What is 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 ellipse 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, then it is extremely possible that a planet is orbiting the star.
- Astronomers take images of exoplanets by removing the glare produced by the star they orbit (remove). Exoplanets are photographed by getting rid of the glow of the star they orbit.
What are the peculiarities of the Gravitational Microlensing
- Light from a distant star is bent and focused by gravity as a planet passes between the star and Earth.
- The orbit of a planet can cause a star to wobble around in space in relation to nearby stars in the sky.