Answer: Jupiter

When it comes to traveling around the Sun, Jupiter takes a lazy 11.86 Earth years to do it. When it comes to rotating on its axis, however, Jupiter is practically whirling like a figure skater. While Earth has a rotation period just shy of 24 hours, Jupiter has an average rotation period of slightly less than 10 hours. If you have a long day ahead of you after reading this bit of trivia, it’s quite possible Jupiter will complete two full rotations before you find yourself in bed.

In fact, the rotation speed of Jupiter is so fast and exerts so much centrifugal force upon the gas giant that it creates an equatorial bulge, causing the planet to be shaped like an oblate spheroid. This means that the diameter across Jupiter’s equator is 5,763 miles (9,275 kilometers) longer than the diameter measured between its poles. This bulge is so pronounced that it can be easily seen from Earth with an amateur telescope.