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COVER STORY
A spacecraft journeys
I
who study space, met in Europe.
f you have a textbook with our
The astronomers voted that there
solar system in it, you've probwould be eight planets instead of
ably crossed out Pluto by now.
nine. Those eight "classical"
The puny, icy object was kicked out
planets include Mercury, Venus,
ofthe planet family on August 24.
Earth, Mars, Jupiter, Saturn,
Planet or not, Pluto and its icy
Uranus, and Neptune.
mysteries are still the destinatioti
of New Horizons. In January, the
Why did astronomers give
1,054-pound spacecraft
Pluto the boot? For
blasted off toward
starters, they came
Pluto, which is
up with a new
akes
3 billion miles
definition for a
Planet?
from Earth.
planet. A planet
:o meets only two of the
must be nearly
If all goes
ttiree new requirements:
round and must
according
to
1. It must orbit the sun.
orbit,
or circle,
plan, the piano. It has to be nearly rbund.
the sun. Its
sized spacecraft
3. Its orbit should not cross
orbit should not
will fly by Pluto
another planet's orbit
cross the orbit of
in 2015. The spaceanother planet. Pluto's
craft will get an uporbit intersects, or crosses,
close look at Pluto and other
Neptune's path.
objects in the Kuiper (KIGHper) belt. The Kuiper belt is a
Since its discovery in 1930,
wide band of icy and rocky
astronomers suspected that Pluto
objects on the outer edges of our
was an oddball when compared
solar system.
with the other planets. New technology has shown that its orbit is
New Horizons—the fastest
oval-shaped. Pluto is also smaller
spacecraft ever built—will
than the other planets. Even Earth's
investigate the former planet,
moon is larger.
measuring its atmosphere and
temperature. The spacecraft will
Orbit and size weren't the only
also beam pictures to Earth.
problems. Pluto is made up of
material that is difFerent from that
ofthe other planets. While the othNew Class System
ers are made up of rocks or gases,
As the spacecraft sped onward,
Pluto consists mostly of ice.
world astronomers, or scientists
WR NEWS Edition 4
Pluto appears to be similar td
other objects in the Kuiper belt. ItJ
status as a planet began to look
bleak when 2003 UB313 was
discovered three years ago. Thai
Kuiper belt object, nicknamec
"Xena," is larger than Pluto. The
discovery prompted astronomers tc
begin thinking about reclassifyin^
the objects in our solar system.
Dwarf Planets
Don't pity Pluto, though. It still
has a place in space. Pluto is now
one of a group of smaller space
objects called dwarf pianetsi
To Pluto and Beyond
Nine years and 3 billion miles after
it left Earth, New Horizons.wM fly by
Pluto. The siiper-speedy craft will gathc
information from the Kuiper belt, a
region at the edge of the solar system.
January 2
Cape Canaveral, Florida.
ird the new dwarf planet.
One member is the largest asteroid,
called Ceres (SIHR-eez). The other
space object is 2003 UB313.
I More dwarf planets are
lexpected to be named as they are
discovered. "These dwarf planets
[are popping up everywhere,"
astronomer Alan Stern told
\WR News. Stem is in charge of
ithe New Horizons mission.
|Fuil Speed Ahead
lAs New Horizons races toward
Pluto, scientists hope the craft
:will offer clues to how our solar
system was formed 4.6 billion
years ago. Many scientists believe
that objects in the Kuiper belt are
leftovers from the formation of
the solar system.
Pluto's downgraded title isn't
stopping scientists from learning
more about the dwarf planet. "We
will continue pursuing exploration of the most scientifically
interesting objects in the solar
system, regardless of how they
are categorized," says NASA
official Paul Hertz.
©
THINK CRITICALLY Not all astronomers
agree wrth the decision to change Pluto's
status. Why might some oppose it?
Pluto's Discovery
Pluto was discovered
in 1930, long after
the other planets, by
American astronomer
Clyde Tombaugh
(1906-1997). He
wasnt the person
to name it, though.
Venetia Burney, an
11-year-old British
girl, gave Pluto its
name. She thought
the new planet
should be named
for the Roman god
of the underworld
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