{{short description|Extrasolar planet orbiting the star 41 Lyncis}} {{Infobox planet | name = 41 Lyncis b / Arkas | image = | caption = | discovery_ref = <ref name="Sato2008"/> | discoverer = Sato et al. | discovery_site = Okayama Planet<br>Search Program,<br>Japan | discovered = February 19, 2008 | discovery_method = radial velocity | extrasolarplanet = yes | alt_names = Arkas | orbit_ref = <ref name="Teng2023"/> | apsis = astron | semimajor = {{convert|0.648|AU|e6km|abbr=unit}} | eccentricity = {{val|0.040|0.022|0.031}} | period = {{val|183.93|0.09|ul=d}} | time_periastron = {{val|2454354.4|80.2|16.9|ul=JD}} | semi-amplitude = {{val|56.42|1.87|1.88|ul=m/s}} | star = 41 Lyncis | physical_ref = <ref name="Teng2023"/> | mass = {{val|1.654|0.054|0.055|p=≥|ul=Jupiter mass}} }}

'''41 Lyncis b''' (abbreviated '''41 Lyn b'''), also designated '''HD 81688 b''' and named '''Arkas''' {{IPAc-en|'|ɑr|k|@|s}},<ref name=":0">Dictionary.com, 'Arcas'</ref> is a candidate exoplanet approximately 276 light-years from Earth in the constellation of Ursa Major.

A gas giant with a mass of 1.654 times that of Jupiter, it orbits the K-type star 41 Lyncis with an orbital period of 183.93 days (corresponding to a semi-major axis of 0.648 AU). <ref name="Teng2023" />It was discovered and announced by Bun'ei Sato on February 19, 2008.<ref name=":0" />

==Name== In July 2014, the International Astronomical Union (IAU) launched NameExoWorlds, a process for giving proper names to certain exoplanets and their host stars.<ref>[http://www.iau.org/news/pressreleases/detail/iau1404/ NameExoWorlds: An IAU Worldwide Contest to Name Exoplanets and their Host Stars]. IAU.org. 9 July 2014</ref> The process involved public nomination and voting for the new names.<ref>{{Cite web |url=http://nameexoworlds.iau.org/process |title=NameExoWorlds The Process |access-date=2015-09-05 |archive-date=2015-08-15 |archive-url=https://web.archive.org/web/20150815025117/http://www.nameexoworlds.iau.org/process |url-status=dead }}</ref> In December 2015, the IAU announced the name Arkas for this planet.<ref>[http://www.iau.org/news/pressreleases/detail/iau1514/ Final Results of NameExoWorlds Public Vote Released], International Astronomical Union, 15 December 2015.</ref> The winning name was submitted by the Okayama Astro Club of Japan. Arkas was the son of Callisto (Ursa Major) in Greek mythology.<ref>{{Cite web |url=http://nameexoworlds.iau.org/names |title=NameExoWorlds The Approved Names |access-date=2015-12-17 |archive-date=2018-02-01 |archive-url=https://web.archive.org/web/20180201043609/http://nameexoworlds.iau.org/names |url-status=dead }}</ref>

==Planet challenged== A 2023 study of planets around evolved stars, while presenting updated parameters for this planet, found that the radial velocity variations are correlated with stellar activity signals, casting doubt on the planet's existence.<ref name="Teng2023"/> Based on this, a 2024 study listed it as one of several doubtful planets around giant stars (along with the other named planets 14 Andromedae b and 42 Draconis b).<ref name="Spaeth2024"/>

==See also== * 18 Delphini b * Xi Aquilae b

==References== <references> <ref name="Sato2008">{{cite journal | title=Planetary Companions around Three Intermediate-Mass G and K Giants: 18 Delphini, ξ Aquilae and HD 81688 | url=https://academic.oup.com/pasj/article/60/3/539/1508408 | last1=Sato | first1=Bun'ei | last2=Izumiura | first2=Hideyuki | last3=Toyota | first3=Eri | last4=Kambe | first4=Eiji | last5=Ikoma | first5=Masahiro | last6=Omiya | first6=Masashi | last7=Masuda | first7=Seiji | last8=Takeda | first8=Yoichi | last9=Murata | first9=Daisuke | last10=Itoh | first10=Yoichi | last11=Ando | first11=Hiroyasu | last12=Yoshida | first12=Michitoshi | last13=Kokubo | first13=Eiichiro | last14=Ida | first14=Shigeru | display-authors=1 | journal=Publications of the Astronomical Society of Japan | volume=60 | issue=3 | pages=539–550 | year=2008 | arxiv=0802.2590 | bibcode=2008PASJ...60..539S | doi=10.1093/pasj/60.3.539}}</ref>

<ref name="Teng2023">{{cite journal |last1=Teng |first1=Huan-Yu |last2=Sato |first2=Bun'ei |display-authors=etal |date=August 2023 |title=Revisiting planetary systems in the Okayama Planet Search Program: A new long-period planet, RV astrometry joint analysis, and a multiplicity-metallicity trend around evolved stars |journal=Publications of the Astronomical Society of Japan |volume=75 |issue=6 |pages=1030–1071 |doi=10.1093/pasj/psad056 |arxiv=2308.05343 |bibcode=2023PASJ...75.1030T}}</ref>

<ref name="Spaeth2024">{{cite journal |last1=Spaeth |first1=Dane |last2=Reffert |first2=Sabine |display-authors=etal |date=September 2024 |title=Non-radial oscillations mimicking a brown dwarf orbiting the cluster giant NGC 4349 No. 127 |journal=Astronomy & Astrophysics |volume=689 |issue= |pages=A91 |doi=10.1051/0004-6361/202450163 |arxiv=2407.21583 |bibcode=2024A&A...689A..91S}}</ref> </references> {{Stars of Ursa Major}}

{{Sky|09|28|40|+|45|36|05|287.9}}

Category:Ursa Major Category:Giant planets Category:Exoplanets discovered in 2008 Category:Exoplanets detected by radial velocity Category:Exoplanets with proper names