4.0—Earth & the Formation of Our Solar System

Before 1995, most people believed that the only planets in the Universe were found in our Solar System. Since 1995, hundreds of “exoplanets,” or planets outside of our Solar System, have been discovered orbiting other stars. The Earth and our Solar System are not as unique as they were once thought to be. Planet formation is now considered to be very common in the Universe, and planets can form in