Obs. : 2009-12-20 Planet Ly alpha (photons/cm^2/sec) Mercury 3.555e+11 Venus 3.513e+11 Earth 3.674e+11 Mars 3.699e+11 Jupiter 3.556e+11 Saturn 3.610e+11 Uranus 3.542e+11 Neptune 3.556e+11 Pluto 3.537e+11