I am reading this very interesting piece about the the history of exoplanetary investigation. It is fun to remember that during the last undergrad physics course I took, back in 1991, the instructor made emphasis saying that there "was no evidence about the existence of planet out of the Solar System". It was true. Now, 25 years after, we have solid reports of circa 2,500 exoplanets.
Five Billion Years of Solitude: The Search for Life Among the Stars Lee Billings