研究:1/4类日恒星拥有类地卫星

　　Researchers who studied stars similar to the Sun found that almost one in four could have small, rocky planets just like the Earth。

　　For their research, scientists spent five years studying 166 Sun-like stars within 80 light year – or 470 trillion miles – of Earth。

　　Researcher Andrew Howard, from the University of California at Berkeley, said: "Of about 100 typical Sun-like stars, one or two have planets the size of Jupiter, roughly six have a planet the size of Neptune, and about 12 have super-Earths between three and ten Earth masses. If we extrapolate down to Earth-size planets between one-half and two times the mass of Earth, we predict that you'd find about 23 for every 100 stars."

　　Last month, astronomers announced the discovery of the most Earth-like planet ever found – a rocky world three times the size of our own world, orbiting a star 20 light years away. The planet appears to have an atmosphere, gravity like our own – and could have flowing water on its surface。

　　The technique can only detect planets orbiting close to their stars. That means the true number of planets could be much higher. Over the next decade, new methods of planet detection and more powerful telescopes could soon be uncovering true Earth-like worlds orbiting distant stars, the scientists said。