Very Large Telescope In Chile Captures Remarkably Sharp Images Of Neptune

Rodiano Bonacci
Luglio 21, 2018

The VLT is made out of four telescopes that sport 8.2 meter mirrors and the photos were taken with laser tomography, which is the new adaptive optics mode on the GALACSI unit. But there isn't now a spacecraft orbiting Neptune, so if scientists want pictures, they need to take them from 2.9 billion miles away.

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.

The ESO says such sharpness is very hard to attain and allows images to be taken that are comparable in sharpness to those taken with the Hubble telescope that doesn't have to deal with the atmosphere at all.

Very Large Telescope (VLT) has achieved first light with a new adaptive optics mode called laser tomography - and has captured remarkably sharp test images of the planet Neptune, star clusters and other objects. The image on the left shows the view of Neptune with the upgrade installed, compared to its previous resolution on the right. If you want to observe from the ground, you have to find a way to correct for the blur, and if you want to know how much blur to correct for, you need to a reference point. Although there is one drawback - the new form of correction (which is also a form of tomography) only works over a small area of the sky. ESO commented that it is now possible to capture images from the ground at visible wavelengths that are "sharper than those from the NASA/ESA Hubble Space Telescope".

The adaptive optics system relies on four bright lasers attached to the VLT-4 telescope that shoot 30-centimetre-wide orange beams into the sky that stimulate sodium atoms in the atmosphere, creating artificial guide stars.

This isn't the observatory's first adaptive-optics rodeo: Another system, GRAAL, is already in use with infrared camera HAWK-I; in a few years, the powerful new ERIS instrument will follow suit.

VLT's MUSE instrument in narrow-field mode was used along with the GALACSI adaptive optics module to correct for turbulence at different altitudes in the atmosphere.

The new method results in sharper and more detailed images. A secondary mirror corrects the atmospheric distortion as turbulence is measured in real time.

No longer limited by atmospheric blur, cosmologists can examine-"in unprecedented detail"-objects like supermassive black holes at the centers of distant galaxies, jets from young stars, globular clusters, supernovae, planets and their satellites, yada yada yada".

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