Astronomers around the world have readied their telescopes to catch a glimpse of a speeding ball of rock that will hurtle past the Earth tonight.
Scientists say the asteroid, which is just under a half a kilometer wide, will pass inside the moon’s orbit and come within 319,000km of Earth at 11:28pm GMT. This is the closest a tracked object this size has come to the planet.
NASA calculates the 400m wide asteroid, known as 2005 YU55, has roughly a one in 10 million chance of hitting Earth in the next century.
Were it to strike, the collision would unleash the equivalent of several thousand megatonnes of TNT.
Even with clear skies, the asteroid will not be visible to the naked eye, but astronomers will turn their telescopes on the rock to learn about its surface and chemical composition.
“Most of the asteroids we see are so far out that we only get a small amount of information from the light reflected off them,” said Kevin Yates, at the Near Earth Objects Information Centre at the National Space Centre in Leicester, England.
“Because this one is coming in so close, we’ll be able to get more radar observations, which will give us a detailed surface map, and be able to get more of a chemical signature on the minerals,” Yates said.
The Arecibo telescope in Puerto Rico last year revealed the asteroid to be remarkably spherical, while its surface is very dark, suggesting it is rich in carbon.
A similar flyby will not happen until 2028, when asteroid 2001 WN5 swings past the Earth at a distance of 229,000km.
“We are finding a whole variety of unusual shapes out there and this asteroid is particularly spherical. If we can characterize them more and understand them more, then if we ever do have a threat from one, understanding the structure and the materials they’re made from would better equip us to divert one. It may be that there are materials on board that could be used as a fuel to drive an engine that would push it into a different orbit over 20 years,” Yates added.
The asteroid is among the most ancient objects in the solar system, having formed from the dust and gas disc that surrounded the sun 4.5 billion years ago.
Though born in the asteroid belt between Mars and Jupiter, the rock was pulled by gravity or nudged by collisions on to its new orbital course.
“These are the building blocks left over from when the solar system formed and this particular carbonaceous asteroid is one of the most primitive types,” Yates said.
“Understanding its chemical composition is like looking into the ingredients book to see how it was put together,” Yates said.
The asteroid will pass close to Venus in 2029, which will disturb its orbit to mean its next passage past Earth, in 2041, could be between 317,000km and nearly 50 million kilometers from the planet. Its close encounter after that will be with Mars in 2072.