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The hunt is on for a gas giant up to four times the mass of Jupiter thought to be lurking in the outer Oort Cloud, the most remote region of the solar system. The orbit of Tyche (pronounced ty-kee), would be 15,000 times farther from the Sun than the Earth's, and 375 times farther than Pluto's, which is why it hasn't been seen so far.
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Tyche will almost certainly be made up mostly of hydrogen and helium and will probably have an atmosphere much like Jupiter's, with colourful spots and bands and clouds, Professor Whitmire said. "You'd also expect it to have moons. All the outer planets have them," he added.
What will make it stand out in the Wise data is its temperature, predicted to be around -73C, four or five times warmer than Pluto. "The heat is left over from its formation," Professor Whitmire said. "It takes an object this size a long time to cool off."
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Professors Matese and Whitmire first proposed the existence of Tyche to explain why many of these long-period comets were coming from the wrong direction. In their latest paper, published in the February issue of Icarus, the international journal of solar system studies, they report that more than 20 per cent too many of the long-period comets observed since 1898 arrive from a band circling the sky at a higher angle than predicted by the galactic-tide theory.
No other proposal has been put forward to explain this anomaly since it was first suggested 12 years ago. But the Tyche hypothesis does have one flaw. Conventional theory holds that the gas giant should also dislodge comets from the inner Oort Cloud, but these have not been observed.
Professor Matese suggests this may be because these comets have already been tugged out of their orbits and, after several passes through the inner solar system, have faded to the point that they are much harder to detect.
