Earth closest to sun on January 4

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 2023, the Northern Hemisphere winter stretches from December 21, 2022, to March 20, 2023. Perihelion occurs within this period, on January 4, 2023. 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.

Earth at perihelion in January

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 2023, that moment happens at 16 UTC (10 a.m. CST) on January 4 … this morning for us in North America. 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).

NASA Earth Fact Sheet with precise perihelion and aphelion distances.

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.

Available now! 2023 EarthSky lunar calendar. A unique and beautiful poster-sized calendar showing phases of the moon every night of the year! Makes a great gift.

Diagram of sun at center with Earth circling, labeled with distances apart during aphelion and perihelion.
Earth is a bit closer to the sun at perihelion. Image via NASA.

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.

Large yellow circle on horizon.
This composite image shows the size of the sun at aphelion (farthest point) and perihelion (closest point). The composite shows an unmistakable size difference of the sun as viewed from Earth, across our yearly orbit. Image via Peter Lowenstein in Mutare, Zimbabwe. Read more about this photo.

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.

Bottom line: In 2023, Earth’s perihelion, its closest point to the sun, is on January 4 at 16 UTC.

January 4, 2023

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