Asteroid 2018 CB is the second asteroid to whizz past Earth this week, NASA reported.
Manager of the Centre for Near-Earth Object Studies at NASA’s Jet Propulsion Laboratory in Pasadena, California, Paul Chodas, 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.”
The space agency said the asteroid will pass the Earth at a distance of 39,000 miles which is close by space standards.
Asteroid 2018 CC was about 114,000 miles away when it passed Earth on Tuesday.
The moon is an average of 240,000 miles from Earth.
Asteroid 2018 CB will pass at just a fifth of the distance between Earth and the moon.
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 rock could be up to 40metres wide which would 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.
NASA says that the newly discovered asteroid will shoot past Earth on Friday 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.
For anyone wanting to watch the asteroid’s flyby, the Virtual Telescope Project will be hosting a live stream from a location in Italy, beginning at 20.00 GMT.