-  A 10th Planet?

-  Does the Sun have a doomsday twin?

-  Disturbance of Comets Hints at Something Out There
 

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A 10th Planet?

A NASA scientist insists a 10th planet may be orbiting the sun even though two space probes have not been able to find any trace of it in the dim outer reaches of the solar system.

Dr. John Anderson, a celestial mechanics investigator with NASA's Pioneer spacecraft project, told reporters at Ames Research Center at Moffett Field Tuesday that if the planet exists, it travels at nearly right angles to the plane of the orbits of the nine known planets in a looping ellipse so elongated it only nears the sun every 700 to 1,000 years.

Anderson, who published his ideas last year in ''The Galaxy and the Solar System'', called his theory ''an important contribution to the understanding of the dynamics of the outer solar system.''

Analysis of the trajectories of the Pioneer 10 and 11 spacecraft during the past five years shows no indication of gravitational effects that would be expected if an unknown planet was in a normal, circular orbit beyond Uranus, but 19th century records indicate the orbits of the outer planets were disturbed in a subtle manner, which Anderson suspects may have been caused by gravitational effects associated with the undiscovered planet.

''The best explanation for an object very likely to have been there for at least 100 years, and then disappearing, is a planet on a greatly elongated orbit,'' Anderson said.

''I think that's the most likely possibility if you take all the current data. It's a good possibility and a good working hypothesis. If it isn't Planet X, then I throw up my hands and can't say what it is'', Anderson said.
 

Does the Sun have a doomsday twin?

By Paul Blakemore

of The Daily Telegraph
(Filed: 18/10/2002)


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-honored 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 paleontologists 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 theorize 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 skeptical. 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."

Disturbance of Comets Hints at Something Out There
A Tenth Planet?

By Kenneth Chang
ABC NEWS

Oct. 7 — Astronomers may have found hints of a massive, distant, still unseen object at the edge of the solar system — perhaps a 10th planet, perhaps a failed companion star — that appears to be shoving comets toward the inner solar system from an orbit 3 trillion miles away.
Two teams of scientists — one in England, one at University of Louisiana at Lafayette — independently report this conclusion based on the highly elliptical orbits of so-called “long-period comets” that originate from an icy cloud of debris far, far beyond Pluto. “We were driven to this by rejecting everything else we could think of,” says University of Louisiana physicist Daniel Whitmire.

Clump of Comets
A couple years ago, Whitmire, along fellow physicists John Matese and Patrick Whitman, noticed the farthest points of the comets’ orbits didn’t appear random but bunched together, tracing a path across the sky.
“We accidentally noticed they weren’t uniform,” Whitmire says.

First, they tried to explain the clumping from the gravitational pull from a main disk of stars in the Milky Way stars. “That ultimately didn’t work,” Whitmire says. “We’ve gone through several other models trying to explain this.”

At around the same time, John Murray, a planetary scientist at The Open University in Great Britain, made a similar observation in similar comet data. “I started puzzling what this might could be,” he says. The most obvious but seemingly unlikely explanation would be a planet. “I thought we’d better rule that out,” he says. But as he analyzed the orbits, the farthest points appeared to fall on a circular orbital path — “which is exactly what you would expect if there was a planet out there.”

As the planet — estimated to have a mass between one and 10 Jupiter's — orbits, its gravitational wake disturbs the icy debris of the outer solar system, causing some of it to plunge toward the sun as comets, sort of like an elephant ambling through a china shop. No one has yet directly observed a 10th planet, and there could still be another cause for the cluster of comets. The University of Louisiana research will be published in an upcoming issue of the journal Icarus. Murray’s paper will appear in Oct. 11 issue of the Monthly Notices of the Royal Astronomical Society.

Very Distant
What’s surprising is just how far out there this supposed planet is. Both Murray and the University of Louisiana physicists put the planet in an orbit about 3 trillion miles — or half a light-year — from the sun. The nearest star is four light-years away. To put this distance in perspective, consider a miniaturized version of the solar system in which Earth is one inch from the sun. On this scale, Pluto, the ninth planet would be a bit more than a yard from the sun. The new planet, by contrast, would be a half-mile distant.

At that great distance, the 10th planet would be too dim to see by current telescopes, although there is some hope that if it exists, the next generation of space-based infrared telescopes might be able to pick it up. Murray hypothesizes the planet may have been wandering through the galaxy before being captured by the solar system’s gravity. Whitmire suggests it is a “brown dwarf,” or a failed star, a companion to the sun that was too small to light up. Although suggestive, the findings are not conclusive. While Murray and the Louisiana physicists agree how distant the new object is, they trace out very different orbits. Murray considers the orbits of 13 comets with the most accurately known orbits; the Louisiana team considers 82.

Too Early to Look for a Name
“It’s possibly suggestive,” comments Brian Marsden, associate director for planetary sciences at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. “I don’t want to bet on it. We’re certainly not going to name it.” Whitmire agrees it’s too early to say definitely there’s something out there. “Until it’s found, you can never be overly confident,” he says. “We know in science you can be fooled by statistics.” But he adds, “If I was betting, it’s better than 50-50 odds that it’s there.”