Telescope Upgrade Brings Super-sharp Images

July 18, 2018
3 minutes read
Telescope Upgrade Brings Super-sharp Images

ESO’s Very Large Telescope (VLT) has just received an upgrade. Experts have attached a new adaptive optics mode called laser tomography.

This new upgrade tells us how far we’ve come.

The Very Large Telescope consists of four telescopes with 8.2-meter (27-foot) mirrors in northern Chile’s Atacama Desert. Today, scientists at the observatory have released the first observations taken with laser tomography. The new adaptive optics mode on its GALACSI unit, which works alongside a spectrograph instrument called MUSE on one of the telescopes.

Adaptive optics produce sharper images by compensating for interference from the atmosphere. To do so, the system tracks a specific star to watch how the atmosphere muddles its light. Then it adjusts the viewing system to reverse that blurring effect, producing images that are much less fuzzy.

The same turbulence in the atmosphere that causes stars to twinkle to the naked eye results in blurred images of the Universe for large telescopes. Light from stars and galaxies becomes distorted as it passes through our atmosphere. So, astronomers have to do something to improve image quality artificially.

Neptune, seen by the Very Large Telescope before and after adaptive optics
Image: ESO/P. Weilbacher (AIP)

Creating Artificial “Stars”

The new picture of Neptune taken from the VLT is breathtaking. But astronomers don’t want to be limited to observing objects located near stars that they can use for this compensation process. So, to avoid this problem of using natural stars, some adaptive-optics systems use lasers to create their own “stars.”

Galacsi is the new system of the VLT that runs adaptive optics in just this way. It relies on four lasers as “guide stars.” The lasers shine bright orange, with each beam stretching about a foot (30 centimeters) across. The VLT then uses the blur on the laser to inform a computer-controlled mirror that constantly changes shape.

The system watches how those lasers change because of atmospheric turbulence. Therefore, it signals the telescope’s bendable mirror to recalibrate in precisely the right manner to invalidate the turbulence. That process repeats about 1,000 times per second, according to the facility.

It’s really important that we keep upgrading our telescopes so that we can keep studying the objects out there and learn more about them.

However, the current update is indeed something great.

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

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