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The science of extra-solar planets is one of the most rapidly changing areas of astrophysics and since 1995 the number of planets known has increased by almost two orders of magnitude. A combination of ground-based surveys and dedicated space missions has resulted in 560-plus planets being detected, and over 1200 that await confirmation. NASA's Kepler mission has opened up the possibility of discovering Earth-like planets in the habitable zone around some of the 100,000 stars it is surveying during its 3 to 4-year lifetime. The new ESA's Gaia mission is expected to discover thousands of new planets around stars within 200 parsecs of the Sun. The key challenge now is moving on from discovery, important though that remains, to characterisation: what are these planets actually like, and why are they as they are?
In the past ten years, we have learned how to obtain the first spectra of exoplanets using transit transmission and emission spectroscopy. With the high stability of Spitzer, Hubble, and large ground-based telescopes the spectra of bright close-in massive planets can be obtained and species like water vapour, methane, carbon monoxide and dioxide have been detected. With transit science came the first tangible remote sensing of these planetary bodies and so one can start to extrapolate from what has been learnt from Solar System probes to what one might plan to learn about their faraway siblings. As we learn more about the atmospheres, surfaces and near-surfaces of these remote bodies, we will begin to build up a clearer picture of their construction, history and suitability for life.
The Exoplanet Characterisation Observatory, EChO, will be the first dedicated mission to investigate the physics and chemistry of Exoplanetary Atmospheres. By characterising spectroscopically more bodies in different environments we will take detailed planetology out of the Solar System and into the Galaxy as a whole.
EChO has now been selected by the European Space Agency to be assessed as one of four M3 mission candidates.
Two major astronomical experiments are underway at the US Amundsen-Scott South Pole Station. The first is the South Pole Telescope, a 10m sub-millimetre telescope designed to measure primary and secondary anisotropies in the CMBR, with the aim of placing constraints on the equation of state for dark energy. The second is the IceCube neutrino observatory, which will be a cubic kilometre array designed to image sources of high energy neutrinos.
The ALADDIN concept is an integrated Antarctic-based L-band experiment whose purpose is to demonstrate nulling interferometry and to prepare the DARWIN mission. Because of their privileged location, the relatively modest collectors (1 m) and baseline (up to 40 m) are sufficient to achieve a sensitivity (in terms of detectable zodi levels) which is about twice better than that of a nulling instrument on a large interferometer (such as GENIE at the VLTI), and to reach the 20-zodi threshold value identified to carry out the DARWIN precursor science. These numbers are based on a preliminary design study by Alcatel Alenia Space and were obtained using the same simulation software as the one employed for GENIE. The integrated design enables top-level optimization and full access to the light collectors for the duration of the experiment, while reducing the complexity of the nulling breadboard.
We have conducted K band interferometric observations of four nearby main-sequence Vega-like stars at the VLTI with very long baselines. The very high resolution allowed us to probe the innermost region of the disks, where planets are supposed to be formed. The diameters of three bright and nearby prototypes β Pictoris, Fomalhaut (α PsA) and ∊ Eridani as well as τ Ceti have been measured with VINCI, the VLTI commissioning instrument, with a high accuracy. The derived diameters were used to constrain their age with help of the evolution code CESAM. The precision achieved with VINCI allowed us to discuss the shape of their photosphere and the possible detection of warm circumstellar material within the narrow interferometric field of view.
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