On January 2, 2021, the Earth is closer the sun in its elliptical orbit than on any other day of the year, marking an annual event called perihelion.
The word perihelion is translated from the Ancient Greek, meaning “near the sun.” According to EarthSky, Earth was expected to reach perihelion Saturday morning at 8:51 am ET.
The sun about 3% more is in the skies Saturday – not enough to be visible to the naked eye. Remember: You should never look at the sun without proper eye protection, and sunglasses are not a sufficient replacement for sunglasses.
Earth’s orbit is not a perfect orbit, meaning sometimes the planet is a little closer to our star, and sometimes it is further away. The distance varies by about 3 million miles over the year – almost 13 times the distance from Earth to the moon.
Perihelion also marks the moment when the Earth moves at the fastest rate in orbit around the sun. The planet is currently racing around the sun at nearly 19 miles per second – about .6 miles per second longer than when it reaches its furthest point from the sun in July.
“If you run east at midnight locally, you move around as fast as you can (at least in mid-solar coordinates) for your position,” NASA said.
Because of this, summer in the Northern Hemisphere lasts about five days longer than winter, according to EarthSky. The opposite is true in the Southern Hemisphere.
Although sunlight is more intense on Saturday, winter is unaffected in the Northern Hemisphere, due to the 23.5-degree tilt on the Earth’s axis. Being closer to the sun does not change the tilt of the Earth, so the North Pole is still filtered away from the sun.
Six months from now, on July 5, the Earth will be at its farthest from the sun, called its aphelion, meaning “far from the sun.” At perihelion, the Earth is about 91.5 million miles from the sun, and at aphelion, it is about 94.5 million miles away.
Between perihelion and aphelion, there is about a 6.7% difference in the intensity of sunlight as it hits our planet. According to NASA, this is one explanation for longer seasons in the Southern Hemisphere compared to the Northern Hemisphere.
The perihelion is not the only celestial event this weekend. Saturday night into Sunday morning will also mark the height of the Quadrant meteor shower – one of the best of the year.