Several times a year, NASA warns of an asteroid perilously close to Earth. The news, not uncommon, is usually met with feigned or even dismissive interest. But now, NASA has estimated that there are around 4,700 asteroids close enough and big enough to pose a risk to Earth.
According to CNN, the asteroids are bigger than 330 feet across and large enough to survive passing through Earth's atmosphere.
"We're paying attention to the issue," said Amy Mainzer, astronomer at NASA's Jet Propulsion Laboratory in California, who also insisted that people shouldn't panic about the news.
NASA also said a 40-meter asteroid would strike the Earth with an impact comparable to a 3-megaton nuclear bomb.
The space agency used the Wide-field Infrared Survey Explorer - better known as WISE - to find the asteroids. From there they estimated how many more were actually out there.