Comet Tempel 1 as it appeared on August 21, 2000, at an infrared wavelength of 10.7 microns. The color scheme is false; least-to-most light is represented by green-to-white. This picture is the composite of 6 separate images of the comet. The image captures about 13,000 km of the sky at the distance of the comet, but the comet is nearly an unresolved point-source; there is very little spatial information here. Most of the light we see is the heat radiation given off by the small, compact nucleus, which is 6 km (3.7 miles) across and had a hemisphere-average temperature (at the time the picture was taken) of about -50° C on the dayside. The images were taken at the Keck I telescope (on Mauna Kea) using the LWS mid-infrared camera by Drs. Y. R. Fernández, M. F. A'Hearn, and C. M. Lisse. The W. M. Keck Observatory is operated by the California Association for Research in Astronomy.
Image Date: 2000 Aug 21