A 10th Planet?
A NASA scientist insists a 10th planet may
be orbiting the sun even though two space probes have not been able to find any
trace of it in the dim outer reaches of the solar system.
Dr. John Anderson, a celestial mechanics investigator with NASA's Pioneer
spacecraft project, told reporters at Ames Research Center at Moffett Field
Tuesday that if the planet exists, it travels at nearly right angles to the
plane of the orbits of the nine known planets in a looping ellipse so elongated
it only nears the sun every 700 to 1,000 years.
Anderson, who published his ideas last year in ''The Galaxy and the Solar
System,'' called his theory ''an important contribution to the understanding of
the dynamics of the outer solar system.''
Analysis of the trajectories of the Pioneer 10 and 11 spacecraft during the
past five years shows no indication of gravitational effects that would be
expected if an unknown planet was in a normal, circular orbit beyond Uranus and
But 19th century records indicate the orbits of the outer planets were
disturbed in a subtle manner, which Anderson suspects may have been caused by
gravitational effects associated with the undiscovered planet.
''The best explanation for an object very likely to have been there for at
least 100 years, and then disappearing, is a planet on a greatly elongated
orbit,'' Anderson said.
''I think that's the most likely possibility if you take all the current data.
It's a good possibility and a good working hypothesis. If it isn't Planet X,
then I throw up my hands and can't say what it is,'' Anderson said.
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