What determines how long a planet's year is?

Answer 1

A planet's year consists of the time it takes it to orbit the Sun. The Earth takes 365 and a quarter days to do this. Every 4 years there is a leap year which catches us up on these fractional days.

The position of a planet in its orbit can be determined by comparing its relative position from Earth when the Earth is in the "same" location (same day of the year). The positions of Venus and Mercury, which are closer to the Sun than Earth, can be observed directly, or indirectly by their "phases." The observation of phases of outer planets is a much more complex process, but also illustrates comparative positions in their orbits.

The location of a planet can be determined with some precision should it experience occultation (blockage) by the Sun. This establishes it on the opposite side of the Sun from Earth.

Answer 2

The length of a year for a planet is defined as the time it takes for that planet to orbit its star.

For example Earth takes about 365 days to orbit its star, the sun, so an Earth year is about 365 days. Jupiter takes about 11.86 Earth years to orbit its star (also the sun), so a Jupiter year is about 11.86 Earth years.

Earth years are often used to describe the length of years on other planets. The length of an Earth year doesn't change if you are on a different planet.

Answer 3

The time a planet takes to go around the Sun (its year) depends on its distance from the Sun.

More precisely, it depends on the semi-major axis of the orbit. That is the average between the apapsis and the periapsis of the planet's orbit (closest and farthest distance) - in other words, the average distance from the Sun (roughly speaking.

The relation between the distance and the period of the orbit is given by Kepler's Third Law.

Answer 4

Revolutions about the Sun are generally regarded as one year, Earth, Mars, Jupiter, or otherwise.

Answer 5

We estimate the distance between the sun and that planet, then we calculate the velocity of the planet.

Answer 6

Earth years are measured with a calendar.