Incredible Image of Neptune Taken From Earth With System of Deformable Mirrors, Lasers

This image of the planet Neptune was obtained during the testing of the Narrow-Field adaptive optics mode of the MUSE/GALACSI instrument on the European Southern Observatory's Very Large Telescope. ESO/P. Weilbacher (AIP)

Using an Earth-based telescope, astronomers have captured a remarkable photo of the planet Neptune—which is sharper even than pictures taken by the Hubble Space Telescope—with the help of an advanced new imaging technique.

The approach involves a new "adaptive optics" system known as "laser tomography," which corrects for turbulence at different altitudes in our planet's atmosphere via a system of deformable mirrors and lasers.

This turbulence, also known as "astronomical seeing," is a problem that all ground-based telescopes face. It causes light from objects in the universe to become distorted as it passes through the atmosphere resulting in blurred images.

European Southern Observatory (ESO) scientists took the picture with the Very Large Telescope in the Atacama Desert, Chile, using the Unit Telescope 4 in combination with the MUSE instrument (Multi Unit Spectroscopic Explorer) and an adaptive optics unit known as GALACSI (Ground Atmospheric Layer Adaptive Corrector for Spectroscopic Imaging).

To counter the atmospheric turbulence, four brilliant lasers attached to UT4 project columns of intense orange light 30 centimeters in diameter into the sky. This excites sodium atoms high in the atmosphere creating an artificial source of light known as a laser "guide star" which is used as a reference.

The adaptive optics system uses the light from the artificial "star" to determine the turbulence in the atmosphere and calculate corrections one thousand times per second. While this is happening, instructions are sent in real-time to a deformable mirror in UT4 which constantly alters its shape to adjust for the distorted light.

"With this new capability, the 8-meter UT4 reaches the theoretical limit of image sharpness and is no longer limited by atmospheric blur," an ESO statement read. "This is extremely difficult to attain in the visible and gives images comparable in sharpness to those from the Hubble Space Telescope."

"It will enable astronomers to study in unprecedented detail fascinating objects such as supermassive black holes at the centers of distant galaxies, jets from young stars, globular clusters, supernovae, planets and their satellites in the Solar System and much more."

The Very Large Telescope is ESO's flagship facility and the world's most advanced visible-light astronomical observatory, consisting of four Unit Telescopes with main mirrors measuring 8.2 meters in diameter.

The telescopes can work together by combining light beams they detect using a complex system of subterranean mirrors in order to reconstruct images with a resolution equivalent to distinguishing the two headlights of a car at the distance of the Moon.