S. Schmalz/ISON

"Wait, what?!" That was the reaction of a lot of people when they heard about the discovery of a sneaky asteroid we didn't know existed until it zipped by Earth (at a safe distance) on July 25. Now we know a lot more about it thanks to telescope observations.

We weren't in danger of losing a chunk of our planet to asteroid 2019 OK, but it was detected just the day before it slipped past, and that's the worrying part.

S. Schmalz / ISON

The European Space Agency had enough time to ask two telescopes in the International Scientific Optical Network (ISON) to take a look at the asteroid right before its flyby. These aren't beauty shots. The asteroid looks like a dark blob, but the observations are helping us learn more about 2019 OK.

We now know the asteroid flew by at a distance of just 40,000 miles (65,000 kilometers). Cosmically, that's fairly close.

The Southern Observatory for Near-Earth Asteroids Research (SONEAR) in Brazil is credited with first noticing the asteroid on July 24. As it turns out, other observatories caught sight of it earlier, but it moved slowly enough across the sky to not be recognizable as an asteroid at the time.

The space rock measured in at about 330 feet (100 meters) wide. "Asteroids the size of 2019 OK size are relatively common in the solar system, but hit Earth on average only every 100,000 years," ESA said in a release on Friday. So that's comforting.

ESA said there isn't an easy answer as to why we missed the asteroid's approach until the last minute. We can at least be glad it didn't come any closer.