IT is not too hot and not too cold, and astronomers believe that a new planetdetected outside our solar system may have a temperature that is just right to support life.

The planet orbits a red dwarf star called Gliese 581 and appears to be three times the mass of the Earth, the team at the University of California, Santa Cruz, and the Carnegie Institution of Washington said.

The team found it using indirect measurements from the Keck telescope in Hawaii, which has been used to scrutinize Gliese 581 for 11 years and has spotted other potentialplanets orbiting it.

"We had planets on both sides of the habitable zone - one too hot and one too cold - and now we have one in the middle that's just right," said Steven Vogt of UC Santa Cruz. "The fact that we were able to detect this planet so quickly and so nearby tells us that planets like this must be really common."

The planet, called Gliese 581g, is 20 light-years away from Earth in the constellation Libra, according to the paper to be published in the Astrophysical Journal.

The researchers use an indirect method radial velocity to detectplanets. As a planet orbits, it makes the star wobble very slightly and this can be measured.

"There are now nearly 500 known extrasolar planets," Vogt's team wrote. "Our Milky Way could be teeming with potentially habitable planets."

This planet, one of six whizzing around the little cool star, orbits every 37 or so days and has estimated temperatures averaging from -31 to -12 degrees C.

It is locked facing its sun, like Mercury, so one side would be hot and the other cold, with the habitable range at the edge.

• planet [´plænit] n.行星 (初中英语单词)
• system [´sistəm] n.系统，体系，制度 (初中英语单词)
• california [,kæli´fɔ:njə] n.加利福尼亚 (初中英语单词)
• institution [,insti´tju:ʃən] n.建立；制定；制度 (初中英语单词)
• journal [´dʒə:nəl] n.日记；日报；杂志 (初中英语单词)
• slightly [´slaitli] ad.轻微地；细长的 (初中英语单词)
• mercury [´mə:kjuri] n.汞；水银柱 (初中英语单词)
• telescope [´teliskəup] n.望远镜 (高中英语单词)
• potential [pə´tenʃəl] n.&a.潜在的；可能的 (高中英语单词)
• detect [di´tekt] vt.发觉；侦察 (高中英语单词)
• indirect [,indi´rekt] a.间接的；迂回的 (英语四级单词)
• constellation [,kɔnstə´leiʃən] n.星座；灿烂的一群 (英语四级单词)
• velocity [vi´lɔsiti] n.速度(率)；迅速 (英语四级单词)
• hawaii [hɑ:´waii:] n.夏威夷(州) (英语六级单词)