A planet's north pole is defined by its position relative to the solar system's invariable plane. The invariable plane is a fixed reference point perpendicular to the solar system's rotation. A planet ...

A planet's year length depends on its distance from the Sun. Planets closer to the Sun have shorter years. A planet's rotation speed is unrelated to its year length. Planets' orbital speeds vary ...

Astronomers using NASA’s Hubble Space Telescope have measured the rotation rate of an extreme exoplanet by observing the varied brightness in its atmosphere. This is the first measurement of the ...