By Alan Boyle

There's a fresh upswing of buzz about the potential for the existence of a large planet on the edge of our solar system, more than 10,000 times farther away from the sun than our planet. Do astronomers already have the evidence for a Planet X, and does this mean all those predictions of a planetary cataclysm in 2012 could actually come true? Not really, and here's why.

First, about that buzz: Astronomers have been wondering for years whether a Planet X, or perhaps an as-yet-undetected brown dwarf, could account for what seems to be an unusual pattern in the influx of comets from the outer solar system.

Such an object would have to be out around the Oort Cloud, the vast swarm of comets that lies far beyond the planets we all know and love. I wrote about this myself ... in 1999 ... and the same astronomers who were involved in the debate back then are keeping it alive today. The latest research paper on the subject, published in the journal Icarus, comes from John Matese and Daniel Whitmire at the University of Louisiana at Lafayette.

Matese and Whitmire say the cometary pattern could be explained by the existence of an object somewhere around one to four times the mass of Jupiter. They also say such an object could explain the weird, wildly looping orbit of the icy world known as Sedna. There's no evidence for such an object yet, but they say it should be "easily detected" by NASA's Wide-field Infrared Survey Explorer, or WISE.

This is pretty much what Matese told me a couple of years ago when I was researching my book, "The Case for Pluto." If such a Planet X exists, WISE should have spotted it. The WISE science team is due to provide the first part of its all-sky survey data in April, and the current buzz has been stirred up by the combination of the Icarus paper's publication and the upcoming data release. The final data release isn't expected to come until about this time next year ... in 2012, that is.

Of course, Matese and Whitmire would be thrilled if the data support their claims for the existence of his Planet X, which has been nicknamed Tyche. "John and I will be doing cartwheels," Britain's Independent newspaper quotes Whitmire as saying. "And that's not easy at our age."
But it's premature to say whether WISE's data set contains such evidence. What Matese told me a couple of years ago still holds true today: If WISE doesn't see any signs of a Jupiter-scale object out there, "then the whole discussion should be concluded." That would give a boost to the alternate explanations for the patterns in cometary paths, such as gravitational perturbations that our solar system experiences as it bobs up and down in the galactic tide.

Even if WISE's readings point to a Planet X, it isn't coming to get us anytime soon. Orbital dynamics dictate that the object would have to hang around the far-flung frontiers of the solar system for many more eons.

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