The comet appears first in the telescope as a small, fuzzy, faintly luminous object. It is approaching our planet on the inward leg of a long journey from the edge of the solar system. As it comes closer, solar energy warms the head of the comet and vaporizes gases. These gases stream out behind the comet's head. Excited to luminescence by the absorption of solar radiation becomes clearly visible to the naked eye as the comet nears the sun.