Related by context. Frequent words. (Click for all words.) 65 planetary nebula 64 X ray emission 63 Orion Nebula 63 planetary nebulae 62 nebula 62 Crab Nebula 61 galaxy cluster 61 Spitzer Space Telescope 61 supernova remnant 61 globular cluster 61 nebulae 60 active galactic nuclei 60 elliptical galaxies 60 dwarf galaxy 60 XMM Newton 60 Hubble observations 60 spiral galaxies 60 colliding galaxies 59 Andromeda galaxy 59 Milky Way Galaxy 59 spiral galaxy 59 supernova remnants 58 supernova explosion 58 visible wavelengths 58 solar corona 58 magnetar 58 interstellar dust 58 supernova explosions 57 ejecta 57 accretion disk 57 galaxies 57 constellation Orion 57 globular clusters 57 solar nebula 57 distant galaxy 57 Mimas 57 galaxy clusters 56 ionized gas 56 infrared wavelengths 56 Milky Way 56 constellation Leo 56 quasar 56 Milky Way galaxy 56 comet nucleus 55 GRB # 55 gamma ray burst 55 Saturn rings 55 starbursts 55 Saturn moon Enceladus 55 quasars 55 Galaxy Evolution 55 supernovae 55 Large Magellanic Cloud 55 auroral 55 NASA Chandra 55 planet orbits 55 Eta Carinae 54 Fomalhaut 54 brown dwarf 54 planet orbiting 54 Kuiper belt 54 supernova 54 NASA ESA Hubble 54 Cancri 54 X ray beam 54 Voyager spacecraft 54 extrasolar planet 54 distant galaxies 54 Andromeda Galaxy 54 Very Large Telescope 54 star Gliese 54 haloes 54 X ray Observatory 54 spectroscopic 53 microlensing 53 interferometry 53 unaided eye 53 MODIS 53 constellation Perseus 53 galaxy 53 striations 53 NASA Cassini spacecraft 53 Iapetus 53 cosmic microwave background 53 rocky planets 53 COROT 53 gravitational lensing 53 galaxy formation 53 celestial object 53 anisotropy 53 ESO Very Large Telescope 53 HD #b [002] 52 Type Ia supernovae 52 dwarf galaxies 52 GRBs 52 meteoroids 52 neutrino 52 cometary 52 extrasolar planets 52 Enceladus 52 ringed planet