The Earth is to have its closest brush with a large asteroid in three decades this week, report NASA scientists - and for amateur astronomers, it's a fantastic chance to get a closer look.
The asteroid is trapped in an orbit that keeps bringing it back into close proximity to the Earth, and this week's pass is the closest it has come in 200 years - though scientists tracking the rock's movements say they're certain it will not have any perceptible gravitational effect here on Earth.
According to Lance Benner of NASA's Jet Propulsion Laboratory, YU55's flyby will be the "closest approach by an asteroid, that large, that we've known about in advance."
NASA hopes to seize the opportunity to capture detailed images of the rock, tracking its progress from its Deep Space Network at Goldstone, California.
But it isn't just NASA's scientists who can get in on the action. According to the agency's Marina Brozovic, the asteroid will be visible to amateur astronomoers too.
"8th November is when it becomes a night time object and that is when you can see it," she told news website Wired. ""400 metres, I'd say, is a moderate size asteroid, but it's still small and very far away. You'll need at least a six inch telescope in order to be able to observe it. You'll see it buzzing really fast along the sky."
The asteroid's path should make it particularly visible to astronomers in western Europe and North America. The British Astronomical Association has produced a star map indicating the object's movements after it becomes visible at 23:28 GMT tomorrow night.