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<b>Smallest Extra-Solar Planet Found</b><br /><br />LINK<br /><br />US astronomers say they have found the smallest planet orbiting outside our Solar System to date. <br /><br />The new world, which is about one fifth the size of Pluto, is the fourth planet to be discovered orbiting around a pulsar called PSR B1257+12. <br /><br />A pulsar is a spinning neutron star producing powerful beams of radiation. <br /><br />The new planet is orbiting inside a large cloud of hot, charged gas that surrounds the pulsar and is some 1,500 light-years away from Earth. <br /><br />Details of the work were announced at an astronomy meeting held in Aspen, US. <br /><br />Pulsars are formed from the collapsed cores of so-called "supergiant" stars that have exploded. <br /><br />The discovery was made by Alex Wolszczan of Pennsylvania State University, US, and Maciej Konacki of the California Institute of Technology (Caltech). <br /><br />The orbit of the new planet is close to the average distance from our Sun to the asteroid belt. <br /><br />The orbits of three planets discovered orbiting the same pulsar in 1992 were almost in exact proportion to the spacings between Mercury, Venus and Earth. <br /><br />Wolszczan and Konacki say the new planet could mark the fringes of the pulsar's planetary system, just like Pluto marks the edge of ours. <br /><br />The new planet was discovered with the Arecibo radio telescope in Puerto Rico. <br /><br />