A truck-sized asteroid has careened past Earth in one of the closest flybys ever recorded – but none of satellites scanning the skies to protect our planet saw the space rock coming.

The previously unseen asteroid, 2020 JJ, whizzed past at a distance of around 7,000 kilometers (4,350 miles) this week. In astronomical terms, that’s an incredibly close shave, and it makes it one of the closest passes of our planet ever recorded.

In a development that might worry those tasked with protecting Earth from being smashed by space objects, the asteroid was only discovered by the Mount Lemmon Survey in Arizona at almost exactly the time it reached its closest point to Earth.