Exoplanets-those that orbit stars oth er than the sun-are one of the hottest topics in astronomy. The first was found in 1992, going round a neutron star (a strange beast made of matter as dense as that in an atomic nucleus) 1,500 light-years from Earth. Planets orbiting more conventional stars turned up three years later, and since then the initial trickle of discoveries has become a flood. The present tally is 843 confirmed and another couple of thou sand probables.
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