Search begins for giant new planet

http://www.independent.co.uk/news/science/up-telescope-a-new-planet-has-scientists-agog-2213119.html

Up telescope! Search begins for giant new planet

Tyche may be bigger than Jupiter and orbit at the outer edge of the  
solar system

By Paul Rodgers

Sunday, 13 February 2011

If you grew up thinking there were nine planets and were shocked when  
Pluto was demoted five years ago, get ready for another surprise.  
There may be nine after all, and Jupiter may not be the largest.
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.

But scientists now believe the proof of its existence has already been  
gathered by a Nasa space telescope, Wise, and is just waiting to be  
analysed.
The first tranche of data is to be released in April, and  
astrophysicists John Matese and Daniel Whitmire from the University of  
Louisiana at Lafayette think it will reveal Tyche within two years.  
"If it does, John and I will be doing cartwheels," Professor Whitmire  
said. "And that's not easy at our age."

Once Tyche has been located, other telescopes could be pointed at it  
to confirm the discovery.

Whether it would become the new ninth planet would be decided by the  
International Astronomical Union (IAU). The main argument against is  
that Tyche probably formed around another star and was later captured  
by the Sun's gravitational field. The IAU may choose to create a whole  
new category for Tyche, Professor Matese said.

The IAU would also have the final say about the gas giant's name. To  
the Greeks, Tyche was the goddess responsible for the destiny of  
cities. Her name was provisionally chosen in reference to an earlier  
hypothesis, now largely abandoned, that the Sun might be part of a  
binary star system with a dim companion, tentatively called Nemesis,  
that was thought responsible for mass extinctions on Earth. In myth,  
Tyche was the good sister of Nemesis.

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."

Most of the billions of objects in the Oort Cloud – a sphere one light  
year in radius stretching a quarter of the distance to Alpha Centauri,  
the brightest star in the southern constellation – are lumps of dirty  
ice at temperatures much closer to absolute zero (-273C).

A few of these are dislodged from their orbits by the galactic tide –  
the combined gravitational pull from the billions of stars towards the  
centre of the Milky Way – and start the long fall into the inner solar  
system.

As these long-period comets get closer to the Sun, some of the ice  
boils off, forming the characteristic tails that make them visible.

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.

So if it is real, Tyche may not only be disrupting the orbits of  
comets, it may also overturn an established scientific theory.

You can download a PDF showing the position of Tyche by clicking here
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