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#太平洋电脑网#大西洋月刊：星际访客的冰冷秘密( 二 )


When the asteroid was first spotted by the Pan-STARRS telescope in Hawaii, ‘Oumuamua was already speeding away from the sun and quickly fading from view. Scientists had only about two weeks to deploy telescopes to soak up the reflected light before the interstellar visitor got too far away. They looked for a coma, a stream of evaporated particles that trails comets as they pass near the sun and their icy contents become heated. ‘Oumuamua had made a fairly close pass to the sun—about a quarter of the distance between the sun and Earth—and telescopes were prepared to spot as little as a sugar cube’s worth of material flying off the object every second.
当第一次被位于夏威夷的泛星计划望远镜发现时 ， 乌穆阿穆阿已经在远离太阳了 ， 并且很快就从人们的视线中消失了 。 科学家们只有大约两周的时间来使用望远镜观测反射而来的光线 ， 直到星际游客走得实在太远 。 他们寻找的是彗尾 ， 这是一股蒸发的粒子 ， 当彗星在靠近太阳的地方经过时 ， 它们的冰冷的物质会被加热 。 乌穆阿穆阿与太阳的距离一度很近 ， 大约是太阳和地球之间距离的四分之一 ， 望远镜也准备好了观测每秒从这个物体上飞离的一块方糖大小的物质 。
“We had data that matched pretty closely with what we’d expect for a body out there,” said Alan Fitzsimmons, an astronomer at Queen’s University Belfast who led the new analysis. “And yet we saw no sign of ice being heated and ejected into space.”
“我们的数据与我们对出现在那里的物体的期望值非常接近 ， ” 领导了这项新的分析工作的贝尔法斯特女王大学的天文学家Alan Fitzsimmons如道 ， “但是我们没有看到任何冰被加热并被喷射到太空中的迹象 。 ”
‘Oumuamua didn’t show signatures of ice or minerals found in rock, which means it’s neither icy nor rocky, at least not exactly. But it did show signs of carbon compounds. Fitzsimmons said previous studies have revealed that when carbon-rich, comet-like objects are exposed to the radiation that would be found in interstellar space, the material forms a crust that acts as insulation. If ‘Oumuamua has ice, as a comet would, it may be hiding beneath a mantle half a meter thick, formed after hundreds of millions—perhaps even billions—of years of bombardment by high-energy particles.
乌穆阿穆阿没有显示在岩石中发现的冰体或矿物的特征 ， 这意味着它既不是冰体 ， 也不是岩石 ， 至少不完全是 。 但它确实显露出了碳化合物的迹象 。 Fitzsimmons说 ， 之前的研究表明 ， 当碳含量高的类似彗星的物体暴露在星际空间中时 ， 这些物质会形成一种类似绝缘体的外壳 。 如果乌穆阿穆阿就像彗星一样存在冰体 ， 在经过几亿年甚至是数十亿年的高能粒子轰击后 ， 它可能隐藏在半米厚的地幔之下 。
【#太平洋电脑网#大西洋月刊：星际访客的冰冷秘密】Fitzsimmons and his colleagues say ‘Oumuamua’s crust may have been able to prevent heat from the sun from penetrating the surface and vaporizing ice particles. According to their thermal models, any ice buried 30 centimeters (12 inches) deep would have remained intact even as the surface of the asteroid reached temperatures of about 600 degrees Kelvin (620 degrees Fahrenheit) during its pass of the sun.
Fitzsimmons和他的同事们说 ， 乌穆阿穆阿的地壳可能能够阻止太阳的热量穿透表面 ， 从而使冰粒子蒸发 。 根据他们的热模型 ， 即便是在这颗小行星从太阳旁通过 ， 其表面温度达到大约600绝对温度(620华氏度)时 ， 任何被埋在30厘米(12英寸)深处的冰都将保持完整 。


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