At more than 4 km above sea level, Lenghu “is known to have exceptionally clear skies,” said Licai Deng, a scientist at the Chinese Academy of Sciences and co-author of the new study. “At the same time, the Lenghu region has spectacular Mars-like scenery.” Deng says the local government, eager to attract tourists interested in astronomy and geography, hired their team to study the area and see if it would be a good place to build an observatory.
Four main factors influence the suitability of a location for astronomical research. The first is whether it tends to have clear skies, which means there are no dense cloud formations and very little light pollution. The second is the stability of air and local weather conditions, and the effect the atmosphere will have on optical and infrared observations at night (even the smallest particles in the air can interfere). The third is whether the site is connected to an infrastructure (such as electricity) and can be accessed without too many problems. And finally, you want an area where the night sky will be protected from human activity.
High altitude places like Lenghu are of great interest to astronomers because there is simply less atmosphere to pass through while looking at objects in space. Researchers monitored the Lenghu area for three years, measuring sky darkness, weather, atmospheric conditions, etc. They found that the area was at least as well ranked for all four factors as other potential sites studied on the Tibetan Plateau. In many ways, the researchers believe, this could be better than existing sites in Hawaii and Chile. There is less variability in air temperatures and more stable atmospheric conditions, and the sky is slightly clearer. The amount of water vapor in the air is also small, which is particularly useful for infrared observations important to cosmology. About three decades of weather records reveal an average of 0.71 inches of rain per year. “In this context, Lenghu has the potential to accommodate large facilities,” explains Deng.
In the long run, Lenghu may be better protected from the effects of human activity than Hawaii or Chile. The city adopted rules in 2017 to preserve the dark skies, so light pollution is expected to be kept to a minimum.
“The results presented for the Lenghu site are almost as good as those found for Mauna Kea, which is widely regarded as one of the best sites in the world,” says Paul hickson, an astronomer at the University of British Columbia in Vancouver, who has previously performed field tests at Dome A in Antarctica. “What is particularly attractive about this place is the attention paid to controlling light pollution.
In some ways, this new research is an affirmation of China’s current astronomical plans for the region around Lenghu. These plans include a 2.5-meter imaging study telescope that began construction this year, a 1-meter infrared solar telescope that will be part of an international array of eight telescopes, and two more at 1.8 meter and 0.8 meter, for planetary science.
As Deng points out, Tsinghua University and the University of Arizona are working together on the construction a 6.5-meter telescope to operate on the summit of Saishiteng mountain. And there are emerging plans for a 12-meter telescope to be installed there as well. “There will be a lot of people at the top of the mountain,” Deng said.
These instruments will go a long way to put China on the map when it comes to infrared and optical astronomy – they are comparable to some of the “big” telescopes operating in places like Chile. But they remain pale in comparison to “extremely large” observatories built around the world, like the giant 24.5-meter Magellan telescope in Chile, the thirty-meter telescope in Hawaii, and the extremely large 39.3-meter telescope in Chile. The kind of science that these instruments could achieve should usher in a new era of astronomy. If China is serious about implementing a more ambitious astronomy program, it will have to catch up fairly quickly.
So it’s a good thing he has the Tibetan plateau. “High, dry, isolated mountains are usually the best places for astronomy,” says Hickson. “There may well be other potential sites, perhaps even better ones, on the Tibetan Plateau that have yet to be explored.”