-
- Two
teams of researchers have proposed the existence
of an unseen planet or
a failed star circling the sun at a distance of
more than 2 trillion
miles, far beyond the orbits of the nine known planets.
The theory,
which seeks to explain patterns in comets' paths, has been
put forward
in research accepted for publication in two separate journals.
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- Speculation about the existence of unseen
celestial companions
dates back far before the discovery of Pluto in
1929 - and even figures
in more recent fringe phenomena such as the
1997 "Heaven's Gate"
tragedy and talk of a new "Planet
X." This latest hypothesis,
however, is aimed at answering nagging
scientific questions about how particular
types of comets make their
way into the inner solar system.
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- Some comets, like Halley's Comet, follow relatively short-period
orbits - circling the sun in less than two hundred years. These comets
are thought to originate in the Kuiper Belt, a disk of cosmic debris that
lies beyond Neptune's orbit.
-
- The best way to think of the distances involved is in
terms of
Astronomical Units. One AU is the distance from Earth to the sun
(93
million miles or 149.6 million kilometers). Pluto, the most distant
of
the planets, is at 39 AU. The Kuiper Belt extends from 30 AU to perhaps
1,000 AU.
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- Even further out is
the Oort Cloud, a spherical haze
of comets surrounding the solar system
at distances between 10,000 AU and
more than 50,000 AU. That's where
long-period comets such as Hale-Bopp
are thought to come from. For some
time, astronomers have noticed that
the directional patterns of these
comets are not completely random. And
after years of study, some
researchers are reporting that the patterns
hint at something big out
there perturbing the cometary paths.
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- No telescope has yet detected this object. But on the
basis of
its gravitational effect, John B. Murray, a planetary scientist
at
Britain's Open University, speculates that the object could be a planet
larger than Jupiter, the biggest of the solar system's known planets.
Murray
puts the object's orbit at 32,000 AU, or 2.98 trillion miles
from the sun.
Murray's proposal appears in the Oct. 11 issue of the
Monthly Notices of
the Royal Astronomical Society.
-
- Meanwhile, researchers at the University
of Louisiana
at Lafayette say the object could be a planet or brown
dwarf - that is,
a dark, failed star - roughly three times the size of
Jupiter and orbiting
at 25,000 AU. The researchers, led by physicist
John Matese, say their
paper has been accepted for publication by the
journal Icarus.
-
- Both studies
acknowledge that other factors could influence
the pattern seen in
long-period comets: for example, the Oort Cloud's interactions
with
passing molecular cloudsor the Milky Way's gravitational tidal effects.
But the Louisiana researchers say the cometary patterns are best explained
by the existence of "a perturber, acting in concert with the galactic
tide."
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- MORE
QUESTIONS
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- How
could such a massive object exist so far from the
sun? The researchers
say it could have coalesced during the formation of
the solar system
billions of years ago, or it might have been a passing
celestial body
captured by the sun's subtle gravitational pull.
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- Another question: Why hasn't it been seen? Murray says
that even a Jupiter-scale planet could not be observed at the immense
distances
involved. Matese and his colleagues say that their
hypothetical brown dwarf
wouldn't have been detected even by the
Infrared Astronomical Satellite,
which surveyed the heavens in 1983 -
but that the yet-to-be-launched Space
Infrared Telescope Facility just
might be able to pick it up.
-
- All this may sound like science fiction, but an expert
in the
field says the hypothesis makes scientific sense.
-
- "We've all wondered whether there was something
out there," said Brian Marsden, who heads the International
Astronomical
Union's Central Bureau for Astronomical Telegrams as well
as the Minor
Planet Center at the Smithsonian Astrophysical
Observatory.
-
- He said Wednesday
that he wasn't familiar with Murray's
research, but noted that Matese
"has been working on this sort of
thing for several years, so
it's
- reasonable that he would come up with
something like
this."
-
- If the latest research holds up, it could open the door
for
renewed speculation on even spookier questions: Some theorists have
proposed that the gravitational effect of such a massive object -
nicknamed
"Nemesis" or the "Death Star" - could set
off periodic
cometary storms, which would increase the chances of a
catastrophic impact
with Earth. Indeed, Matese and fellow researcher
Daniel Whitmire, who is
a co-author of the new research, laid out just
such a scenario in 1985
to explain mass extinctions on Earth, such as
the demise of the dinosaurs.
-
- An
earlier version of this story misstated the conversion
from
Astronomical Units to miles.
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