From a reliable source, find the surface (or cloud-top, as appropriate)
temperatures, in degrees Kelvin, of Mercury, Venus, Earth, Mars, Jupiter,
Saturn, Uranus, Neptune, Pluto, any comet, and a typical incandescent light
bulb filament.  Find the wavelength of light at which the thermal radiation
spectrum peaks for each object.  Remembering that human eyes can only see
radiation between 300 and 700 nanometers in wavelength, how many of these
objects' thermal radiation is visible to our unaided eyes?