Good news, everyone! Astronomers have pinpointed the best location on Earth for studying the stars. But if you’re an amateur astronomer hoping to take advantage of this astronomical sweet spot, you’ll have to bundle up, as it’s in the heart of Antarctica, one of the coldest places on the planet.
Dome A — the highest ice dome in the Antarctic Plateau — allows for the clearest views of the starry sky at night, according to new research published this week in Nature. Ice domes are the uppermost portions of ice sheets, rising high above the frozen terrain. Antarctica’s Dome A, while an ideal spot for stargazing, is one of the coldest places on Earth, featuring temperatures as low as -90 degrees Celsius. That’s akin to nighttime on Mars.
Brrr.
So while the new paper proposes an optimal location for doing astronomy, the remote location of Dome A, also known as Dome Argus, presents some considerable challenges. Scientists hoping to set up camp in this location will, in addition to dealing with the extreme cold, have to travel 1,200 kilometres into the interior of the Antarctic continent.
Light pollution poses a problem for both professional and amateur astronomers, but there’s more to a clear view of the night sky than avoiding street lights and skyscrapers. Atmospheric turbulence, while giving stars their characteristic twinkle-twinkle, can hinder clear views into space. Telescopes at mid-latitudes and high elevations, such as those in Hawai’i and Chile, are ideal in this respect, as these observatories take advantage of the weaker turbulence found at these locations.
Astronomers have a metric, called the seeing number, to denote the quality of the night sky view, which they measure in arcseconds. The lower the number, the lower the turbulence, and thus a better view of stars, galaxies, nebulae, and whatever else astronomers are hoping to see. In Hawai’i and Chile, the seeing number is around 0.6 to 0.8 arcseconds.
At Dome C, another ice dome located on the Antarctic Plateau, this number is between 0.23 to 0.36 arcseconds, highlighting the frozen continent as an ideal place to view the night sky. Here, the boundary layer — the lowest part of the Earth’s atmosphere — is exceptionally thin, resulting in less turbulence.
Dome C is great, but as the new paper shows, Dome A is probably better. An international team from China, Canada, and Australia made nighttime measurements at this location, which hadn’t been done before, finding a median seeing number of 0.31 arcseconds and a low of 0.13 arcseconds.
The researchers also did a comparative analysis of the two Antarctic sites. Measurements from Dome A at a height of 8 metres were far better than measurements taken at the same height at Dome C. In fact, measurements from Dome A at this height were equivalent to measurements made at 20 metres at Dome C, revealing the former as the superior location.
“A telescope located at Dome A could out-perform a similar telescope located at any other astronomical site on the planet,” explained Paul Hickson, an astronomer at the University of British Columbia and a co-author of the study, in a UBC press release. “The combination of high altitude, low temperature, long periods of continuous darkness, and an exceptionally stable atmosphere, makes Dome A a very attractive location for optical and infrared astronomy. A telescope located there would have sharper images and could detect fainter objects.”
Not surprisingly, the cold had a detrimental effect on the instruments used in the study, as the researchers’ equipment was disadvantaged by frost. An uncrewed station equipped with a differential image motion monitor tracked Antarctic skies for seven months, with temperatures plummeting to -75 degrees Celsius at times. In the press release, Bin Ma, the first author of the study and a scientist from the Chinese Academy of Sciences in Beijing, said: “In and of itself, that’s a technological breakthrough.” A solution to the frosty problem could improve viewing by 10% to 12%, according to the study.
In addition to astronomy, Dome A “is a natural laboratory for studies of the formation and dissipation of turbulence within the boundary layer,” wrote the authors in their paper. “Future measurements of weather, seeing and the low-altitude turbulence profile could contribute to a better understanding of the Antarctic atmosphere.”
Clearly, building an observatory on the Antarctic Plateau would be a huge logistical undertaking. Supplies and personnel would have to be flown in, while the structure itself would have to endure the extreme cold and possibly even shifts in the ice. Climate change would likely pose additional complications.
Scientists have finally pinpointed the best spot on Earth to do astronomy, but will they actually make it happen? We’re excited to find out.