SWAS Spacecraft
The Submillimeter Wave Astronomy Satellite
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The Kuiper belt, located beyond the orbit of Neptune, contains many billions of icy objects (of which Pluto is the largest currently known.) Most Kuiper belt objects orbit the Sun quietly and unobserved, except very occasionally when one of them is deflected onto an elliptical orbit that takes it close to the Sun. As a comet comes close to the Sun, it heats up and starts to vaporize, yielding a fuzzy coma and a tail. Giant stars like IRC+10216 have grown roughly ten thousand times more luminous than the Sun and are now so luminous that they vaporize comets even at the distance of the Kuiper belt. The SWAS observations suggest that IRC+10216 is surrounded by a belt of comets similar to our Kuiper belt; these comets are now all vaporizing en masse and depositing large amounts of water vapor into the surrounding space.

Figure courtesy of Johns Hopkins University


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