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London: You might not
be safe from asteroid hits even if state-of-the-art NASA tracking
systems are in place, because the 'Yarkovsky effect' can force
these objects out of their orbits and into ours, says a study.
A prime example is an asteroid 1999 RQ36, nearly half a kilometre
across, expected to zoom past the Earth in 2135, which has already
drifted nearly 100 miles out of its path in the last 12 years,
thanks to the 'Yarkovksy effect'.
"This 'Yarkovsky effect' can actually push an asteroid into or out
of the path of the Earth," said researcher Josh Emery of the
University of Tennessee, Knoxville, US.
"Understanding this force and how it affects an asteroid is
critical for determining whether or not that asteroid will hit
us," Emery added, reported the Daily Mail.
Emery's work using NASA's Spitzer Space Telescope in 2007 helped
work out the effect. He measured the asteroid's heat
characteristics using infrared emissions and found the space rock
was covered in an insulating blanket of fine material.
"The longer a surface can hold heat, the stronger the Yarkovsky
effect," said Emery.
"Therefore if the asteroid was made up of solid rock, the force
would be stronger because it would retain heat longer. But fine
material such as dust or sand heat up and cool down quickly so the
effect is weaker."
The Yarkovsky effect is named for the nineteenth-century Russian
engineer who first proposed the idea that a small rocky space
object would, over long periods of time, be noticeably nudged in
its orbit when it absorbs sunlight and then re-emits that energy
as heat.
The effect is difficult to measure because it's so infinitesimally
small.
The effect was discovered on 1999 RQ36 in an effort to determine
the mass of the asteroid from millions of miles away. The
scientists needed the space rock's size, thermal properties,
propulsive force (Yarkovsky effect), and orbit to calculate the
bulk.
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