[Economist]Blowing in the windSpace dust 太空尘埃 Blowing in the wind 飘 Oct 11th 2007 From The Economist print edition The building blocks of planets and people come from black holes 星球与人都从黑洞中走来 WHEN the writer of Genesis said man was made of dust, he spoke true. And not just man. The whole Earth was made from dust particles in orbit around the primitive sun, as were all the other solid objects in the solar system. But how did the dust itself come into existence? 《创世纪》的作者说人是尘土做的，此话不假。而且不仅仅人是尘土造的，包括地球在内的、整个太阳系的固体物质都是由环绕早期太阳的尘埃造的。但是尘埃本身又是如何形成的呢？ That is a puzzle. Modern space dust blows off stars that formed about 10 billion years ago. These stars would have been too young to have shed much of the stuff by the time that the solar system formed, 4.5 billion years ago. The universe's primordial dust must therefore have come from somewhere else—and a team of researchers led by Ciska Markwick-Kemper of the University of Manchester think they know where. The answer is from black holes. 这是个未解之谜。现代太空尘埃由恒星形成100亿年之后喷发出来。但太阳系形成于45亿年前，似乎这些恒星都过于年轻而不可能产生这如此之多的尘埃。那么宇宙间的早期尘埃肯定来自什么别的地方——由曼彻斯特大学（University of Manchester）的Ciska Markwick-Kemper领衔的研究组认为他们知道尘埃来自何方——那就是黑洞。 The black holes in question are at the centres of quasars. These formed shortly after the universe began and they came to the attention of earthling astronomers because quasars are powerful radio sources. The radio waves (and lots of other radiation) are the result of matter being drawn into the black hole and releasing energy as it falls. But not all this matter is swallowed. Some is baked, transformed and spat out again. It was this transformation that interested Dr Markwick-Kemper. 我们所讨论的黑洞位于类星体的中心。它们紧随宇宙伊始而形成，并因类星体是巨大的无线电波发射源而进入天文学家的视野。物质被吸入黑洞的过程，以及其下落时释放能量的过程，都会产生无线电波（还有大量其他射线）。但不是所有的这种物质都被吞噬进去了。其中一些在经过烘培、转化之后，又被释放出来。Markwick-Kemper博士所感兴趣的正是这种转化。 Suspecting that it might be the source of primordial dust, she recruited a space telescope called Spitzer to look at a quasar called PG 2112+059 in more detail. Spitzer is tuned to pick up infra-red radiation—the sort of radiation emitted by dust that has been heated. And the details of the spectrum of infra-red radiation given off by a speck of dust will betray its composition. Markwick-Kemper博士将名为PG2112+059的类星体假想成早期尘埃的来源，启用了太空望远镜——斯匹策红（Spitzer）对其进行了更为细致的观察。斯匹策红用来分离红外线，这是被加热过后的尘埃所放射出的一种射线。通过对少量尘埃放射的红外线进行光谱分析，就可以得到尘埃的构成成分。 Dr Markwick-Kemper and her colleagues report their findings in a forthcoming edition of Astrophysical Journal Letters. The dust around PG 2112+059 contains large quantities of rock-forming minerals, including crystalline forms of silica (essentially, small sand grains), a form of aluminium oxide called corundum (better known on Earth as the principal ingredient of rubies and sapphires) and a form of magnesium oxide called periclase (which is present in marble). Markwick-Kemper博士及其同事将在新一期的《天体物理杂志通讯》(Astrophysical Journal Letters)发表他们的发现。PG 2112+059类星体周围的尘埃含有大量形成岩石的矿物，包括硅晶石（基本上是小沙粒），被称作刚玉的铝氧化物（更为通俗易懂的说法是红宝石和蓝宝石的主要成分），以及镁氧化物——方镁石（存在于大理石中）。 These minerals must have been produced by the quasar, Dr Markwick-Kemper argues, because their crystal structures would not survive long in the hostile conditions of outer space. Cosmic rays would zap them into an amorphous, glass-like state. Moreover, corundum and periclase have not been detected in space dust before. Their association with the quasar is therefore strong evidence that this is the object that created them. A human being may still be a handful of dust. But that dust has had an exciting history. Dr Markwick-Kemper认为，这些矿物肯定是类星体产生的，因为在外太空它们的晶状结构很难长时间存在。宇宙射线会将它们打回到无定形玻璃态。而且，此前在太空尘埃中还未侦测到刚玉和方镁石。因此存在于类星体中的事实为类星体创造了它们提供了强有力的证据。人类可能就是一抷土。不过这抷土有着饶有兴趣的历史。 |
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