View source for Jupiter radius

{{Short description|Unit of length in astronomy}}
{{Infobox unit
| name         = Jupiter radius
| image        = Jupiter, Earth size comparison.jpg
| caption      = The size of Jupiter compared to Earth
| standard     = [[astronomy]]
| quantity     = [[length]]
| symbol       = {{Jupiter radius}}
| symbol2       = {{Jupiter radius|jup=y}},{{Jupiter radius|greek=y}}
| units1       = [[SI base unit]]s
| inunits1     = {{val|7.1492|e=7|u=m}}<ref name = "IAU XXIX">{{cite arXiv |eprint=1510.07674|last1=Mamajek|first1=E. E|title=IAU 2015 Resolution B3 on Recommended Nominal Conversion Constants for Selected Solar and Planetary Properties| last2=Prsa|first2=A|last3=Torres|first3=G|last4=Harmanec|first4=P|last5=Asplund|first5=M|last6=Bennett|first6=P. D|last7=Capitaine|first7=N|last8=Christensen-Dalsgaard|first8=J|last9=Depagne|first9=E|last10=Folkner|first10=W. M|last11=Haberreiter|first11=M|last12=Hekker|first12=S|last13=Hilton|first13=J. L|last14=Kostov|first14=V|last15=Kurtz|first15=D. W|last16=Laskar|first16=J|last17=Mason|first17=B. D|last18=Milone|first18=E. F|last19=Montgomery|first19=M. M|last20=Richards|first20=M. T|last21=Schou|first21=J|last22=Stewart|first22=S. G|class=astro-ph.SR|year=2015|display-authors= 3}}</ref>
| units2       = [[ English units]]
| inunits2     = {{val|44423|ul=miles}}
}}

The '''Jupiter radius''' or '''Jovian radius''' ({{Jupiter radius}} or {{Jupiter radius|Jup=y}})  has a value of {{convert|71492|km|mi|abbr=on}}, or 11.2 [[Earth radius|Earth radii]] ({{Earth radius}})<ref name="jupfact"/> (one Earth radius equals {{Jupiter radius|0.08921}}). The [[Jupiter]] radius is a [[unit of length]] used in [[astronomy]] to describe the radii of [[gas giants]] and some [[exoplanet]]s. It is also used in describing [[brown dwarf]]s.

The general shape of the planet [[Jupiter]] has been directly measured from [[radio occultation]]s of passing spacecraft, starting with the [[Pioneer program|Pioneer]] and [[Voyager program|Voyager]] missions. This gives an overall [[margin of error]] of about 5&nbsp;km. Estimates of the radii at one bar pressure are then determined through extrapolation. The planet Jupiter has the approximate shape of an [[oblate spheroid]], which is mainly set by the rate of rotation. This gives a difference of about 10% between the polar and equatorial radii. The polar radius has been determined with an accuracy of ±10&nbsp;km, as of 1987. Density fluctuations within the planet can create variations in the equatorial radius of up to 30&nbsp;km. The winds in the outer atmosphere can vary the radius by up to 4&nbsp;km.<ref>{{cite journal
 | title=The Shape of Jupiter and Saturn Based on Atmospheric Dynamics, Radio Occultations and Gravity Measurements
 | last1=Galanti | first1=E. | last2=Kaspi | first2=Y. | last3=Guillot | first3=T.
 | journal=Geophysical Research Letters | volume=50 | issue=6 | id=e2022GL102321
 | date=March 2023 | doi=10.1029/2022GL102321 
 | arxiv=2305.02647 | bibcode=2023GeoRL..5002321G | s2cid=257543496 }}</ref>

In 2015, the [[International Astronomical Union]] defined the ''nominal equatorial Jovian radius'' to remain constant regardless of subsequent improvements in measurement precision of {{Jupiter radius}}. This constant is defined as exactly:
:<math>\mathcal{R}^\mathrm N_\mathrm {eJ}</math> = {{val|7.1492|e=7|u=m}}
Similarly, the ''nominal polar Jovian radius'' is defined to be exactly:
:<math>\mathcal{R}^\mathrm N_\mathrm {pJ}</math> = {{val|6.6854|e=7|u=m}}<ref name = "IAU XXIX"/>
These values correspond to the radius of Jupiter at 1 [[Bar (unit)|bar]] of pressure. The common usage is to refer to the equatorial radius, unless the polar radius is specifically needed.

== Comparison ==
{| class="wikitable sortable" style="margin-left: 20px;"
|+ Radii of noteworthy [[astronomical object]]s relative to Jupiter
|-
! Object
! {{Jupiter radius}} / ''R<sub>object</sub>''
! class="unsortable"|Ref
|-
| [[Lunar radius]]
| 41
| align="center" |<!--No citation is needed. These qualify as routine calculations under WP:OR using (referenced) radii of solar system objects-->
|-
|[[Earth radius]]
| 11.209
| align="center" | <ref name="jupfact">{{cite web |url=http://nssdc.gsfc.nasa.gov/planetary/factsheet/jupiterfact.html |title=Jupiter Fact Sheet |publisher=[[NASA]] |last=Williams |first=Dr. David R. |access-date=2009-07-16 |date=2 November 2007}}</ref>
|-
| [[Jupiter]]
| '''{{val|1}}'''
| by definition
|-
| [[Solar radius]]
| 0.10045
| align="center" |<!--No citation is needed. These qualify as routine calculations under WP:OR using (referenced) radii of solar system objects-->
|}

For comparison, one Solar radius is equivalent to:
* 400 Lunar radius ({{Lunar radius}})
* 109 Earth radius ({{Earth radius}})
* 9.955 Jupiter radius ({{Jupiter radius}})

== References ==
{{Reflist}}

{{Jupiter}}

[[Category:Planetary science]]
[[Category:Units of measurement in astronomy]]
[[Category:Jupiter|Radius]]
[[Category:Units of length]]
[[Category:Radii]]