近日，一名俄罗斯科学家发现了一颗山峰大小的小行星每三年都会经过地球的运行轨道。 

 

Vladimir Lipunov, a professor at Moscow State University, said the space rock, named '2014 UR116', poses no immediate² threat.

 

But he warned that it could hit the Earth with an explosion 1,000 times greater than the surprise 2013 impact of a bus-sized meteor in Russia. That object entered Earth’s atmosphere over the city ofChelyabinsk, resulting in a series of ferocious³ blasts that blew out windows and damaged buildings for miles around.

 

Prof Lipunov said it is difficult to calculate the orbit of big rocks like '2014 UR116' because their trajectories⁴ are constantly being changed by the gravitational pull of other planets

 

And he warns that its existence proves how little scientists know about other asteroids⁵ which could cause harm to the planet.

 

"We need to permanently⁶ track this asteroid, because even a small mistake in calculations could have serious consequences," he said.

 

Of 100,000 near-Earth objects which can cross our planet's orbit and are large enough to be dangerous, only about 11,000 have so far been tracked and cataloged.

 

However NASA warned that '2014 UR116' did not pass close enough to the Earth to be considered a threat.

 

"While this approximately 400-meter-sized asteroid has a three-year orbital period around the sun and returns to the Earth's neighborhood periodically, it does not represent a threat because its orbital path does not pass sufficiently⁷ close to the Earth's orbit," NASA's Near Earth Object Program Office said in a statement.

 

NASA said that computer models showed that the asteroid would be an impact threat for at least 150 years.

 

Systems are already in place to track large asteroids, but recent research suggests that rocks as small as 164 feet across would still be big enough to cause devastating⁸ results on Earth.

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