An exoplanet (also named extrasolar planet) is a planet that is found beyond the solar system. Due to the great distances that separate us from the rest of stars, and consequently from other planets, the detection of extrasolar planets is very complicated.
For this reason, the vast majority of exoplanets have been discovered during the last decade, thanks to different telescopes sent to orbit.
The number of discovered exoplanets
Until now, approximately 5,200 planets have been discovered and considered confirmed, in 3,811 different stellar systems.
In addition, there are still 9,000 extrasolar planets that are still unconfirmed, that to say, they have been detected using some of the methods for the detection of exoplanets, but their existence has to be proven using other detection methods, or waiting more time.
How do we find them?
Currently, there are 5 main methods that scientists use to detect exoplanets around other stars. In the following grid we show these 5 methods, with a brief description, and the number of exoplanets that every approach has allowed to discover:
| Technique | Number of planets |
| Transit Measuring small dips in the brightness of a star, which indicates there is a planet | 3938 |
| Radial Velocity Observing the effects in the light of the star (caused by its wobbling) when there is a planet around | 1020 |
| Direct Imaging Taking pictures of the exoplanet | 62 |
| Gravitational Microlensing The light emitted by a body found behind a star (for example) is curved due to the gravity of the star, and can reach us | 145 |
| Astrometry Observing the changes in the position of a star | 2 |
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