C. Snodgrass1, J. Skottfelt2, C. Mackay3, M. Dominik4 and the GravityCam Consortium 1 Institute for Astronomy, University of Edinburgh, UK. csn@roe.ac.uk 2 Centre for Electronic Imaging, The Open University, Milton Keynes, UK, 3 Institute for Astronomy, University of Cambridge, UK, 4 Centre for Exoplanet Science, SUPA School of Physics & Astronomy, University of St Andrews, UK GravityCam: A wide-field high-resolution imager for the NTT Other scientific applications 1. Einstein, A., “Erklarung der perihelbewegung des merkur aus der allgemeinen relativitatstheorie“, Sitzungsber. Kgl. Preuss. Akad. Wiss. , 831{839 (1915). 2. Paczynski, B., “Gravitational microlensing by the galactic halo”, ApJ 304, 1{5 (May 1986). 3. Bennett, D. P. and Rhie, S. H., “Simulation of a Space-based Microlensing Survey for Terrestrial Extrasolar Planets”, ApJ 574, 985{1003 (Aug. 2002). 4. OGLE-IV http://ogle.astrouw.edu.pl 5. Beaulieu, J. P. et al. , “Discovery of a cool planet of 5.5 Earth masses through gravitational microlensing”, Nature 439, 437{440 (Jan. 2006). 6. Ivezic, Z. et al., “LSST: from Science Drivers to Reference Design and Anticipated Data Products”, ArXiv e-prints (May 2008). 7. Baldwin, J. E. et al., “Difraction limited 800 nm imaging with the 2.56 m Nordic Optical Telescope”, A&A 368, L1-L4 (Mar. 2001). 8. Mackay, C. D. et al., “Subelectron read noise at MHz pixel rates”, Proc. SPIE 4306, 289{298 (May 2001). Abstract With its high frame-rate and wide-field, GravityCam can: • Provide a unique database for optical variability • stellar variability and asteroseismology • sub-second variability from accretion onto compact objects • Explore galactic star clusters • detection of tight binaries and their eclipse features • proper motion measurements for kinematic studies • Trace Dark Matter in the Universe through weak gravitational lensing • Study Solar System objects • resolve the orbits of binary asteroids • discovery of small bodies in the Kuiper Belt and Oort Cloud. We have developed a new concept for a ground-based imaging instrument called GravityCam, capable of delivering significantly sharper images from the ground than is normally possible without adaptive optics. Images recorded at high speed can be aligned before combination and can yield a 2-3 fold improvement in image resolution, or be used separately for high-cadence photometry. Very wide survey fields are possible with wide-field telescope optics. GravityCam is proposed to be installed at the NTT, where it will enable detection of Earth sized planets by gravitational microlensing and weak shear studies of dark matter distribution in distant clusters of galaxies, produce a vast dataset for asteroseismology and stellar variability, and help us understand the population of the Kuiper belt and the Oort cloud via stellar occultations. Lucky Imaging Next steps Gravitational microlensing1,2 is the only way to obtain population statistics of cool low-mass exoplanets and exomoons. A GravityCam microlensing survey will provide sensitivity down to Lunar mass, a territory widely considered to be reserved for space missions like WFIRST3. High spatial resolution means that it will be sensitive to fainter source stars and thereby be able to detect planets 100 less massive than what is possible with the current state-of-the-art survey OGLE-IV4. Detecting lunar-mass exoplanets GravityCam will detect planets that are virtually undetectable by other methods. This figure shows the planets detected to date where we see that for planets of Earth-mass and below detections are very few though we expect there are vast numbers of them. Lucky Imaging6,7 takes images rapidly (10-30 Hz) and aligns them, almost completely eliminating the tip-tilt distortions caused by atmospheric turbulence, improving the median seeing by a factor between 2.5 and 3. If we use a small fraction of the images and add the sharpest ones together we find that image resolution is improved further to a total of a factor of 4 wit