When astronomers started finding planets around other stars in the 1990s, they fully expected to see the general structure of our own solar system repeated throughout the cosmos. (discovermagazine.com)
But there was no observational evidence, because it's extremely difficult to see planets of other stars. (astrobio.net)
Nearly 2,000 planets have been confirmed to be orbiting other stars in our galaxy. (hubblesite.org)