According to one of the recent New Scientist's report,there are at least 23 planets in our solar syatem..Because planets cannot emit light...it is hard for the scientists to detect their existances...Those planets are normally located between 1000AU to 10,000 AU where sunlight is hardly reached ...However scientists havent found out how many planets are in the universe.For my own guess will be more then a billion.查看原帖>>