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| Simulated Optical View of Comet Tempel 1 | Simulated Infrared View of Comet Tempel 1 |
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.
At the time of these early observations, March 25-27, 2005,Tempel 1 was
still far enough away from the Sun that it had not yet developed its
characteristic halo of evaporating gas.
Hubble and Spitzer observed the comet in visible and infrared light, respectively.
The comet appeared only as an unresolved dot due to the great distance, but
its general shape, size and color could be deduced from the way the visible
and infrared brightness varied over time.
The animation simulates an optical view of the comet, followed by its
appearance in infrared. Spitzer detects the comet's infrared energy or heat,
depicted by the reddish glow. The movement of the comet has been dramatically
sped up to 13 seconds per rotation versus its normal rotation of about 40 hours.
As the comet slowly rotates, the sunlit side heats up while the dark side cools down.
