Large ground based telescopes can make images as sharp as or sharper than the Hubble Space Telescope, but only if atmospheric blurring is corrected. Previously, the deformable mirrors available to do this were small, flat, and relatively inflexible. They could be used only as part of complex instruments attached to conventional telescopes.
But in this new work, one of the two mirrors that make up the telescope optics is used to make the correction directly. The new secondary mirror makes the entire correction with no other optics required, making for a more efficient and cleaner system.
Like other secondary mirrors, this one is made of glass over 2 feet in diameter and is a steeply curved dome shape. But under the surface, it is like no other. The glass is less than 2 millimeters thick (less than eight-hundredths of an inch). It literally floats in a magnetic field and changes shape in milliseconds, virtually real-time. Electro-magnetically gripped by 336 computer-controlled “actuators” that tweak it into place, nanometer by nanometer, the adaptive secondary mirror focuses star light as steadily as if Earth had no atmosphere. Astronomers can study precisely sharpened objects rather than blurry blobs of twinkling light.
Source (emphasis added by me):
Cool!