What is Perihelion Day? Know All Key Facts About The Astronomical Event When Earth Is Closest To The Sun

Here is the first astronomical event of the year 2024. Today, 3rd January marks Perihelion Day, a fascinating astronomical event when Earth comes to a point closest to the Sun in its elliptical orbit. While you won't witness a dramatic shift in our planet's environment however it is a day to appreciate the dynamic relationship between Earth and the Sun that shape our planet and its place within the vast universe. Remember, even slight changes in the intricate symphony of celestial forces can have profound consequences for Earth's environment and the life it sustains.

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What is Perihelion Day?

Image: NASA

Unlike a perfect circle, Earth's path around the Sun resembles an elongated oval, an ellipse. This means our distance from the Sun constantly changes throughout the year. Perihelion Day is the annual astronomical event when Earth reaches its closest point to the Sun in its elliptical orbit.

On Perihelion Day, Earth comes closer to the Sun although the difference in distance is relatively small. At perihelion, Earth is roughly 147 million kilometres (91 million miles) away from the Sun, compared to its furthest point (aphelion) of about 152 million kilometres (94 million miles). This translates to a difference of only about 3%, which is not enough to significantly impact Earth's temperature or weather patterns.

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Does Earth get hotter on Perihelion Day?

Surprisingly, not really! Earth's seasons are mainly determined by the tilt of its axis, not its distance to the Sun. So, Perihelion Day in January won't bring a sudden heat wave, even in the Southern Hemisphere which is experiencing summer at that time.

What is the significance of Perihelion Day?

Higher tides: The Sun's gravitational pull does intensify slightly at perihelion, influencing Earth's tides. Expect a small increase in high tide heights and a corresponding decrease in low tide levels, primarily noticeable in the Southern Hemisphere. The changes, however, are subtle and unlikely to be impactful for most coastal regions.

Climate clues: Studying perihelion and its effects helps scientists understand Earth's long-term orbital cycles and their influence on climate patterns.

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Is Perihelion Day a visual event?

Unfortunately, no. Perihelion itself is an astronomical event, not a visual spectacle. You won't see the Sun looking any bigger or brighter on 3rd January.

Fun Fact: Other planets in our solar system also have elliptical orbits and their own perihelion and aphelion points. For example, Mercury, the closest planet to the Sun, experiences a dramatic 46% temperature swing between its Perihelion and Aphelion Day! On its Perihelion Day, Mercury is only 46 million km from the Sun's centre while 70 million km on Aphelion Day.

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