Three planets orbit the dead star PSR B1257+12 in this artist's concept. The dead star is a pulsar, which an extremely dense neutron star that spins rapidly, beaming energy into space. The pulsar formed when a massive star exploded as a supernova. The planets, which were the first comfirmed worlds detected outside our solar system, probably formed from debris from the exploded star and its original system of planets and other material. The discovery was announced in January 1992. [NASA/JPL]
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Planets may be as common as snowflakes on an Iowa cornfield on a January day. Astronomers have discovered planets orbiting stars big and little, hot and cool. They’ve found them wandering through space on their own, and orbiting systems of two and even three stars. And they’ve even found them around dead stars.
In fact, the first planets discovered outside our own solar system orbit the corpse of a star that blasted itself to bits. The discovery was announced 20 years ago this week.
Alexander Wolszczan and Dale Frail found the planets by listening to the “ticking” of a pulsar — the collapsed core of a once-mighty star that exploded as a supernova.
The pulsar spins hundreds of times a second, emitting a beam of energy that sweeps across Earth like a lighthouse, creating brief “pulses” of radio waves. The astronomers measured tiny changes in the timing of these pulses, caused by the tug of orbiting planets.
Two of the planets are a few times as massive as Earth, while one is only about as big as the Moon. All three are much closer to the pulsar than Earth is to the Sun.
It’s likely that the planets were born from debris from the supernova. The explosion itself would have destroyed any planets orbiting the star. The planets are zapped by intense radiation from the pulsar, so it’s highly unlikely that anything could live there.
Still, they show us that planets can form just about anywhere — even from the fragments of a dead star.
Script by Damond Benningfield, Copyright 2011
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