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Posted: Jun 10, 2014
First images from exoplanet hunter SPHERE
(Nanowerk News) The European SPHERE instrument has been successfully installed on ESO's Very Large Telescope (VLT) and has achieved first light. This powerful new facility can directly image gas-giant exoplanets and dust discs orbiting nearby stars (up to 300 light years away) with unparalleled precision and contrast. SPHERE (the Spectro-Polarimetric High-contrast Exoplanet REsearch) instrument was developed by a European consortium (1) led by the Institut de Planétologie et Astrophysique de Grenoble (IPAG, CNRS/Université Joseph Fourier) with the French Aerospace Lab ONERA, Laboratoire d'Astrophysique de Marseille (CNRS/AMU), Laboratoire d’Etudes Spatiales et d’Instrumentation en Astrophysique (Observatoire de Paris/CNRS/UPMC/Université Paris Diderot), Laboratoire Lagrange (Observatoire de la Côte d’Azur/CNRS/Université Nice-Sophia Antipolis), together with institutes in Germany, Italy, Switzerland and the Netherlands, in partnership with ESO (European Southern Observatory). The instrument will be made available to the astronomical community in 2015.
During its first light observations, SPHERE validated its various observation modes and captured unprecedented images, demonstrating its impressive ability to suppress the glare of the bright star at the center of the image. Led by the Principal Investigator Jean-Luc Beuzit, CNRS senior researcher at IPAG, the researchers were able to obtain one of the best images to date of the ring of dust around the star HR 4796A, very high definition images of Titan, and the first examples of detection of faint companions to nearby stars. These first images confirm the impressive performance of the instrument.
The existence of over a thousand planets orbiting stars other than the Sun has already been established. Most of them were discovered by observing the variations in brightness caused by a planet passing in front of its host star (planetary transit technique) or by observing the motion of a star caused by planets in orbit around it (radial velocity technique). Until now, only a few planets have been detected by direct imaging of the planet next to its host star.
SPHERE's main goal is to detect and characterize giant exoplanets orbiting nearby stars by direct imaging. This is a major challenge as such planets are both very close to their host stars and also very faint. SPHERE will be able to detect the signal from a planet up to a million times fainter than its host star, which is more than an order of magnitude better than existing instruments. In a normal image, even if obtained under the best conditions, the light from the star completely swamps the weak glow from the planet. The whole design of SPHERE is therefore based on the need to obtain the highest possible contrast in the immediate neighborhood of the star. By analogy, if SPHERE were in Paris, it would be able to detect the light of a candle 50 cm from a lighthouse in Marseille.
Meeting both technological and scientific challenges, SPHERE is one of the most complex ground-based astronomical instruments ever built. In particular, it includes an advanced adaptive optics system that uses a deformable mirror comprising over 1300 actuators that correct the effects of atmospheric turbulence, on the nanometer scale, more than 1200 times per second. SPHERE also includes coronographic masks to block out the light from the central star, and three light detection modules using differential imaging, spectroscopic and polarimetric techniques at visible and near infrared wavelengths. SPHERE's powerful performance was achieved through the early development of new technologies, particularly in the areas of adaptive optics, special detectors and coronographic components.
It took more than twelve years for all the laboratories and organizations involved to design and build SPHERE. Around 120 researchers, engineers and technicians took part in the various stages of the project. SPHERE's materials budget amounts to €10 million, funded by ESO, the European OPTICON program, and national agencies, including €1 million for CNRS.