Huge asteroid headed for close encounter with Earth

CAPE CANAVERAL, Fla, (Reuters) – A huge asteroid will  pass closer to Earth than the moon on Tuesday, giving  scientists a rare chance for study without having to go through  the time and expense of launching a probe, officials said.
Earth’s close encounter with Asteroid 2005 YU 55 will occur  at 6:28 p.m. EST (2328 GMT) on Tuesday, as the space rock sails  about 201,000 miles (323,469 km) from the planet.
“It is the first time since 1976 that an object of this  size has passed this closely to the Earth. It gives us a great  — and rare — chance to study a near-Earth object like this,”  astronomer Scott Fisher, a program director with the National  Science Foundation, said on Thursday during a Web chat with  reporters.
The orbit and position of the asteroid, which is about  1,312 feet (400 meters) in diameter, is well known, added  senior research scientist Don Yeomans, with NASA’s Jet  Propulsion Laboratory in Pasadena, California.
“There is no chance that this object will collide with the  Earth or moon,” Yeomans said.
Thousands of amateur and professional astronomers are  expected to track YU 55’s approach, which will be visible from  the planet’s northern hemisphere. It will be too dim to be seen  with the naked eye, however, and it will be moving too fast for  viewing by the Hubble Space Telescope.
“The best time to observe it would be in the early evening  on Nov. 8 from the East Coast of the United States,” Yeomans  said. “It is going to be very faint, even at its closest  approach. You will need a decent-sized telescope to be able to  actually see the object as it flies by.”
Scientists suspect YU 55 has been visiting Earth for  thousands of years, but because gravitational tugs from the  planets occasionally tweak its path, they cannot tell for sure  how long the asteroid has been in its present orbit.
“These sorts of events have been happening for most of the  lifetime of the Earth, about 4.5 billion years,” Fisher said.
Computer models showing the asteroid’s path for the next  100 years show there is no chance it will hit Earth during that  time, added Yeomans.
“We do not think that it will ever impact the Earth or moon  (but) we only have its orbit calculated for the next 100  years,” he said.
Previous studies show the asteroid, which is blacker than  charcoal, is what is called a C-type asteroid that is likely  made of carbon-based materials and some silicate rock.
More information about its composition and structure are  expected from radar images and chemical studies of its light as  the asteroid passes by the planet.
“I’ve read that we will be able to see details down to a  size of about 15 feet (4.5 meters) across on the surface of the  asteroid,” Fisher said.
NASA is working on a mission to return soil samples from an  asteroid known as 1999 RQ36 in 2020, followed by a human  mission to another asteroid in the mid-2020s.

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