The discovery is a tentative one because the planet–30,000 light-years away–was not observed directly. None (outside the eight others in our own solar system) ever has been; a planet’s existence is inferred from its gravitational effect on the stars it orbits. The British astronomers trained their radio telescopes on a pulsar, a rapidly rotating neutron star that emits regular bursts of radio waves as it spins. Over a five-year period, they found the star’s radio signals varied in a predictable fashion, coming slightly earlier than expected for three months at a time, then slightly later. Their proposed explanation: a planet orbiting the star every six months, tugging it first closer to the Earth, then farther away.
Unfortunately from the point of view of extraterrestrial life, the vicinity of a pulsar is the last place you’d expect to find any. Current theory holds that it is the dense remnant of a massive star that exploded in the cosmic blast known as a “supernova,” undoubtedly wiping out any trace of life in the surrounding planets. In fact, what is puzzling about the discovery is that astronomers would expect the supernova to wipe out any planets themselves, or at the very least knock them into highly eccentric orbits. So the discovery, if it is confirmed, will require some new thinking from astronomers about the way planets form and stars behave–and won’t settle one way or the other the question that everyone else wants answered.
