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大西洋月刊:星际访客的冰冷秘密

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原文地址:https://www.theatlantic.com

原创翻译:龙腾网翻译:飞雪似炀花

正文翻译:

The Icy Secrets of an Interstellar Visitor

星际访客的酷寒秘密

The mysterious space object 'Oumuamua may harbor ice under a crust hardened by cosmic radiation.

这个神秘的太空物体“乌穆阿穆阿”可能在其被宇宙辐射硬化的外壳之下藏匿着一块冰体。

To telescopes, ‘Oumuamua, the interstellar asteroid that made itself known to Earth in October, looks like a point of light in the dark, much like a star in the night sky—a perhaps underwhelming picture of a significant discovery.

在千里镜上,乌穆阿穆阿这颗在10月被发明的星际小行星所地球上的人们所知,它看起来就像是在黑阴郁发光的一个小点,很像是夜空中的一颗星星——这大概是一幅无法给人留下深刻印象的重大年夜发明的画面。

But for astronomers, the tiny speck—the sunlight reflected by the asteroid—can reveal a trove of information. They can break down the light from an object into a spectrum of individual wavelengths, from which they can infer the object’s shape, chemical composition, and other properties. As astronomers like to say, if a picture is worth a thousand words, then a spectrum is worth a thousand pictures.

然则对付天文学家来说,由小行星反射的微小的斑点可以反应出大年夜量的信息。他们可以将一个物体的光分化成一张拥有各类波长的光谱,从中可以揣摸出物体的外形、化学因素和其他的性状。正如天文学家所爱好说的,假如一张图片赛过千言万语,那么一张光谱就赛过了一千张图片。

The astronomy community has spent weeks sorting through these pictures of ‘Oumuamua, captured by telescopes around the world as the asteroid sped away from the sun and faded from view. The earliest analysis of the light from ‘Oumuamua, conducted by its discoverers in Hawaii, revealed a strange, fast-spinning, cigar-like object unlike anything they’ve ever seen. The latest analyses continue to produce tantalizing results, further challenging long-standing predictions for the first visitor to our solar system.

天文学团体花了几个礼拜的光阴来收拾这些图片,这些照片是由天下各地的天文千里镜在小行星转离太阳后徐徐消掉的的历程中拍摄的。由夏威夷的发明者进行的最早的阐发发明它是一个稀罕的、快速扭转的、类似于雪茄的物体,这与他们之前所见过的任何器械都不一样。最新的阐发继承发清楚明了令人激动的结果,从而进一步寻衅了对第一个到我们太阳系的访客的存在已久的猜测。

‘Oumuamua has a thick crust of carbon-rich material, hardened by years of exposure to cosmic radiation in interstellar space, that could be protecting an icy interior, according to a new analysis in Nature Astronomy of the object in visible and near-infrared wavelengths. The coating could explain why ‘Oumuamua shows no signs of being a comet, the kind of object scientists long expected would coast into our solar system.

根据一项自然天文学中对可见光和近红外波长光谱的阐发,乌穆阿穆阿有一层厚厚的富含碳的物质,它在星际空间的宇宙辐掷中裸露了多年,可能起到了保护一个酷寒内部核心的感化。这种涂层可以解释为什么乌穆阿穆阿没有显现出彗星的迹象——科学家们经久以来不停觉得进入我们的太阳系中的物体会是彗星。

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千里镜发明时,乌穆阿穆阿已经在阔别太阳了,并且很快就从人们的视线中消掉了。科学家们只有大年夜约两周的光阴来应用千里镜不雅测反射而来的毫光,直到星际旅客走得其实太远。他们探求的是彗尾,这是一股蒸发的粒子,当彗星在接近太阳的地方颠末时,它们的酷寒的物质会被加热。乌穆阿穆阿与太阳的间隔一度很近,大年夜约是太阳和地球之间间隔的四分之一,千里镜也筹备好了不雅测每秒从这个物体上飞离的一块方糖大年夜小的物质。

“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呈现在那里的物体的期望值异常靠近,” 引导了这项新的阐发事情的贝尔法斯特女王大年夜学的天文学家Alan Fitzsimmons如道,“然则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明的冰体或矿物的特性,这意味着它既不是冰体,也不是岩石,至少不完全是。但它确凿显露出了碳化合物的迹象。Fitzsimmons说,之前的钻研注解,当碳含量高的类似彗星的物体裸露在星际空间中时,这些物质会形成一种类似绝缘体的外壳。假如乌穆阿穆阿就像彗星一样存在冰体,在颠末几亿年以致是数十亿年的高能粒子轰击后,它可能暗藏在半米厚的地幔之下。

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拦太阳的热量穿透外面,从而使冰粒子蒸发。根据他们的热模型,即就是在这颗小行星从太阳旁经由过程,其外面温度达到大年夜约600绝对温度(620华氏度)时,任何被埋在30厘米(12英寸)深处的冰都将维持完备。

“Comets are absolutely excellent insulators,” said Karen Meech, one of ‘Oumuamua’s discoverers at the University of Hawaii, who was not involved in this new analysis.“They’re very fluffy and porous, like a down jacket.”

“彗星是异常好的绝缘体,”,夏威夷大年夜学中乌穆阿穆阿的发明者之一Karen Meech——他没有介入这项新的阐发事情——说道,“它们很蓬松,很多孔,就像一件羽绒服。”

Scientists will likely never know for sure what lies inside ‘Oumuamua. When astronomers study the light reflected from the asteroid, they’re only examining the top few microns of its surface, a width smaller than that of a human red blood cell. “We can infer only so much about these little dots of light,” said Michele Bannister, an astronomer at Queen’s University Belfast and a coauthor on the new study.

科学家们可能永世也不会确切地知道乌穆阿穆阿内部是什么。当天文学家钻研小行星上反射的毫光时,他们只是反省到了其顶层几微米厚的范围,这比人类红细胞的宽度都要小。“我们可以揣摸出这些小点的光,”贝尔法斯特女王大年夜学的天文学家、也是这项新钻研的合著者Michele Bannister说道。

Astronomers also have a finite amount of data to work with. Most of their ground-based telescope observations were carried out in the two weeks after ‘Oumuamua was discovered, when it was still visible enough to get good measurements. The majority of research on ‘Oumuamua—the attempts to explain its weird shape, its nonstop spinning, its unexpected hardiness—will come out of this data set.

天文学家可以处置惩罚的数据异常有限。他们的大年夜部分地面千里镜不雅测事情都是在乌穆阿穆阿被发明后的两周内进行的,当时它仍旧足够显眼,可以得到不错的丈量数据。大年夜多半关于乌穆阿穆阿的钻研成果——它们试图解释它怪异的外形、它不绝扭转的特性,它意想不到的硬度——都将从这个数据中孕育发生。

The rest may come from yet-to-be published observations by space telescopes like the Hubble, which has tracked ‘Oumuamua to help astronomers better understand its trajectory and where it came from. The asteroid is now about twice the distance between the Earth and the sun from our planet. Even to Hubble, the producer of countless, radiant images of distant stars and galaxies, ‘Oumuamua, a small object about 400 meters long, will look like a small point of light.

剩下的部分可能就要来自尚未公布的太空千里镜——如哈勃千里镜——的不雅测结果了,它追踪了乌穆阿穆阿,以赞助天文学家更好地懂得它的轨迹和它的起源。这颗小行星现在与地球的间隔是地球和太阳间隔的两倍。纵然是在拍摄了无数的迢遥恒星和星系的辐射图像的哈勃千里镜看来,乌穆阿穆阿这个大年夜约400米长的小物体看起来也就像是一个小光点。

“It could be icy inside, and we’ll never know,” Meech said.

“里面可能存在冰体,但我们永世也不会知道,”Meech如斯说道。

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