A big space rock the height of Buckingham Palace is zooming towards our planet at 21,362mph.
But NASA only spotted it on Christmas Day – 48 hours before it is due to skim past Earth 140,000 miles away.
The asteroid has been called 2017 YZ4, and will pass between the Earth and Moon today.
SKIMMED: The Buckingham Palace sized asteroid will brush past Earth tomorrow
It is estimated to be between 7 and 15 metres (22.6 to 49 feet) in diameter.
To give an idea of the sheer size, Buckingham Palace – home of the Queen – stands at 24 metres tall.
Although it’s not as huge as some asteroids that have passed Earth, it could cause injuries if it hit Earth.
CLOSE ONE: The asteroid will come within 140,000 miles of Earth
In February 2013, an unknown 19-metre meteor exploded in the sky above Chelyabinsk, Russia, with the force of 500,000 tonnes of TNT.
The energy released shattered the windows of hundreds of buildings and left more than 1,000 people injured.
A NASA spokesman told the Daily Express: “This is the first known asteroid to flyby Earth within one lunar distance since two such asteroids flew past us 35 minutes apart on November 21, and the 52nd this year.
“As of December 24, there are 17,495 known Near-Earth Objects (NEOs) around our planet; 17,389 are asteroids.
“This year, we discovered 1,985 new near-Earth asteroids. There were 1888 such objects discovered in 2016 and 1,571 in 2015.”
2017 YZ4 is from the Apollo group of asteroids, a group of near-Earth asteroids that regularly cross the planet.