There is no chance of it hitting the planet on Friday since it will pass seven times the distance from earth to the moon.
NASA’s Center for Near Earth Object Studies estimates the space rock is between 210 metres and 480 metres across.
That means the asteroid could be similar in size to New York City’s Empire State Building.
Discovered in 2008, the asteroid is designated as 2008 OS7.
It will not be back our way again until 2032 – but it will be a much more distant encounter then, staying 72 million km away.
The harmless flyby is one of several encounters this week.
Three much smaller asteroids also will harmlessly buzz earth on Friday, no more than tens of metres across, with another two on Saturday.
On Sunday, an asteroid roughly half the size of 2008 0S7 will swing by, staying 7.3 million km away.