Perihelion
From Wikipedia, a free encyclopedia written in simple English for easy reading.
The perihelion is the point in the orbit of a planet, asteroid or comet where it is nearest to the sun.
The word perihelion stems from root words "peri" (meaning "near") and "helios" (meaning "sun").
All planets, comets and asteroids in our solar system have non-circular orbits. Thus, they all have a closest and a farthest point from the sun: a perhelion and an aphelion.
Earth comes closest to the sun every year in early January. It is farthest from the sun every year in early July. The difference in distance between Earth's nearest point to the sun in January and farthest point from the sun in July is not very great. Earth is about 146 million kilometers from the sun in early January, in contrast to about 150 million kilometers in early July.
When Earth is closest to the sun, it is winter in the northern hemisphere and summer in the southern hemisphere. Thus it is possible to see that Earth's distance from the sun does not cause the season to change. Instead, Earth's seasons come and go because Earth does not orbit exactly upright with respect to the plane of our world’s orbit around the sun. Earth's axis is tilted to that plane by 23-and-a-half degrees. Winter falls on that part of the globe where sunlight strikes least directly. Summer falls on that part of the globe where sunlight strikes most directly.
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