For us, 365 days make up a year because Earth takes as many days to complete one orbit of the Sun. But have you ever wondered how many days make up a year on other planets?
What determines the length of a year?
The length of a year on any planet depends on where the planet is orbiting. Planets that are closer to the Sun than Earth will have fewer days in a year, while those rotating farther away will take many more days to make up a year. This is because of two reasons – planets that are closer to the Sun will take a shorter time to orbit it than those farther away, and the closer a planet orbits the Sun, the Sun’s gravity can pull on the planet, making the planet orbit faster.
Why should we care?
To send a spacecraft to another planet, we need to know where the planet is in orbit. This will help us plan and manoeuvre the spacecraft accordingly. Imagine not knowing where a planet is in orbit; we’d be looking all over the universe for that one planet!
How long each planet takes to orbit the Sun (in Earth days):
Mercury: 88 days
Venus: 225 days
Earth: 365 days
Mars: 687 days
Jupiter: 4,333 days
Saturn: 10,759 days
Uranus: 30,687 days
Neptune: 60,190 days