Exoplanet transits in foreign solar systems

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Exoplanets and their discovery

An extrasolar planet (Exoplanet) is a planet in another solar system. The planet is in an orbit of a different star. Until the year 1990 astronomers only could make science based assumptions about the existence of planets nearby other stars. Till then the proof about the existence of planets also outside of our solar system was not possible even with big telescope systems.

The timing method
In the year 1990 for the first time two planets could be detected nearby a foreign star by the polish astronomer Aleksander Wolszczan by measuring the period change of the beam of the pulsar star PSR 1257+12. But this solar system is not comparable with one like our solar system.

The radial velocity method
The first exoplanet in an orbit of a sun like star was discovered 1995 by Michel Mayor from Departement for Astronomy of the University Geneva and his cooperator Didier Queloz using the radial velocity method. The discovered planet got the designation Pegasi 51b and is in an orbit of the star Pegasi 51 in the constellation Pegasus and about 40 light year away. Using the radial velocity method blue and red shifts of the light because of the Doppler effect are analyzed. This shifts are caused by the movement of the star around a combined centre of gravity.

The transit method
In February 2016 about 1285 exoplanets in 730 solar systems are known, with orbit plane oriented in the direction of Earth. So this planets are passing in front of the star disk during an orbit. In this exoplanet systems a data capturing also with the transit method is possible. If a dark planet is passing in front of a bright star disk the overall brightness becomes dimmed a little bit for the transit duration. This event can be captured with an appropriate number of accurate images. For useful results brightness changes caused by the planet transit in the range of 0.27 to 3.7 percent must be captured with accurate times. This images will be evaluated later with adequate and accurate methodes. In this way the transit curve with known tolerances can be generated. From the resulting curve shape the details about the orbit plane and the occultation sequence can be derived.

Further methodes used by professional for confirmation of an exoplanet are microlensing and direct imaging. Although some few amateurs were able to use a selfmade spectrometer system for the radial velocity method the transit method mostly is the only one method that can be realized by amateur astronomers. And in fact some new exoplanets could be detected in this way by amateurs.