Obs. : 2009-01-17 Planet Ly alpha (photons/cm^2/sec) Mercury 3.529e+11 Venus 3.505e+11 Earth 3.489e+11 Mars 3.477e+11 Jupiter 3.529e+11 Saturn 3.448e+11 Uranus 3.505e+11 Neptune 3.550e+11 Pluto 3.444e+11