The asteroid known as 2018 CB which was only discovered by boffins at NASA last Sunday is Earth-bound tonight and traveling at more the 18,000mph.
The asteroid, the space agency says, could be up to 40 metres long – making it much longer than the blue whale, the biggest creature to have ever existed on Earth.
NASA also says that it could be double the size to the meteor that almost wiped out Chelyabinsk.
In 2013, a 20 metre meteor exploded over the Russian city which smashed windows and caused injuries to more than 1,000 people.
Experts predict the asteroid called 2018 CB will whizz past Earth just 39,000 miles away – just a fifth of the distance between the Earth and the moon.
But there are margins for error.
Anything that comes closer than 4,650,000 miles of Earth is classified by NASA as a “near-Earth object” (NEO).
The asteroid will be travelling at hypersonic speeds as it flies by at close to five miles per SECOND – making it four times faster than the speediest ever man-made machine, the North American X-15 which can travel at 4,520 miles per hour.
The giant space rock is predicted to shoot past Earth tonight at around 22.30 GMT.
Experts say it is likely to be between 15 to 40 metres in size and that space rocks like these only come this close “once or twice” a year.
Paul Chodas, manager of the Centre for Near-Earth Object Studies at Nasa’s Jet Propulsion Laboratory , said: “Although 2018 CB is quite small, it might well be larger than the asteroid that entered the atmosphere over Chelyabinsk, Russia, almost exactly five years ago, in 2013.
“Asteroids of this size do not often approach this close to our planet – maybe only once or twice a year.”