Adaptive optics bring sky into focus
Blurry images of space could soon be a thing of the past. Astronomers at the European Southern Observatory's (ESO) Very Large Telescope (VLT) have obtained their first corrected pictures of space with the Multi-Conjugate Adaptive Optics Demonstrator (MAD). The MAD device allowed the scientists to obtain corrected (non-blurred) images in spite of atmospheric turbulence. This meant the images they received were of near-space quality, a world premiere, and also a promising sign for the crucial technology to be used in Extremely Large Telescopes, according to ESO. 'Telescopes on the ground suffer from the blurring effect induced by atmospheric turbulence. This turbulence causes the stars to twinkle in a way which delights the poets but frustrates the astronomers, since it blurs the fine details of the images,' said ESO. The images were obtained using Adaptive Optics (AO) techniques. Adaptive Optics systems work by means of a computer-controlled deformable mirror (DM) that counteracts the image distortion induced by atmospheric turbulence. It is based on real-time optical corrections computed from image data obtained by a 'wavefront sensor' (a special camera) at very high speed, many hundreds of times each second. Although the technique dates back to 1989 when it was first used at the La Silla Observatory, it wasn't until now that AO systems have been able to correct distortion for small portion of the sky, in this case up to 15 arcseconds. The test 'pictures' were taken on 25 March and centred on three 11 magnitude stars within a 1.5 arcminute diameter circle of sky in Omega Centauri. The telescope will now be used to observe this region for a number of nights so as to determine how well the equipment performs depending on different viewing conditions. 'The aim of MAD is to prove the feasibility and performances of new adaptive optics techniques,' said Norbert Hubin, head of the AO group at ESO. The findings from these tests will prove critical to the development of future instruments, for both the Very Large Telescope and the Extremely Large Telescope, he explained. The Director General of ESO, Catherine Cesarsky, said: 'This is a tremendous achievement that opens new perspectives in the era of extremely large telescopes.'