Our planet had two recent visitors. An asteroid was expected, a meteor in Russia was not.
Scientists say this is the largest known asteroid ever to come this close to Earth. The asteroid named DA14 came closer than some satellites.
NASA scientists watched the asteroid's rotation to track where it's going. Scientists also want to know what it's made of, to figure out what sort of threat it might pose.
"This piece of fragment of meteor is almost pure iron nickel. It has a very high density. This rock is much lower density. It's much like a pebble you'd stub your toe on walking to work in the morning, and I'd much rather be smashed in the head with this rock than with this rock," said Tim Knauer, UK Observatory's Director.
Most of us would probably run far away from an asteroid, but Knauer can't get close enough.
"I think everybody grows up with a need, a want to look at the night sky, and I was able to turn it into a career. It's the job of a lifetime," said Knauer.
Scientists estimate the asteroid is the size of half a football field. Imagine the damage a rock that size could do crashing down from outer space.
"It would leave a hole about 10, or 20 times bigger than its size. So, it's half the size of a football field, say 50 Meters, it would leave a hole 500 Meters, or a Kilometer, so it's about half a mile," said Knauer.
That did not happen. The asteroid passed Earth safely.
But in Russia, a meteor exploded injuring more than 1,000. It had nothing to do with the asteroid, except it added tension to the audience watching here.
"The rock passing us this afternoon had absolutely no relation to the rock that hit Russia this morning, other than that they are both rocks that orbit the sun," said Knauer.
He predicts the asteroid will pass by the Bluegrass around 8 PM Friday night, but we won't be able to see it.