The giant lump of rock is currently hurtling through space at 40,000 miles an hour. The asteroid’s exact size is still unclear though it is estimated to be between 0.7miles metres and 1.6 miles wide - more than 15 times bigger than other asteroids currently on Nasa’s radar.
A collision would be nothing short of catastrophic with the rock fragment thought to be around a quarter of the size of Mount Everest.
Nasa has released an animated projection of the asteroid's path, which you can watch below. 86666 appears from the top left of the screen as it nears Earth's orbit.
NASA has released this projection of the asteroid's path
It makes 2014-YB35, which had worried astronomers around the world watching the skies in March, pale into insignificance.
The impact would eclipse the devastating 1908 Tunguska Event which saw a 50-metre wide asteroid crash into Siberia.
It flattened around 80 million trees and sent a shock wave across Russia measuring five on the Richter scale. The event is held by scientists as a benchmark for the catastrophic consequence of an asteroid impact with earth.
Thankfully despite Nasa labelling it a 'near-Earth event' 86666 is several million miles away and unlikely to hit Earth.
Bill Napier, professor of astronomy at the University of Buckinghamshire, said if a sizeable asteroid hit Earth it could “take out a small country”.
Source: http://www.express.co.uk/news/science/610777/NASA-asteroid-warning-86666-near-miss-planet-Earth-48-hours