Credit: NASA/JPL-Caltech/T. Pyle (SSC)

These artist's concepts of Tempel 1 simulate an optical view of the comet (left), next to the simulated infrared view (right). The images illustrate the comet's shape, reflectivity, rotation rate and surface temperature, based on information from NASA's Hubble Space Telescope and Spitzer Space Telescope.

Measurements from the Great Observatories indicate that the comet is a matte black object roughly 14 by 4 kilometers (8.7 by 2.5 miles), or about one-half the size of Manhattan.

Spitzer detects the comet's infrared energy or heat, depicted by the reddish glow.

The sunlit side of the nucleus is glowing warmly, and the nightside is about the temperature of deep space.