PHOENIX, Ariz (KSAZ) - An asteroid nearly missed Earth this past week, coming within about 1.5 million miles of the planet.
NASA says anything closer than 4 million miles is cause for concern.
Astronomers are discovering more asteroids in our solar system than ever before.
This isn't necessarily new, it just means technology is getting better. This can help protect us should an asteroid head straight for Earth.
But first, let's get a better understanding of meteorites and asteroids.
"A meteorite is a rock from space, a rock from space that's landed on Earth, and it's actually a piece of an asteroid. And asteroids are rocky bodies that are the remnants from the formation of the solar system," said David Williams, an associate research professor at ASU's School of Earth and Space Exploration.
Now that we know what an asteroid is, let's talk about how space experts can spot them.
"The larger an asteroid is, the easier it is to detect using a telescope based on Earth. And there are many telescopes that are engaged on the search," Williams said.
Williams says small asteroids are hard to detect, but are less of a threat because they can burn up coming through the Earth's atmosphere.
And about 95 percent of large asteroids have already been spotted by telescopes, which helps scientists study their orbit.
"If there is one that could potentially be on a collision course with Earth, the soonest we can determine its orbit, the further away it is, then the greater likelihood that we'd be able to do something about it," Williams said. "NASA's exploring the options on whether you'd want to send some sort of a space craft that could intercept it."
Space experts are also trying to figure out what makes up an asteroid.
A mission was launched recently to get that information.
"The goal of this mission is to orbit it, study its surface geology and dock with it, collect a sample and return that sample to Earth in 2023," Williams said.
Scientists believe they'll be spotting even more asteroids in 2018. But again, it's nothing to worry about. It just means technology is advancing.