NASA

Astronomers over the weekend discovered a small asteroid that passed twice as close to your head as most of the man-made satellites in orbit.

Asteroid 2017 UJ2 buzzed our planet Friday at a distance of about 11,154 miles (17,951 km). That's nearly four times as close as Asteroid 2012 TC4, which generated headlines earlier this month for giving our atmosphere a return fly-by that astronomers used to practice for the possibility of a future asteroid on an all-out collision course with Earth.

The reason you probably haven't heard about this latest sneaky space rock is that it's much smaller than 2012 TC4 and most others seen passing close by. It's only about the size of a large refrigerator, so if it were on a collision course with our planet, it would probably burn up in the atmosphere or leave just a small chunk to impact the surface.

This also wasn't the closest an asteroid has buzzed us this year: Asteroid 2017 GM passed about 900 miles closer in April.

But October has been a very busy month for natural space traffic around Earth. In addition to 2012 TC4 and 2017 UJ2, half a dozen other asteroids have flown within one lunar distance, or about 238,856 miles (384,402 km), of the only home we've ever known.

It's enough to make you thankful there are so many telescopes and astronomers keeping an eye on all those rogue space rocks up there, but we could still use more. Asteroid 2017 UJ2 is another case where it was first spotted in the cosmic rearview, a day after making its close pass.

Sometimes asteroids sneak up on us completely without warning, like the 2013 meteor that was never detected until it was exploding above Russia.

Heads up, everyone!

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