What methods can be used in detecting the exoplanets?
Exoplanets can be detected using the following two methods:
- The radial-velocity method
- The transit method
The radial-velocity method:
- Also known as Doppler spectroscopy
- This method is indirectly used in finding exoplanets and brown dwarfs from radial-velocity measurements by the observation of the Doppler shifts in the spectrum of the planets parent star.
- This relies on the fact that a star does not stay completely stationary when it is orbiting a planet, it moves very slightly in a small elipse shape responding to the gravitational pull of its smaller companion, these small movements affect the stars light spectrum. If the star is moving towards the observer, the spectrum will slightly shift towards the blue. If the star is moving away from the observer, the spectrum will slightly shift towards the red.
The transit method:
- Transit photometry.
- Detects planets that are far away by measuring the slight drop in brightness of a star as a planet passes between the star and Earth, this passage is called a transit. If this change in brightness is detected at regular intervals and lasts for a set period of time, then it is extremely possible that a planet is orbiting the star.