starship-design: New 'rebel' planet found

[kgstar@most.fw.hac.com (Kelly Starks x7066 MS 10-39)]

New 'rebel' planet found outside solar system It's 'roller-coaster orbit' stuns
 scientists

       October 23, 1996
        Web posted at: 11:00 p.m. EDT

TUCSON, Arizona (AP) -- A new planet that
breaks all the rules about how and where
planets form has been identified in orbit of a
twin star about 70 light years from Earth in a
constellation commonly known as the
 Northern Cross.

The new planet has a roller-coaster like orbit that swoops down close to
its central
star and then swings far out into frigid fringes, following a strange
egg-shaped orbit
that is unlike that of any other known planet.

"We don't understand how it could have formed in such an orbit," said William D.
Cochran, head of University of Texas team that discovered the planet at the same
time that a group from San Francisco State found it independently.

The researchers presented papers on the new planet Wednesday at a national
meeting
of the American Astronomical Society's planetary division. The new planet is the
latest in a series of bodies found in orbit of stars outside the solar
system and is part
of a quickening effort by astronomers to find distant worlds.

Cochran said the planet orbits the smaller of twin stars in the
constellation Cygnus, a
prominent stellar grouping known as the Northern Cross. The planet's star
is called
16 Cygni B and the larger companion star is 16 Cygni A.

"Of all the stars you might see in the sky, Cygni B is the most similar to
our sun,"
said Cochran. It has the same mass and temperature as the sun, but the
nearby twin
 star of Cygni B creates an entirely different type of environment.

Every 250,000 years, Cygni A and B pass within 65 billion miles of each other, a
grazing passage by stellar standards. Cochran said the stars are so close,
that the
gravitational tug of Cygni A may have pulled the new planet into its wildly
eccentric
orbit.

It is unlikely that life exists on the new planet, said Cochran, because it
probably is
more like the gaseous planets, such as Jupiter or Saturn, than the rocky
planets such
as Earth or Mars.

The wide-swinging orbit of the planet would also cause extreme fluctuations in
temperature, he said.

 During one part of its 804-day-long year, the planet would pass within 67
million
miles of its sun. This would be the planet's summer, said Cochran. Then the
planet
would swing far out, reaching a point 158 million miles from the star. This
would be
its winter and it would last more than 500 days, the researcher said.

 Most planets in the solar system have an almost circular orbit, like that
of the Earth,
and most theories about how planets form are based on them settling into a
circular
orbit. The eccentric orbit of the new planet adds a new dimension that
astronomers
will have to consider in theories about planetary formation, Cochran said.

 The University of Texas and San Francisco astronomers found the new planet by
studying the movement of Cygni B. They discovered that the star tended to change
its speed of motion in a way that could only be explained by the presence of an
orbiting companion.

Cygni A has no such motion, said Cochran, suggesting it has no planet.

By some counts, the new planet is the ninth to be found outside the solar
system,
although some astronomers say there have been up to 11 found. Cochran said the
exact number is controversial because not all of the discoveries have been
generally
accepted as actual planets.

And there were skeptics even of the Cochran discovery.

 "It is a really nice piece of work" said David Black of the Lunar and Planetary
Institute in Houston. "But I really question whether this is a planet or a brown
 dwarf."

A brown dwarf is a failed star, an object that never collected enough mass
to start
stellar burning. Black said it is possible that most of the recently
discovered planets
are really brown dwarfs.


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Kelly Starks                    Phone: (219) 429-7066    Fax: (219) 429-6859
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