By Li Hongmei
According to a study published in the Proceedings of the National Academy of Sciences, there may be about 9bln Erath-like planets out there in our Milky Way galaxy, all in the habitable temperature zone that is not too cold and not too hot for harboring life.
The figure is a trustworthy estimate based on the observation of 42,000 star systems carried out by NASA's now-crippled Kepler orbital telescope in the four years since it was launched in 2009.
The next step, scientists say, is to look for atmospheres on these planets to find further clues to whether any of them do, in fact, harbor life.
The Kepler team's latest findings also raise a blaring question. "If we aren't alone, why is there a deafening silence in our Milky Way galaxy from advanced civilizations?", study co-author Dr Geoff Marcy has been quoted as wondering.
