Which planet has the longest day sunrise to sunrise?

Answer 1

Venus has the longest sidereal day (period of rotation or spin). This "day" is 243.0185 Earth days long and Venus rotates in the opposite direction of Earth. This day on Venus is actually longer than its "year". It takes more time for the planet to turn one time on its axis than it takes to go around the Sun. A "year" on Venus takes only 224.7 Earth days.

However, the longest solar day occurs on Mercury, which completes its slow spin about once every 59 Earth days but also circles the Sun in just 88 Earth days. This tidally-locked combination leads to a solar day (roughly sunrise to sunrise) of 176 Earth days, twice as long as the "year".

On Venus, because it rotates clockwise but orbits counter-clockwise, the effect is to make a solar day ("daytime" is brighter, but there's no sunrise through the clouds) about 116.75 Earth days.

Minor comment: The actual question may be asking something different, but that's not clear.

Answer 2

Venus, with a rotational period of 243 Earth days. Since the year on Venus is 224.7 Earth days, the "day" is substantially longer than the "year"!

Edit: Those facts are right, but unfortunately it's not the right answer. The

correct answer is Mercury, because it has the longest "solar day", even though it doesn't have the longest rotation period ("sidereal day").

The "solar day" is (more or less) the time from "sunrise to sunrise". So, the planet with the longest "solar day" has the longest daylight, from "sunrise to sunset".

(Venus spins on its axis in the opposite direction to Mercury. That results in

Mercury having a longer solar day than Venus.)
It is Mercury. It is NOT Venus.

Venus rotates more slowly than Mercury, but Mercury has a longer "solar day",

which is "sunrise to sunrise" (roughly). So, Mercury also has the longest periods

of daylight, "sunrise to sunset".

(Venus rotates in the opposite direction to most planets and that's why its

solar day is not as long as Mercury's solar day.)

Answer 3

Many people think it's Venus, but it's not. The answer is Mercury. The important

point is that Mercury has the longest "solar day".

The solar day is (roughly) "sunrise to sunrise". So, the planet with the longest "solar day" will also have the longest "daytime" (from sunrise to sunset).

Venus rotates more slowly than Mercury, but in the opposite direction.

The result is that Mercury has the longest "solar day" in the solar system.

Answer 4

The longest day on any planet is at its poles, where the sun rises and sets once per orbit. Therefore, the longest sunrise to sunrise duration is on the planet with the largest orbit or the farthest one from the sun, Neptune. After the sun rises at one of Neptune's poles it doesn't rise again until 164.8 Earth years later.

Speaking equatorially, the longest period from one sunrise to the next is about 176 Earth days, on Mercury.

Answer 5

Venus has the longest day from sunrise to sunrise, lasting about 117 Earth days. Due to its extremely slow rotation on its axis, a day on Venus is longer than its year.