Related by context. Frequent words. (Click for all words.) 60 Gliese #g 58 habitable planets 58 extrasolar planet 57 exoplanet 57 Cassini Huygens 56 Melosh 56 HD #b [002] 55 exoplanets 55 extrasolar planets 55 NASA Kepler 55 habitable planet 54 planetary 54 COROT 54 planetary scientist 54 Cassini imaging 54 journal Astronomy 54 Carolyn Porco 54 Astrophysicist 53 Hubble observations 53 Astrophysicists 53 cosmologists 53 astrophysicists 52 planets orbiting 52 super Earths 52 XMM Newton 52 astronomers 52 astronomer 52 planetoid 52 EPOXI 52 Paabo 52 Poinar 52 Gliese 52 solar corona 52 astrobiologists 51 Cassini 51 HiRISE 51 magnetar 51 planets 51 Voyager spacecraft 51 distant galaxy 51 Astrophysical Journal 51 Colaprete 51 Phil Plait 51 magnetic reconnection 51 planets circling 51 planet orbiting 51 particle physicist 51 rocky planets 50 Saturn rings 50 astronomical observations 50 Galaxy Evolution 50 Astrophysical Journal Letters 50 Chicxulub 50 Keck Observatory 50 Jupiter moons 50 meteoroid 50 gravitational lensing 50 Einstein theory 50 Neil deGrasse Tyson 50 planetary science 50 Saturn moon 50 terrestrial planets 50 NICMOS 50 MARSIS 50 Type Ia supernovae 50 Carl Sagan 50 cometary 50 Johannes Kepler 49 Astrophysics 49 Astrobiology 49 Planck 49 Enceladus 49 Sedna 49 NASA Cassini spacecraft 49 PALCA 49 Niels Bohr Institute 49 A'Hearn 49 asteroid 49 physicist 49 astrophysical 49 Stephen Wolfram 49 GRBs 49 microlensing 49 alien civilizations 49 galaxy formation 48 Planetary Science 48 outer planets 48 Kuiper belt 48 brown dwarfs 48 Phobos 48 planetary nebulae 48 redshift 48 Saturn moons 48 astronomer Carl Sagan 48 dynamical 48 Lowell Observatory 48 cosmic ray 48 Apophis 48 NASA Goddard 48 GRB # 48 astrobiology