Alien sky at sunset. Computer artwork of a sky seen from a hypothetical alien (extrasolar) planet,showing another sun (orange,centre left),a spiral galaxy (upper centre) and an orbiting moon (right). If a planet is to have a surface temperature suitable for liquid water,and to retain an atmosphere,it must be a suitable size and distance from its star. The number of habitable planets in the Milky Way galaxy is not known,but has been estimated at anything between 1 (just Earth) and as many as 10 billion. Many planets have already been discovered orbiting nearby stars | |
Lizenzart: | Lizenzpflichtig |
Credit: | Science Photo Library / Van Ravenswaay, Detlev |
Bildgröße: | 2598 px × 3898 px |
Modell-Rechte: | nicht erforderlich |
Eigentums-Rechte: | nicht erforderlich |
Restrictions: | - |