Scientists believe they may have found a new planet in the far reaches of the solar system, up to four times the mass of Jupiter. It was first proposed in 1999 by astronomer John Matese of the University of Louisiana at Lafayette. They gave the name "Tyche" after the name of an ancient Greek goddess Tyche. They speculate that this gas giant may have moons because all outer planets do, and that it will still be hot due to its enormous mass. They believe that Tyche orbits at a distance of approximately 500 times Neptune's distance, equivalent to 15,000 AU from the Sun, a little less than one quarter of a light year, which could explain why it has so far remained undiscovered. you can read more here.