Florence: Largest asteroid in century to safely fly by Earth - BBC News
I'll see your rock and raise you a bigger rock.
The largest asteroid in more than a century is set to pass by Earth at a relatively close distance of 4.4 million miles (7 million km), Nasa says.
While other asteroids have passed closer to Earth, they were all estimated to be smaller.
Asteroids are the rubble left over from the formation of the Sun and planets.
The 2017 encounter is the closest by this asteroid since 1890 and the closest it will ever be until after 2500, the US space agency added.
An object of Florence's size would have global effects were it to hit the Earth. Scientists believe they have now identified more than 90% of such monster rocks moving through space near our planet.
Scientists plan to study the asteroid up close, using ground-based radar imaging in California and Puerto Rico.