Planet K2-18 b

Name K2-18 b
Planet Status Confirmed
Discovered in 2015
Mass 0.02807 ( -0.00503 +0.00535 ) MJ
Mass*sin(i)
Semi-Major Axis 0.1429 ( -0.0065 +0.006 ) AU
Orbital Period 32.939623 ( -0.0001 +9.5e-05 ) day
Eccentricity 0.2 (± 0.08)
ω -5.7 ( -33.8 +46.4 ) deg
Tperi
Radius 0.211 ( -0.02 +0.02 ) RJ
Inclination 89.5785 ( -0.0088 +0.0079 ) deg
Update 2021-02-05
Detection Method Primary Transit
Mass Detection Method Theoretical
Radius Detection Method Primary Transit
Primary transit 2457264.39144 (± 0.00065) JD
Secondary transit
λ
Impact Parameter b
Time Vr=0
Velocity Semiamplitude K 3.55 ( -0.58 +0.57 ) m/s
Calculated temperature 284.0 ( -15.0 +15.0 ) K
Measured temperature
Hottest point longitude
Geometric albedo
Surface gravity log(g/gH)
Alternate Names EPIC 201912552 b, 2MASS J11301450+0735180 b, EPIC 201912552.01, WISE J113014.45+073516.8 b

Star

K2-18
Name K2-18
Distance 38.07 ( -0.08 +0.08 ) pc
Spectral type M2.5 V
Apparent magnitude V 13.5
Mass 0.36 ( -0.05 +0.05 ) MSun
Age
Effective temperature 3457.0 ( -39.0 +39.0 ) K
Radius 0.41 ( -0.04 +0.04 ) RSun
Metallicity [Fe/H] 0.12 ( -0.16 +0.16 )
Detected Disc
Magnetic Field
RA2000 11:30:14.5
Dec2000 +07:35:18
Alternate Names EPIC 201912552, 2MASS J11301450+0735180, WISE J113014.45+073516.8
Planetary system
2 planets

More data

Atmospheric parameters

Temperatures

Data Source Type Result Value Result Figure Notes Reference

Molecules

Molecule Data Source Type Result Value Result Figure Notes Reference
CH4 Measurements Detected 2020 - MADHUSUDHAN N.
H2O Measurements Detected 2020 - MADHUSUDHAN N.
Measurements Detected 2019 - BENNEKE B.
Measurements Detected 2019 - TSIARAS A.
NH3 Measurements Detected 2020 - MADHUSUDHAN N.

Observability Predictor


Related publications

Modeling the Transmission and Emission Spectra of K2-18b: Determining the Surfaces of Exoplanets with Hydrogen Dominated Atmospheres
2023 NICHOLSON L., HOOD C., FORTNEY J. & YU X.
Res. Notes AAS, 7, 87
paper  

Characterising atmospheres of cloudy temperate mini-neptunes with JWST
2022 CONSTANTINOU S. & MADHUSUDHAN N.
MNRAS, 514, 2073
paper  

CAMEMBERT: A Mini-Neptunes General Circulation Model Intercomparison, Protocol Version 1.0.A CUISINES Model Intercomparison Project
2022 CHRISTIE D., MEE A., INNES H., NOTI P., CHARNAY B. et al.
Plan. Sci. J., 3, 261
paper  

Revisiting Radial Velocity Measurements of the K2-18 System with the Line-by-Line Framework
2022 RADICA M., ARTIGAU E., LEFRENIERE D., CADIEUX Ch., COOK N. et al.
MNRAS, 517, 5050
paper   arxiv  

1D atmospheric study of the temperate sub-Neptune K2-18b
2021 BLAIN D., CHARNAY B. & BEZARD B.
Astron. & Astrophys., 646, A15
paper  

How to identify exoplanet surfaces using atmospheric trace species in hydrogen-dominated atmospheres
2021 YU X., MOSES J., FORTNEY J. & ZHANG X.
ApJ, 914, 38
paper   arxiv

Deep Characterization of the Atmosphere of a Temperate Sub-Neptune
2021 HU R. et al.
JWST GO Programme
abstract

Chemical Disequilibrium in a Temperate Sub-Neptune
2021 MADHUSUDHAB N.
JWST GO Programme
abstract

How Deep Is the Ocean? Exploring the phase structure of water-rich sub-Neptunes
2021 NIXON M. & MADHUSUDHAN N.
MNRAS, 505, 3414
paper   arxiv  

Unveiling shrouded oceans on temperate sub-Neptunes via transit signatures of solubility equilibria vs. gas thermochemistry
2021 HU R., DAMIANIO M., SCHEUCHER M., KITE E., SEAGER S. & RAUER H.
ApJ. Letters, 921, L8
paper   arxiv  

Stellar surface inhomogeneities as a potential source of the atmospheric signal detected in the K2-18 b transmission spectrum
2021 BARCLAY Th., KOSTOV V., COLON K., QUINTANA E., SCHLIEDER J. et al.
Astron. J., accepted
arxiv

Photochemistry and Spectral Characterization of Temperate and Gas-rich Exoplanets
2021 HU R.
ApJ, 921, 27
paper  

The interior and atmosphere of the habitable-zone exoplanet K2-18b
2020 MADHUSUDHAN N., NIXON M., WELBANKS L., PIETTE A. & BOOTH R.
ApJ. Letters, accepted
arxiv  

Disentangling Atmospheric Compositions of K2-18 b with Next Generation Facilities
2020 CHANGEAT Q., EDWARDS B., AL-REFAIE A., TSIARAS A., WALDMANN I. & TINETTI G.
ApJ, submitted
arxiv  

Formation of secondary atmospheres on terrestrial planets by late disk accretion
2020 KRAL Q., DAVOULT J. & CHARNAY B.
Nature Astronomy, 4, 769
paper   arxiv  

Consistently Simulating a Wide Range of Atmospheric Scenarios for K2-18b with a Flexible Radiative Transfer Module
2020 SCHEUCHER M., WUNDERLICH F., GRENFELL J., GODOLT M., SCHREIER F. et al.
ApJ., 898, 44
paper  arxiv

Tidal evolution of exoplanetary systems hosting potentially habitable exoplanets. The cases of LHS-1140 b-c and K2-18 b-c
2020 GOMES G. & FERRAZ-MELLO S.
MNRAS, 494, 5082
paper   arxiv

On the Temperature Profiles and Emission Spectra of Mini-Neptune Atmospheres
2020 PIETTE A. & MADHUSUDHAN N.
ApJ, accepted
arxiv

The high-energy environment and atmospheric escape of the mini-Neptune K2-18 b
2020 dos SANTOS L., EHRENREICH D., BOURRIER V., ASTUDILLO-DEFRU N., BONFILS X. et al.
Astron. & Astrophys., 634, L4
paper  arxiv  

Water vapour in the atmosphere of the habitable- zone eight-Earth-mass planet K2-18 b
2019 TSIARAS A., WALDMANN I., TINETTI G., TENNYSON J. & YOURCHENKO S.
Nature Astronomy, in press, 3
paper  arxiv  

The weight of a world
2019 Anonymous
Nature Astronomy, 3, 875
paper  

The K2-18b Planetary System: Estimates of the Age and X-UV Irradiances of a Habitable Zone "Wet" Sub-Neptune Planet
2019 GUINAN E. & ENGIE S.
Res. Notes AAS, 3, 189
paper  

Mass-Radius relationship for M dwarf exoplanets: Comparing nonparametric and parametric methods
2019 KANODIA Sh., WOLFGANG A., STEFANSSON G., NING B. & MAHADEVAN S.
ApJ, submitted
arxiv  

Water Vapor on the Habitable-Zone Exoplanet K2-18b
2019 BENNEKE B., WONG I., PIAULET C., KNUTSON H., CROSSFIELD I. et al.
ApJ. Letters, 887, L14
paper  arxiv  

The CARMENES search for exoplanets around M dwarfs: A low-mass planet in the temperate zone of the nearby K2-18
2018 PAULA S., HENNING Th., MARTIN K., TRIFON T., ZECHMEISTER L., et al.
Astron. J., accepted
arxiv  

The CARMENES Search for Exoplanets around M Dwarfs: A Low-mass Planet in the Temperate Zone of the Nearby K2-18
2018 SARKIS P., HENNING Th., KÜRSTER M., TRIFONOV T., ZECHMEISTER M. et al.
Astron. J., 155, 257
arxiv  

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
2017 CLOUTIER R., ASTUDILLO-DEFRU N., DOYON R., BONFILS X., ALMENARA J. et al.
Astron. & Astrophys., 608, A35
paper  arxiv   ADS  

Spitzer Observations Confirm and Rescue the Habitable-Zone Super-Earth K2-18b for Future Characterization
2016 BENNEKE B., WERNER M., PETIGURA E., KNUTSON H., DRESSING C. et al.
ApJ, 834, 187
paper  arxiv  ADS  

Stellar and Planetary Properties of K2 Campaign 1 Candidates and Validation of 17 Systems, Including a Planet Receiving Earth-like Insolation
2015 MONTET B., MORTON T., FOREMAN-MACKEY D., JOHNSON J., HOGG D. et 4 additional authors
ApJ, 809, 25
arxiv   paper   ADS