Obs. : 2008-09-21 Planet Ly alpha (photons/cm^2/sec) Mercury 3.459e+11 Venus 3.459e+11 Earth 3.480e+11 Mars 3.459e+11 Jupiter 3.543e+11 Saturn 3.346e+11 Uranus 3.454e+11 Neptune 3.486e+11 Pluto 3.551e+11