Tonight

Earth closest to sun on January 3-4, 2022

Cartoon by Sara Zimmerman of Unearthed Comics showing Earth in a dance with the sun
Cartoon via Sara Zimmerman at UnEarthed Comics.

Earth at aphelion and perihelion

Earth’s orbit around the sun isn’t a circle. Instead, it’s an ellipse. So it makes sense that Earth swings closest to the sun once each year. For 2022, that moment will happen on January 4, at 6:52 UTC (1:52 a.m. Eastern Time EST). This closest Earth-sun distance is called perihelion, from the Greek roots peri meaning near and helios meaning sun. In early January, we’re about 3% closer to the sun — roughly 3 million miles (5 million km) — than we are during Earth’s aphelion (farthest point from the sun) in early July. That’s in contrast to our average distance of about 93 million miles (150 million km).

Precise perihelion and aphelion distances here o

So Earth is closest to the sun every year in early January, when it’s winter for the Northern Hemisphere.

And we’re farthest away from the sun in early July, during our Northern Hemisphere summer.

Earth’s orbit doesn’t cause seasons

So Earth’s orbit isn’t a circle. But it’s very nearly circular. And it’s not our distance from the sun that creates winter and summer on Earth. Instead, it is the tilt of our world’s axis that causes seasons.

In winter, your part of Earth is tilted away from the sun. In summer, your part of Earth is tilted toward the sun. The day of maximum tilt toward or away from the sun is the December or June solstice.

Diagram of Earth orbit showing perihelion and aphelion.
Image via NASA.
Two images of the sun appear aso yellow disks side by side, each with a few dark splotches that are sunspots. The disk on the left, the sun at aphelion, is slightly smaller.
Two images of the sun taken six months apart. The image on the left shows the sun at aphelion, as it appeared on the first week of July in 2012, when it was about 94.5 million miles (152.1 million km) away. On the right is an image of the sun taken 6 months later, at perihelion, when it was 3 million miles (5 million km) closer compared to aphelion. It is slightly larger than the image on the left, but by a barely noticeable amount. Image via Zoltán Bánfalvy / Flickr.com.

Earth’s orbit slightly affects length of the season

Though not responsible for the seasons, Earth’s closest and farthest points to the sun do affect seasonal lengths. When the Earth comes closest to the sun for the year, as we do every year in early January, our world is moving fastest in orbit. Earth is rushing along now at almost 19 miles per second (30.3 km/sec) – moving about 0.6 miles per second (one km/sec) faster than when Earth is farthest from the sun in early July. Thus the Northern Hemisphere winter and – simultaneously – the Southern Hemisphere summer are the shortest seasons as Earth rushes from the solstice in December to the equinox in March.

In the Northern Hemisphere, the summer season (June solstice to September equinox) lasts nearly five days longer than our winter season. And, of course, the corresponding seasons in the Southern Hemisphere are opposite. Southern Hemisphere winter is nearly five days longer than Southern Hemisphere summer.

The 30-second YouTube video below illustrates how a planetary body speeds up around perihelion and slows down at aphelion. It’s due to Kepler’s second law of planetary motion: a line connecting the sun and a planet sweeps out equal areas in equal times.

A diagram of an ellipse representing the Earth’s elliptical orbit. The equinox and solstice positions are marked along the orbit, as are the aphelion and perihelion positions. The ellipse is divided into four quadrants to show when the seasons occur during Earth’s orbit around the sun.
For 2022, the Northern Hemisphere winter stretches from December 21, 2021 to March 20, 2022. Perihelion occurs within this period, on January 4, 2022. Since Earth moves faster the closer it is to the sun, the Northern Hemisphere winter period is shorter by almost 5 days compared to the Northern Hemisphere summer when the Earth is moving more slowly in its orbit.

Bottom line: In 2022, Earth’s perihelion, its closest point to the sun, is on January 4 at 06:52 UTC.

Posted 
January 3, 2022
 in 
Tonight

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