How Long Does It Take the Earth to Complete an Orbit Around the Sun?
It takes roughly 365 days, or 1 year, for the Earth to complete its orbit around the Sun. Although it is an elliptical orbit, it is almost circular, so there is only a slight difference between the closest and farthest points from the Sun throughout the orbit. The two-dimensional plane occupied by the Earth's orbit is called the ecliptic.
To complete its orbit in 365 days, the Earth travels around the Sun at a speed of about 67,000 miles an hour. The changing yearly seasons are the result of the Earth's orbit around the Sun combined with its own rotation and the 23.5-degree tilt away from the perpendicular of that rotational axis. The Earth's tilt remains fixed; it always points to the pole star, Polaris. This causes the Earth's top and bottom halves, the Northern and Southern Hemispheres, to be tilted away from the Sun during opposite points in the yearly orbit. This results in the change of seasons and accounts for why the seasons are reversed on either side of Earth's equator.
In terms of mass, the Sun is about 330,000 times the mass of the Earth. It is almost a perfect sphere with a diameter about 109 times the Earth's and accounts for approximately 99.86 percent of the Solar System's total mass.