Abstract

Exoplanet research is a rapidly growing field in modern astrophysics and today more than 5400 planets and planet candidates are known outside our Solar System. The overwhelming majority of theses objects were found by indirect observing techniques (the radial velocity (RV) method and the transit method), where the existence of the planet is inferred from periodic changes in the light signal of the host star. No photons coming from the planets themselves were recorded. RV and transit observations are best suited for, and biased towards, the detection of planets orbiting very close to the star. In order to investigate longer-period planets and to get a more complete census of the exoplanet population, other observing techniques are required. Also, RV and transit observations yield basic orbital parameters of the planets and constrain their mass (RV) or size (transit), but to determine the physical and chemical properties of the planets’ atmospheres (e.g. temperature, molecular composition, potential habitability) detecting direct emission from the planets is crucial. In some cases primary transit/secondary eclipse measurement can be used to constrain properties of exoplanet atmospheres. However, these studies are confined to short-period transiting planets and the vast majority of exoplanets do not transit in front of their host star. In this talk I will discuss the current state of the field of the complementary ‘Direct Imaging’ technique and show that it can address some of the questions that cannot be tackled by RV or transit observations. I will briefly discuss the challenges that one faces when trying to detect the exoplanet’s signal (image or spectrum) and that of its host star simultaneously, but spatially separated, on the detector. I will then describe how these challenges can – at least partially – overcome and summarise some key science results from the last years. Finally, I will conclude with an outlook what we can expect from Direct Imaging in the future in particular in the era of Extremely Large Telescopes.