This story was updated to reflect 2020’s perihelion.

In the wee hours of Sunday (2:47 a.m. Eastern time, to be exact), Earth will make its closest approach to the sun and reach a point in its orbit known as perihelion. Chilly as winter may feel in the Northern Hemisphere, we’re more than three million miles closer to our fiery star than we were in the dead of summer.

The change in distance occurs because our planet’s orbit is stretched into an ellipse — so Earth snuggles up to the Sun every January and dips farther out into the outer solar system every July, at a point known as aphelion.

Although three million miles sounds vast, it’s not much on the scale of our solar system. In fact, despite the planet’s elliptical path through the heavens, most astronomers say that Earth’s orbit is basically circular. On a scale of 0 to 100 percent, where 0 is a perfect circle and nearly 100 is a very thin oval, Earth only scores a 1.7.

It’s a defining trait that keeps our planet at roughly the same distance from our sun, and keeps the climate relatively stable. This has led many astronomers to wonder whether a circular orbit just might be a crucial ingredient in the cocktail of life — and a key factor to consider as they search for signs of alien life around the thousands of exoplanets known to be circling other stars within the galaxy.