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Links: Polyphonic Ringtones |
ASTEROIDS: Asteroids are rocky-metallic objects which range in size from about 1 to 1000 km. They orbit the Sun and are thought to be leftover material from the formation of the planets in our solar system. Most of the asteroids are found in the Asteroid Belt which lies between the orbits of Mars and Jupiter. Astronomers have also identified a group of asteroids whose orbits cross Earth's orbit. The infrared radiation from an asteroid can be used to get information about its location, composition, rotation and its shape and size. The IRAS mission discovered over 400 new asteroids and also provided infrared data on about 1800 previously known asteroids. COMETS: Comets are basically dusty snowballs which orbit the Sun. They consist of an icy nucleus surrounded by a large cloud of gas and dust (called the coma). The coma is created as the ice in the nucleus is warmed and vaporizes. Comets have 2 tails, a straight gas tail and a curved dust tail. The gas tail is created by the solar wind whose magnetic fields pull the gas away from the comet's coma. The dust in the coma is not affected by magnetic fields but is pushed out by the Sun's radiation. The dust in the tail reflects sunlight and radiates in the infrared. The infrared emission from comets can be used to get information on the nature of the dust they contain as well as on the rate at which material is being lost from the nucleus. Using IRAS, astronomers discovered that dust from comets fills the Solar System and that comets are dustier than they were thought to be. Many of the meteors which are seen as they streak through our atmosphere may be the larger pieces of this comet dust. IRAS was the first satellite to discover a comet (comet IRAS-Araki-Alcock). In all, IRAS discovered 6 new comets and collected infrared data on 25 previously known comets. COMET IMPACT WITH JUPITER: In 1994 several fragments of comet Shoemaker-Levy 9, which had broken apart during its previous orbit in 1992, collided with the planet Jupiter. These impacts released a tremendous amount of energy into Jupiter's atmosphere. Spectacular images of comet Shoemaker-Levy's collision with Jupiter were taken in the infrared. The first image shows the impact of fragment A (Courtesy of NASA/NSSDC, Tom Herbst, Max-Planck-Institut fuer Astronomie, Heidelberg, Doug Hamilton, Max-Planck-Institut fuer Kernphysik, Heidelberg, Hermann Boehnhardt, Universitaets-Sternewarte, Muenchen, and Jose Luis Ortiz Moreno, Instituto de Astrofisica de Andalucia, Granada) The second image is an infrared color composite showing fragments A,E F,G and H impacting Jupiter (Courtesy of NASA/NSSDC). |