"Moving Planets Around covers the laws of celestial mechanics and gravity in the Newtonian limit, with a focus on the time evolution of planetary systems ranging from our own Solar System to the myriad extrasolar planetary systems we now know exist in the universe"--
... Schrijver , H. , Bernacca , P. L. , Evans , D. W. , Falin , J. L. , Froeschlé , M. , Grenon , M. , Hering , R. , Høg , E. , Kovalevsky , J. , Mignard ... Phillips , J. A. , Thorsett , S. E. , and Kulkarni , S. R. ( editors ) , 1993.
An unprecedented number of planets outside of the solar system have been found, with an explosion in the number of discoveries in recent years.
Two decades ago astronomers confirmed the existence of planets orbiting stars other than our Sun.