View source for Pollux b

{{Short description|Candidate gas giant exoplanet orbiting Pollux}}
{{Infobox planet
| name = Pollux b / Thestias
| image = Pollux b (Thestias).png
| caption = Artist's impression of Pollux b
<!-- DISCOVERY           -->
| discovery_ref = <ref name="Hatzes2006"/>
| discoverer = [[Artie P. Hatzes|Hatzes]] ''et al.''
| discovery_site = United States
| discovered = 16 June 2006
| discovery_method = [[Radial velocity]]
<!-- DESIGNATIONS        -->
| alt_names = β Geminorum b, HD 62509 b, Thestias<ref name="iaunaming"/>
<!-- ORBITAL             -->
| orbit_ref = <ref name="Hatzes2006"/>
| apsis = astron
| semimajor = {{convert|1.64|±|0.27|AU|e6km|abbr=unit}}
| eccentricity = 0.02 ± 0.03
| period = 589.64 ± 0.81 [[day|d]]<br>1.61432 ± 0.00222 [[year|y]]
| time_periastron = 2,447,739.02 ± 4.5
| semi-amplitude = 41.0 ± 1.6
| star = [[Pollux (star)|Pollux]]
<!-- PHYS CHARS          -->
| physical_ref = <ref name="Hatzes2006"/>
| mass = {{val|2.30|0.45|p=≥|ul=Jupiter mass}}
<!-- ATMOSPHERE          -->
<!-- NOTES               -->
}}
'''Pollux b''', formally named '''Thestias''' {{IPAc-en|'|θ|E|s|t|i|@|s}}, is an [[exoplanet]] candidate orbiting the [[star]] [[Pollux (star)|Pollux]] approximately 34 [[light-year]]s away in the [[constellation]] of [[Gemini (constellation)|Gemini]] (the [[Twin]]s). It is also designated β Geminorum b ([[Latinisation of names|Latinized]] to Beta Geminorum b, abbreviated β Gem b) or HD 62509 b. If this planet exists, it has a [[minimum mass]] of about twice the [[mass of Jupiter]], and it moves around Pollux in 1.61 years at a distance of {{val|1.64|ul=AU|fmt=commas}} in a nearly circular orbit.<ref name="Hatzes2006"/> However, its existence has been disputed.<ref name="Aurière2021"/>

==History of observations==
The discovery of Pollux b was announced in 2006 by astronomer [[Artie P. Hatzes]] and co-authors using the [[radial velocity method]].<ref name="Hatzes2006"/> A planet orbiting Pollux had previously been hypothesized by Hatzes in 1993, though at that time it was thought more likely that the radial velocity variations were caused by intrinsic stellar variability.<ref name="Hatzes1993"/>

An independent study published shortly after the discovery paper supported the existence of Pollux b, but expressed some uncertainty, leaving a non-planetary explanation for the radial velocity variations a possibility.<ref name="Reffert2006"/> Another independent study in 2008 also supported the planet.<ref name="Han2008"/>

The planet's existence has been questioned by two subsequent studies, one in 2013 and its 2021 follow-up.<ref name="Aurière2014" /><ref name="Aurière2021" /> A weak [[stellar magnetic field|magnetic field]] in Pollux was detected in 2009,<ref name="Aurière2009"/> and it was suggested that magnetic variability in the star, as opposed to a planet, might be the cause of the observed radial velocity variations. The stellar rotation period was found to be close to the proposed period of Pollux b, casting some doubt on the planet's existence.<ref name="Aurière2014"/> The 2021 study monitored Pollux for 4.25 years and found the [[rotational period]] to be {{Val|660|15|u=days}}, close to Pollux b's orbital period of 590 days. Even though both values aren't equal, there might still be systematic errors in the rotational period.<ref name="Aurière2021" />

==Naming==
In July 2014 the [[International Astronomical Union]] 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://nameexoworlds.iau.org/process |url-status=dead }}</ref> In December 2015, the IAU announced the winning name was Thestias for this planet.<ref name="iaunaming">[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 based on that originally submitted by [[theSkyNet]] of [[Australia]]; namely [[Leda (mythology)|Leda]], Pollux's mother in [[Greek mythology|Greek]] and [[Roman mythology]]. At the request of the IAU, 'Thestias' (the [[Patronymic|patronym]] of Leda, a daughter of [[Thestius]]) was substituted. This was because 'Leda' was already attributed to [[38 Leda|an asteroid]] and to [[Leda (moon)|one of Jupiter's satellites]].<ref>{{Cite web |url=http://nameexoworlds.iau.org/names |title=NameExoWorlds The Approved Names |access-date=2016-01-04 |archive-date=2018-02-01 |archive-url=https://web.archive.org/web/20180201043609/http://nameexoworlds.iau.org/names |url-status=dead }}</ref><ref>[http://www.theskynet.org/news/67?locale=en YOU helped name an exoplanet!] {{Webarchive|url=https://web.archive.org/web/20180507155200/https://www.theskynet.org/news/67?locale=en |date=2018-05-07 }}, TheSkyNet, 2015-12-17</ref>

== See also ==
*[[Gemini in Chinese astronomy]]
*[[Cancer Minor (constellation)]] – Obsolete constellation inside modern Gemini
*[[Sudarsky's gas giant classification#Class III: Cloudless|Sudarsky's gas giant classification]]

== References ==
{{Reflist|refs=

<ref name="Hatzes1993">{{cite journal | bibcode=1993ApJ...413..339H | author=A. P. Hatzes | display-authors=etal| title=Long-period radial velocity variations in three K giants | journal=[[The Astrophysical Journal]] | volume=413 |date=1993 | pages=339–348| doi=10.1086/173002| doi-access=free }}</ref>

<ref name="Hatzes2006">{{cite journal |author=A. P. Hatzes |display-authors=etal|title=Confirmation of the planet hypothesis for the long-period radial velocity variations of β Geminorum  |journal = [[Astronomy and Astrophysics]] | volume=457 | issue=1 | date=2006 | pages=335–341|doi=10.1051/0004-6361:20065445 | bibcode=2006A&A...457..335H|arxiv = astro-ph/0606517 |s2cid=14319327}}</ref>

<ref name="Reffert2006">{{cite journal | author=S. Reffert | display-authors=etal | title=Precise Radial Velocities of Giant Stars. II. Pollux and Its Planetary Companion  | journal=[[The Astrophysical Journal]] | volume=652 | issue=1 | date=2006 | pages=661–665 | doi=10.1086/507516 | bibcode=2006ApJ...652..661R|arxiv = astro-ph/0607136 | s2cid=18252884 }}</ref>

<ref name="Han2008">{{cite journal |last1=Han |first1=In-Woo |last2=Lee |first2=Byeong-Cheol |display-authors=etal |date=June 2008 |title=Confirmation of the Exoplanet around β GEM from the RV Observations Using Boes |journal=[[Journal of the Korean Astronomical Society]] |volume=41 |issue=3 |pages=59–64 |doi=10.5303/JKAS.2008.41.3.059 |bibcode=2008JKAS...41...59H}}</ref>

<ref name="Aurière2009">{{citation | display-authors=1 | last1=Aurière | first1=M. | last2=Wade | first2=G. A. | last3=Konstantinova-Antova | first3=R. | last4=Charbonnel | first4=C. | last5=Catala | first5=C. | last6=Weiss | first6=W. W. | last7=Roudier | first7=T. | last8=Petit | first8=P. | last9=Donati | first9=J.-F. | title=Discovery of a weak magnetic field in the photosphere of the single giant Pollux | journal=Astronomy and Astrophysics | volume=504 | issue=1 | pages=231–237 |date=September 2009 | doi=10.1051/0004-6361/200912050 | bibcode=2009A&A...504..231A |arxiv = 0907.1423| s2cid=14295272 }}</ref>

<ref name="Aurière2014">{{cite conference |last1=Aurière |first1=Michel |last2=Konstantinova-Antova |first2=Renada |display-authors=etal |date=August 2014 |title=Pollux: a stable weak dipolar magnetic field but no planet? |book-title=Proceedings of the International Astronomical Union |volume=302 |pages=359–362 |conference=Magnetic Fields throughout Stellar Evolution |doi=10.1017/S1743921314002476 |arxiv=1310.6907 |bibcode=2014IAUS..302..359A}}</ref>

<ref name="Aurière2021">{{cite journal |last1=Aurière |first1=M. |last2=Petit |first2=P. |display-authors=etal |date=February 2021 |title=Pollux: A weak dynamo-driven dipolar magnetic field and implications for its probable planet |journal=[[Astronomy & Astrophysics]] |volume=646 |issue= |pages=A130 |doi=10.1051/0004-6361/202039573 |arxiv=2101.02016 |bibcode=2021A&A...646A.130A}}</ref>

}}

== External links ==
* {{cite web |url=http://www.solstation.com/stars2/pollux.htm |title=Pollux |access-date=<!--2008-06-24-->2005-11-21 |work=SolStation}}

{{Sky|07|45|19.4|+|28|01|35|34}}{{Stars of Gemini}}
{{Portal bar|Astronomy|Stars|Outer space}}

[[Category:Pollux (star)]]
[[Category:Gemini (constellation)]]
[[Category:Giant planets]]
[[Category:Exoplanets discovered in 2006]]
[[Category:Exoplanets detected by radial velocity]]
[[Category:Exoplanets with proper names]]
[[Category:Leda (mythology)]]