Related by context. Frequent words. (Click for all words.) 61 polar vortex 58 X ray emission 57 aurorae 57 aerosol particles 56 cirrus clouds 56 solar corona 56 planetary nebulae 55 tropospheric 55 ionized gas 55 solar nebula 55 magnetic reconnection 55 water vapor 54 planetary nebula 54 Galaxy Evolution 54 explosive eruptions 53 protoplanetary disk 53 Bose Einstein condensate 53 Earth magnetosphere 53 Geminids 53 interplanetary spacecraft 53 convective 53 extrasolar planet 52 Supernovae 52 auroral 52 galaxy formation 52 phytoplankton blooms 52 constellation Perseus 52 Gamma ray bursts 52 interstellar medium 52 Galileo spacecraft 52 polar regions 52 Earthlike 52 SIRTF 52 Ultraviolet light 52 comet tail 52 volcanic plume 52 Sulfur dioxide 51 supernova explosions 51 interstellar dust 51 active galactic nuclei 51 XMM Newton 51 mid latitudes 51 Saturn moon Enceladus 51 Nitrogen oxides 51 temperature inversion 51 dust devils 51 Gamma rays 51 respiratory irritant 51 astronomical objects 51 Hubble observations 51 WASP #b 51 ultra violet radiation 51 equatorial Pacific Ocean 51 osmium 51 cirrus 51 rocky planets 51 substorms 50 isoprene 50 silicates 50 clouds 50 cosmic microwave background 50 Hawking radiation 50 Cosmic rays 50 solar irradiance 50 aurora 50 upwellings 50 quasar 50 Comet McNaught 50 Oort Cloud 50 Polar Regions 50 ionisation 50 -# degrees Fahrenheit [002] 50 equatorial Pacific 50 EPOXI 50 Today Mostly sunny 50 perihelion 50 Type Ia supernovae 50 radial velocity 50 liquid droplets 50 NASA Aqua 50 astronomical observations 50 microlensing 50 Geminid meteor shower 49 ionised 49 carbonic acid 49 quark gluon plasma 49 superfluidity 49 silicate 49 COROT 49 hydrothermal vent 49 rubidium atoms 49 cryosphere 49 harmful ultraviolet radiation 49 Cassini radar 49 Perseids 49 cumulus clouds 49 NASA Cassini 49 inversion layer 49 ozone depletion 49 cumulus 49 photoluminescence