That's about three times the size of its moon, which clocks in at a width of about 0.5 kilometers (.3 miles).
These big rocks have been frequent flyers in our planet's neighborhood for a long time.
Two asteroids - one almost a mile wide and and another, smaller one orbiting it - are rocketing its way through out solar system, and will pass close to the Earth (in astronomical terms, at least) on May 25.
The main asteroid is about a mile wide, and looks a bit like a spinning top thanks to a ridge that wraps around the rock's equator.
Since the asteroid and its moon are two bodies moving together, the duo form a binary system. LINEAR is a collaboration of NASA, the US Air Force, and Massachusetts Institute of Technology (MIT), and was formed to track objects that come near Earth and are potentially hazardous space travellers that could intersect Earth's path. The asteroid will travel by the Earth at a safe distance of 3.2 million miles, or roughly more than 13 times the distance from the Earth to the moon.
And to further complicate matters, the space rock will shoot past the planet at breakneck speeds of 21.51km per second or 48,116mph. It is believed that the YORP effect is also one of the causes for the creation of binary asteroids such as the 1999 KW4.
Another pass this close isn't expected until 2036, according to the ESA.
Though the asteroid will undoubtedly be hard to spot, there are some amateur astronomers who will take initiative and attempt to locate it as it passes by Earth.
The astronomers will use this weekend's approach to see if 1999 KW4 follows the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect. In fact, they won't even come close enough to see with the naked eye.
199 KW4, which was discovered 20 years ago, will make its closest approach to Earth on Saturday evening, and will be visible until May 27, CBS News reported. "And that's when it will be at its very closest to Earth".