What Is An Exoplanet?
QUICK ANSWER
An exoplanet is a planet outside our solar system, orbiting a star other than the Sun. NASA has confirmed more than 6,000 exoplanets, with thousands more candidates awaiting verification. Exoplanets come in many types, including gas giants, rocky worlds, and ice giants, similar to and different from the planets in our solar system.
An exoplanet is any planet outside our solar system. The first exoplanet around a Sun-like star was confirmed in 1995, and the field has exploded since then. NASA has now confirmed more than 6,000 exoplanets, with thousands more candidates awaiting confirmation. The variety is enormous: gas giants, rocky worlds, ice giants, and types of planets that don't exist in our solar system at all.
How many exoplanets have been found?
More than 6,000 confirmed. According to NASA, the official count of confirmed exoplanets reached 6,000 in late 2025, a major milestone for a field that didn't even have its first confirmed exoplanet until 1995. Thousands more candidates await confirmation. Some host stars have multiple exoplanets: TRAPPIST-1 has seven Earth-sized planets, three of which lie in the habitable zone. NASA's TESS mission and the Kepler mission (now retired) have been the most prolific exoplanet finders.
How do astronomers find exoplanets?
Mostly indirectly. The most common method is the transit method: watching a star carefully and looking for tiny periodic dimming when a planet passes in front of the star. The dimming pattern reveals the planet's size and orbital period. Another method is radial velocity, looking for wobbles in a star's motion caused by orbiting planets. Direct imaging is possible only for large planets far from their stars. Microlensing uses the gravity of a passing star and its planets to magnify light from a more distant star.
What kinds of exoplanets exist?
Many more types than just gas giants and rocky planets. Hot Jupiters are giant planets orbiting close to their stars (much closer than Mercury orbits the Sun). Super-Earths are larger than Earth but smaller than Neptune (no equivalent in our solar system). Mini-Neptunes are smaller versions of the ice giants. Ocean worlds may be completely covered in water. Lava worlds have molten surfaces from being too close to their stars. Some exoplanets even orbit two or three stars in binary or triple star systems.
Are any exoplanets like Earth?
Some are similar, but none are confirmed twins. Several exoplanets have been found in the habitable zones of their stars (where liquid water could exist on the surface) and are roughly Earth-sized, but confirming Earth-like surface conditions requires more detailed observations than current telescopes can provide. The James Webb Space Telescope and upcoming missions like the Habitable Worlds Observatory will look closer at potentially habitable exoplanets. Whether any of them actually host life remains an open question.
An exoplanet is a planet outside our solar system, with more than 6,000 now confirmed. The variety of exoplanet types is enormous, including planets unlike anything in our solar system. Some are roughly Earth-sized and orbit in their stars' habitable zones, making them targets for future life-detection missions. The first exoplanet around a Sun-like star was found in 1995; the field has come a long way in just three decades.
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