Perihelion Day

Perihelion is the point when a planet, comet, or asteroid is at its closest to the Sun. It’s the reason why Perihelion Day is observed at the beginning of January. This holiday celebrates the Earth being at the closest point to the Sun’s center, an event that occurs approximately 2 weeks after the December Solstice each year.

This places it around January 4th each year, approximately 6 months before Aphelion Day. For those wondering, Aphelion Day occurs around July 4th each year, and it’s the point when the Earth is the most distant from the center of the Sun.

The History of Perihelion Day

Perihelion Day is a holiday that was never officially created. It’s just the day when this particular astronomical occurrence is observed. Although ancient peoples such as the Babylonians observed the motions of planets thousands of years ago, the fact that the Earth orbits the Sun in an ellipse, not a circle, wasn’t discovered until the 17th century.

This is when astronomer Johannes Kepler published two of his three laws of planetary motion. It was then that the perihelion of the planet was officially observed and noted for the first time.

Some Quick Facts About Perihelion

Even though we believe that we have covered most of the facts that we know about perihelion, we thought that we’d list a few extra facts to make sure that we have covered all of our bases. With that being said, let’s take a look at the following facts below.

  • The word perihelion comes from the Greek words “peri,” meaning “near,” and “Helios,” the name for the Greek god of the sun.
  • All asteroids, comets, and planets in our solar system have a perihelion and an aphelion due to their elliptical orbits.
  • In early January, Earth is about 91.4 million miles from the Sun.
  • In early July, Earth is about 94.5 million miles from the Sun.
  • In January, it’s winter in the Northern Hemisphere and summer in the Southern Hemisphere.

Observing Perihelion Day

How do you observe Perihelion Day? Well, there are several things that a person can do on this day. They can throw a Perihelion Party for their friends and family members, they can look up astronomical data on the internet, or they can simply acknowledge to themselves that the Earth is a little bit closer to the Sun. People can also use the hashtag #PerihelionDay to spread the word about this day.

When is it?
This year (2024)
January 3 Wednesday
Next year (2025)
January 4 Saturday
Last year (2023)
January 4 Wednesday
Nature & Environment