By Mark Brown, Wired UK
An asteroid the size of an aircraft carrier is to soar past the Earth this week and, while NASA is certain that the space rock will not hit us, it will be our closest encounter with such a large chunk of rock in three decades.
The 400-yard-wide asteroid is called 2005 YU55and at the point of closest approach it will graze our planet at 201,700 miles — about 10 percent closer to Earth than the Moon’s typical orbit.It is the “closest approach by an asteroid, that large, that we’ve known about in advance,” said principal investigator Lance Benner, from NASA’s Jet Propulsion Laboratory, in an educational announcement. This gives the space agency an unprecedented view of such a rare flyby — and it will take full advantage.
NASA will track 2005 YU55 from the Deep Space Network at Goldstone California, and provide radar observations from the Arecibo Planetary Radar Facility in Puerto Rico. This should reveal a wealth of detail about the asteroid’s surface features, shape, and dimensions.
The Arecibo radar telescope spotted the asteroid back in April 2010, and those observations provided the ghostly image of YU55, above. NASA hopes to get higher resolution snaps — with details as fine as two meters per pixel — this month.
But what about amateur astronomers, will they be able to see it? “Absolutely,” said NASA astronomer and YU55 investigator Marina Brozovic in the announcement. “8 November is when it becomes a nighttime object and that is when you can see it.”
“400 meters, 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,” said Brozovic.
“The pass’ track is especially favorable for western Europe and North America. But you’ll need to know exactly where and when to look,” wrote Kelly Beatty, senior contributing editor of Sky and Telescope magazine.
The when is 23:28 UK time on 8 November. As for the where, Beatty wrote that, “the object will traverse the 70 degrees of sky eastward from Aquila to central Pegasus in just 10 hours, clipping along at seven arcseconds per second.” A star chart is available here.
2005 YU55 is trapped in an orbit that frequently brings it back to Earth and our nearby neighboring planets — but the 2011 encounter with Earth is the closest this space rock has come for at least the last 200 years. NASA is certain that it will miss us, and “the gravitational influence of the asteroid will have no detectable effect on anything here on Earth, including our planet’s tides or tectonic plates.”
Plus, “we have a very good idea about its orbit for the following hundred years and there is no chance of impact,” said Brozovic in the announcement. “We believe with these upcoming measurements at Arecibo and Goldstone we will remove this threat even further — probably for many centuries.”
Updated: Nov. 7, 2011; 12:40 p.m. EST
Astronomers around the world have readied their telescopes to catch a glimpse of a speeding ball of rock that will hurtle past the Earth on Tuesday night.
Scientists say the asteroid, which is about a quarter of a mile wide, will pass inside the moon’s orbit and come within 198,000 miles (319,000km) of Earth at 23.28GMT. This is the closest a tracked object this size has come to the planet.
Nasa calculates the 400-metre (1,312ft) wide asteroid, known as 2005 YU55, has roughly a one in 10m 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 professional and amateur astronomers will turn their telescopes on the rock to learn about its surface and chemical composition.
Because the asteroid is approaching from the sun’s direction, there will be too much glare to observe the rock with optical or infra-red telescopes until the day of closest approach.
“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. “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 it’s made up from.”
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.
Observatories at Nasa’s Goldstone Deep Space Communications Complex, in the Mojave desert of California, and at Green Bank, West Virginia, will join forces with Arecibo to watch the asteroid pass this week. Operators have called on scores of amateur astronomers to help with observations, using 10-12in telescopes with special filters.
A similar flyby will not happen until 2028 when asteroid 2001 WN5 swings past the Earth at a distance of 143,000 miles.
“We are finding a whole variety of unusual shapes out there and this asteroid is particularly spherical. If we can characterise 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 4.5bn 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.”
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 198,000 miles and nearly 30m miles from the planet. The close encounter after that will be with Mars in 2072.