This audiobook is narrated by a digital voice.

The idea of planets existing beyond our solar system was once purely speculative, a concept entertained more in science fiction than in scientific circles. However, with the advancement of astronomical tools and techniques, the discovery of exoplanets—planets orbiting stars outside our solar system—has transformed this speculation into a dynamic and rapidly growing field of research. The journey began in earnest in the late 20th century, when astronomers began detecting subtle clues that hinted at the presence of distant worlds.

One of the earliest milestones in exoplanet research was the 1992 discovery of planets orbiting a pulsar, PSR B1257+12. These planets were unlike anything in our own solar system, challenging preconceived notions of what planetary systems should look like. Then, in 1995, the detection of 51 Pegasi b—a gas giant orbiting a Sun-like star—confirmed that exoplanets could be found around stars similar to our own. This discovery opened the floodgates for a new era in astronomy, leading to a rapid increase in the number of known exoplanets.

Detecting these far-off worlds, however, is no simple task. Because exoplanets are small and dim compared to their host stars, they are incredibly difficult to observe directly. As a result, astronomers have developed indirect methods for detection. The radial velocity method measures the slight wobble of a star caused by the gravitational pull of an orbiting planet. The transit method, perhaps the most prolific in terms of discoveries, involves observing the slight dip in a star's brightness when a planet crosses in front of it.