Pluto Demoted

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Pluto demoted, no longer considered a true planet

- David Perlman, Chronicle Science Editor

Thursday, August 24, 2006

 

(08-24) 08:21 PDT -- Pluto was shafted by the world's astronomers today,

demoted to the lowly status of " dwarf planet " and leaving the solar system

with its original eight true planets plus countless other objects that must

now be called " small solar system bodies. "

 

After more than two years of controversy that started when astronomer Mike

Brown of Caltech announced his team had discovered a " 10th planet " and was

finding many more far out in the icy region billions of miles beyond the

sun where comets are born, the International Astronomical Union voted a set

of rules defining just what a planet is and what it's not.

 

Delegates to the Union meeting in Prague and representing 9,000 members

decided that everything in the heavens that's massive enough for its own

gravity to keep it roughly round is henceforth officially a planet.

 

Ceres, round and firm and fully packed, is the largest object in the

asteroid belt where thousands of rocky chunks mostly orbit the sun between

Mars and Jupiter, and many astronomers wanted to call it a full-fledged

planet. But now it's only a dwarf planet, the IAU decided.

 

And Pluto's moon Charon, which the astronomers had first decided to link to

Pluto and call a " double planet, " also joined the lowly status of dwarf

planet.

 

And so do all the objects Brown's team discovered -- the ones with

unofficial names like Xena and Sedna and Quaoar -- they're all " dwarf

planets " now, too.

 

Said Brown in a television interview with reporters from his office at

Caltech in Pasadena:

 

" Scientifically, it's the right decision, it's sensible, it's acceptable

and it's streamlined. There may be a lot of gnashing and wailing because

Pluto is demoted, but Pluto overwhelmingly is not a planet, and it was a

mistake to call it one when it was discovered more than 75 years ago. "

 

E-mail David Perlman at dperlman.

 

 

URL:

http://sfgate.com/cgi-bin/article.cgi?file=/c/a/2006/08/24/MNG43KOBTD4.DTL