In 1995, two Swiss astronomers detected the first confirmed planet orbiting another star. Before that moment, astronomers could only speculate whether planets existed beyond our own system. Today, we've confirmed over 5,500 exoplanets, and we're discovering dozens more every month.

The challenge is extraordinary. Stars are billions of times brighter than the planets orbiting them. Detecting an exoplanet directly is like trying to spot a firefly next to a searchlight from a thousand miles away. Almost all confirmed exoplanets have been found indirectly.

The two main methods are ingenious. The first, radial velocity, watches for tiny wobbles in a star's motion caused by a planet's gravitational pull. If a planet is there, the star doesn't stay still — it orbits the center of mass of the system. That motion causes the star's light to shift slightly redder, then bluer, then redder again. Sensitive spectrometers can detect these shifts at speeds as low as 1 meter per second — essentially walking pace — from trillions of kilometers away.

The second method, transit photometry, catches planets that happen to pass between their star and our telescopes. As the planet crosses, it blocks a fraction of the star's light. The dip is tiny — for an Earth-sized planet around a sun-like star, the star dims by only 0.01%. But by watching thousands of stars continuously, NASA's Kepler telescope found over 2,600 planets this way.

The results have transformed our view of the universe. Planets aren't rare — they're the norm. On average, every star in the Milky Way has at least one planet orbiting it. That's over 100 billion planets in our galaxy alone, and there are about 100 billion galaxies we can see.

The diversity is stunning. We've found hot Jupiters orbiting so close to their stars they complete a year in under 24 hours. We've found planets in binary systems with two sunsets, like Tatooine. We've found water worlds, lava planets, and rogue planets drifting through space without any star. We've also found planets in the 'habitable zone' — the right distance from their star for liquid water — around common star types.

The James Webb Space Telescope can now directly analyze the atmospheres of some exoplanets, looking for chemical signatures that might indicate life. The next generation of telescopes may answer humanity's oldest question: are we alone?