# How many Earth days are equal to one day on Jupiter?

## 2 Answers

Samuel Chiltern answered
Jupiter has the fastest rotation of any planet in the Solar System. A day on Jupiter lasts for just 9.92 hours approximately.

This is less than half of a day on Earth - if you divide a Jovian day by the number of hours in an Earth day, you get 0.41 Earth days to every Jovian day.

How Did We Work Out the Length of a Day on Jupiter?
Jupiter doesn't have a solid surface, so at first it was very hard for scientists to establish how long a day on Jupiter actually lasted for. In the end, they measured fluctuations in Jupiter's magnetic field to establish the rotational period and speed.

Other parts of the planet rotate at different speeds to the core, but it is the rotation of Jupiter's magnetic field that is considered to be the official measurement.

At the equator, Jupiter rotates at a speed of 45,300 kilometres an hour. The planet is 'squashed' by this speed, making its diameter 9,275 kilometres wider at the equator than than the diameter from pole-to-pole.

The slowest rotational speeds can be found at the polar extremes, which take five minutes longer to complete their daily cycle.

Despite its short days, Jupiter has incredibly long years - it takes almost 12 Earth years for the planet to travel around the Sun. This is the same as 10,475 Jovian days.
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Nathan Corrie answered
About 0.41 Earth days. No, I haven't gotten it wrong. Despite its enormous size, Jupiter has the fastest rotation period (on its own axis) of all the planets - just 9 hours 55 minutes approximately.
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