What Are Perihelion and Aphelion?

When Earth is Closest and Farthest from Sun in 2020

December 31, 2019
Earth Near Sun

Sunset over Earth oceans as seen from the International Space Station.

JSC/NASA

Earth reaches at its closest approach to the Sun near midnight on January 4–5, 2020. We call this point in Earth’s orbit around the Sun “perihelion.” Interestingly, we’re closest to our fiery star in the winter and farthest away in the hot summer. Learn more.

In 2020, Earth is at perihelion on January 5, 2020, at 2:48 a.m. Eastern Time, 1:48 a.m. Central Time, and 12:48 a.m. Mountain Time. This translates to January 4, 2020, at 11:48 p.m. Pacific Time, 10:48 p.m. Alaskan Time and 9:48 p.m. Hawaiian Time.

In 2020, Earth is at aphelion on July 4, 2020, at 7:34 a.m. Eastern Time, 6:34 a.m. Central Time, 5:34 a.m. Mountain Time, 4:34 a.m. Pacific Time, 3:34 a.m. Alaskan Time, and 2:34 a.m. Hawaiian Time.

What are Perihelion and Aphelion?

The terms perihelion and aphelion describe different points in the Earth’s orbit of the Sun.

Remember that the Earth orbits the Sun in an elliptical path—which is oval, not circular. It’s 3 million miles nearer every January than in July at its farthest point.

  • Aphelion is the point of the Earth’s orbit that is farthest away from the Sun.
  • Perihelion is the point of the Earth’s orbit that is nearest to the Sun.

The words come from Ancient Greek, in which helios means “Sun,” apo means “far,” and peri means “close.”

orbit-3_0.jpg
Image credit: NASA (Note that “perihelon” should be spelled “perihelion” in above graphic.

When are Aphelion and Perihelion?

  • Aphelion always happens in early July. About two weeks after the June solstice, Earth is farthest from the Sun.
  • Perihelion always happens in early January. About two weeks after the December Solstice, Earth is closest to the Sun.

Isn’t it interesting that the Earth is farthest from the Sun during the hot summer months and closest during the winter months? 

  • Though this doesn’t seem to make sense, it’s the not the distance from the Sun that causes our seasons. Seasons happen because Earth’s axis is tilted at an angle. It’s because Earth orbits the Sun on a tilt that our planet gets more or less of the Sun’s direct rays at different times of the year.

Did you know that the Moon’s orbit around the Earth is also elliptical? The point in the Moon’s orbit that is closest to the Earth is called the “perigee” and the point farthest from the Earth is known as the “apogee.” Perigee and Apogee are often confused.

Aphelion and Perihelion on Mars

Though aphelion and perihelion are terms mostly used in reference to Earth since it’s our home planet, they are also relevant to other planets orbiting the Sun. Every planet has points in the orbits when they are farthest or closest away from their star.

For example, planet Mars has an even more elliptical orbit than Earth. In comparison, Earth’s orbit seems almost circular; this almost-circular orbit may be why Earth’s climate is relatively stable.

Mars also has four seasons but they are twice as long because it takes about two Earth years for Mars to go around the Sun. The southern hemisphere of Mars has a warmer, shorter spring and summer than in the north, as Mars is closest to the Sun towards the end of southern spring. The southern winter is longer because Mars is farthest away from the Sun then, moving more slowly in its elliptical orbit around the Sun.

For Mars, going from a colder winter to a warmer spring can be quite dramatic.

mars-orbit-year-seasons-winter-spring-summer-autumn-aphelion-perihelion_0_full_width.jpg
Image credit: JPL.NASA.gov

Discover more about the Reasons for the Seasons.

Reader Comments

Leave a Comment

Aphelion

I'm confused. It can't just be a coincidence that Aphelion ~ the Earth's *furthest distance* from the Sun, is so close to the Summer Solstice ~ when the Earth has its *maximum tilt* towards the Sun. And yet, if there *were* a connection between the two phenomena (maybe having to do with the gravitational pull between the two bodies?), then I'd think they'd have their "zeniths" on the same day: the furthest distance and maximum tilt would be marked by the same day, namely, the longest day of the year.

aphelion/perihelion and solstices

Good question! However, as it happens, aphelion and perihelion are not related to the summer and winter solstices. The times of aphelion/perihelion are slowly shifting. In 1246 a.d., for example, perihelion and the December solstice were on the same day. Now, they are a few weeks apart. In 6430 a.d., perihelion is expected to align with the March equinox.