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SatJan 4

Perihelion Day – January 4, 2025

Perihelion Day is on January 4 this year. It occurs about two weeks after every December Solstice, and on this day, Earth’s center is approximately 91,402,500 miles from the sun’s center. Numerical integration is required to make precise predictions of perihelion passage. It is quite interesting to see what goes on in the universe and the planet on which we live. Perihelion is one of those many interesting occurrences. On this day, we can keep a lookout for the big ball of fire being at its largest.

History of Perihelion Day

Perihelion is an astronomical occurrence that happens around two weeks from the December Solstice. Even though it is winter in the Northern Hemisphere during this period, Earth reaches the closest point of over 91 million miles to the sun on this day. Perihelion does not directly affect Earth’s temperature; it does not make us feel any warmer, nor does it provide respite from the chilling temperature. However, it does indirectly affect seasons because Earth’s orbital speed is at its maximum at perihelion. On this day, the sun appears the largest in the sky for the entire year, gradually growing smaller through the remainder of the year. 

In 1246, Perihelion Day was on the December Solstice. Every 58 years since then, the date has changed by a day. Perihelion Day varies each year due to precession and orbital factors that follow specific cyclical patterns known as the Milankovitch cycles. Another cause is the moon’s presence, which can make the date vary by up to two days from one year to another. While the Earth-Moon barycenter moves on a stable orbit around the sun, Earth’s center, which is around 2,900 mi from the barycenter, can shift in any direction from it, thus affecting the actual time of the perihelion. 

In 2000, the longitude of the perihelion was about 282.895°, and by 2010, it had become around 283.067°. According to astronomers, in the year 6430, the perihelion will happen simultaneously as the March Equinox.

Perihelion Day timeline

The Term is Coined

Johannes Kepler coins the terms ‘Perihelion’ and ‘Aphelion.’

17th Century
Orbit Laws are Discovered

Johannes Kepler and Isaac Newton discover the basic planetary laws which the orbits follow.

19th Century
Mercury's Perihelion Shift

It is observed that Mercury's perihelion shift is different by about 43 arcseconds per century from what the classical gravitational theory predicted.

Theory of Relativity

Albert Einstein’s general theory of relativity gives a more detailed description of Kepler's orbit laws.

May 11, 1984
Observing the Earth

Earth is observed in transit from Mars across the solar disk.

Tidal Ranges are Enhanced

Sumich, J.L., reports that during Earth’s perihelion, the tidal ranges are enhanced.

Perihelion Day FAQs

Is perihelion the same as perigee?

No. ‘Perihelion’ refers to a celestial body orbiting the sun, while ‘Perigee’ refers to a celestial body orbiting Earth.

What part of Earth is closest to the sun?

The summit of the Chimborazo volcano in Ecuador is considered the closest to the sun. The volcano is furthest from the center of Earth, which makes it the nearest point to the sun.

Which is the closest star to Earth?

The Alpha Centauri triple-star system is the closest to our planet, and it is roughly 4.37 light-years away.

How to Observe Perihelion Day

  1. Read about astronomy

    Many astronomical events occur that we are not aware of and don’t understand. For instance, if perihelion means Earth is closest to the sun, it should also mean we would experience hotter temperatures, right? Wrong. This occurrence falls during winter! Brush up on your astronomy to understand the science behind this.

  2. Do a science project

    This day can be an excellent excuse to do a little science project just like the old days. Make cardboard cutouts of the sun and the earth, and show how planet Earth is closest to the sun on this day. It will be a fantastic way for kids to learn science.

  3. Visit a planetarium

    Planetariums offer a unique experience of space without going to space, which is quite tricky if you’re not an astronaut. Visit a planetarium on Perihelion Day, view planets from a telescope, attend a show about the planets and stars, and learn more about how the galaxies function.

5 Important Facts About Perihelion

  1. A Greek word

    The name comes from the Greek words ‘peri’ (near) and ‘helios’ (sun).

  2. The aphelion is the exact opposite

    The opposite of perihelion is aphelion, which is when Earth is farthest from the sun.

  3. Distance is still very far

    The difference in distance between Earth's nearest point to the sun in January and the farthest point from the sun in July is 3.1 million miles, only a 7% difference.

  4. Seasons during the Perihelion

    On perihelion, it is winter in the northern hemisphere and summer in the southern hemisphere.

  5. It affects the seasons in some way

    Perihelion doesn’t make the seasons happen, but Earth moves faster as it gets closer to the sun, which means a five-day shorter winter in the Northern Hemisphere and summer in the Southern Hemisphere.

Why Perihelion Day is Important

  1. It’s a remarkable astronomical occurrence

    The earth's closeness to the sun is a rather unique event, happening only once a year. Many such instances occur in space that affect the way our planet works.

  2. It teaches us about the seasons

    We learn that even though the earth is closest to the sun, we don’t experience blazing hot temperatures during this holiday. Due to the earth’s tilted axis, it does not affect the seasons directly. The northern hemisphere will be wearing layers of clothes to keep warm from the freezing temperatures today.

  3. We appreciate the professionals

    Determining the perihelion or any other astronomical event isn’t easy. It requires a great deal of calculation and work. Highly qualified astronomers and mathematicians have to work with utmost precision and clarity to determine such occurrences.

Perihelion Day dates

2022January 4Tuesday
2023January 4Wednesday
2024January 3Wednesday
2025January 4Saturday
2026January 3Saturday

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