Is the Earth's Orbit Round?

Significance

• The average distance from the Sun to the Earth while in its orbit is 93 million miles. This is called one astronomical unit and is a useful measurement when gauging distances within the solar system.

Size

• The closest the Earth approaches the Sun, known as its perihelion, is 91.4 million miles, while the furthest the Earth is from the Sun, its aphelion, is 94.8 million miles.

Time Frame

• Perihelion occurs around January 2 each year while the aphelion stage of its orbit falls around July 2.

Considerations

• Astronomers employ a term known as eccentricity to measure how far from perfectly circular a heavenly body's orbit is. The Earth has an eccentricity of 0.017--only Venus and Neptune have orbits closer to being perfectly round.

Effects

• The distance from the Sun that the Earth is does not cause the seasons. The Earth tilts on its own axis about 23.5 degrees as it goes around the Sun, meaning when the northern hemisphere is tilted towards the Sun on its way around the star it is summer and when it tilts away, it is the winter season.