Definition for Extrasolar planet
From Biology Forums Dictionary
An extrasolar planet, or exoplanet, is a planet outside the Solar System. A total of 763 such planets (in 611 planetary systems and 101 multiple planetary systems) have been identified as of April 24, 2012. Estimates of the frequency of systems strongly suggest that more than 50% of Sun-like stars harbor at least one planet. In a 2012 study, each star of the 100 billion or so in our Milky Way galaxy is estimated to host on average at least 1.6 planets. Accordingly, at least 160 billion star-bound planets may exist in the Milky Way Galaxy alone. Unbound free-floating planetary-mass bodies in the Milky Way may number in the trillions with 100,000 objects larger than Pluto for every main-sequence star
