Perihelion Day 2025: When Will the Sun Be Closest to Earth? Date, Time, and Astronomical Significance

Perihelion Day 2025: When Will the Sun Be Closest to Earth? Date, Time, and Astronomical Significance

As Earth journeys through its elliptical orbit around the sun, there comes a point each year when it reaches its closest proximity to our star. This event, known as perihelion, occurs in early January. In 2025, perihelion will happen on January 4 at 13:00 UTC (7:00 a.m. CST). At this moment, Earth will be approximately 91,405,993 miles (147,103,686 km) away from the sun.

Perihelion: Why Does It Happen?

Earth’s orbit around the sun is not a perfect circle. Instead, it is slightly elliptical, resembling a flattened circle or oval. This elliptical shape means that Earth has a closest point, called perihelion, and a farthest point, known as aphelion, in its orbit each year.

At perihelion, Earth is about 3% closer to the sun than at aphelion, which occurs in early July. This translates to a difference of roughly 1.5 million miles (2.5 million km). On average, Earth is about 93 million miles (150 million km) from the sun. While this variation in distance is fascinating, it’s not enough to impact the seasons or temperatures significantly.

Why Earth’s Distance from the Sun Doesn’t Cause Seasons?

It’s a common misconception that Earth’s proximity to the sun determines the seasons. In reality, the seasons are caused by the tilt of Earth’s axis, not the distance from the sun.

When it’s winter in the Northern Hemisphere, that part of Earth is tilted away from the sun, resulting in shorter days and less direct sunlight. Conversely, during summer, the Northern Hemisphere is tilted toward the sun, receiving more direct sunlight and longer days. The same principle applies to the Southern Hemisphere, where the seasons are opposite.

The Role of Earth’s Orbit in Seasonal Lengths

While Earth’s distance from the sun doesn’t cause the seasons, it does influence their duration. Earth moves fastest in its orbit when it is closest to the sun, due to the gravitational pull being stronger. This increased speed shortens the length of winter in the Northern Hemisphere and summer in the Southern Hemisphere.

For example, Northern Hemisphere winter lasts nearly five days shorter than summer. The Southern Hemisphere experiences the opposite, with winter being longer than summer. This phenomenon aligns with Kepler’s second law of planetary motion, which states that a planet moves faster when it is closer to the sun and slower when it is farther away.

How Perihelion Affects the Sun’s Appearance? 

At perihelion, the sun appears slightly larger in the sky than at aphelion due to its closer proximity. However, this size difference is subtle and not noticeable to the naked eye. It’s important to remember that one should never look directly at the sun without proper eye protection.

Perihelion 2025: Astronomical Significance

Perihelion provides a unique opportunity to observe and appreciate the mechanics of Earth’s orbit and its interaction with the sun. It serves as a reminder of the delicate balance and precision of celestial movements that govern life on our planet.

As Earth races through its orbit at a speed of nearly 19 miles per second (30.3 km/s) during perihelion, we gain a greater understanding of our place in the cosmos. This event is a testament to the principles of physics and astronomy that continue to shape our understanding of the universe.

Perihelion Day on January 4, 2025, marks an astronomical milestone that highlights Earth’s dynamic relationship with the sun. While it may not have a direct impact on our daily lives, it underscores the intricate workings of the solar system. Whether you’re an astronomy enthusiast or simply curious about the natural world, Perihelion Day offers a chance to marvel at the wonders of our celestial neighbourhood.

Also Read | Perihelion Day 2025: Know date and time when the Sun will be biggest and closest to Earth