Observing the sky from Earth is often hindered by the whims of our atmosphere, which blurs the light from stars and galaxies. A recent mathematical innovation could change the game by making images from ground-based telescopes as sharp as possible, without needing to leave our planet.
The new algorithm, named ImageMM, was developed by mathematician Yashil Sukurdeep from Johns Hopkins University. It relies on the Majorization-Minimization method, a mathematical approach that models how light passes through the turbulent atmosphere. By understanding these distortions, the algorithm can correct them digitally, revealing details that were once hidden. Tests on the 8-meter (26-foot) Subaru telescope, located on Mauna Kea in Hawaii, showed significant improvements over previous techniques.
Comparison of a typical Subaru image (left), its enhancement with previous techniques (center), and the final result with ImageMM (right).
Credit: Yashil Sukurdeep (Johns Hopkins University) et al/Subaru Telescope. Earth's atmosphere acts like a moving veil, distorting light through variations in temperature, pressure, and suspended particles. This phenomenon, called "seeing" by astronomers, makes stars twinkle and reduces image sharpness. To address this, scientists use adaptive optics systems that adjust telescope mirrors in real time, but these methods don't eliminate all imperfections. ImageMM goes further by analyzing a series of imperfect observations to reconstruct an almost ideal image, as if viewing through perfectly calm air.
The intended application for ImageMM is the Vera C. Rubin Observatory in Chile, which will begin its scientific operations this year. One of its goals is to map dark matter in the Universe by measuring how its mass slightly distorts light from galaxies, an effect called weak gravitational lensing. By refining images, the algorithm will enable detection of these distortions with increased accuracy, essential for unraveling the mysteries of this invisible component of the Universe.
Although space telescopes like Hubble and James Webb provide higher quality images, they have a limited field of view. In contrast, Vera C. Rubin covers a large portion of the sky, equivalent to seven full moons. By combining this coverage with the sharpness provided by ImageMM, astronomers will be able to conduct large-scale studies with improved resolution. As emphasized by Tamás Budavári from Johns Hopkins, even a small gain in quality can have a huge impact on observations from billion-dollar ground-based observatories.
The promising results from ImageMM pave the way for a new era in ground-based astronomy. By pushing the limits of resolution, this tool could help answer fundamental questions about the structure of the Universe. The work has been published in
The Astronomical Journal, marking an important step toward clearer and more precise observations from our planet.
Adaptive optics: correcting atmospheric turbulence in real time
Adaptive optics is a technology used in large ground-based telescopes to compensate for atmospheric effects. It works by projecting a laser into the sky to create an artificial reference star, whose fluctuations are continuously measured.
A computer analyzes this data and commands actuators that slightly deform the telescope mirror, several hundred times per second. These adjustments counteract atmospheric distortions, allowing for sharper images.
This technique is particularly useful for observing planets, stars, and nearby galaxies, where resolution is crucial. It has enabled competition with space telescopes for certain applications, without the high launch costs.
However, adaptive optics doesn't completely eliminate blur and can be limited by weather conditions. This is why algorithms like ImageMM complement these systems through post-processing to achieve optimal image quality.