Which planet has the shortest day?
Quick answer
Jupiter has the shortest day of any planet in our solar system: it spins once on its axis about every 9 hours and 56 minutes. That’s remarkably fast for the largest planet, and the spin is so quick that Jupiter bulges noticeably at its equator.
How long is a day on each planet?
| Planet | One rotation (sidereal day) | Notes |
|---|---|---|
| Mercury | ~59 Earth days | Its sunrise-to-sunrise day lasts about 176 Earth days |
| Venus | ~243 Earth days | Longest day; it spins backward |
| Earth | 23 h 56 min | A solar day is 24 hours |
| Mars | 24 h 37 min | Very similar to Earth’s |
| Jupiter | 9 h 56 min | Shortest day |
| Saturn | ~10 h 33 min | A close second |
| Uranus | ~17 h 14 min | Spins on its side |
| Neptune | ~16 h 6 min |
Why Jupiter spins so fast
Planets formed from spinning clouds of gas and dust. As material came together, it spun faster, just as an ice skater spins faster when pulling in their arms. Giant planets like Jupiter and Saturn collected so much spinning material that they still rotate rapidly billions of years later.
Effects of a fast spin
- Jupiter is about 7% wider at its equator than from pole to pole.
- Its fast rotation helps drive powerful jet streams and its colorful cloud bands.
- It also strengthens Jupiter’s enormous magnetic field.
Day vs year
A day is one spin on a planet’s axis; a year is one trip around the Sun. On Venus, a day is actually longer than its year (225 Earth days).
Jupiter is also the biggest planet; see what the largest planet is. For a planet that spins on its side, see which planet rotates on its side.
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