New technology allows ground telescope to capture sharper images than Hubble

In 1610, Galileo used a telescope to discover Jupiter's four largest moons, and for more than two hundred years the only way to better see the night sky was to build a larger telescope. In the 19th century, astronomers began carrying telescopes up the mountains to reduce the amount of atmospheric interference blurring their sightings. In 1968, astronomers reached the ultimate high-altitude telescope by successfully launching the first orbiting space telescope, the Orbit Observatory in Orbit 2 (OAO-2).

Scientists working on OAO missions may have thought that they had finally discovered the best type of telescope, a high above deforming air from the atmosphere. But by using a new technology called Adaptive Optics – a deformable mirror system with lasers that can correct atmospheric interference in real time – astronomers have managed to take a sharper Neptune image with a ground telescope than even the powerful Hubble Space Telescope.

ESO / P. Weibacher (AIP) / NASA, ESA and MH Wong and J. Tollefson (UC Berkeley)

The Very Large Telescope (VLT) in the Atacama Desert in Chile, operated by the European Southern Observatory (ESO), has been steadily improving its adaptive optics for almost two years. The GALACSI system (Adaptive Atmospheric Layer Corrector for Spectroscopic Imaging) works with a variety of instruments on the telescope – four 8.2 meter telescopes – to perform observations over a wide range of the electromagnetic spectrum ( different wavelengths or colors of light).

The latest update combines GALACSI with the Multi Unit Spectroscopic Explorer (MUSE) instrument, working with the VLT 4 Unit telescope. MUSE is able to Imagine the Night Sky Both Field Fields Previously, in wide field mode, GALACSI and MUSE were used to correct atmospheric interference up to one kilometer above the telescope.

ESO / P. Weibacher (AIP)

Now, in narrow field mode, GALACSI and MUSE have used a new adaptive optics technology called laser tomography to correct almost all atmospheric interferences disturbing the telescope, although for a smaller area of ​​the sky. The technology works by firing four orange lasers into the sky, each 30 centimeters in diameter, to serve as artificial guiding stars. Thick lasers excite the sodium atoms in the upper atmosphere, revealing the amount of turbulence in the air. The system can then measure atmospheric interference and use actuators to deform a thin and flexible secondary mirror up to a thousand times per second to correct fuzzy light.

The resulting images are almost as sharp as if the telescope were in space, and the VLT telescopes are more than three times the size of Hubble, the images of space are even more fantastic. The new Adaptive Optics technology has been used for the Neptune image, as well as clusters of stars and other objects.

ESO / S. Kammann (LJMU)

Adaptive optics was invented for the first time in the 1950s, but it was only in the 1990s that the computer has evolved sufficiently to allow a mirror to be made with the required speed and accuracy. However, what was true for Galileo is still true for astronomers today – if you want to better see the night sky, build a larger telescope – that's why ESO is working on a telescope monster to drown even the VLT: Extremely Large Telescope (ELT).

When we turn on the ELT, equipped with adaptive optics technology, just like the VLT, who knows what we'll see.

Roland Bacon