CAPE CANAVERAL, Fla. -- Another asteroid is headed our way -- the second this week -- but there's no need to worry. The newly discovered space rock will pass within 39,000 miles (64,000 kilometers) of Earth on Friday afternoon. That's less than one-fifth the distance to the moon.



Designated 2018 CB, the asteroid is an estimated 50 feet to 130 feet (15 meters to 40 meters) in size, possibly bigger than the one that exploded over Russia five years ago this month.



The manager of NASA's Center for Near-Earth Object Studies, Paul Chodas, said asteroids this size usually don't come this close - just once or twice a year.

While Friday's close approach isn't a huge deal, Chodas said in an email, "it is a reminder that asteroids can pass very close to our planet and it's important that we find these objects when they do get close."

This comes after an asteroid generated a lot of hype, for coming close to the Earth right before the Super Bowl. The asteroid, dubbed 2002 AJ129 by NASA, is classified as a "Potentially Hazardous Asteroid" (PHA) but poses no threat to Earth for at least another century.

In October, a house-sized asteroid came within 26,000 miles of the planet. NASA used that relatively close encounter to test how well its planetary defense system would work if an asteroid were on a collision course for Earth.

A whopper asteroid named Apophis -- estimated at approximately 1,000 feet or more than 300 meters -- will pass at just one-tenth the distance between Earth and the moon in 2029. In the meantime, astronomers are on the lookout for asteroids lurking in the cosmic shadows.



"These asteroids are simply too small to be detected until they get really close to our planet," he wrote.



That was the case when a meteor made impact over Chelyabinsk, Russia on Feb. 15, 2013, catching everyone by surprise. It caused an intense fireball as it entered the atmosphere and the shock waves shattered glass for miles around.