Mountain-size 'planet killer' asteroid will make a close approach to Earth today

A massive "planet killer" asteroid will make a very close approach to Earth today (June 27), safely zipping past our planet at around 58,000 mph (93,000 km/h). The "potentially hazardous," mountain-size object is one of the largest space rocks to pass close to Earth in more than a century — and you can watch the close encounter live.

The asteroid, 2011 UL21, is a near-Earth asteroid, meaning its orbit occasionally puts it within 1.3 astronomical units (AU) of the sun — or roughly 1.3 times the average distance between Earth and the sun.

It orbits our home star once every three years. Based on past observations, the space rock is somewhere between 1.1 and 2.4 miles (1.7 to 3.9 kilometers) wide, according to SpaceReference.org, meaning it's larger than 99% of known near-Earth asteroids, according to the European Space Agency (ESA).

2011 UL21 is likely at least 10 times smaller than the largest space rock to ever hit Earth, the Vredefort asteroid, and around five times smaller than the rock that wiped out the dinosaurs around 66 million years ago.

https://www.livescience.com/space/asteroids/mountain-size-planet-killer-asteroid-will-make-a-close-approach-to-earth-this-week-and-you-can-watch-it-live