Stargazers will be looking to the skies on Wednesday as an asteroid up to a mile wide will pass Earth 1.1 million miles away.
The asteroid, known as J025, will be the largest to come this close to our planet for the past 13 years.
It will be just five times as far away from Earth as the Moon is - a close pass in cosmic terms.
But we can all breath easy, as NASA says there is no chance it will hit Earth.
The object, discovered in 2014, will not be visible to the naked eye but it will be bright enough to be seen through a home telescope for one or two nights from Wednesday.
A NASA graphic shows how close the asteroid will come to Earth
Scientists do not know exactly how big it is, but they have estimated it is between 600 metres and 1,400 metres wide.
Smaller asteroids routinely make closer passes to Earth.
"We know the time that the object is going to be closest within seconds, and the distance is known within hundreds of kilometres," said Davide Farnocchia, a mathematician at NASA's near-Earth object programme.
He said having several years of data of the asteroids trajectory meant they were able to confidently predict how close to the Earth it will come.
In January NASA announced two new missions to study asteroids in our solar system
Mr Farnocchia said he and his colleagues have already moved on to tracking even closer encounters between the Earth and other asteroids in the future, such as the asteroid 1999 AN10.
In 2004, a 3.1 mile-wide asteroid Toutatis, passed within a million miles of Earth.