Retrograde, Planet orbiting Reversed

Retrograde, Planet orbiting Reversed. how come?
The planet orbits the star general in the direction of rotation of the star. However, several different planets, orbiting in the opposite direction. The planet is called retrograde planet or planets orbiting reversed.
One planet is retrograde planet HAT-P-7b is orbiting a star 1,040 light-years away in the constellation Cygnus. The planet was discovered in 2008. Astronomers wondered, why the planet can move opposite to the direction of the star.
The answer is revealed from the results Japanese astronomers. Through observations with the Subaru Telescope Facility in Hilo, Hawaii, they found the cause rollovers orbit of HAT-P-7b. They found a Jupiter-sized planet HAT-7c orbiting close to its parent star HAT-P-7b.

"The researchers think that their neighboring stars and other planets play a role in shaping and maintaining the planet's orbit (HAT-P-7b) are reversed," said officials of the Subaru Telescope Facility as quoted Space, Thursday (01/24/2013).
According to a team of astronomers, HAT-P-tc located between orbiting planet HAT-P reverse-7b and the newly discovered star. Stars and planets newly discovered planet orbits affect HAT-P-7b.
The study was led by Norio Narita, Yasuhiro Takahashi, Masayuki Kuzuhara, and Teruyuki Hirano from the National Astronomical Observatory of Japan and the University of Tokyo. Conclusions obtained, the effects of gravity can affect the formation of double inverted orbiting planet.