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- Scientists have
discovered a new object orbiting the
Sun after a spaceprobe was
mysteriously knocked off course.
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- Researchers have yet to
identify the object, but they
are confident it exists because of the
way it appears to have deflected
the tiny Pioneer 10 craft, which is
hurtling out towards the stars.
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- If the observations are confirmed by other astronomers,
it will be only the second time in history that a Solar System object has
been discovered by its gravitational effect alone.
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- The first was the planet
Neptune which was discovered
in 1846. Its position was predicted
because of its gravitational tug on
the planet Uranus, which appeared
to be behaving oddly following its discovery
59 years earlier.
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- The new body, found
by a team at Queen Mary and Westfield
College in London, UK, and the
Jet Propulsion Laboratory in California,
is probably a so-called Kuiper
Belt object.
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- The astronomers looked at Pioneer 10's tracking data
obtained
with the Nasa Deep Space Network, an array of large radio telescopes
designed to communicate with far-off space probes.
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- Rocky
swarm
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- On 8 December, 1992, when Pioneer was 8.4 billion km
(5.2
billion miles) away, they saw that it had been deflected from its
course for about 25 days.
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- The scientists have been looking for such an effect for
years and are currently analysing the data using several different methods
to confirm their findings.
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- In a few weeks time, they are expected to be able to
place an upper limit on the mass of the object and make predictions about
its position. Early indications suggest it may be an object that is being
ejected from our Solar System after encountering a major planet.
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- "We are quite
excited that we have found one of
these events. It is a very neat
signal," Dr Giacomo Giampieri of Queen
Mary and Westfield College
told BBC News Online.
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- If confirmed, it would be one of over 100 known icy and
rocky objects that circle the Sun at vast distances, mostly beyond the
most distant planet Pluto.
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- They are small in planetary terms, just a few hundred
kilometres at most, but astronomers believe there are millions of them
swarming around the Sun in a vast belt. The first one was detected in
1992.
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- Starbound probe
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- The Pioneer 10 spacecraft was
launched in March 1972
and has lived up to its name.
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- It was the first
spacecraft to travel through the asteroid
belt, the ring of rocky
debris that orbits the Sun between Mars and Jupiter.
Before it
successfully traversed this region of space, scientists did not
know if
a spacecraft could get through unharmed.
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- It was also the first craft to
reach a gas-giant planet,
Jupiter, after which it left the solar system
becoming the first craft
to effectively leave the Sun's planetary
system, even though it has not
yet passed into interstellar
space.
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- It
is currently 11 billion km (6.8 billion miles) away
and still
transmitting even though Nasa ceased monitoring its signals in
1997
after it had spent 25 years in space.
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- Earlier this year, scientists
were puzzled by what was
described as a mysterious force acting on the
probe. It led to speculation
that there was something wrong in our
understanding of the force of gravity.
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- Eventually the effect was
tracked down to the probe itself,
which was unexpectedly pushing itself
in one particular direction.
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- Pioneer 10 will reach the stars of the constellation
of Taurus in about two million years.
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