BEIJING, Aug. 21 (Xinhuanet) -- Some
3,000 astronomers are now dabating in Prague, the Czech Republic, and
expected to vote on Friday a newly proposed definition of "planet."
For the first time, a high-level committee of the
International Astronomical Union was recommending the word "planet" be
officially defined according to both scientific and historic standards
-- every round object orbiting the sun is a planet, unless it orbits
another planet.
The committee also said it is considering giving
planet status to "a dozen or two" more objects discovered in recent years,
including far away, planet-like bodies informally named Sedna, Quaoar, Orcus,
Varuna and Ixion.
A planet, said the committee headed by Harvard
astronomer Owen Gingerich, is an object that orbits a star like the sun; is
massive enough so its own gravity keeps it roughly round; and isn't a satellite
of another planet, like the moon.
However, opponents complained the definition
just confuses matters further, declaring new planets that are smaller than
Earth's moon. Worse, under the new definition, dozens of planets could be added
as other objects are found at the outer edges of the solar system.
For instance, Xena, the so-called 10th planet.
Michael Brown of Caltech and other scientists discovered it three years ago and
have since found many more, which some astronomers argued are not entitled to be
called planets.
Xena and other comets all lie millions of miles
beyond Neptune and Pluto in what is known as the Kuiper Belt, where countless
comets are born and still more planet-like objects await discovery.
Pluto is also within the Kuiper Belt but has been accepted
as a planet by virtually all astronomers since its discovery in 1930.
"I'm totally confused," Brown said. "They
say Xena's a planet, but Sedna and Quaoar also fit the definition, so why aren't
they being called planets, too?"
"And Charon's a satellite of Pluto, so why is it a
planet? It's not, it's a moon. That committee's definition is an effort to
combine science and culture, and it doesn't do either."
Brown said that with all the new round orbiting
objects that his team and other astronomers have detected in the Kuiper Belt,
the number of planets should total at least 53 -- not the paltry dozen the
committee is recommending.
In truth, the solar neighborhood started going
downhill with the admission of Pluto. Less than half the size of Mercury, it
orbits outside the plane of the other recognized planets and has long been
considered a questionable addition. Enditem
(Agencies)
