地球和太陽的鏡像

地球和太陽的鏡像

Among the more than 4,000 known exoplanets, KOI-456.04 is something special: less than twice the size of Earth, it orbits a Sun-like star. And it does so with a star-planet distance that could permit planetary surface temperatures conducive to life. The object was discovered by a team led by the Max Planck Institute for Solar System Research in Göttingen.

在4000多顆已知的系外行星中，KOI-456.04很特別:它的大小不到地球的兩倍，它圍繞著一顆類太陽的恒星運行。而且恒星與行星之間的距離可以使行星表面的溫度有利于生命的存在。該物體是由位于哥廷根的馬克斯·普朗克太陽系研究所領(lǐng)導(dǎo)的一個小組發(fā)現(xiàn)的。

Its host star, called Kepler-160, actually emits visible light; the central stars of almost all other exoplanets, on the other hand, emit infrared radiation, are smaller and fainter than the Sun and therefore belong to the class of red dwarf stars.

它的主星開普勒-160實際上是在發(fā)射可見光;另一方面，幾乎所有其他系外行星的中心恒星都發(fā)出紅外輻射，它們比太陽更小更弱，因此屬于紅矮星。

Space telescopes such as CoRoT, Kepler, and TESS have allowed scientists the discovery of about 4000 extrasolar planets (planets around distant stars) within the past 14 years. Most of these planets are the size of the gas giant planet Neptune, about four times the size of the Earth, and in relatively close orbits around their respective host stars.

在過去的14年里，諸如CoRoT、開普勒和TESS等太空望遠(yuǎn)鏡已經(jīng)讓科學(xué)家們發(fā)現(xiàn)了大約4000顆太陽系外行星(圍繞遙遠(yuǎn)恒星運行的行星)。這些行星中的大多數(shù)都是氣態(tài)巨行星海王星的大小，大約是地球的四倍，它們圍繞各自的主恒星運行的軌道相對較近。

But scientists have also discovered some exoplanets as small as the Earth that could potentially be rocky. And a handful of these small planets are also at the right distance to their host star to potentially have moderate surface temperatures for the presence of liquid surface water – the essential ingredient for life on Earth.

但科學(xué)家也發(fā)現(xiàn)了一些與地球一樣小的系外行星，它們可能是巖石構(gòu)成的。而且，這些小型行星中有一小部分與它們的主星距離合適，有可能擁有中等的表面溫度，從而有可能存在液態(tài)水——這是地球上生命的必要成分。

“The full picture of habitability, however, involves a look at the qualities of the star too”, explains MPS scientist and lead author of the new study Dr. René Heller. So far, almost all exoplanets less than twice the size of Earth that have a potential for clement surface temperatures are in orbit around a red dwarf.

“然而，對可居住性的全面了解還需要考察恒星的質(zhì)量”，新研究的主要作者，下院議員科學(xué)家雷內(nèi)·海勒博士解釋說。到目前為止，幾乎所有體積小于地球兩倍、表面溫度可能溫和的系外行星都在一顆紅矮星的軌道上運行。

Red dwarf stars are known for their extremely long lifetimes. Life on an exoplanet in orbit around an old red dwarf star could potentially have had twice as much time than life on Earth to form and evolve. But the radiation from a red dwarf star is mostly infrared rather than visible light as we know it.

紅矮星以其極其漫長的生命而聞名。在圍繞一顆老紅矮星運行的系外行星上，生命形成和進(jìn)化的時間可能是地球上生命的兩倍。但紅矮星發(fā)出的輻射大多是紅外線，而不是我們所知的可見光。

Many red dwarfs would later become habitable, with enhanced stellar luminosities as long as these stars are young. Moreover, their faintness requires any habitable planet to be so close to the star that the stellar gravity starts to deform the planet substantially.

許多紅矮星后來變得適宜居住，只要這些恒星還年輕，它們的亮度就會增強。此外，它們的稀薄性要求任何宜居行星必須離恒星非常近，以至于恒星的引力開始使行星發(fā)生實質(zhì)上的變形。

The resulting tidal heating in the planet could trigger fatal global volcanism. All things combined, the habitability of planets around red dwarf stars is heavily debated in the scientific community.

地球潮汐加熱可能引發(fā)致命的全球火山活動。所有這些因素結(jié)合在一起，圍繞紅矮星的行星是否適合居住在科學(xué)界備受爭議。