Perihelion, the day Earth is closest to the sun: What to know

On Jan. 4, 2017, the Earth will be the closest it gets to the sun, but don’t expect to be warmer because of it.

The day marks the perihelion, or the day of the year when the Earth is the closest to the sun.

Jackie Faherty, staff astronomer at the American Museum of Natural History, said the perihelion could be considered a “supersun,” comparing it to the supermoon, when a full moon coincides with the moon’s closest distance to Earth.

But unfortunately, being closer to the sun doesn’t mean it will be warmer. Read on to learn more about what the perihelion is.

How close is the Earth to the sun at perihelion?

The Earth will be about 147 million kilometers, or 91 million miles, from the sun at perihelion. This is closest distance in it’s orbit around the sun. At aphelion, the Earth is the farthest from the sun, about 152 million kilometers, or 95 million miles.

Does the perihelion happen at the same time every year?

In recent years, the perihelion has fallen in early January, about two weeks after the winter solstice, but the day of the perihelion is not consistent.

“It’s actually just a coincidence that the perihelion happens close to the solstice,” Faherty said. “They don’t actually have anything to do with each other.”

The date of perihelion will continue to drift in the future, moving further from the winter solstice and then back again, she said.

Does it affect the weather?

No, the perihelion does not affect seasons, as it occurs when the northern hemisphere is in winter and the southern hemisphere is in summer. The perihelion is a reminder that the sun doesn’t impact us the way we intuitively think it would, Faherty said, explaining that just because we are closer to the sun, doesn’t mean it will be warmer.

Since the sun is so far away, the 3 to 4 million mile difference in distance does not have an impact. The tilt of the Earth, not its proximity to the sun, is what affects seasons.

Will we notice the perihelion?

“No one is going to notice the difference,” Faherty said. The change in size is even more minute than the change in size of a supermoon since it is farther away.

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