行星地球面對面 危險近在咫尺？

A mountain-sized asteroid which crosses paths with the Earth every three years has been discovered by a Russian scientist.

近日，一名俄羅斯科學家發現了一顆山峰大小的小行星每三年都會經過地球的運行軌道。

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

莫斯科國立大學（Moscow State University）教授弗拉基米爾（Vladimir Lipunov）表示，這顆名為“2014 UR116”的太空巖石目前對地球并未造成直接威脅。

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 inRussia. That object entered Earth’s atmosphere over the city ofChelyabinsk, resulting in a series of ferocious blasts that blew out windows and damaged buildings for miles around.

但是，如果這顆小行星撞擊地球，其產生的爆炸強度將會是2013年襲擊俄羅斯的那顆公交車般大小的流星的1000倍。那顆流星穿越地球大氣層，在車里雅賓斯克（Chelyabinsk）上空爆炸，火花四濺，擊破了窗戶，損壞了方圓數英里內的建筑。

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

弗拉基米爾教授表示，像“2014 UR116”這類大型的石塊常常會受到其他行星萬有引力的影響，不停地改變其運行軌跡。因此，很難計算出它們的運行軌道。

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

他還表示，這顆小行星的存在同時也說明，科學家對其他能對地球造成危害的行星所知甚少。

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

他表示，有必要對這顆小行星的運行軌跡進行長期的觀察，因為計算中的一個細微的錯誤都可能帶來嚴重后果。

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.

目前，有十萬顆大型近地星體可以穿過地球的運行軌道并可能造成一定程度破壞。其中，能追蹤并計算出軌跡的大約只有1萬1千顆。

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

然而，美國國家航空航天局（NASA）表示，“2014 UR116”經過地球的運行軌道后，與地球的距離不算太近，因此不會構成威脅。

"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 sufficiently close to the Earth's orbit," NASA's Near Earth Object Program Office said in a statement.

美國國家航空航天局“近地星體”項目處（Near Earth Object Program Office）發表聲明稱，這顆直徑約400米的小行星圍繞太陽運轉的軌道周期為3年，之后又會定期繞回地球附近。盡管它的運行軌道穿過了地球的運行軌道，但距離不近，因此不會構成威脅。

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

美國國家航空航天局表示，據計算機模型顯示，這顆小行星至少需要150年的時間才能帶來具有沖擊性的威脅。

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 devastating results on Earth.

追蹤大型小行星的系統已經啟用。但近期研究認為，就算164英尺（約49.99米）大小的石塊也足以給地球造成毀滅性的傷害。

（翻譯 hyylf 編輯 Helen）