Ahora el Sistema Solar tiene ocho planetas, Plutón ya no lo es. Es una decisión
histórica, aunque emocionalmente lo de Plutón pueda sentirse como una "pérdida".

Saludos
Sami Rozenbaum
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Astronomers say Pluto is not a planet



Leading astronomers declared Thursday that Pluto is no longer a planet under
historic new guidelines that downsize the solar system from nine planets to
eight.

After a tumultuous week of clashing over the essence of the cosmos, the
International Astronomical Union stripped Pluto of the planetary status it has
held since its discovery in 1930. The new definition of what is — and isn't — a
planet fills a centuries-old black hole for scientists who have labored since
Copernicus without one.
Although astronomers applauded after the vote, Jocelyn Bell Burnell — a
specialist in neutron stars from Northern Ireland who oversaw the proceedings —
urged those who might be "quite disappointed" to look on the bright side.

"It could be argued that we are creating an umbrella called 'planet' under
which the dwarf planets exist," she said, drawing laughter by waving a stuffed
Pluto of Walt Disney fame beneath a real umbrella.

The decision by the prestigious international group spells out the basic tests
that celestial objects will have to meet before they can be considered for
admission to the elite cosmic club.

For now, membership will be restricted to the eight "classical" planets in the
solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
Much-maligned Pluto doesn't make the grade under the new rules for a planet:
"a celestial body that is in orbit around the sun, has sufficient mass for its
self-gravity to overcome rigid body forces so that it assumes a ... nearly round
shape, and has cleared the neighborhood around its orbit."

Pluto is automatically disqualified because its oblong orbit overlaps with
Neptune's.
Instead, it will be reclassified in a new category of "dwarf planets," similar
to what long have been termed "minor planets." The definition also lays out a
third class of lesser objects that orbit the sun — "small solar system bodies,"
a term that will apply to numerous asteroids, comets and other natural
satellites.

It was unclear how Pluto's demotion might affect the mission of NASA's New
Horizons spacecraft, which earlier this year began a 9 1/2-year journey to the
oddball object to unearth more of its secrets.

The decision at a conference of 2,500 astronomers from 75 countries was a
dramatic shift from just a week ago, when the group's leaders floated a proposal
that would have reaffirmed Pluto's planetary status and made planets of its
largest moon and two other objects.

That plan proved highly unpopular, splitting astronomers into factions and
triggering days of sometimes combative debate that led to Pluto's undoing.

Now, two of the objects that at one point were cruising toward possible
full-fledged planethood will join Pluto as dwarfs: the asteroid Ceres, which was
a planet in the 1800s before it got demoted, and 2003 UB313, an icy object
slightly larger than Pluto whose discoverer, Michael Brown of the California
Institute of Technology in Pasadena has nicknamed Xena.

Charon, the largest of Pluto's three moons, is no longer under consideration
for any special designation.



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