Astrophysicists Daniel Whitmire and John Matese from the U of Louisiana say that the NASA Wise telescope has provided data that a giant gas planet four times the size of Jupiter may be lurking in the outer solar system, far beyond Pluto and 15,000 times farther away from the sun than Earth. 

http://news.blogs.cnn.com/2011/02/15/scientists-telescope-hunt-massive-hidden-object-in-space/?hpt=C2

This massive object was first hypothesized in 1984 as Nemesis, a brown dwarf star companion to the sun.  Now, evidence exists that the object may be a giant gas planet, which Matese and Whitmire have named  Tyche, after the good sister of the goddess Nemesis in Greek mythology.   Within 2 years there should be direct evidence of this gas planet, if it exists.  If it’s there, it will probably be composed of hydrogen and helium and have colorful spots, bands and clouds like Jupiter.

The presence of such a massive object in the outermost reaches of our solar system could explain a barrage of comets from an unexpected direction.  

http://www.space.com/9612-giant-stealth-planet-explain-rain-comets-solar-system-edge.html

Also, its 27 million-year orbit could explain a pattern of mass extinctions on Earth.

http://www.space.com/8028-sun-nemesis-pelted-earth-comets-study-suggests.html

Tyche was the goddess of fortune, chance, providence and fate – the divinity guiding and conducting the affairs of the world.  Nemesis was regarded as the downside of Tyche who provided a check on extravagant fortune. The pair were often depicted as companions in Greek vase painting.  In the picture below, Nemesis is shown with her arm around Tyche.