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A red dwarf star 20 light-years away is again providing hints that it hosts the first definitively habitable planet outside our Solar System, BBC reports.

The planet Gliese 581d is at the colder outer edge of the "Goldilocks zone" in which liquid water can be sustained.

Now a study in Astrophysical Journal Letters suggests its atmosphere may keep things warm enough for water.

French researchers have run computer simulations of the planet's atmosphere, arguing that it is likely to contain high concentrations of carbon dioxide.

They contend that conditions could be suitable for oceans of liquid water as well as clouds and rainfall. But Gliese 581d's denser air and dim red light from its host star would make for a murky environment that would be toxic to humans.

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科学家发现可居住星球

       据英国广播公司报道，距离地球20光年的一颗红色行星显示它是太阳系外第一颗适合地球生命居住的行星。

       这颗名为葛利斯581d的行星正好位于温度稍低的“可居住区”内，可以保证液态水的存在。

       《天体物理学快报》上发表的一项研究认为，这里的大气层可以保温，因此水才得以存在。

       法国科学家通过电脑模拟该行星上的大气层发现，大气层中的二氧化碳含量过高。

       他们认为那里的条件适宜于液态水形成海洋、云和降雨，但由于那里的天空呈混沌、暗红色，整个昏暗的环境可能对人体有害。

(China.org.cn May 20, 2011)