Scientists Announce Smallest Extra-Solar Planet Yet Discovered
University Park PA (SPX) Feb 08, 2005
Penn State's Alex Wolszczan, the discoverer in 1992 of the first planets ever found outside our solar system, now has discovered with Caltech's Maciej Konacki the smallest planet yet detected,in that same far-away planetary system.
Immersed in an extended cloud of ionized gas, the new planet orbits a rapidly spinning neutron star called a pulsar.
The discovery, to be announced during a press conference at a meeting concerning planetary formation and detection in Aspen, Colorado, on 7 February, yields an astonishingly complete description of the pulsar planetary system and confirms that it is remarkably like a half-size version of our own solar system-even though the star these planets orbit is quite different from our Sun.
"Despite the extreme conditions that must have existed at the time these planets were forming, Nature has managed to create a planetary system that looks like a scaled-down copy of our own inner solar system," Wolszczan reports.
The star at the center of this system is a pulsar named PSR B1257+12-the extremely dense and compact neutron star left over from a massive star that died in a violent explosion 1,500 light years away in the constellation Virgo.
Wolszczan and his colleagues earlier had discovered three terrestrial planets around the pulsar, with their orbits in an almost exact proportion to the spacings between Mercury, Venus, and Earth.
The newly discovered fourth planet has an orbit approximately six times larger than that of the third planet in the system, which Konacki says is amazingly close to the average distance from our Sun to our solar system's asteroid belt, located between the orbits of Mars and Jupiter.
"Because our observations practically rule out a possible presence of an even more distant, massive planet or planets around the pulsar, it is quite possible that the tiny fourth planet is the largest member of a cloud of interplanetary debris at the outer edge of the pulsar's planetary system, a remnant of the original protoplanetary disk that created the three inner planets," Wolszczan explains.
The small planet, about one-fifth of the mass of Pluto, may occupy the same outer-boundary position in its planetary system as Pluto does in our solar system. "Surprisingly, the planetary system around this pulsar resembles our own solar system more than any extrasolar planetary system discovered around a Sun-like star," Konacki says.
Fifteen years ago, before Wolszczan's discovery of the first extrasolar planets, astronomers did not seriously entertain the idea that planets could survive around pulsars because they would have been blasted with the unimaginable force of the radiation and remnants of their exploding parent star....