Related by context. Frequent words. (Click for all words.) 73 auroras 72 aurora borealis 64 Aurora Borealis 61 meteor shower 57 sunspot 57 Perseids 56 gamma ray burst 56 meteor showers 56 nebula 55 meteors 55 sunspots 54 gamma ray bursts 54 cosmic ray 54 quasar 53 comet 53 supernova 53 astronomers 53 distant galaxy 53 nebulae 52 solar flares 52 gravitational waves 52 quasars 52 Cassiopeia 52 constellations 51 Saturn rings 51 THEMIS 51 extrasolar planets 51 lunar eclipse 50 infrared radiation 50 Enceladus 50 neutron star 50 convective 50 astronomer 50 amateur astronomer 50 ionosphere 50 celestial objects 50 flyby 50 meteor 50 magnetosphere 50 total lunar eclipse 50 volcanism 50 infrared wavelengths 49 pulsars 49 supernovae 49 astrophysical 49 oscillations 49 Pleiades 49 polar 49 neutrino 48 distant galaxies 48 starlight 48 astronomy 47 planets 47 planet orbiting 47 comets 47 sunrises 47 total solar eclipse 47 neutron stars 47 NASA Cassini spacecraft 47 vortices 47 geomagnetic field 47 partial eclipse 47 supernovas 47 galaxies 47 equinox 47 cosmic rays 47 infrared 46 telescope 46 volcanic activity 46 northern latitudes 46 nova 46 Astronomy 46 exoplanet 46 equator 46 brown dwarf 46 planets orbiting 46 Cassini 46 astrophysicists 46 starburst 46 rocky planets 46 Astronomical Society 46 HiRISE 45 celestial 45 convection 45 Halley Comet 45 pulsar 45 Milky Way 45 solar eclipse 45 gamma rays 45 Milky Way galaxy 45 Astronomers 45 wavelengths 45 upwelling 45 gamma ray 45 Telescope 45 corona 45 Iapetus 45 water vapor 45 Astrophysical Journal Letters 45 supermassive black hole 44 Sedna