死裡逃生的行星（圖）
06-01
死裡逃生的行星（圖）
「V391派格西b」經歷了紅巨星階段
Will the sun destroy Earth? Astronomers come closer to an answer.
有朝一日，太陽會摧毀地球嗎？天文學家們距離搞到答案又靠近了一步……
Planet Survived Brush with Red Giant
| 天文學家們發現了第一顆圍繞著經歷過紅巨星階段的恆星而旋轉的行星。紅巨星階段是指，類似太陽的恆星開始將核燃料燃盡時所經歷的大規模膨脹階段。 | Astronomers have detected the first planet orbiting a star that has passed through the red giant phase, the massive bloating that befalls sun-like stars when their nuclear fuel begins to run out. |
| 發表在《自然》雜誌上的一篇研究論文指出：儘管這顆所謂的系外行星一度跟其恆星的距離大約相當於地球跟太陽的距離，但它很可能跟其恆星——「V391派格西」發生了一次近距離衝突，卻倖存了下來。 | The so-called exoplanet likely survived a close brush with its star, V391 Pegasi, despite on |
| 研究人員相信，在五六十億年之後，太陽變為紅巨星的時候，水星和金星將會被吞沒；但他們不敢確定地球未來的命運將會如何。太陽風會將我們賴以生存的行星汽化掉嗎？地球會不會落入太陽之中？義大利那不勒斯卡波第蒙特天文台的天體物理學家羅伯托·塞爾瓦蒂指出，這項發現還不能夠揭示地球的命運如何，但是對類似恆星系統的進一步觀測可能會導致系列模型的誕生，這些模型可以揭示地球的命運。 | Researchers believe that when the sun goes red giant in five billion or six billion years, it will swallow Mercury and Venus, but they are unsure about Earth"s future. Will solar wind vaporize our home planet? Could it tumble into the sun? The discovery does not reveal Earth"s destiny, but it suggests that further observations of similar star systems could lead to models that can, says astrophysicist Roberto Silvotti of the Capodimonte Observatory in Naples, Italy. |
| 當一顆類似太陽的、中等大小的恆星燒完絕大部分核燃料，就會發生塌縮，然後膨脹為溫度較低的紅巨星。最終，紅巨星的新外包層大部分會飄散掉，但是有大約2%的紅巨星會失去幾乎所有的外包層。 | When a medium-size star like the sun burns most of its nuclear fuel, it collapses and then balloons into a cooler red giant. Eventually much of this new outer envelope blows away, but in about 2 percent of cases, stars lose nearly their entire envelope. |
| 研究人員認為，「V391派格西」就是一顆這樣的恆星，被稱為B 型亞矮星。該恆星年輕時約相當於太陽質量的0.9倍，現在已萎縮成太陽質量的0.5倍。據了解，少數幾個B 型亞矮星每隔幾分鐘都會發生有節律的跳動，亮度也隨之變化，「V391派格西」就是其中之一。 | Researchers believe V391 Pegasi is such a star, called a B subdwarf B , that shrunk from about 0.9 solar mass during its youth to 0.5 solar mass today. It is also on |
| 在塞爾瓦蒂及同事對這種律動長達七年的研究中，偶然發現了新行星「V391派格西b」。在尋找恆星「V391派格西」的結構線索時，研究人員注意到，該恆星在跳動的時間上發生了規則的變化，這暗示著有顆行星至少是木星質量的3.2倍，在吸引著這顆恆星來回移動。 | Silvotti and his colleagues chanced upon the new planet, V391 Pegasi b, during a seven-year study of these pulsations. Looking for clues to the star"s structure, they noticed a regular variation in the timing of the pulses, which implied the presence of a planet at least 3.2 times the mass of Jupiter tugging the star back and forth. |
| 這些變化說明，行星「V391派格西b」在大約1.6億英里處圍繞著其恆星旋轉，這個距離相當於地球跟太陽距離的1.7倍，即1.7天文單位（AU）。研究人員稱，可能性最大的設想是：該行星一度距其恆星「V391派格西」約一個天文單位，在紅巨星階段，距離縮短到0.3天文單位，最終「V391派格西」失去了外圍的質量，使該恆星又回到較遠的距離上運動。 | The variations indicate that V391 Pegasi b orbits at about 160 million miles, or 1.7 times Earth"s distance from the sun, called an astronomical unit (AU). The most likely scenario, the researchers say, is that the planet on |
| 英國萊斯特大學的天體物理學家馬特·伯利說：「這個發現確實表明了，我們太陽系至少有些行星將會度過紅巨星階段。」伯利指出，該發現也增加了在白矮星周圍發現行星的可能性。白矮星是類似太陽的恆星經歷了較大的二期紅巨星階段之後所形成的殘核。 | The finding "does suggest at least some of the planets in our solar system will survive through the red giant phase," says astrophysicist Matt Burleigh of the University of Leicester in England. He says it also boosts the odds of discovering planets around white dwarfs, the typical remnants of stars like our sun that have passed through a second, bigger red giant phase. |
| 或許這樣的行星最終能夠說明地球的命運。伯利說：「在白矮星周圍找到行星之前，理論家們只能進行猜測。」 | Such planets could finally spell out Earth"s fate. "Until you start finding planets around these stars," Burleigh says, "theoreticians can on |
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