Poor Pluto! Not only has the ice-ball been demoted from planet-status, but, as of 1995, scientists have determined that there are other planets in other solar systems. They're known as "extrasolar planets" or "exoplanets." As one might guess, detecting them can often be difficult. Scientists must observe the effects they have on other objects in order to infer their existence. Learn more about this procedure in this short article and interactive site by the American Museum of Natural History. The site has a good Teacher Resource page.
American Museum of Natural History
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