What is Earth's Perihelion and Aphelion?

Size

• The Earth travels around the Sun in a more circular orbit that most of the other planets in the solar system. This means that the Sun is more or less in the center of the orbital path. The perihelion of Earth in regards to the Sun is 91 million miles; its aphelion is 95 million miles. This puts the Earth at an average distance of 93 million miles from the Sun.

Significance

• The distance that the Earth is from the Sun is vital to life on the planet. Too close and the heat of the entire planet would increase. Too far and the Earth would turn into a frozen world. The distance Earth is from the Sun during perihelion and aphelion does not make enough of a difference to affect the planet's climate. If it had an orbit shaped such as Mercury does, with a perihelion of 28 million miles and an aphelion of 44 million, the drastic change would be disastrous.

Types

• There are different types of orbit around the Sun. One is a more or less circular one such as Earth enjoys, as do most of the planets, although they are far from perfect circles. Another is a more elliptical orbit, the type that planets like Mercury and the dwarf planet Pluto have. An elliptical orbit means that the path around an object is shaped like a circle that has been "pulled on" and "stretched out." It is more of an oval, taking the planet much further from the Sun at aphelion than it is at perihelion. Comets have extremely elliptical orbits as well, with some going well out of the solar system before the Sun's gravitational pull brings them back around it.

Misconceptions

• People often misconstrue the reasons for the seasons on Earth, thinking that when the Earth is at aphelion, farthest away from the Sun, that it is winter. However, the real cause of the seasons is the tilt of the Earth on its axis as it orbits the Sun. As the planet travels around the sun the hemisphere that is tilted towards it experiences summer; the one tilted away undergoes winter. Sunlight traveling directly to the Earth's surface as that hemisphere is tilted towards it accounts for the warmer temps. Indeed, Earth is at perihelion, closest to the star, in January, right in the middle of the northern hemisphere's coldest season.

Considerations

• The word perihelion comes from the Greek, with "peri" meaning near and "helios" meaning the Sun. Conversely, "apo" in Greek means away from. When the Earth is its farthest from the Sun it is said to be at apogee. When it is closest it is at perigee.