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COURTESY: PAUL WIEGERT, UNIVERSITY OF WESTERN ONTARIO, CANADA
This artist's concept illustrates the first known Earth Trojan asteroid. The asteroid is shown in gray and its extreme orbit is shown in green. Earth's orbit around the sun is indicated by blue dots.
IMAGE BY C. VEILLET 2011 - (C)CFHT
2010 TK7 is seen as a speck of light in the center of this image, which is the addition of three individual exposures taken with the MegaCam camera at CFHT. The telescope was tracking the motion of the asteroid, leading to the image of the stars to be trailed. With three exposures added, stars end up looking like a broken trail.
COURTESY: NASA/JPL-CALTECH/UCLA
Asteroid 2010 TK7 is circled in green, in this single frame taken by NASA's Wide-field Infrared Survey Explorer, or WISE. The majority of the other dots are stars or galaxies far beyond our solar system.
Canada
This artist's concept illustrates the first known Earth Trojan asteroid. The asteroid is shown in gray and its extreme orbit is shown in green. Earth's orbit around the sun is indicated by blue dots.
NEW YORK >> Like a poodle on a leash, a tiny asteroid runs ahead of Earth on the planet’s yearlong strolls around the sun, scientists report.
The discovery of this companion, which measures only about 300 yards across, makes Earth the fourth planet in the solar system that’s known to share its orbit with an asteroid.
Imagine Earth and the asteroid traveling around a clock face, with the sun in the middle. Generally, the asteroid runs about two numbers ahead.
However, the asteroid sometimes ranges so far ahead that it’s on the opposite side of the sun from Earth, said Martin Connors of Canada’s Athabasca University in Alberta. He reports the work with colleagues in Thursday’s issue of the journal Nature.
Asteroids are giant space rocks that orbit the sun, and ones that share an orbit with a planet are called Trojans. Scientists had previously found a few for Mars and Neptune and nearly 5,000 for Jupiter. Spotting one in Earth’s orbit is difficult from the ground because the potential locations are generally in the daytime sky.
The newfound object, called 2010 TK7, was discovered last year by NASA’s WISE satellite. Connors and colleagues were able to focus the Canada-France-Hawaii Telescope on Mauna Kea on it in April, determining its orbit with enough precision to show it was a Trojan.
Donald K. Yeomans, manager of NASA’s Near-Earth Object Program Office, who didn’t participate in the discovery, agreed that the asteroid is a Trojan. Most scientists suspected Earth had them, he said, and “I would guess there’s others.”
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Online:
Nature: http://nature.com/nature
