --- --- ---
CAII LOG RHK
-5.183 --- --- --- --- --- --- --- --- --- --- --- ---
Sp. T
--- --- --- --- --- --- M2.5 V --- --- --- --- --- ---
γ
(km/s)
--- --- --- --- --- 0.6537±0.0009 --- --- --- --- --- --- ---
Prot
(days)
--- --- --- --- 39.63±0.50 38.6±0.5 --- --- --- --- --- --- ---
Print
Status
Confirmed Planet
Controversial
Detected By
Radial Velocity
Tools
Planetary Systems
K2 Names
K2 Planets and Candidates
Source Cloutier et al. 2017
Teq
(K)
363±14
Mp sin i
(M⨁)
7.51±1.33
Mp sin i
(MJup)
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
Print
Status
Confirmed Planet
Detected By
Radial Velocity, Transit
Tools
Planetary Systems
Transit Prediction Service
TOI
K2 Names
K2 Planets and Candidates
Transit
NExoList: JWST
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
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
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
TC
(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)
Teq
(K)
284±15
281.0+14.0-12.0
 254.9±3.9 235±9 --- --- 272±15 --- 260.441655848903 --- ---
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 --- ---
Rp
(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
Rp
(RJup)
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
ω
(deg)
-5.70+46.40-33.80
 --- --- --- --- --- --- --- --- --- ---
Mp
(M⨁)
8.920+1.700-1.600
7.2+1.5-1.4
 8.63±1.35 7.96±1.91 --- --- --- --- --- --- ---
Mp
(MJup)
0.02807+0.00535-0.00503
0.023+0.005-0.004
 0.0272±0.0042 0.0250±0.0060 --- --- --- --- --- --- ---
e
0.20±0.08 --- --- <0.43 0 --- --- --- --- --- ---
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 --- --- --- --- --- --- ---
K
(m/s)
3.55+0.57-0.58
 --- --- 3.18±0.71 --- --- --- --- --- --- ---
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 --- --- --- ---
b
--- --- 0.641±0.015 ---
0.601+0.013-0.011
 --- --- --- --- --- 0.68
Rp/R✶
--- --- 0.05375±0.00012 ---
0.05295+0.00061-0.00059
 0.0517±0.0021 ---
0.0517 +0.0017-0.0038
--- --- 0.05389
a/R✶
--- --- --- --- --- --- 83.83±9.03
94.3 +14.6-6.6
--- --- ---
i
(deg)
--- --- ---
89.5785+0.0079-0.0088
89.5785+0.0079-0.0088
 --- --- --- --- --- ---
Print
Known Objects
2 Confirmed Planets
1 K2 Targets
2 2MASS Point Source Catalog
Data Files
1 K2 Time Series
2 Associated Literature Data
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  • Candidate
  • False Positive Planet
  • Controversial
  • False Positive
  • Aliases
  • Data Access
  • Transit Prediction Service
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