- In 1846, researchers noticed that Uranus was wobbling
in a way that confounded Newton's Law of Motion. This meant they had two
options: rewrite the most time-honoured of the laws of physics, or "invent"
a new planet to account for the extra gravitational pull. Compared to Newton's
reputation, an eighth planet seemed much less massive and Neptune was discovered.
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- Today scientists working in the University of Louisiana
have discovered a statistical anomaly of similar proportions. Professors
John Matese, Patrick Whitman and Daniel Whitmire have studied the orbits
of comets for 20 years, and their recent findings have led to startling
theories.
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- Intrigued by the work of two palaeontologists working
for the University of Chicago, Prof Whitmire, along with Nasa colleague
Dr Al Jackson, had earlier attempted to explain the amazing discovery that
six apocalyptic events, including the extinction of the dinosaurs, have
all occurred, like clockwork, every 26 to 30 million years. To try to explain
this mass extinction cycle, they looked to the possibility that comet showers
were to blame.
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- The latest effort of Matese, Whitman and Whitmire studies
82 comets from the huge cloud of comets, called the Oort cloud, that exists
around our solar system. They took the aphelia of these comets, the points
on their orbit that are farthest from our Sun, and plotted them on a globe.
Expecting to find an even distribution, they instead found that a particular
band of sky, about one sixth the total, contained more than one quarter
of all the comets, and that about 25 per cent of the comets coming from
this cloud have anomalous paths.
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- So what was affecting the orbits? They went on to theorise
that the best explanation is the existence of a previously unknown body
- that our solar system is made up of the Sun and a shadowy partner, either
a brown dwarf or a massive planet, in a wide binary system. In effect,
the solar system had two stars, the Sun and a dark companion, spinning
around each other.
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- Now I know what you're thinking Surely I'd have noticed
a second Sun in the sky? But, as Prof Whitmire explained, the process of
assumption based on statistical anomalies has always been a cornerstone
of scientific discovery. According to their current theory, he says, "the
companion is a brown dwarf star or massive planet of mass between two and
six times the mass of Jupiter". A brown dwarf is a star too small
to sustain the nuclear fusion that powers our Sun, and so is relatively
cool (surface temperature of less than 1500C) and so also very dim, being
barely hot enough to give off light.
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- But it gets worse. Under their original theory, called
the Nemesis theory, this small dark star, which lurks at around 90,000
times farther away than the Earth is from the Sun, may be on an orbit that,
once every 30 million years, ploughs it into the densely packed inner cloud.
Here its immense gravitational pull would drag out several of the Oort
comets and give them the "kick" needed to send them towards the
Sun on orbits perilously close to the Earth. This explains, in the professor's
view, the ominous mass extinction cycle, due to regular periods of increased
cometary activity every 30 million years.
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- However, before we head for the bomb shelters, we should
take heed of the professor's words: "As a practical matter our models
will never be generally accepted (and shouldn't be) until the actual object
is found." However stressing that they are "sufficiently plausible
to give incentives for others to look".
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- Today, their current paper has moved away from the Nemesis
theory and proposed, on the basis of comet orbits, a less massive planet
about three times the mass of Jupiter. None the less, with an explanation
for the mass extinction cycle yet to be found, he has admitted that they
may not be mutually exclusive; and that there could be two dark stars,
one a failed partner to our own, and another one that is acting almost
as an alarm clock for doomsday. Even so, he says: "I'm still hopeful
that ultimately these might turn out to be the same object.".
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- "An original idea in science is often a gut instinct,
but this should not influence the development of the idea," says the
professor. "I always try to be my own worst critic". The scientific
world remains intrigued but sceptical. However, the recent bombardment
of Jupiter is a reminder that if the team is right, there may not be many
around to hear them say: "I told you so."
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