Flattening

The flattening of an ellipsoid is the relative difference between its equatorial radius a and its polar radius b':

 f = (a - b) / a
 

• The flattening of the Earth is 1:298,25 (which corresponds to a radius difference of 21 km of the Earth radius 6357 - 6378 km) and would not be realized visually from space,
• whereas the flattening of Jupiter is 1:16 (which can be seen even in a small telescope, or that of Saturn ~ 1:10
• and of the Sun less than 1:1000.

The amount of flattening depends on

• the relation between gravity and centrifugal force, and in detail on
• size and density of the celestial body - see Figure of the Earth, last chapter
• the rotation of the planet or star
• the elasticity of the body.

See also: Astronomy, planetography, Earth rotation, gravity field

See also: Flattening, Astronomy, Centrifugal force, Density, Earth, Earth radius, Elasticity, Ellipsoid, Equator, Figure of the Earth