Related by context. Frequent words. (Click for all words.) 57 planets 51 observable universe 50 earths 50 lunar soil 50 Kuiper belt 50 spherical shape 50 gravitational attraction 50 celestial bodies 50 fermions 49 habitable planets 49 spacetime 49 galaxy formation 49 singularities 49 Venusian 49 gravitation 49 cosmological 49 rocky planets 49 relativistic 48 habitable planet 48 gravitational 48 WIMPs 47 dwarf planets 47 asteroid 47 cosmic 47 Earth asteroids 47 symmetries 47 planetary 47 meteoroid 47 terrestrial planets 47 Jupiter moons 46 asteroids 46 orbits 46 super Earths 46 meteoroids 46 spherical 46 extrasolar planets 46 polar caps 46 astrophysical 46 lithosphere 46 atomic nucleus 46 cosmology 46 hot Jupiters 46 quantum gravity 46 Outer Space Treaty 46 planetoid 46 outer planets 46 astronomical observations 46 Meridiani 46 Einstein theory 45 Earth magnetosphere 45 magnetar 45 Earths 45 globular cluster 45 galactic 45 Gliese #g 45 habitability 45 universe 45 regolith 45 theoretic 45 brown dwarfs 45 plate tectonics 45 universals 45 subatomic 45 Earth orbit 45 gravitationally 45 heliosphere 45 interplanetary spacecraft 45 theistic 45 angular momentum 45 elliptical galaxies 45 exoplanets 44 solar nebula 44 celestial object 44 continental crust 44 moon Europa 44 spiral galaxies 44 antigravity 44 planet orbits 44 ellipse 44 Andromeda Galaxy 44 bosons 44 supersymmetry 44 Uranus 44 ecliptic 44 HD #b [002] 44 satellites orbiting 44 planets orbiting 44 circular orbit 44 NEOs 44 singularity 44 martian 44 orbiting 44 lunar poles 44 general relativity 44 quantum theory 44 interstellar 44 spacecrafts 44 subatomic particle 44 astronomical objects 44 gravitational lensing 44 dynamical