Video screenshot by Michael Franco/CNET

In the past week, astronomers discovered three never-before-seen asteroids as they whizzed by Earth significantly closer than the vast majority of passing space rocks.

The trio pose no threat to our planet, but it is a little unsettling that the largest of the three (Asteroid 2017 SQ2) was spotted in our cosmic rearview on Monday, nearly four days after the warehouse-sized hunk passed a little over 120,000 miles (193,000 kilometers) above our heads.

Asteroid 2017 SM2 is about half that size and passed us early Wednesday morning over 188,000 miles (303,000 kilometers) away.

The closest and smallest piece of space debris just found in our neighborhood is Asteroid 2017 SR2, which is probably about the size of a bus and set to be closest to Earth at around 1:30 p.m. PT Wednesday when it whips by about 55,000 miles (88,500 kilometers) from us.

There are a lot of asteroids floating around our part of the solar system and astronomers are discovering new ones flying by earth just about every day or so. Most of them pass by at a very comfortable distance several times farther away than the moon. When the rare one passes closer than that space between us and our natural satellite, it's worth noting, so finding three new asteroids as they fly nearby makes for a pretty dramatic week.

We've now seen 31 asteroids pass by closer than the distance to the moon in 2017. The closest was back in April when a car-sized rock passed far closer than the orbit of most artificial satellites.

But the closest buzz of the year could come next month when house-sized Asteroid 2012 TC4 could pass within 5,000 miles of us on Oct. 12. NASA is confident that specific one won't strike Earth, but there's still reason to be concerned: the 2013 bolide explosion over Russia was caused by a small asteroid that went completely undetected until it collided with our planet's atmosphere.

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