An Etymological Dictionary of Astronomy and Astrophysics

A facility at → European Southern Observatory (ESO)’s → La Silla Observatory funded by the European Research Council and the French Agence National de la Recherche with the purpose of detecting and studying → transiting  → exoplanets. ExTrA will search for Earth-sized planets orbiting nearby → red dwarf stars.

It uses three 0.6-metre telescopes. They regularly monitor the amount of light received from many red dwarf stars and look for a slight dip in brightness that could be caused by a planet passing across a star’s disk and obscuring some of its light.

The three ExTra telescopes collect light from the target star and four comparison stars and that light is then fed through optical fibres into a → multi-object spectrograph. This innovative approach of adding → spectroscopic information to traditional photometry helps mitigate the disruptive effect of Earth’s atmosphere, as well as effects introduced by instruments and detectors, thus increasing the precision achievable.

See also: ExTrA, short for Exoplanets in Transits and their Atmospheres, → exoplanet; → transit; → atmosphere.