Celebrating Perihelion Day

What is Perihelion Day?

Perihelion Day is an astronomical event that occurs once a year, typically around two weeks after the December Solstice¹. On this day, Earth reaches its closest point to the Sun in its elliptical orbit¹. In 2024, Perihelion Day will be observed on January 3²³⁴, with Earth’s center approximately 91,402,500 miles from the Sun’s center².

Understanding Perihelion

The term ‘Perihelion’ comes from ancient Greek, where ‘peri’ means close, and ‘helios’ means the Sun¹. The Earth orbits the Sun in an elliptical path, which means that there is one point on the path closest to the Sun (Perihelion) and one point that is farthest away from the Sun (Aphelion)¹.

The shape of Earth’s orbital path varies due to the gravitational influences of other planetary objects, particularly the Moon¹. Approximately every 100,000 years, the Earth’s orbital path changes from being nearly circular to elliptical¹. The difference of the Earth’s orbital shape from a perfect circle is known as its eccentricity¹.

Perihelion and Seasons

Interestingly, the Earth is closest to the Sun, or at the perihelion, about two weeks after the December solstice, when it is winter in the Northern Hemisphere¹. Conversely, the Earth is farthest away from the Sun, at the aphelion point, two weeks after the June solstice, when the Northern Hemisphere is enjoying warm summer months¹.

The Shift in Perihelion

Due to variations in the eccentricity of the Earth’s orbit, the dates when the Earth reaches its perihelion or aphelion are not fixed¹. In 1246, the December Solstice was on the same day as the Earth reached its perihelion¹. Since then, the perihelion and aphelion dates have drifted by a day every 58 years¹. In the short-term, the dates can vary up to two days from one year to another¹. Mathematicians and astronomers estimate that in 6430, over 4000 years from now, the perihelion will coincide with the March equinox¹.

Conclusion

Perihelion Day is a fascinating reminder of our planet’s dynamic relationship with the Sun. As we continue to explore and understand the intricacies of our universe, events like Perihelion Day serve to remind us of the grandeur and mystery of the cosmos that surrounds us.

Source: Conversation with Bing, 12/23/2023
(1) Perihelion and Aphelion 2023 / 2024 – timeanddate.com. https://www.timeanddate.com/astronomy/perihelion-aphelion-solstice.html.
(2) PERIHELION DAY – January 3, 2024 – National Today. https://nationaltoday.com/perihelion-day/.
(3) PERIHELION DAY – January 3, 2024 – National Today. https://bing.com/search?q=Perihelion+Day.
(4) EARTH AT PERIHELION – January 3, 2024 – National Today. https://nationaltoday.com/earth-at-perihelion/.
(5) Perihelion: What is it and when does it occur? | Space. https://www.space.com/what-is-perihelion.