The first telescope was probably invented in 1608 by Hans Lippershey. The Orbiting Astronomical Observatory 2 was the first space telescope launched on December 7, 1968. As of February 2, 2019, about 3,891 exoplanets are discovered. The Milky Way galaxy has more than 100–400 billion stars and more than 100 billion planets. There are about 2 trillion galaxies in the observable universe.