Detection Techniques for Exoplanets

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The research area of detecting exoplanets, planets outside our own solar system, is a huge area of interest and funding. The importance of being able to detect these planets is they can give us information and an insight into planetary formation, to help the search for ”Earth- like” planets in the habitable zone, and of course the ever-present question of extraterrestrial life. So on order to attempt to gather information about these things we must be have solid detection techniques in place for exoplanets. A few of the important methods shall be discussed here, including the radial velocity method, transit method, direct imaging and gravitational microlensing among others .
The Radial Velocity method, also known as Doppler spectroscope/method for detection of exoplanets is based on the principles that a star that has an orbiting planet will experience a gravitational force from the planet and hence move in its own small orbit in response. This will result in changes in the speed of the star as it moves towards and away from the observer i.e Earth and this shall be seen as variations in the radial velocity of the star with respect to the Earth. The radial velocity of the star can be worked out from the shifting of spectral lines in spectra of the star due to the Doppler effect and from here the variations can be determined and if they apply then the presence of an exoplanet can be confirmed.
High precision spectrometers such as HARPS are required to preform observations as very high signal to noise ratio. HARPS is a high resolution fiber-fed echelle spectrograph. To maximize the chance of detecting an exoplanet certain requirements have to be met by potential targets. The targets chosen to be studied by HARPS are selected from COR...

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... Experiment” (OGLE) are two missions which monitor these microlensing events. Planets around low mass stars are easier to detect with this method as the ratio of the planet to stars mass will increase and so the gravitational microlensing effect will be larger.
The characteristic scale of gravitational mi- crolensing is the radius of the Einstein ring RE. The Einstein ring occurs when lens and source are aligned and the light from the source is shaped into a ring through the gravitational lensing by the gravitational field of the ”lensing” ob- ject.
R =

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