New force can propel asteroids onto earth's path
London, June 4 (IANS) 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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