The first exoplanets discovered were two rocky objects orbiting a pulsar in the constellation Virgo, announced in 1992 by Aleksander Wolszczan and Dale Frail. As of 2007, 242 exoplanets are known, with at least 10% of Sun-like stars suspected to have planets. PSR B1257+12B and PSR B1257+12C are about four times the mass of Earth and orbit respectively 0.36 AU and 0.46 AU from their star. The pulsar emits massive amounts of radiation, making it unlikely to support life.
The first exoplanets discovered were a pair of rocky objects orbiting PSR B1257+12, a pulsar in the constellation Virgo, 980 light-years from Earth. The discovery was attributed to radio astronomers Aleksander Wolszczan (Polish) and Dale Frail (Canadian), which was announced in 1992 and quickly confirmed.
As of 2007, 242 exoplanets are known. At least 10% of Sun-like stars are suspected to have planets, although the actual value may be much higher. The discovery of planets orbiting PSR B1257+12 came as a surprise to astronomers at the time, because they were pulsar planets, and it was generally assumed that planets formed only around main-sequence stars.
The two exoplanets are now known as PSR B1257+12B and PSR B1257+12C. A third planet, PSR B1257+12A, which orbits closer to the star, was discovered a couple of years after the others. The two largest planets are about four times the mass of Earth. The pulsar they orbit is the remnant of a supernova. Whether these extrasolar planets formed before the supernova is unknown, possibly being the rocky cores of former gas giants stripped of most of their mass during the nova or during a post-nova planet formation cycle. The exoplanets orbit respectively 0.36 AU (astronomical units, 1 AU equals the distance from the Earth to the Sun) and 0.46 AU from their star.
PSR B1257+12 is a millisecond pulsar, a type of neutron star, and was discovered in 1990 by Wolszczan using the Arecibo Space Telescope. Irregularities in its pulsation period led Wolszczan and Frail to carefully study the system for possible extrasolar planets. Sure, they were successful. Pulsars emit massive amounts of radiation, more than enough to fry any life on the surface of orbiting planets, so PSR B1257+12B and PSR B1257+12C are the last places we’d look for extraterrestrial life. The pulsar has a rotational period of 6.22 milliseconds and is 800 million years old.
Although not the first to be discovered, the most famous exoplanet is probably Gliese 581c, due to its relative proximity (20 light-years), Earth-like mass, and location within Earth’s “habitable zone”. its star, an area that could theoretically support life.
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