In 1995, a pair of scientists discovered a planet outside our solar system orbiting a solar-type star. Since that finding—which won the scientists a portion of the 2019 Nobel Prize in Physics—researchers have discovered more than 5,000 exoplanets, including some Earth-like planets that have the potential to harbor life. These are worlds in the “habitable zone” where liquid water could exist and may be the key to answering questions about whether life exists beyond Earth.