What is perihelion? Here's what happens when Earth is nearest to the sun
Here's how the astronomical phenomenon influences our planet—from the length of our seasons to the way Earth moves through space.
At the start of the year, Earth will quietly reach a milestone in its orbit around the sun. Known as perihelion, this is the moment when our planet is closer to the sun than at any other point in the year.
In 2026, Earth's perihelion occurs on January 3 at 12:15 p.m. EST or 17:15 UTC. This astronomical event occurs about two weeks after the December solstice. The exact timing shifts slightly from year to year because the Gregorian calendar doesn't perfectly line up with Earth's orbit. However, leap years account for some of that discrepancy.
It might sound counterintuitive to some that Earth is closest to the sun right now—after all, January is winter across much of the Northern Hemisphere. But Earth's axial tilt is actually the dominant driver of seasons, not Earth's distance from the sun.
Perihelion does influence the Earth, from how fast our planet moves through space to how long each season lasts. However, it doesn’t mean that the sun will appear substantially larger in the sky. Here’s everything you need to know about this annual astronomical event.
What is perihelion?
While you might expect Earth's path around the sun to be a perfect circle, it's actually an ellipse, with the sun positioned just slightly off-center. As a result, the distance between Earth and the sun changes continuously over the course of a year.
"At its simplest, perihelion is the point in the orbit of a planet, comet, or other astronomical body where it is closest to the sun," says Seth McGowan, president of the Adirondack Sky Center in upstate New York . Its counterpart is aphelion, or a celestial body's farthest distance from the sun.
The change in Earth’s distance from the sun is fairly minimal, however, and perihelion isn't something you'd notice with the naked eye. At perihelion, Earth is about 91.4 million miles from the sun compared to roughly 94.5 million miles at aphelion in July.
"The Earth's orbit is also constantly changing from interactions with the other planets in the solar system, especially the Moon and Jupiter, so the time of perihelion can shift by a few hours," says Jason Steffen, assistant professor of physics at the University of Nevada, Las Vegas.
What perihelion does (and doesn't) change
While Earth's changing distance from the sun does affect our climate, perihelion does not have a drastic impact on our seasons.
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"Earth's 23.5-degree axial tilt is the primary driver of our weather and temperature shifts," says McGowan. As Earth orbits the sun, its tilted axis causes each hemisphere to alternately lean toward or away from the sun. When a hemisphere tilts toward the sun, days grow longer, and sunlight strikes the surface more directly. When it tilts away, days shorten, and sunlight arrives at a shallow angle. Together, these effects change the amount of solar energy reaching Earth’s surface by roughly 50 percent in the mid-latitudes, and by much more at high latitudes.
By comparison, perihelion increases the intensity of sunlight reaching Earth by about seven percent compared to aphelion. Since perihelion happens in January, that extra energy primarily affects the Southern Hemisphere, which is tilted toward the sun at the time. While that means Southern Hemisphere summers are slightly more intense than Northern Hemisphere summers, the impact on temperature remains modest. "The southern hemisphere is mostly water, which doesn't have the large temperature swings as the land," says Steffen.
(Every season actually begins twice—here’s why.)
Although perihelion doesn't cause the seasons, it does influence their length. One of the most important effects of Earth's elliptical orbit around the sun is orbital speed. As Earth approaches the sun, it accelerates—a consequence of gravity described by Kepler's second law of planetary motion. "Earth travels about 2,000 miles per hour faster at perihelion than it does at aphelion," says McGowan.
(Read more about Earth's dance around the sun.)
Because Earth moves faster in early January, the seasons that occur during that time pass more quickly. "It makes the summer in the Southern Hemisphere slightly longer than the winter, and the winter in the Northern Hemisphere slightly shorter than the summer, but only by a few days," says Steffen.
Over much longer timescales, perihelion even plays a role in Earth's climate trends. According to NASA, the eccentricity of Earth's elliptical orbit changes slightly in a 100,000-year cycle. Currently, it's slightly decreasing. Serbian scientist Milutin Milankovitch theorized that this shift, in combination with cyclical changes in the Earth's axial tilt, is what has triggered glaciation periods throughout Earth's history. Proven by ice core samples from Greenland and Antarctica, these orbital cycles are now known as Milankovitch cycles.
Why this small orbital shift matters
Although perihelion and aphelion don't cause heat waves or blizzards, scientists still track Earth's orbit closely. "It is useful to know where the Earth is located in its orbit," Steffen says. "There are a variety of reasons, the most dramatic being that when we discover asteroids that cross the Earth's orbit, we want to know if they are going to hit us."
McGowan points to additional applications. "Space agencies like NASA must account for Earth's changing velocity and position for satellite positioning and deep-space mission trajectories," he says.
(NASA's Artemis Il ushers in a new era of human exploration.)
Perihelion might pass without spectacle, but it’s a fascinating reminder that the choreography of the solar system—and its effect on our lives—is more complicated than you might think.
