Jupiterradius

Jupiterradius, often abbreviated as Rjup or RJ, is the standard unit of planetary radius based on Jupiter, the largest planet in the Solar System. It is defined by Jupiter’s equatorial radius and is used to express the sizes of gas giants and exoplanets in a relative scale.

Jupiter is an oblate spheroid because of its rapid rotation. Its equatorial radius is about 71,492 kilometers, its polar radius about 66,854 kilometers, and its mean radius about 69,911 kilometers. In meters these are 7.1492×10^7 m, 6.6854×10^7 m, and 6.9911×10^7 m, respectively. In Earth radii this corresponds roughly to 11.21, 10.49, and 10.97 Earth radii. The equatorial radius is commonly used to define 1 Rjup, while the other radii reflect the planet's flattening.

Because Jupiter is not a perfect sphere, its radius varies with latitude; the planet’s flattening is about 0.0649. In astronomical literature, Rjup is used as a convenient scale for comparing the sizes of gas giants, including many exoplanets whose radii are expressed in units of Jupiter radii.

Rjup is not a fundamental constant; it depends on the model of Jupiter’s shape and on the adopted reference radius. Nonetheless it remains a widely used reference in planetary science and exoplanet research.