Pluto takes approximately 6.4 Earth days to spin once on its rotational axis. Pluto's moon Charon orbits Pluto once every 6.4 days as well. Astronomers refer to this phenomenon as tidal locking.
Astronomical data reveals that Pluto spins on its axis in an east-to-west direction like the planet Venus. The other planets, including Earth, spin west to east. This retrograde rotation suggests that at some point in the past, another object collided with Pluto, reversing the direction of its spin and perhaps contributing to its highly inclined, eccentric orbit around the sun.
Astronomers once thought that Pluto was an escaped moon of Uranus or Neptune. The consensus has changed in recent years, however, and the leading theory is that Pluto is one of several frozen dwarf planets in the Kuiper Belt, a region of the solar system beyond the orbit of Neptune. Short-term comets like Halley's Comet are believed to originate in the Kuiper Belt.