類日恆星周圍的三個「超級地球」（圖）

05-30

類日恆星周圍的三個「超級地球」（圖）

2008年6月16日，歐洲一組天文學家宣布發現了三個「超級地球」——比地球大，比土星和木星小的行星。

Three "Super-Earths" Found Orbiting Sun-Like Star

A trio of "super-Earths" have been found near a sun-like star, a team of European astronomers announced today.	歐洲一組天文學家今天宣布，在一顆類日恆星附近發現了三個「超級地球」。
The planets orbiting the star HD 40307—which is 42 light-years away—were found using an advanced "planet searcher" instrument at the European Southern Observatory in La Silla, Chile, the French and Swiss astronomers said.	法國和瑞士的天文學家們稱，他們在智利臘希拉的歐洲南方天文台，利用一台尖端的「行星搜尋儀」，發現了三顆行星環繞在距地球42光年處的恆星HD 40307周圍。
The part of the sky being studied contains 45 potential planets that are smaller than 30 times the mass of Earth, the astronomers said. Most of them orbit HD 40307 quickly—every 50 days or less.	天文學家們說，他們正在研究的那片天區可能含有45顆行星，質量都小於地球的30倍，其中絕大多數在快速地圍繞著HD 40307旋轉，每50天左右環繞一周。
"We are convinced that there are plenty of planets everywhere," said Didier Queloz, a member of the research team from the Observatoire de Genève in Switzerland.	「我們相信到處都有許多行星，」瑞士日內瓦天文台的研究小組成員狄迪埃爾·魁洛茲表示。
The discovery is creating a buzz throughout the astronomy community.	這個發現正在天文界引起一場轟動。
David Charbonneau, an exoplanet expert from Harvard University who was not involved with the new find, said it heralds a new age: "We have entered the Epoch of the Super-Earths," he said.	哈佛大學的系外行星專家大衛·夏波諾沒有參與這項新發現，但他說這預示著一個新時代的到來：「我們進入了『超級地球』時代。」
The announcement of HD 40307"s planets came out of an international workshop called Extra Solar Super-Earths in Nantes, France.	HD 40307的行星情況公告來自於法國南特的一個國際合作研究室，該研究室被稱為「系外超級地球」。
Rapid Discovery	行星的發現進展迅速
The study of exoplanets really didn"t get under way until 1995, Queloz said. That"s about the time Queloz and his colleague Michel Mayor, also from Observatoire de Genève, discovered a planet around the star 51 Pegasi. Since then more than 270 exoplanets have been found, most of them around sun-like stars. Many are giants like Jupiter or Saturn, and current statistics show that about 1 out of 14 stars harbors that kind of planet.	魁洛茲說，直到1995年系外行星的研究才真正地開始進行，那大約也是魁洛茲及來自同一天文台的同事米歇爾·梅厄在恆星「51派格西」周圍發現了一顆行星的時間。從那以後，發現了270多顆系外行星，其中絕大多數環繞在類日恆星周圍，許多是類似木星和土星的巨型行星，而且目前的統計數據顯示，每14顆恆星中便有一顆周圍藏有那種巨型行星。
Queloz said the largest extrasolar planets—gas giants as massive as Jupiter—were found first because they were easiest to detect. "The biggest ones are certainly the most difficult to form,」 he added. 「Everyone is kind of expecting that there are many more small mass planets than big planets."	魁洛茲說，首先發現的是最大型的系外行星，屬於氣態巨星，就象木星那麼大，因為這些行星是最容易被發現的。「最大的行星肯定是最不易形成的，」他接著指出，「但從某種程度上說，人人都在期待會存在更多小質量行星，而不是大質量行星。」
Better Eyes	觀測儀器更為先進
The astronomers say better technology developed in recent years will enable researchers to see ever-smaller planets around other sun-like stars. Now super-Earths—planets that are more massive than Earth but less massive than Uranus and Neptune—mark the threshold for detection.	天文學家們稱，近年來開發出了較為先進的技術，使研究人員能夠觀測到其他類日恆星周圍的較小型的行星。現在所發現的「超級地球」——比地球更大，但比天王星和海王星更小的行星，標誌著可探測行星的限度。
The three newly discovered planets are 4.2, 6.7, and 9.4 times more massive than Earth and orbit the star in periods of 4.3, 9.6, and 20.4 days, respectively. Their orbits cause a disruption in the motion of their parent star, which allowed the researchers to infer their presence using a popular technique called the "wobble method."	三顆新發現的行星分別比地球大4.2、6.7和9.4倍，繞其恆星一周的周期分別是4.3、9.6和20.4天。這些行星繞軌道運行，干擾了其主恆星的運動，使得研究人員可以利用一種叫做「擺動法」的流行技術，來推知這些行星的存在。
"The perturbations induced by the planets are really tiny," said team member Fran?ois Bouchy, from the Institut d"Astrophysique de Paris in France.	「由這些行星引起的擺動是極其微小的，」研究小組成員、法國巴黎天體物理學研究院的弗朗索瓦·布希說。
"The mass of the smallest planets is one hundred thousand times smaller than that of the star, and only the high sensitivity of HARPS made it possible to detect them," he said, referring to the High Accuracy Radial Velocity Planet Searcher instrument, which attaches to the observatory"s telescope.	提到天文台望遠鏡上安裝的「高精度徑向速度行星搜尋儀（HARPS）」，布希說：「最小行星的質量比其恆星的質量小10萬倍，只有具有高靈敏度的HARPS搜尋儀才可能探測到這些行星。」
Study team member Queloz said it』s only a matter of time before astronomy"s eyes get sharp enough to find planets no bigger than Earth.	研究小組成員魁洛茲指出，天文觀測儀可以變得非常敏銳，足以找到僅僅相當於地球大小的行星，但這只是一個時間早晚問題。
Closer to Life	系外生命更近一步
At the same conference, the team of astronomers announced the discovery of two other planetary systems, also found with the HARPS instrument.	在同一次會議上，這一組天文學家還宣布發現了另外兩個行星系統，也是利用HARPS搜尋儀發現的。
One of these systems has seven times the mass of Earth and orbits the star HD 181433 in just under ten days. That star also hosts a Jupiter-like planet with an orbit that takes close to three years.	其中一個行星系統是地球質量的7倍，圍繞著恆星HD 181433旋轉一周僅用不到10天的時間。該恆星還擁有一顆類似木星的行星，繞軌道旋轉一周只需要近三天的時間。
The other system contains a planet that is 22 times more massive than Earth, with an orbital period of four days, as well as a Saturn-like planet with a three-year orbit.	另一個行星系統包含的一個行星，其大小是地球的22倍，繞軌道的旋轉周期為4天，還有一個類似土星的行星，繞軌道一周需要3年。
"Clearly these planets are only the tip of the iceberg," study team member Mayor said.	「顯然這些行星只是冰山一角，」研究小組成員梅厄說。
Drake Deming, a scientist at the Goddard Space Flight Center in Maryland, called the new study a major breakthrough in exoplanet research. "It is among the super-Earths that many workers in this field hope to find the first evidence for biomarkers, and thus the first evidence for extrasolar life," he said.	馬里蘭州戈達德太空飛行中心的科學家德雷克·戴明將這項新研究稱為「系外行星研究方面的重大突破」。他說：「該領域的研究人員希望在這些超級地球當中發現生物標記物的初步跡象，進而找到系外生命的初步跡象。」
To find biological indications of life, he said, astronomers will need to know something about the atmospheres of the potential planets. And that work requires planets that pass in front of their parent stars.	戴明指出，要想發現生命的生物學跡象，天文學家們需要了解潛在的行星上大氣的某些情況，而該研究工作需要行星從其主恆星前面經過。
"Since only a relatively small fraction of planets will transit, finding large numbers of them will be of tremendous benefit," Deming said.	「由於只有相對一小部分行星為凌日行星，找到大量的此類行星將會對研究大有助益，」戴明說。