Why did all the planet-forming dust around this star disappear in only three years? 为什么恒星周围的星尘三年内全部消失 Back in 1983, astronomers discovered a star 450 light-years away that was surrounded by a cloud of dust — a textbook example of a solar system in the making. Now, nearly thirty years later, the cloud has suddenly and mysteriously disappeared. 在1983年，天文学家发现了一颗被星尘环绕距离我们450光年的恒星，这颗恒星可以作为太阳系如何形成的教科书。现在，几乎三十年过去了，恒星周围的星尘突然神秘的消失了。 This discovery could mean that everything we thought we knew about the birth of planets is wrong. 这项发现可能会否定我们所有对于行星诞生的感知。 This is one of those observations that, on the face of it, doesn't make a lot of sense. Astronomers have always believed that it takes hundreds of thousands of years — if not millions — for the dust orbiting a young star to congeal and form planets. This recent observation, however, indicates that planets may form significantly faster than we thought. Or alternatively, that these dust clouds behave in ways unknown to us. 虽然这项发现从某种角度来说没有什么意义。天文学家总是相信要形成一颗行星，需要星尘在其周围环绕上百年才可以形成。但是这最近的发现却暗示行星可能超出我们想象的速度形成。换句话说，这些尘云以我们不知道的方式运动着。 Making sure the data is correct 确认数据正确。 To confirm and cross-reference this strange discovery, researchers were pooled from a number of institutions, including universities from Georgia, San Diego, Los Angeles, California-Polytechnic, and Australia. This was a team effort. 要确认并互相参照这项发现，研究人员被从各项机构里选出包括乔治亚、圣迭戈、洛杉矶、澳大利亚、加州理工大学。 这需要团队合作。 What troubled these scientists was that the cloud of dust circling a star in the Scorpius-Centaurus stellar nursery simply disappeared within the span of three years. 困惑这些科学家的是来自天蝎星系中一颗行星被发现其周围的星尘子在三年内消失不见。 The researchers used data from a wide array of sources, including a mid-infrared imager at the Gemini South Observatory in Chile, NASA's Wide-field Infrared Survey Explorer, the Japanese AKARI telescope, and the European Space Agency's Photodetector Array Camera and Spectrometer. Looking at all the data provided by these instruments, the scientists could not help but conclude that, from the period 2008 to 2009 the infrared emissions dropped by nearly two-thirds (indicating a dramatic decrease in dust), and that by 2010 the dust cloud had all but vanished. 调查人员运用了各种途径的数据，包括来自智利的南双子星天文台的中红外线成像器，美国航天局的广角红外线探测研究器，日本的星野望远镜和欧洲空间局的探测器阵列相机和光谱。仔细研究这些仪器提供的数据，科学家不得不承认从2008到2009年红外线辐射下降了近二分之三（代表星尘的锐减），然后到2010年所有的星尘就此消失。 Okay, so what happened to all the dust? 好吧。那到底发生了什么？ With the data largely confirmed, the scientists were forced to come up with theories explaining the anomaly. 由于这些确凿的证据，科学家们不得不为此提供一个解释。 One suggestion, as absurd as it sounds, is that it doesn't take long for planets to form given certain conditions — what is dubbed "runaway accretion." In such a scenario, the growth of dust and rocks snowballs quickly, leading to the rapid, nearly instantaneous formation of planets. If true, this would completely reset our notions of just how quick and easy it is for planets to form around a star. 其中一个荒谬的假设是在某些特定的条件下行星可以迅速形成，因此被称作“失控吸积”。在这种情况下，星尘的成长和石头的形成很快，导致行星迅速形成。如果这是真的，那么这大概会彻底重置我们对于星球形成的速度的观念。 But three years? Really? It would be nice to see computer models prove this idea. Moreover, if this theory is true, a new planet should be orbiting this star. Hopefully, using more advanced telescopes than we have now, we might someday be able to find it. 但是真的只需三年吗？希望电脑模型能证明这一点。进一步来讲，如果这项理论是真实的话，一个新的行星需要来环绕这个恒星。希望今后运用更加先进的望远镜我们能发现它们。 Another possibility is what the scientists call "collisional avalanche." This theory suggests that the dust was expelled from the sun's orbit. Because these dust particles are so small — smaller than a grain of sand — the constant stream of photons emanating from the sun could push them away and into each other until they leave the sun's orbit. The problem with this theory, however, is that it makes planetary formation sound rare and difficult, which we know it certainly is not. 另一个可能的假设是被科学家们称作“碰撞雪崩”。这项理论说明星尘可能被从太阳运动轨道中抛出。由于这些颗粒太小，比普通的沙子还要小，从太阳中释放出来的质子流可以使它们相互碰撞直到它们离开太阳的轨道。但这项理论的问题是，这使得行星的形成变得奇怪和困难。我们知道行星的形成不可能这样。 And yet another theory suggests that the sun swallowed all the dust in one gigantic gulp. Again, another unsatisfying answer. As Nola Taylor-Redd noted in a recent Space.com article, "[This] theory, known as the collisional cascade model, would likely require time scales longer than two years to clear the dust from the system." 然后另一项理论表示这些星尘被太阳吸收了。然而 再次这不是个满意的答案。就像 Nola Taylor-Redd在最近一篇space.con上发表的文章中提到的那样“我认为这个被称作碰撞瀑布模型的理论，需要至少两年的时间才可能将星尘从系统中清除。 Clearly more work needs to be done, and the researchers are planning their next move. Specifically, they want to analyze old observations like the one made in 1983 and compare them to new data pulled from modern telescopic techniques, to make a systematic search for other stars that may have recently gone through a similar phase. 很明显更多的工作需要做，研究人员现在正在计划下一步的工作。具体的，他们希望能分析在1983年所做的研究并将他们和新的来自现代望远镜的数据进行对比，做个对其他有着相似周期恒星的系统性研究。 These results were published today (July 5) in the journal Nature. 这些结果在今天（7.5）的自然杂志上刊登。 Sources: Daily Mail, Space.com. 参考文献：每日邮报 space.com 
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