How long is a day on different planets?

Answer 1

The length of a planet's "day" is normally determined by its rotational speed, which varies and is fastest on the larger planets. For two inner planets, the rotation is so slow that the "solar day" (sunrise to sunrise) is determined primary by their revolution around the Sun. For Uranus, its tilt means that the day or night is determined by its 84 Earth year orbit around the Sun.

Mercury:

rotates once every 58.6 Earth days - solar day is 176 Earth days

(twice the length of its year)

Venus :

rotates once every 243 Earth days, east to west - solar day is 116.75 Earth days

(its year is 224 Earth days).

Earth:

rotates once every 23.93 hours - solar day is 24 hours

(Earth rotates 366.25 times a year)

Mars :

rotates once every 24.66 Earth hours - solar day is 24.6 Earth hours

(the much longer year means the number of rotations roughly equals the number of days)

Jupiter :

rotates once 9.925 earth hours - solar day is 9.925 Earth hours

(the atmosphere in the equatorial regions takes only 9.84 hours to rotate - it is a gas planet)

Saturn :

rotates once every 10.65 Earth hours - solar day is 10.65 Earth hours

(the atmosphere in the equatorial regions takes only 10.23 hours to rotate)

Uranus :

rotates once every 17.24 Earth hours - solar day is 42 Earth years

(the planet is tipped on its side - each pole spends 42 Earth years in sunlight or darkness)

Neptune :

rotates once every 16.1 hours - solar day is 12 to 18 Earth hours

(the gases of Neptune's atmosphere rotate fastest at the poles: 1.5 times faster than the equator)

Dwarf planet Pluto:

rotates once every 6.39 Earth days - solar day varies by location (as long as 100 years)

(axial tilt is 120 degrees, 60 degrees from its orbital plane - areas of the planet can be in sunlight for decades at a a time)