奇怪：環恆星盤消失啦！（圖）
06-01
奇怪：環恆星盤消失啦！（圖）
這張藝術家繪製的概念圖顯示，一顆年輕的恆星在不到兩年的時間裡就失去了這個塵埃盤。
Planet-Forming Disk Vanishes Into Thin Air
| Some 460 light-years away in the constellation Centaurus, a thick disk of dust swirled around a young star named TYC 8241 2652 1, where rocky planets like our own were arising. Then, in less than 2 years, the disk just vanished. That"s the unprecedented observation astronomers report in a new study, out today. Even more intriguing: The same thing may have happened in our own solar system. | 在大約460光年之外的人馬座，一個厚厚的塵埃盤圍繞著一顆叫做TYC 8241 2652 1的恆星旋轉，類似我們地球的岩石行星正在那個塵埃盤中形成。後來，在不到兩年的時間裡，該塵埃盤卻不見啦！今天，天文學家們在一項新研究中報道說，這次觀察到的情況是前所未有的，更有趣的是，我們太陽系也有可能發生過同樣的事情。 |
| Born about 10 million years ago, the TYC 8241 2652 1 system was chugging along just fine before 2009. Its so-called circumstellar disk glowed at the infrared wavelength of 10 microns, indicating it was warm and lay close to a star—in the same sort of region that, in our own sun"s neighborhood, gave rise to the terrestrial planets Mercury, Venus, Earth, and Mars. The infrared data reveal that the dust was about 180°C and located as close to its star as Mercury is to the sun. | TYC 8241 2652 1系統大約誕生於1000萬年前，在2009年以前演化順利，其所謂的「環恆星盤」在波長為10微米的紅外狀態下發光，這說明圓盤是溫暖的，而且距離恆星很近，在太陽周圍大致同樣距離的附近區域，曾經產生了水星、金星、地球和火星等類地行星。紅外資料顯示，塵埃大約為180°C，跟其恆星的距離相當於水星跟太陽的距離。 |
| By January 2010, however, nearly all infrared light from the dusty disk had vanished. "We had never seen anything like this before," says astronomer Carl Melis of the University of California, San Diego. "We were all scratching our heads and wondering what the hell did we do wrong?" But subsequent observations with both infrared satellites and ground-based telescopes confirmed the surprising discovery, he says: "The disk was gone." | 然而，到2010年1月，來自那個塵埃盤的所有紅外光幾乎全部消失。「我們以前從未看到過類似的情況，」加州大學聖迭戈分校的天文學家卡爾·梅里斯說，「我們大家都感到迷惑不解，不知道什麼地方做錯了。」他說：但是，後來的觀察兼用紅外衛星和地面望遠鏡，證實了這個令人吃驚的發現——那個塵埃盤就是不見啦！ |
| Melis and his colleagues report the mystery online today in Nature—but they don"t know what caused it. "It"s very bizarre," he says. "Nothing like this was ever predicted." He says there"s no way something could eclipse the infrared-emitting disk for more than 2 years, because such an object would be immense. Furthermore, the star itself didn"t fade. | 今天，梅里斯及同事在《自然》雜誌在線版上報道了這個難以理解的事件，但是他們不清楚這是怎麼引起的。「事情非常奇怪，」他說，「像這樣的情況事先根本沒有預料到。」他表示，不可能是有什麼物體遮擋了那個發射紅外線的圓盤達兩年多時間，因為如果有的話，這樣的物體就會太巨大了。況且，恆星本身並沒有變得暗淡。 |
| Melis speculates that an earlier collision between two objects—perhaps two boulders, two asteroids, or even two planets —orbiting the star produced the dust grains that emitted the infrared light. Then either the star"s light blew the dust out of the planetary system or the dust plunged into the star. | 梅里斯推測：早些時候，環繞恆星的兩個物體之間發生了碰撞，產生了發出紅外光的塵埃顆粒；這種碰撞的物體可能是兩塊巨石、兩顆小行星，或者甚至是兩顆行星。然後，要麼是恆星的光將塵埃驅逐出這個行星系統，要麼就是塵埃跌進了恆星之中。 |
| "It"s a really interesting mystery," says astronomer Scott Kenyon of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, who was not affiliated with the discovery team. "The observations certainly seem correct. It"s sort of amazing to have the dust in one of these disks go away so quickly. It"s hard to know exactly what happened." | 「這的確是個非常有趣的謎，」馬薩諸塞州劍橋市哈佛史密森天體物理中心的天文學家斯科特·凱尼恩說，「看來這些觀察肯定是正確的。其中一個圓盤裡的塵埃這麼快就消失了，這真令人感到驚訝！我們很難知道到底發生了什麼。」凱尼恩並沒有參加這個研究小組。 |
| "This is a whole new insight into the violent processes like the ones that formed the moon and that must be going on where terrestrial planets are forming and first evolving in other planetary systems," adds astronomer George Rieke of the University of Arizona in Tucson. Rieke says the discovery shows what happens after members of a nascent planetary system collide. His team has recently found milder infrared dimming in two somewhat older stars, indicating that similar events may be occurring there. | 「這對於像形成月球這樣的撞擊過程是一個全新的認識：這種撞擊過程一定在類地行星正在形成的地方進行著，而且該過程最初一定是在其他行星系統中展開的，」圖森市亞利桑那大學的天文學家喬治·里克接著說。里克還說，該發現表明了新生行星系統中的行星碰撞之後所發生的情況。他的研究小組最近發現，在兩顆稍微古老一些的恆星系統中紅外光發生了比較輕微的變暗，這表明那裡可能正在發生同樣的情況。 |
| The discovery may offer clues to the violence that surrounded the formation of Earth. In particular, Earth is the only known terrestrial planet with a large moon, whose tides may have helped life advance by pushing it from sea to land; but no one knows how many Earthlike planets sport large satellites. The moon arose when a Mars-sized object hit our planet, a collision that presumably spewed lots of dust into space. The new observations suggest this dust could have disappeared fast. | 該發現可以提供線索，讓科學家們了解跟地球形成密切相關的撞擊事件。尤其是，地球是所了解到的唯一一顆帶有巨大衛星的類地行星，這顆衛星引起的潮水把生命從海洋推向陸地，從而可能幫助了生命的進化。但是，沒有人知道有多少顆類地行星擁有大型衛星。當一顆火星大小的物體撞擊了地球之後，產生了月球，據推測那次碰撞將大量的塵土噴射到太空。新的觀察表明，當時噴射到太空的塵土可能很快就消失了。 |
| However, with only one dust-vanishing event ever seen, Melis doesn"t know how common the phenomenon is. So his team plans to monitor not only this star but also others like it. "We have to wait and see if we ever catch another one," he says. | 然而，只憑看到一次塵埃消失的事件，梅里斯不知道這種現象是否普遍。因此，他的研究小組計劃不僅要監視這顆恆星，而且還要監視其他類似的恆星。「我們必須等待，看一看是否能夠觀察到另外一顆類似的恆星，」他說。 |
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