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Science and technology
科學技術(shù)
Another Earth?
另一個地球？
Home away from home
遠離家鄉(xiāng)的家
ONE of the more memorable slogans to come out of the climate-change talks in Durban over the past few days is:
在過去幾天的Durban氣候變化會談上提出的較難忘的口號之一就是:
there is no planet B.
沒有星球B，
But what if there were?
但是如果有呢？
Over the past couple of decades astronomers have logged thousands of so-called exoplanets
在過去的幾十年內(nèi)，天文學家記載了數(shù)以千計的所謂的外行星
worlds which orbit stars other than the sun.
饒?zhí)栆酝獾男乔蜍壍肋\行的宇宙。
On December 5th the scientists in charge of Kepler, a space telescope designed to look for such planets, confirmed their instrument's discovery of its first Earthlike world.
12月5號，負責開普勒號的科學家確認他們的儀器發(fā)現(xiàn)了第一個類地球星體，
It is dubbed, rather unromantically, Kepler 22b.
開普勒號是專門為尋找這樣的類地球星體而設計的太空望遠鏡。
The existence of this planet, which circles a star 600 light-years away, in the constellation of Lyra,
存在這么一個行星，它環(huán)繞天琴座星系中一顆600光年遠的恒星運行，之前被懷疑的不存在，
had previously been suspected. Kepler, which belongs to NASA, America's space agency, works by observing dips in a star's brightness as a planet passes in front of it.
開普勒號，隸屬于美國國家航空與宇宙航行局，即美國航天局，它通過觀察當行星通過時恒星光亮度的變化來工作。
It flags likely looking reductions as candidate planets, of which Kepler 22b was one.
它標識顯現(xiàn)的光度弱化可能為候選行星，開普勒22b就是一個。
But three passes are needed to confirm a planet's existence, and Kepler 22b has now passed this test. Crucially, it orbits well within its star's Goldilocks zone:
但是一個行星的確認需要通過三個檢測，開普勒22b現(xiàn)在已經(jīng)通過檢驗。最重要的是，他環(huán)繞著其恒星的適居帶很好地運行；
neither too close nor too far away for liquid water to exist on its surface.
不會太近也不太遠液體水可能存在在上面。
It joins two other Earthlike planets.
它加入了另外兩個類地球行星。
Gliese 581d and HD 85512 b—discovered by another instrument within the past few years.
Gliese 581d 和HD 85512 b—在過去的幾年里被另外的儀器發(fā)現(xiàn)的。
In truth, the term Earthlike is a stretch.
事實上，類地球行星這個詞言過其實，
Kepler 22b has a radius 2.4 times that of Earth, and if it is made from roughly the same stuff its surface gravity will also be about 2.4 times as strong.
Kepler 22b半徑是地球的2.4倍，如果它和地球的組成大致相同，它的表面引力也將大約高達地球引力的2.4倍。
But NASA's astronomers remain unsure whether it is predominantly gaseous, liquid or solid.
但是美國國家航天與宇宙航行局的天文學家仍不能確定它主要是氣體的、液體的或是固體的。
Nevertheless, Kepler 22b is the most promising exoplanet yet found.
然而，Kepler 22b 是目前發(fā)現(xiàn)的最有希望的外行星。
Unlike the others, which skirt the edges of their stars' Goldilocks zones, Kepler 22b orbits comfortably within its own.
不像其他行星不在恒星的適居帶，Kepler 22b 在它的適居帶舒適地運行。
NASA's researchers reckon its surface temperature is about 22C, compared with 15C on Earth.
美國國家航空與宇宙航行局的研究人員通過與地球表面溫度15C比較，估算出它表面的溫度大概是22C。
Its parent star is similar to the sun, again unlike those of the other two candidates, both of which orbit cooler, dimmer stars.
它的母恒星與太陽相似，這又與其他兩個候選外行星不同，其他兩個候選外行星都環(huán)繞較冷的、較昏暗的恒星運行。
Indeed Gliese 581d's parent is a red dwarf—the tiniest stellar species.
Gliese 581d的母恒星確實是一個紅矮星-最小的星系。
That means its Goldilocks zone is so close to it that the planet may be tidally locked, as the moon is to the Earth.
那意味著'適居帶非常接近它以至于行星可能被潮汐力鎖住，就像月亮對于地球一樣。
If that were the case, one side of Gliese 581d would be permanently lit while the other experienced unending darkness.
如果是那樣的話，Gliese 581d的一面將會是常年光亮的，而另一面將會是無盡的黑暗。
These three potentially habitable exoplanets may soon be joined by many more.
很快可能有更多的外行星加入這三個可能適合居住的外行星中。
In the two and a half years since its launch, Kepler has spotted 2,326 candidate planets.
Kepler自發(fā)射以來的2年半里已經(jīng)發(fā)現(xiàn)了2,326候選行星。
About 650 others have been discovered by other instruments.
其他儀器大約發(fā)現(xiàn)了另外650個行星。
That plethora allows astronomers to start drawing conclusions about how common various sorts of planets are.
大量的行星使天文學家開始得出行星種類繁多的結(jié)論。
Of Kepler's haul, 9% seem to be of a similar size to Earth;
Kepler捕獲的行星中9%大小與地球相似；
a further 29% are Super Earths—planets substantially larger than Earth that are nevertheless rocky.
Kepler 發(fā)現(xiàn)的行星29%是超級地球-實質(zhì)上比地球大，不過地球是巖石類行星。
Forty-eight of Kepler's unconfirmed candidates look as if they orbit within their stars' habitable zones; of those, ten seem to be Earth-sized.
Kepler未能確認的候選行星48%看起來似乎是在適居帶運行；其中，有10個與地球大小類似。
The ultimate goal, of course, is to let astronomers make a plausible estimate of the total number of planets in the galaxy, of the number that could conceivably support life, and of the fraction of those that could sustain human colonists.
當然最終的目標是讓天文學家對銀河系的行星總數(shù)、確定可以維持生命的行星數(shù)和那些可以維持人類殖民者生命的行星比例做出一個接近可信的估算。
If only a few of Kepler's possible Earthlike planets turn out to be real, that third number is likely to be in the millions.
如果Kepler類地行星中只有很少被證明是真的，第三個數(shù)可能是數(shù)百萬。
Such knowledge will mark an historic transition, says Chris Lintott, an astronomer at Oxford University who is giving the Kepler team a hand with the data analysis,
一位牛津大學的天文學家Chris Lintoot說這些知識是歷史轉(zhuǎn)變的標志，他對Kepler團隊給以數(shù)據(jù)分析的援助，
since the uncertainties around the question of whether life exists elsewhere will cease to be astronomical and become purely biological.
從此關于其他地方是否存在生命問題的不確定性將不再是天文學問題，
Based on the preliminary data, it looks as if there are numerous suitable planets.
而是變成了純粹的生物問題基于這些初始數(shù)據(jù)，似乎有許多合適的行星，
The science of exobiology may soon cease to be an oxymoron.
外空生物學將不再是一個矛盾修飾。
