|
Does the Sun have a doomsday
twin?
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.
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.
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.
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.
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.
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.
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.
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".
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.".
"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."
Paul Blakemore was second in the younger category of The Daily
Telegraph/BASF science writer awards. The competition will
be launched again in a few weeks.
 |
 |
|
 |
