Don't panic, but Earth has a celestial stalker. An asteroid discovered last fall moves in roughly the same orbit as Earth does. However, there's no need for a restraining order. Computer models indicate that for the foreseeable future, the object (denoted with an arrow in the photo) will stay at least 19 million kilometers away from our planet and, therefore, doesn't threaten a collision. Right now, the asteroid, dubbed 2010 SO16, is making one of its closest approaches to Earth, researchers at the Armagh Observatory in the United Kingdom report in April's Monthly Notices of the Royal Astronomical Society. Relative to Earth, the asteroid, which likely ranges between 200 meters and 400 meters across, moves in a horseshoe-shaped path that sometimes carries it to the far side of the sun. Simulations suggest that unlike the paths followed by three other known asteroids in such orbits, 2010 SO16's orbit has been stable for at least 250,000 years and will likely remain so for at least 200,000 years into the future.

 地球有一個天體尾隨其后，但是不要驚慌。去年秋季，科學(xué)家們發(fā)現(xiàn)了一個小行星在大約跟地球相同的軌道上運行。然而，沒有必要對它頒布禁止尾隨的命令。計算機模擬顯示，在可以預(yù)見的未來的時間里，該天體（見照片中箭頭所示）將會呆在距我們地球至少1900萬公里之外的地方，因此不會有撞擊地球的危險。英國阿爾馬天文臺的研究人員在4月份出版的《皇家天文學(xué)會月報》上報道說：眼下，這顆被稱為“2010 SO16”的小行星正在一個最接近地球的距離上運行。跟地球相比，該小行星很小，可能直徑在200米至400米之間，而且在馬蹄狀的軌道上運行，因此有時會運行到太陽的另一面。模擬表明，不像其他三個已知的小行星所繞行的軌道，2010 SO16的軌道至少在過去的25萬年中一直是很穩(wěn)定的，而且很可能在未來至少20萬年的時間里將會繼續(xù)保持穩(wěn)定。