Two Suns in the sky: the TEST telescope on the quest for planets around binary stars

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The Tautenburg Exoplanet Search Telescope is a robotic 30cm Schmidt telescope to find extra-solar planets. It monitors celestial fields selected beforehand to detect extrasolar planets. Being a robotic telescope, its participation in the Dwarf network is essential. This network consists of 20 mostly European telescopes and looks for planets around a particular class of binary stars, the so-called eclipsing binaries.These binaries revolve around each other in a way so that one star transits in front of the other and thus shades its light. This results in a substantial and strictly periodical dimming of the total brightness of the system, the so-called eclipses. Therefore, one can conclude on the binary nature of the system by monitoring the brightness, even though the two components cannot be resolved due to the large distance.If a planet is in an orbit around this binary, both the planet and the binary move around a common centre of mass, strictly speaking. Therefore, the distance of the binary varies periodically and thus the light travel time of the binary, too. This results in a measurable variation of the exact eclipse times and can be measured more precisely the brighter the binary and the larger the telescope.The TEST telescope will be optimised for the observation of such eclipsing binaries. The observing schedule for tens of binaries will be organised automatically in a way so that many eclipses of many stars are observed efficiently.In order to increase the success of the Dwarf network, the best binary targets need to be identified and monitored. Being one of the smallest telescopes in the Dwarf network, the TEST is perfectly suited to find the most promising targets among hundreds of candidates while the larger telescope are used for the ambitious monitoring of the eclipse times of the best candidates. Moreover, the TEST will contribute to the Dwarf campaign by measuring eclipse times for selected bright objects. Finally, the project will provide resources to analyse the large amount of eclipse time measurements collected by the Dwarf project.The project ensures the operation and development of an advanced telescope over the next years and at the same time contributes to ambitious and seminal science. The development of automated observations will advance the search for planets around binary stars.