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2025-04-17T07:49:15Z

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{{Starbox begin
| name=K2-18
}}
{{Starbox image
| image = [[File: Exoplanet K2-18 b (illustration) (weic2321a).tiff|250px]]
| caption = 藝術家對繞紅矮星K2-18（左）運行的系外行星[[K2-18b]]（右）的想像。顯示在它們之間的是另一顆系外行星[[K2-18c]]。
| credit = ESA/Hubble
}}
{{Starbox image
| image=
{{Location mark
|image=Leo constellation map.svg|alt=|float=center|width=260
|label=|position=right
|mark=Red circle.svg|mark_width=10|mark_link=δ Leonis
|x=215|y=724
}}
|caption=K2-18大致二維位置（紅色圓圈）；[[西上將]]是最近的亮星，位於南邊。
}}
{{Starbox observe
| constell = [[獅子座]]
| epoch = J2000.0
| ra = {{RA|11|30|14.51774}}<ref name=dr3/>
| dec = {{DEC|+07|35|18.2553}}<ref name=dr3/>
| appmag_v = 13.50<ref name=UCAC4/>
}}
{{Starbox character
| type = [[紅矮星]]
| class = M2.8<ref name=montet2015/>
| variable =
}}
{{Starbox astrometry
| radial_v = {{val|0.02|0.52}}<ref name=dr3/>
| prop_mo_ra = {{val|-80.479}}
| prop_mo_dec = {{val|-133.007}}
| pm_footnote = <ref name=dr3/>
| parallax = 26.2469
| p_error = 0.0266
| parallax_footnote = <ref name=dr3/>
| absmag_v
}}
{{Starbox detail
| mass = {{val|0.495|0.004}}<ref name="Cloutier2019" />
| radius = {{val|0.469|0.010}}<ref name="Cloutier2019" />
| luminosity = 0.0234<ref name=arturo2017/>
| temperature = {{val|3645|52|fmt=commas}}<ref name=Sairam2025/>
| metal_fe = +{{val|0.10|0.12}}<ref name=Sairam2025/>
| rotation = 38.9 to 40.2<ref name=Sairam2025/> days
| rotational_velocity =
| age_gyr = 2.9 to 3.1<ref name=Sairam2025/>
}}
{{Starbox catalogue
| names = {{odlist | 2MASS=J11301450+0735180 | EPIC=201912552 | Gaia DR3=3910747531814692736 }}<ref name="Simbad"/>
}}
{{Starbox reference
| Simbad = K2-18
}}
{{Starbox end}}
'''K2-18'''，也稱為'''EPIC 201912552'''，是一顆[[紅矮星]]，已知有兩顆[[行星]]，距離[[地球]]124[[光年]]（38[[秒差距]]）<ref name="Cloutier2019"/>，位於[[獅子座]]。

K2-18的名字來自K2任務，該任務在兩個反作用輪發生故障後延長了[[開普勒太空望遠鏡]]的任務。

== 參考資料 ==
{{Reflist|refs=

<ref name=dr3>{{cite Gaia DR3|3910747531814692736}}</ref>

<ref name=arturo2017>{{cite journal | title=Stellar and Planetary Parameters for K2's Late-type Dwarf Systems from C1 to C5 | last1=Martinez | first1=Arturo O. | last2=Crossfield | first2=Ian J. M. | last3=Schlieder | first3=Joshua E. | last4=Dressing | first4=Courtney D. | last5=Obermeier | first5=Christian | last6=Livingston | first6=John | last7=Ciceri | first7=Simona | last8=Peacock | first8=Sarah | last9=Beichman | first9=Charles A. | last10=Lépine | first10=Sébastien | last11=Aller | first11=Kimberly M. | last12=Chance | first12=Quadry A. | last13=Petigura | first13=Erik A. | last14=Howard | first14=Andrew W. | last15=Werner | first15=Michael W. | display-authors=1 | journal=The Astrophysical Journal | volume=837 | issue=1 | article-number=72 | year=2017 | page=72 | arxiv=1701.00588 | bibcode=2017ApJ...837...72M | bibcode-access=free | doi=10.3847/1538-4357/aa56c7 | doi-access=free | s2cid=25502982 }}</ref>

<ref name=Sairam2025>{{Cite arXiv |last=Sairam |first=Lalitha |last2=Madhusudhan |first2=Nikku |title=Characterising M dwarf host stars of two candidate Hycean worlds |date=2025-03-25 |arxiv=2503.19908 }}</ref>

<ref name=montet2015>{{cite journal | title=Stellar and Planetary Properties of K2 Campaign 1 Candidates and Validation of 17 Planets, Including a Planet Receiving Earth-like Insolation | first1=Benjamin T. | last1= Montet | first2=Timothy D. | last2=Morton | first3=Daniel | last3=Foreman-Mackey | first4=John Asher | last4=Johnson | first5=David W. |last5=Hogg | first6=Brendan P. | last6=Bowler | first7=David W. | last7=Latham | first8=Allyson | last8=Bieryla | first9=Andrew W. | last9=Mann | display-authors=1 | journal = [[The Astrophysical Journal]] | volume=809 | issue=1 | article-number=25 | date=5 August 2015 | page=25 | arxiv=1503.07866 | bibcode=2015ApJ...809...25M | bibcode-access=free | doi=10.1088/0004-637X/809/1/25 | doi-access=free | s2cid=33348734 }}</ref>

<ref name=exmachina>{{cite web| url = http://www.drewexmachina.com/2015/05/12/habitable-planet-reality-check-epic-201912552b/ | title = EPIC 201912552 b reality check drewexmachina 11-22-2015 | publisher = Drew ExMachina| date = 7 March 2016| access-date =12 September 2019}}</ref>

<ref name=habitable>{{cite web| url = http://phl.upr.edu/projects/habitable-exoplanets-catalog | title = HABITABLE EXOPLANETS CATALOG | publisher = UPR | date = 7 March 2016| access-date =12 September 2019}}</ref>

<ref name=UCAC4>{{cite journal |bibcode=2012yCat.1322....0Z |title=VizieR Online Data Catalog: UCAC4 Catalogue (Zacharias+, 2012) |journal=VizieR On-line Data Catalog |last1=Zacharias |first1=N. |last2=Finch |first2=C. T. |last3=Girard |first3=T. M. |last4=Henden |first4=A. |last5=Bartlett |first5=J. L. |author5-link=Jennifer Bartlett (astronomer)|last6=Monet |first6=D. G. |last7=Zacharias |first7=M. I. |year=2012 }}</ref>

<ref name="Cloutier2017">{{cite journal |last1=Cloutier |first1=R. |last2=Astudillo-Defru |first2=N. |display-authors=etal |date=December 2017 |title=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 |journal=[[Astronomy & Astrophysics]] |volume=608 |issue= |pages=A35 |doi=10.1051/0004-6361/201731558 |arxiv=1707.04292 |bibcode=2017A&A...608A..35C}}</ref>

<ref name="Sarkis2018">{{cite journal |last1=Sarkis |first1=Paula |last2=Henning |first2=Thomas |display-authors=etal |date=June 2018 |title=The CARMENES Search for Exoplanets around M Dwarfs: A Low-mass Planet in the Temperate Zone of the Nearby K2-18 |journal=[[The Astronomical Journal]] |volume=155 |issue=6 |pages=257 |doi=10.3847/1538-3881/aac108 |arxiv=1805.00830 |bibcode=2018AJ....155..257S |doi-access=free }}</ref>

<ref name="Cloutier2019">{{cite journal | title=Confirmation of the radial velocity super-Earth K2-18c with HARPS and CARMENES | first1=Ryan | last1=Cloutier | first2=Nicola | last2=Astudillo-Defru | first3=René | last3=Doyon | first4=Xavier | last4=Bonfils | first5=José M. | last5=Almenara | first6=François | last6=Bouchy | first7=Xavier | last7=Delfosse | first8=Thierry | last8=Forveille | first9=Christophe | last9=Lovis | first10=Michel | last10=Mayor | first11=Kristen | last11=Menou | first12=Felipe | last12=Murgas | first13=Francesco | last13=Pepe | first14=Nuno C. | last14=Santos | first15=Stéphane | last15=Udry | first16=Anaël | last16=Wünsche | display-authors=1 | journal=[[Astronomy & Astrophysics]] | volume=621 | article-number=A49 | date=7 January 2019 | pages=A49 | arxiv=1810.04731 | bibcode=2019A&A...621A..49C | bibcode-access=free | doi=10.1051/0004-6361/201833995 | doi-access=free | s2cid=118828975 }}</ref>

<ref name="Benneke2019">{{Cite journal |last1=Benneke |first1=Björn |last2=Wong |first2=Ian |last3=Piaulet |first3=Caroline |last4=Knutson |first4=Heather A. |last5=Lothringer |first5=Joshua |last6=Morley |first6=Caroline V. |last7=Crossfield |first7=Ian J. M. |last8=Gao |first8=Peter |last9=Greene |first9=Thomas P. |last10=Dressing |first10=Courtney |last11=Dragomir |first11=Diana |last12=Howard |first12=Andrew W. |last13=McCullough |first13=Peter R. |last14=Kempton |first14=Eliza M.-R. |last15=Fortney |first15=Jonathan J. |last16=Fraine |first16=Jonathan |title=Water Vapor and Clouds on the Habitable-zone Sub-Neptune Exoplanet K2-18b |journal=The Astrophysical Journal Letters |date=December 2019 |volume=887 |issue=1 |pages=L14 |doi=10.3847/2041-8213/ab59dc |arxiv=1909.04642 |bibcode=2019ApJ...887L..14B |s2cid=209324670 |language=en |issn=2041-8205 |doi-access=free }}</ref>

<ref name=Gomes2020>{{cite journal|arxiv=2005.10318|doi=10.1093/mnras/staa1110|title=Tidal evolution of exoplanetary systems hosting potentially habitable exoplanets. The cases of LHS-1140 b-c and K2-18 b-c|year=2020|last1=Ferraz-Mello|first1=S.|last2=Gomes|first2=G. O.|journal=Monthly Notices of the Royal Astronomical Society|volume=494|issue=4|pages=5082–5090|doi-access=free |bibcode=2020MNRAS.494.5082G|s2cid=218763252}}</ref>

<ref name="Radica2022">{{cite journal |last1=Radica |first1=Michael |last2=Artigau |first2=Étienne |display-authors=etal |date=December 2022 |title=Revisiting radial velocity measurements of the K2-18 system with the line-by-line framework |journal=[[Monthly Notices of the Royal Astronomical Society]] |volume=517 |issue=4 |pages=5050–5062 |doi=10.1093/mnras/stac3024 |doi-access=free |arxiv=2210.08078 |bibcode=2022MNRAS.517.5050R}}</ref>

<ref name="Madhusudhan2023">{{cite journal |last1=Madhusudhan |first1=Nikku |last2=Sarkar |first2=Subhajit |last3=Constantinou |first3=Savvas |last4=Holmberg |first4=Måns |last5=Piette |first5=Anjali A. A. |last6=Moses |first6=Julianne I. |title=Carbon-bearing Molecules in a Possible Hycean Atmosphere |journal=The Astrophysical Journal Letters |date=1 October 2023 |volume=956 |issue=1 |pages=L13 |doi=10.3847/2041-8213/acf577 |arxiv=2309.05566 |bibcode=2023ApJ...956L..13M |doi-access=free }}</ref>

<ref name="Simbad">{{cite simbad | title=K2-18 | accessdate=2024-04-13 }}</ref>

}}

{{Sky|11|30|14.518|+|07|35|18.257|124}}

{{狮子座恒星}}

==外部連結==
* [https://www.msn.com/en-us/news/technology/nasa-says-distant-planet-could-hold-life-after-they-spot-signs-of-rare-water-ocean/ar-AA1gOuta?rc=1&ocid=winp1taskbar&cvid=b0a89305eba942b8ab2a3ed18ff223b0&ei=14 NASA says distant planet could hold life after they spot signs of rare water ocean - MSN News]

[[Category:紅矮星]]

K2-18 - 版本历史

imported>Hikaru Genji：​/* 參考資料 */

imported>Hikaru Genji：/* 參考資料 */