Ever since Galileo pointed his telescope at the sky 400 years ago, astronomers have been using ever-larger telescopes to explore deeper into our universe. In spite of tremendous advances in mirror technologies, telescope structures and detectors, the main factor that has limited the sensitivity and resolution of ground-based astronomical telescopes has been the inherent turbulent structure of the atmosphere. Atmospheric turbulence can limit the angular resolution of long-exposure ground-based images to about an arcsecond, irrespective of the diameter of the telescope.
However, within the last decade there has been a profound revolution in ground-based optical and infrared astronomy. The development of "adaptive optics" has demonstrated that the blurring effects of atmospheric turbulence can be analysed and corrected. Recent work by Roberto Ragazzoni of the Astronomical Observatory of Padova in Italy, Enrico Marchetti of the Galileo Galilei Centre in Spain and Gianpaolo Valente at Padova University has moved this revolution into an even higher gear (Nature 403 54) with the demonstration that they could correct for the 3-D turbulent structure above their 3.6 m telescope using mathematical techniques similar to those used in medical imaging.
These experiments validate a new approach to adaptive optics that promises the possibility of producing diffraction-limited images from the ground using telescopes with apertures as large as 100 m. The findings have reinvigorated the whole debate on the future of ground-based telescopes and astronomy.
In the April issue of Physics World magazine, Matt Mountain and François Rigaut at the Gemini Observatory, Hawaii, US describe the advantages of adaptive optics.