ROANOKE TIMES
Copyright (c) 1996, Roanoke Times
DATE: Thursday, October 24, 1996 TAG: 9610240062
SECTION: NATIONAL/INTERNATIONAL PAGE: A-8 EDITION: METRO
SOURCE: The Washington Post
Planet-hunting astronomers Wednesday announced the discovery of a world so eccentric it gives the phrase ``global climate change'' a whole new dimension and shatters at least one theory about the nature of planets.
One and a half times the mass of Jupiter, the new planet is in the constellation Cygnus (the Swan), about 85 light-years from Earth. While planets, in theory, travel in circles, this one follows an egg-shaped orbit - an ``eccentric orbit,'' as astronomers say. In fact, its path is by far more out of round than that of any known planet or planetlike body, including Pluto, inside or outside the solar system.
This means that every 2.2 years, it swings farther out than Mars from the warmth of its star, and then sweeps in as close as Venus.
``This drives very large seasonal changes,'' said co-discoverer William D. Cochran of the University of Texas. ``You could have cloud-top temperatures near the boiling point of water'' as the planet accelerates during its close pass around its sun, then ``near the freezing point of water'' during the more prolonged winter as the planet heads toward the chill outer boundary of its range.
During this 800-day orbit, the planet ``moves through the classic habitable zones'' - temperature ranges in which life might arise - Cochran said. At this point, however, nothing is known about the planet's composition.
The newfound planet orbits the star 16 Cygni B, long known as a ``solar twin'' because it is so similar to the sun in mass, age and composition. It is one of three stars that orbit each other in Cygnus. Two other planets previously have been found orbiting stars in multistar systems.
In the year since the first planet was detected around a sunlike star outside our solar system, astronomers working at a frenetic pace have found a total of eight, including some that in theory could harbor life. The list leaves out a couple of unconfirmed planet detections, three planets found around extremely unsunlike dead stars known as pulsars, and at least one brown dwarf, an object larger than a planet but smaller than a star. Each discovery has broken the conventional mold in some way.
``What we're learning is a little humility,'' said Geoffrey W. Marcy of San Francisco State University, a co-discoverer of the new planet and five others. ``We really know extraordinarily little about how planets form. We have to go back to square one and figure out where our solar system fits in and what made it a friendly place for life.''
Theorists are scrambling to explain this latest twist in planetary evolution. Among the possibilities: two fledgling planets colliding like billiard balls, distorting their orbits and possibly ejecting one into interstellar space; gravitationally induced waves or warps in the disk of debris from which planets form; a ``kick'' supplied by the passing companion star sweeping in on its own eccentric orbit.
Cochran said that, to assume that all ``normal'' planets must orbit in circles just because the familiar planets in the sun's family do, and that any departures from that pattern are weird, ``is, if you'll pardon me for saying it, circular reasoning.''
LENGTH: Medium: 60 linesby CNB