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Red dwarf star in the constellation Leo
K2-18 , also known as EPIC 201912552 , is a
red dwarf
star with two planetary companions located 124
light-years (38
parsecs )
[4] from
Earth , in the
constellation of
Leo .
Its name is due to the fact that it was discovered by the
K2 Mission , which extended the mission of the Kepler Space Telescope after failure of two of its reaction wheels.
Planetary system
The star has a transiting
exoplanet , called
K2-18b , a
super-Earth located within the
habitable zone of K2-18.
[9]
[10] It was discovered in 2015 by the
Kepler space telescope in its
K2 mission .
[3] It is the first exoplanet in the habitable zone, albeit a hydrogen-rich sub-Neptune,
[11] to have its atmosphere characterized; initially thought to contain
water vapor ,
[12] more recent observations have instead detected
methane and
carbon dioxide .
[13] The presence of these molecules and non-detection of
ammonia is consistent with predictions for a
hycean planet .
[13]
A second, non-transiting planet, K2-18c, was discovered in 2017 by
radial velocity with
HARPS .
[14] This planet was challenged by another team with
CARMENES data,
[15] but its existence was reaffirmed by the discovery team based on both HARPS and CARMENES data.
[4] This planet has also been confirmed by a later independent study.
[16] System tidal simulation suggests that K2-18c is a gas-rich, Neptune-like planet, similar to K2-18b.
[17]
References
^
a
b
c
d
e Vallenari, A.; et al. (Gaia collaboration) (2023).
"Gaia Data Release 3. Summary of the content and survey properties" . Astronomy and Astrophysics . 674 : A1.
arXiv :
2208.00211 .
Bibcode :
2023A&A...674A...1G .
doi :
10.1051/0004-6361/202243940 .
S2CID
244398875 .
Gaia DR3 record for this source at
VizieR .
^ Zacharias, N.; Finch, C. T.; Girard, T. M.; Henden, A.;
Bartlett, J. L. ; Monet, D. G.; Zacharias, M. I. (2012). "VizieR Online Data Catalog: UCAC4 Catalogue (Zacharias+, 2012)". VizieR On-line Data Catalog .
Bibcode :
2012yCat.1322....0Z .
^
a
b Montet, Benjamin T.; et al. (5 August 2015).
"Stellar and Planetary Properties of K2 Campaign 1 Candidates and Validation of 17 Planets, Including a Planet Receiving Earth-like Insolation" .
The Astrophysical Journal . 809 (1) 25: 25.
arXiv :
1503.07866 .
Bibcode :
2015ApJ...809...25M .
doi :
10.1088/0004-637X/809/1/25 .
S2CID
33348734 .
^
a
b
c
d
e Cloutier, Ryan; et al. (7 January 2019).
"Confirmation of the radial velocity super-Earth K2-18c with HARPS and CARMENES" .
Astronomy & Astrophysics . 621 A49: A49.
arXiv :
1810.04731 .
Bibcode :
2019A&A...621A..49C .
doi :
10.1051/0004-6361/201833995 .
S2CID
118828975 .
^ Martinez, Arturo O.; et al. (2017).
"Stellar and Planetary Parameters for K2's Late-type Dwarf Systems from C1 to C5" . The Astrophysical Journal . 837 (1) 72: 72.
arXiv :
1701.00588 .
Bibcode :
2017ApJ...837...72M .
doi :
10.3847/1538-4357/aa56c7 .
S2CID
25502982 .
^ Benneke, Björn; et al. (2017).
"Spitzer Observations Confirm and Rescue the Habitable-zone Super-Earth K2-18b for Future Characterization" . The Astrophysical Journal . 834 (2) 187: 187.
arXiv :
1610.07249 .
Bibcode :
2017ApJ...834..187B .
doi :
10.3847/1538-4357/834/2/187 .
S2CID
12988198 .
^
a
b Guinan, Edward F.; Engle, Scott G. (2019-12-12).
"The K2-18b Planetary System: Estimates of the Age and X-UV Irradiances of a Habitable Zone "Wet" Sub-Neptune Planet" . Research Notes of the AAS . 3 (12): 189.
Bibcode :
2019RNAAS...3..189G .
doi :
10.3847/2515-5172/ab6086 .
ISSN
2515-5172 .
^
"K2-18" .
SIMBAD .
Centre de données astronomiques de Strasbourg . Retrieved 2024-04-13 .
^
"HABITABLE EXOPLANETS CATALOG" . UPR. 7 March 2016. Retrieved 12 September 2019 .
^
"EPIC 201912552 b reality check drewexmachina 11-22-2015" . Drew ExMachina. 7 March 2016. Retrieved 12 September 2019 .
^
No, the Exoplanet K2-18b Is Not Habitable
^ Benneke, Björn; Wong, Ian; Piaulet, Caroline; Knutson, Heather A.; Lothringer, Joshua; Morley, Caroline V.; Crossfield, Ian J. M.; Gao, Peter; Greene, Thomas P.; Dressing, Courtney; Dragomir, Diana; Howard, Andrew W.; McCullough, Peter R.; Kempton, Eliza M.-R.; Fortney, Jonathan J.; Fraine, Jonathan (December 2019).
"Water Vapor and Clouds on the Habitable-zone Sub-Neptune Exoplanet K2-18b" . The Astrophysical Journal Letters . 887 (1): L14.
arXiv :
1909.04642 .
Bibcode :
2019ApJ...887L..14B .
doi :
10.3847/2041-8213/ab59dc .
ISSN
2041-8205 .
S2CID
209324670 .
^
a
b Madhusudhan, Nikku; Sarkar, Subhajit; Constantinou, Savvas; Holmberg, Måns; Piette, Anjali A. A.; Moses, Julianne I. (1 October 2023).
"Carbon-bearing Molecules in a Possible Hycean Atmosphere" . The Astrophysical Journal Letters . 956 (1): L13.
arXiv :
2309.05566 .
Bibcode :
2023ApJ...956L..13M .
doi :
10.3847/2041-8213/acf577 .
^ Cloutier, R.; Astudillo-Defru, N.; et al. (December 2017). "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".
Astronomy & Astrophysics . 608 : A35.
arXiv :
1707.04292 .
Bibcode :
2017A&A...608A..35C .
doi :
10.1051/0004-6361/201731558 .
^ Sarkis, Paula; Henning, Thomas; et al. (June 2018).
"The CARMENES Search for Exoplanets around M Dwarfs: A Low-mass Planet in the Temperate Zone of the Nearby K2-18" .
The Astronomical Journal . 155 (6): 257.
arXiv :
1805.00830 .
Bibcode :
2018AJ....155..257S .
doi :
10.3847/1538-3881/aac108 .
^
a
b Radica, Michael; Artigau, Étienne; et al. (December 2022). "Revisiting radial velocity measurements of the K2-18 system with the line-by-line framework".
Monthly Notices of the Royal Astronomical Society . 517 (4): 5050–5062.
arXiv :
2210.08078 .
Bibcode :
2022MNRAS.517.5050R .
doi :
10.1093/mnras/stac3024 .
^
a
b Ferraz-Mello, S.; Gomes, G. O. (2020). "Tidal evolution of exoplanetary systems hosting potentially habitable exoplanets. The cases of LHS-1140 b-c and K2-18 b-c". Monthly Notices of the Royal Astronomical Society . 494 (4): 5082–5090.
arXiv :
2005.10318 .
Bibcode :
2020MNRAS.494.5082G .
doi :
10.1093/mnras/staa1110 .
S2CID
218763252 .
External links