Celestia是一个免费的开放源代码天文类软件，通过它你不仅可以鸟瞰地球，还可以畅游太阳系，以及其它多达10万颗星，甚至是银河系以外的星座。-Celestia is a free open source software astronomy class, through which you can not only aerial view of the Earth, you can tour the solar system, and