We have decades old speculations about the exoplanets, but a solid conclusion about it happened in the year 1995 when a Jupiter sized exoplanet was discovered closed to a star and named 51 Peg. The researchers while observing the star as part of another experiment accidentally observed the wobbling caused by the huge planet.
There are three methods to detect exoplanets- Doppler method, transit method or eclipse method and direct observation method.
The two main indirect methods used to detect the exoplanets are Doppler method and transit method.
Doppler method: The first discovery of exoplanet was with the Doppler method in 1995. And many more Jovian size planets were discovered with the same method. It was extensively used for the first 15 years. Doppler method is still used by the exoplanet hunters and it still generates discoveries every week.
A giant planet or even a small planet can exert a pull on the parent star with respect to the common centre of gravity, thus creating a reflex motion. The reflex motion is difficult to detect from the earth. But the wobble created by the reflex motion induces a Doppler shift which can be detected. And that can be detected if only the orientation of the orbit is near the pain of the sky.
Very high resolution spectroscopy is used in this method.
Eclipse method or Transit method: After the launch of the Kepler telescope the transit method is widely used and more earth like and giant earth like exoplanets were spotted, thus making it enormously successful method in finding exoplanets. In this, the system has to be working in the equatorial plain, coming towards us or away from us. The planet pass right in front of the star and eclipses it slightly for a short while. The multiple transits confirm the presence of the planet.
Since 1995 almost 3000 exoplanets are already discovered using these two indirect methods and the researchers are combing the neighbourhood for more .
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