The night sky is clearest from a hill in Antarctica
Antarctica / Alamy
The best place in the world from which to look at the night sky is on top of a hill of ice in Antarctica called Dome A. The hill is one of the coldest locations on Earth.
The telescope images we take on the surface of Earth are often spoiled by the atmosphere, which can be turbulent and make the pictures blurry so that it is difficult to see faint objects clearly. Astronomical “seeing” is how we refer to that blurring.
“Bad seeing smears your images from a telescope,” says Zhaohui Shang at the Chinese Academy of Sciences in Beijing. “At a site with good seeing, a telescope can outperform a similar telescope at a site with worse seeing.”
Shang’s team used a specialised telescope to measure the seeing at Dome A for the first time – researchers already suspected that it had some of the best seeing in the world due to the cold, dry air and the height of the hill.
One of the most important factors for astronomical seeing is the thickness of the boundary layer of the atmosphere, which is where most of the air turbulence caused by weather takes place. Above the boundary layer is the free atmosphere, which is more stable, so it doesn’t blur images as badly.
“At a temperate site, the boundary layer is usually hundreds of metres high or higher, preventing one from reaching the free atmosphere,” says Shang. “However, the median thickness of the boundary layer at Dome A is only 13.9 metres, making it much easier to build telescopes above it.”
A large telescope built on Dome A could take clearer images of fainter objects than a telescope anywhere else on Earth.
Journal reference: Nature, DOI: 10.1038/s41586-020-2489-0
More on these topics: