Related by context. Frequent words. (Click for all words.) 81 Milky Way galaxy 78 Milky Way 74 galaxy 71 galaxies 69 spiral galaxy 69 distant galaxies 69 nebula 68 distant galaxy 68 neutron star 68 supermassive black holes 67 supermassive black hole 67 planets 65 quasars 65 Solar System 65 galaxy clusters 64 planets orbiting 64 planet orbiting 63 supernovae 63 exoplanets 63 rocky planets 63 extrasolar planets 63 quasar 63 neutron stars 62 dwarf galaxies 61 supernovas 61 Kuiper Belt 61 supernova 60 comet 60 brown dwarf 60 brown dwarfs 60 nebulae 60 galactic 60 exoplanet 59 gamma ray bursts 59 pulsar 59 gamma ray burst 59 comets 58 redshift 58 orbits 58 Saturn rings 57 astronomers 57 fainter 57 magnetosphere 57 asteroid belt 57 celestial objects 56 cosmic rays 56 Spitzer Space Telescope 56 pulsars 56 cosmic microwave background 56 asteroids 55 orbiting 55 Enceladus 55 Sedna 55 gamma rays 55 gravitational waves 55 infrared wavelengths 55 suns 55 universe 55 Andromeda 53 Astronomers 53 cosmos 53 moons 53 asteroid 53 celestial bodies 53 Galaxies 53 X ray Observatory 53 astrophysical 53 Iapetus 52 Pleiades 52 planet 52 NASA Chandra 52 neutrino 52 corona 51 moon Titan 51 starlight 51 habitable zone 51 interstellar space 51 Uranus 51 Gliese 51 constellation 50 nuclei 50 ellipse 50 Earths 50 Halley Comet 50 comet Tempel 1 50 planetary 50 neutrinos 50 Perseids 50 solar flares 49 telescopes 49 Arcturus 49 constellations 49 astrophysicists 49 Earth 49 equator 49 cosmic ray 49 Saturn moon 49 SDSS 49 impactor 49 outer layers 49 magnetic fields