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(gè)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(gè)小行星在大約跟地球相同的軌道上運(yùn)行。然而，沒有必要對(duì)它頒布禁止尾隨的命令。計(jì)算機(jī)模擬顯示，在可以預(yù)見的未來(lái)的時(shí)間里，該天體（見照片中箭頭所示）將會(huì)呆在距我們地球至少1900萬(wàn)公里之外的地方，因此不會(huì)有撞擊地球的危險(xiǎn)。英國(guó)阿爾馬天文臺(tái)的研究人員在4月份出版的《皇家天文學(xué)會(huì)月報(bào)》上報(bào)道說：眼下，這顆被稱為“2010 SO16”的小行星正在一個(gè)最接近地球的距離上運(yùn)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(yùn)行，因此有時(shí)會(huì)運(yùn)行到太陽(yáng)的另一面。模擬表明，不像其他三個(gè)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(wàn)年中一直是很穩(wěn)定的，而且很可能在未來(lái)至少20萬(wàn)年的時(shí)間里將會(huì)繼續(xù)保持穩(wěn)定。