As the new year begins, a significant celestial event occurs without fanfare. Earth reaches the point in its elliptical orbit where it is closest to the Sun, known as perihelion. In 2026, this moment is scheduled for January 3 at 12:15 p.m. EST (17:15 UTC). This annual event typically follows the December solstice by about two weeks.
What is Perihelion and Why Does the Date Shift?
Perihelion is the precise point where Earth, or any orbiting body, is nearest to the Sun. The opposite point, when Earth is farthest, is called aphelion and occurs in July. Earth's orbit is not a perfect circle but an ellipse, causing the distance to vary throughout the year.
At perihelion, the distance shrinks to approximately 91.4 million miles (about 147 million kilometers). In contrast, at aphelion in July, Earth is about 94.5 million miles (152 million kilometers) away. This 3-million-mile difference is not perceptible to the naked eye.
The exact timing of perihelion shifts slightly each year. "The Earth's orbit is 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," explains Jason Steffen, assistant professor of physics at the University of Nevada, Las Vegas. The mismatch between our Gregorian calendar and Earth's orbital period also contributes to the annual date variation, though leap years help correct it.
Seasons Are Tilt-Driven, Not Distance-Driven
A common misconception is that Earth's proximity to the Sun causes summer. However, perihelion occurs during the Northern Hemisphere's winter. Seasons are primarily dictated by Earth's 23.5-degree axial tilt, not by the relatively small changes in distance.
"Earth's 23.5-degree axial tilt is the primary driver of our weather and temperature shifts," says Seth McGowan, president of the Adirondack Sky Center. This tilt means different hemispheres lean toward or away from the Sun at different times of the year, changing the angle and duration of sunlight.
The tilt can alter solar energy reaching the ground by about 50% in middle latitudes. In comparison, the distance variation between perihelion and aphelion changes sunlight intensity by only about 7%. The extra solar energy during January's perihelion mostly bathes the Southern Hemisphere in its summer, making southern summers marginally more intense. However, the vast oceanic cover of the Southern Hemisphere moderates this effect.
Orbital Speed and Long-Term Climate Impacts
Perihelion influences more than just sunlight. It significantly affects Earth's orbital speed. "Earth travels about 2,000 miles per hour faster at perihelion than it does at aphelion," notes McGowan. This increased velocity slightly shortens the season occurring at that time.
"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," clarifies Steffen.
On a grander scale, these orbital variations are part of larger climate patterns. Over a 100,000-year cycle, the shape of Earth's orbit changes. Serbian scientist Milutin Milankovitch linked these orbital changes, along with shifts in Earth's tilt, to historical ice age cycles. These Milankovitch cycles are now supported by evidence from ice cores in Greenland and Antarctica.
Why Tracking Earth's Orbit Matters for Science and Safety
While perihelion doesn't trigger extreme weather, precise knowledge of Earth's orbital position is crucial. "It is useful to know where the Earth is located in its orbit... when we discover asteroids that cross the Earth's orbit, we want to know if they are going to hit us," states Steffen, highlighting planetary defense applications.
Furthermore, space missions rely on this data. "Space agencies like NASA must account for Earth's changing velocity and position for satellite positioning and deep-space mission trajectories," adds McGowan.
Perihelion is a quiet annual marker in our planet's journey—a testament to the precise, rhythmic dance of celestial mechanics. From subtly influencing season lengths to guiding spacecraft, this event plays a small but integral role in the story of our solar system.
