Jupiter radius

The Jupiter radius or Jovian radius (Template:Jupiter radius or Template:Jupiter radius) has a value of , or 11.2 Earth radii (Template:Earth radius) (one Earth radius equals Template:Jupiter radius). The Jupiter radius is a unit of length used in astronomy to describe the radii of gas giants and some exoplanets. It is also used in describing brown dwarfs.

The general shape of the planet Jupiter has been directly measured from radio occultations of passing spacecraft, starting with the Pioneer and Voyager missions. This gives an overall margin of error of about 5 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 km, as of 1987. Density fluctuations within the planet can create variations in the equatorial radius of up to 30 km. The winds in the outer atmosphere can vary the radius by up to 4 km.

In 2015, the International Astronomical Union defined the nominal equatorial Jovian radius to remain constant regardless of subsequent improvements in measurement precision of Template:Jupiter radius. This constant is defined as exactly:

${{ℛ}}_{\mathrm{e}\mathrm{J}}^{\mathrm{N}}$ =

Similarly, the nominal polar Jovian radius is defined to be exactly:

${{ℛ}}_{\mathrm{p}\mathrm{J}}^{\mathrm{N}}$ =

These values correspond to the radius of Jupiter at 1 bar of pressure. The common usage is to refer to the equatorial radius, unless the polar radius is specifically needed.

Comparison

Radii of noteworthy astronomical objects relative to Jupiter

Object	Template:Jupiter radius / Robject	Ref
Lunar radius	41
Earth radius	11.209
Jupiter		by definition
Solar radius	0.10045

For comparison, one Solar radius is equivalent to:

• 400 Lunar radius (Template:Lunar radius)
• 109 Earth radius (Template:Earth radius)
• 9.955 Jupiter radius (Template:Jupiter radius)