Washington - An asteroid playing a cat-and-mouse game with Earth will pull to its closest point in almost a century on Monday before swinging away for another 95 years, Nasa said in a statement.
Asteroid 2002 AA29 is like a mouse teasing a cat, approaching Earth first on one side and then on another, without ever making contact or actually passing our planet as the two bodies circle the sun, the astronomers said on Thursday.
At just 60m, the tiny asteroid will get within 6 000 000km on Monday.
This particular asteroid is the first ever found to orbit the sun in nearly the same path as Earth, but never manages to pass it, the National Aeronautics and Space Administration said.
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"In some ways, the Earth and this asteroid are like two race cars on a circular track," said Paul Chodas of Nasa's Jet Propulsion Laboratory. "Right now the asteroid is on a slightly slower track just outside Earth's, and our planet is catching up."
"The combined gravitational effects of the Earth and sun will nudge the asteroid onto a slightly faster track just inside Earth's, and it will begin to pull ahead," he said.
In 95 years, the asteroid will have advanced all the way around to where it is catching up to the Earth from behind. A similar interaction with gravity from both the Earth and sun will then push the asteroid back onto a slower outside track, and the pattern will repeat.
To an observer moving with the Earth, the asteroid appears to trace out a horse-shoe pattern, Nasa said.
"There's no possibility that this asteroid could hit Earth, because Earth's gravity rebuffs its periodic advances and keeps it at bay," said Don Yeomans of JPL in Pasadena, California. "The asteroid and Earth take turns sneaking up on each other, but they never get too close."
In about 600 years, though, the little asteroid could start looping around Earth like a distant mini-moon for about 40 years before returning to its cat-and-mouse ways, the astronomers said.
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