科学家发现奇特系外行星群 或由钻石构成

　　An exoplanet, called WASP-12b which is about 1,200 light years from Earth and 1.4 times the mass of Jupiter has been considered suitable for life existence, although a little hot. And its sibling planets could even be made of diamonds, according to new research findings。

　　A team led by researcher Nikku Madhusudhan of Princeton University and scientist Joe Harrington of the University of Central Florida monitor WASP-12b during one of its orbits, particularly in the instants before it passed behind its home star. In those brief moments, the light from the star would flow through the planet's atmosphere, allowing astronomers to study the wavelengths produced and infer the atmosphere's chemical composition。

　　They found some exoplanets, WASP-12b included, have carbon-rich chemistry: Some have atmospheres with a carbon-to-oxygen ratio of about 0.5. As for WASP-12b, however, there was more than twice the concentration of carbon as usual and almost 100 times more methane than expected。

　　That has big implications for extraterrestrial biology, since life is based on carbon, and methane - which is made up of carbon and hydrogen - is a byproduct of metabolism. The planet's carbon-heavy atmosphere could retain heat and light, providing energy for life to get started and thrive. That life would have to survive on comparatively little oxygen and water, and would have to be very tolerant of methane。

　　As for some of the planets formed along with WASP-12b, they could easily be smaller, with rocky formations made not of silica, like Earth's, but of graphite or - given enough time and enough pressure - precious diamonds。

　　美国《时代》周刊8日报道称，最新研究结果显示，一颗名为WASP-12b、距离地球1200光年、质量为木星1.4倍的系外行星适合生命存在，尽管热了一点。而与其同属一个星系的情况更甚：它们有可能由钻石构成。

　　由美国普林斯顿大学的研究员尼库．马杜苏丹和佛罗里达中部大学的科学家乔．哈林顿领导的一个研究小组检测WASP-12b的一次绕轨运行情况，特别是在它从其母恒星后面经过的那一刻。在这一刹那，恒星发出的光会穿透行星的大气，天文学家得以研究产生的波长，并推断行星大气的化学成分。

　　他们发现，一些包括WASP-12b在内的系外行星具有碳浓度高的化学特性，即它们大气中的碳氧比率约为0.5。不过，WASP-12b的碳浓度要比通常情况高出一倍多，而且甲烷的浓度几乎是预计的100倍。

　　这对于地外生命学来说意义重大。因为生命建立在碳的基础上，而由碳和氢构成的甲烷是新陈代谢的副产品。大气中高浓度的碳可以留住光和热，为生命的出现和茁壮成长提供能量。这些生命要再氧气和水相对较少的环境下生存，而且要能够忍受甲烷。

　　而和WASP-12b一起形成的另外一些行星很可能体积更小，岩层不像地球那样由硅石构成，而是由石墨或者——如果有充足的时间和压力——钻石这样的珍贵材料构成。