Scientists just watched a newfound asteroid zoom by Earth. Then they saw its moon.

One of Earth's premier instruments for studying nearby asteroids is back to work after being rattled by earthquakes, and its first new observations show that a newly discovered space rock is actually two separate asteroids.

The instrument is the planetary radar system at the Arecibo Observatory in Puerto Rico. The observatory was closed for most of January, after a series of earthquakes hit the island beginning on Dec. 28, 2019. The observatory reopened on Jan. 29. Meanwhile, on Jan. 27, scientists using a telescope on Mauna Loa in Hawaii spotted an asteroid that astronomers hadn't seen before. The team dubbed the newfound space rock 2020 BX12 based on a formula recognizing its discovery date.

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(Image credit: Arecibo Observatory/NASA/NSF)

Radar images show the binary asteroid 2020 BX12, which scientists discovered this year.

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Radar imagery of binary asteroid 2020 BX12 was obtained using the Arecibo Observatory on Feb. 4-5, 2020 when it was about 188,000 miles (302,000 km) from Earth.