View source for 38 Virginis b

{{Short description|Super-Jupiter exoplanet orbiting 38 Virginis}}
{{Infobox planet
| name                     = 38 Virginis b
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<!-- DISCOVERY           -->
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| discovered               = 29 August 2016
| discovery_method         = [[radial velocity method|radial velocity]]
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| semimajor                = 1.82 (± 0.07) AU<ref name="Borgniet2017"/>
| mean_orbit_radius        = 
| eccentricity             = 0.03 (± 0.04)<ref name="Borgniet2017"/>
| period                   = 825.9 (± 6.2)<ref name="Borgniet2017"/> [[day|d]]
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| time_periastron          = 2455490.2 ± 177.3<ref name="Borgniet2017"/>
| arg_peri                 = −87.3 ± 77.7<ref name="Borgniet2017"/>
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| star                     = [[38 Virginis]]
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| mass                     = 4.51 (± 0.5)<ref name="Borgniet2017"/> {{Jupiter mass|link=y}}
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}}
'''38 Virginis b''' is a [[super-Jupiter]] [[exoplanet]] orbiting within the [[habitable zone]]<!--resulting effective temperature indicates it is--> of the star [[38 Virginis]] about 108.5 [[light-year]]s (33.26 [[parsec]]s) from Earth in the constellation [[Virgo (constellation)|Virgo]].  The exoplanet was found by using the [[Doppler spectroscopy|radial velocity method]], from [[radial velocity|radial-velocity]] measurements via observation of [[Doppler shift]]s in the [[spectrum]] of the [[planet|planet's]] parent star.

==Characteristics==

===Mass===
38 Virginis b is a [[super-Jupiter]], an exoplanet that has a mass larger than that of the planet [[Jupiter]]. It has a [[minimum mass]] of 4.51 {{Jupiter mass|link=y}}.<ref name="Borgniet2017"/>

===Host star===
{{main|38 Virginis}}
The planet orbits a ([[Stellar classification#Class F|F-type]]) [[star]] named [[38 Virginis]]. The star has a mass of 1.18 {{Solar mass|link=y}} and a radius of around 1.46 {{Solar radius|link=y}}. It has a temperature of 6557 [[Kelvin|K]] and is about 1.9 billion years old. In comparison, the Sun is about 4.6 billion years old<ref>{{cite web |url=http://www.universetoday.com/18237/how-old-is-the-sun/ |title=How Old is the Sun? |author=Fraser Cain |date=16 September 2008 |publisher=[[Universe Today]] |access-date=19 February 2011}}</ref> and has a temperature of 5778 K.<ref>{{cite web |url=http://www.universetoday.com/18092/temperature-of-the-sun/ |title=Temperature of the Sun |author=Fraser Cain |date=September 15, 2008 |publisher=Universe Today |access-date=19 February 2011}}</ref> The star is metal-rich, with a [[metallicity]] ([Fe/H]) of 0.16, or 117% the solar amount. Its luminosity ({{solar luminosity|link=y}}) is 3.48 times that of the Sun.<ref group="note">From <math>\begin{smallmatrix}L=4 \pi R^2 \sigma T_{\rm eff}^4 \end{smallmatrix}</math>, where <math>\begin{smallmatrix}L \end{smallmatrix}</math> is the luminosity, <math>\begin{smallmatrix}R \end{smallmatrix}</math> is the radius, <math>\begin{smallmatrix}T_{\rm eff}\end{smallmatrix}</math> is the effective surface temperature and <math>\begin{smallmatrix}\sigma \end{smallmatrix}</math> is the [[Stefan–Boltzmann constant]].</ref>

The star's [[apparent magnitude]], or how bright it appears from Earth's perspective, is 6.11. Therefore, 38 Virginis is on the edge of not being visible to the naked eye, but it can be clearly spotted with binoculars.

===Orbit and habitability===
38 Virginis b orbits its star every 825 days at a semi-major axis of 1.82 [[astronomical unit|AU]] (this separation is comparable to [[Mars]]'s semi-major axis, which is 1.53 AU). It likely receives as much [[stellar flux|sunlight]] as the Earth does from the Sun, due to its equilibrium temperature (assuming an [[albedo]] of 0.3) being only 3 degrees higher than that of Earth.<ref>{{Cite web |title=38 Vir b |url=http://www.exoplanetkyoto.org/exohtml/38_Vir_b.html |access-date=2024-09-21 |website=www.exoplanetkyoto.org}}</ref> Since 38 Virginis b is almost a gas giant, the [[Habitability of natural satellites|habitability]] is instead considered for its hypothetical exomoons.<ref>{{Cite web |last=Cowing |first=Keith |date=2024-09-20 |title=The Habitability Of F-Type Star Systems |url=https://astrobiology.com/2024/09/the-habitability-of-f-type-star-systems.html |access-date=2024-09-21 |website=Astrobiology |language=en-US}}</ref>

==Discovery==
The search for 38 Virginis b started when its host star was chosen an ideal target for a planet search using the [[radial velocity method]] (in which the gravitational pull of a planet on its star is measured by observing the resulting [[Doppler shift]]), as stellar activity would not overly mask or mimic [[Doppler spectroscopy]] measurements. It was also confirmed that 38 Virginis is neither a binary star nor a quickly rotating star, common [[false positive]]s when searching for transiting planets. Analysis of the resulting data found that the radial velocity variations most likely indicated the existence of a planet.<ref name="Borgniet2017"/> The net result was an estimate of a 4.52 {{Jupiter mass}} planetary companion orbiting the star at a distance of 1.82 AU with an eccentricity of 0.03.

The discovery of 38 Virginis b was reported in the online archive [[arXiv]] on August 29, 2016.

==Notes==
<references group="note"/>

==References==
{{Reflist|refs=

<ref name="Borgniet2017">{{cite journal | title=Extrasolar planets and brown dwarfs around AF-type stars. IX. The HARPS southern sample | url=https://www.aanda.org/articles/aa/full_html/2017/03/aa28805-16/aa28805-16.html | last1=Borgniet | first1=S. | last2=Lagrange | first2=A.-M. | last3=Meunier | first3=N. | last4=Galland | first4=F. | display-authors=1 | journal=Astronomy and Astrophysics | volume=599 | at=A57 | year=2017 | arxiv=1608.08257 | bibcode=2017A&A...599A..57B | doi=10.1051/0004-6361/201628805 }}</ref>

}}

{{Sky|12|53|11.3|-|03|33|11}}
{{2016 in space|state=collapsed}}
{{Virgo (constellation)}}

[[Category:Exoplanets discovered in 2016]]
[[Category:Virgo (constellation)]]
[[Category:Exoplanets detected by radial velocity]]
[[Category:Giant planets in the habitable zone]]