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A space rock the size of a building will buzz near Earth tomorrow. There’s no risk of it hitting us. But it’s a reminder that other members of the solar system often pass this way. And some of them could be hazardous.

Asteroid 2014 US7 will miss Earth by about 750,000 miles — three times the distance to the Moon. Most of the time, the asteroid stays well inside Earth’s orbit. But its orbital path is elongated, so it sometimes passes close to our planet.

2014 US7 probably is between about 40 and 100 feet wide. That’s about the same size as an asteroid that exploded over Russia in 2013. The explosion shattered windows and caused other damage.

Asteroids in this size range pass near Earth all the time. This year alone, in fact, several dozen of them have passed inside the Moon’s orbit. And one of them actually hit us. It was only about six feet wide, so it wasn’t discovered until a few hours before impact. It exploded harmlessly over southern Africa in June, raining small fragments on the surface.

Astronomers have been hunting and plotting the orbits of near-Earth asteroids over the past quarter century. The goal is to identify anything on a collision course long before it could hit us. And they’ve found most of the big asteroids, which could decimate life on a regional or global scale. Now they’re trying to find ones that are smaller, but still big enough to cause big problems — trying to keep Earth safe from space rocks.

Script by Damond Benningfield