Related by context. Frequent words. (Click for all words.) 64 planets 63 rocky planets 62 planet 59 planet orbiting 58 distant galaxy 58 exoplanets 57 Milky Way Galaxy 56 planets orbiting 56 Solar System 56 exoplanet 56 Milky Way galaxy 56 planetary 54 habitable zone 54 galaxy 54 Alpha Centauri 54 outer planets 53 extrasolar planets 53 brown dwarfs 53 supernovae 53 supernova 53 Earths 52 asteroids 52 asteroid 52 comet 51 universe 51 brown dwarf 51 comets 51 supernovas 51 interstellar space 51 organic molecules 51 neutron star 51 distant galaxies 51 moon Titan 51 multiverse 50 asteroid belt 50 orbiting 50 Enceladus 50 habitable 50 galaxies 50 cosmos 49 Sedna 49 supermassive black holes 49 Saturn moon 49 globular clusters 49 pulsars 48 astrobiology 48 nebulae 48 gamma ray bursts 48 cometary 48 dwarf planet 48 martian 48 galactic 48 Gliese 48 Martian 48 dwarf galaxies 48 Milky Way 48 Betelgeuse 48 habitability 48 Earth 47 Spitzer Space Telescope 47 spacetime 47 Red Planet 47 Mars 47 nebula 47 Kuiper Belt 47 UB# [003] 47 single celled 47 magnetosphere 47 cosmological 47 neutrino 47 astrophysical 47 celestial bodies 47 celestial objects 46 universes 46 interstellar medium 46 neutron stars 46 orbits 46 extraterrestrial 46 quasars 46 heliosphere 46 Saturn rings 46 Uranus 46 Martian surface 46 Einstein theory 46 supermassive black hole 46 spiral galaxies 45 antimatter 45 cosmologists 45 astronomers 45 moons 45 unaided eye 45 biosphere 45 gamma ray burst 45 quasar 45 planetary scientist 45 radioactive decay 45 pulsar 45 Iapetus 45 interstellar 44 Pluto 44 galaxy clusters