ISO views Comet Hale-Bopp

The main image is from ISO's camera ISOCAM, one of a series obtained at various infrared wavelengths in October 1996. The chief feature is the cloud of dust in the comet's head (coma). The bright region is about 100 000 km across, or more than seven times wider than Earth. At the time, the tail was largely hidden behind the coma, because of the relative angles of the comet, the Sun and Earth. An image by visible light, obtained by the Hubble Space Telescope just a week earlier, is shown for comparison. It covers a region of the sky (and the comet) one-fifth as wide as the ISO image. At least five jets of dust are seen emanating from the nucleus, lit by sunlight. The third item is a spectrum covering a huge range of infrared wavelengths from ISO's ISOPHOT photometer. Here the instrument is taking the temperature of the comet's dust cloud. The crosses are the measurements by ISOPHOT and the continuous line is the emission expected from an object with a temperature of 220 K. The cloud was much warmer than in March 1996, when the same instrument obtained a temperature of 153 K. [Image Date: 23-09-96] [97.07.008-004]