From Space.com:

A duo of planetary astronomers has grabbed media attention by claiming a planet four times the size of Jupiter may be lurking in the outer solar system. They call the planet Tyche.

Many astronomers, however, say it probably isn’t there.

The claim by John Matese and Daniel Whitmire of the University of Lousiana-Lafayette is not new: They have been making a case for Tyche since 1999, suggesting that the giant planet’s presence in a far-flung region of solar system called the Oort cloud would explain the unusual orbital paths of some comets that originate there.

The Independent is more optimistic:

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.

If the International Astonomers Union does decide that there is a new planet, it may not get to keep the name Tyche.  You may remember the new planet Eris was originally called Xena by its discoverer, Mike Brown, and the planet Uranus was originally called Herschel after its discoverer.  The name Tyche could be wishful thinking – she was a goddess of good fortune and seen to preside over world affairs.