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Stephen Chen

Astronomer Liu Yu remembers vividly the scare he got when he watched one of his teammates collapse to the ground last year. Face swollen, lips cracked, he could barely breath, gasping for what little oxygen he could suck from the thin air.
Fighting a headache of his own, Dr Liu pulled out one of their last oxygen bags. His partner seized it and inhaled hungrily. The bag was empty in just minutes.

Liu cursed the lifeless wasteland around them. This wasn't another planet, it was Ali prefecture, Tibet. Altitude: 4,500 metres. And these astronomers were on a mission.
The oxygen bags had been graciously supplied for free by the prefecture's governor, who was hoping to curry favour with the men. The bags were said to be the best in the region. They leaked.
It was a dire scenario that Liu does not want to repeat.
A researcher with the Yunnan Astronomical Observatory, Liu is the leader of a mainland astronomy team conducting site surveys for the location of an unprecedented solar telescope, construction of which is slated to begin in 2016.
Because of its thin atmosphere and clear skies, Tibet is perfect for the study of astronomy. But it's hell for astronomers.
The Chinese Giant Solar Telescope, as it is being referred to, would be by far the world's largest "eye" on the sun if construction finishes in 2020, as hoped. There are other potential sites, such as in Yunnan and Sichuan provinces, but the strong possibility of using Tibet has generated controversy.
"Tibet is one of the few places on earth where you want to both stay and escape at the same time," Liu said.
"When I introduced Tibet as a candidate, some of my colleagues jumped up and questioned our sanity. With the region's average altitude of more than 4,500 metres, most scientists working there would be troubled by headaches or altitude sickness caused by the lack of oxygen. Some of the world's best astronomers said they would not visit if we built the facility in Tibet."
And the challenges extend far beyond simply the risk of altitude sickness. Ali prefecture has about 95,000 residents spread out over an area of just over 300,000 square kilometres.
"We won't be able to hire enough local hands to build the huge facility," Liu said. "And to maintain a sophisticated scientific base in a region that can't even supply reliable oxygen bags, the cost will be astronomical."
Putting the world's largest solar telescope in Tibet would also make a strong political statement. Liu said some government agencies have insisted they put the telescope in Tibet, because of the value to China politically.
Since the Dalai Lama fled Tibet for India in the 1950s, the Chinese government has been under constant international pressure to give Tibet greater freedom and autonomy. The monumental telescope, with an investment of more than US$80 million, according to Xinhua, would signify China's control and presence in the region.
"The political element plays an important role in a large telescope's location," Liu said. "Our telescope atop Dome A, [the highest ice feature] in Antarctica, is a similar example."
The new project was prompted because of mankind's limited understanding of the sun.
Though it had been known for more than a century that the sun had an active magnetic field, which affects communications on Earth, it wasn't until recently that scientists realised the strongest solar magnetic activity did not occur on the sun's surface, but on its corona - a rare gaseous envelope that is normally visible only during a total solar eclipse. Scientists hope that mapping the magnetic field of the corona, which would be one of the key missions of the Chinese solar telescope, can give us clues to solving some of the biggest mysteries about the sun.
For example, it could help scientists develop much more precise mathematic models to describe and predict solar magnetic storms that have adverse effects on earth, from interfering with cellphone reception to putting astronauts in the International Space Station at risk.
But coronal magnetic fields are hard to measure, as the corona is darker than the surface of the sun. As light goes through a magnetic field, its spectrum splits. The stronger the field, the more splits occur on a spectrograph. Scientists have used this phenomenon to measure the magnetic field of the sun.
But the dimness of the corona means help is required from a telescope larger than any that has been built, in order to capture enough "splits" for extremely accurate measurements.
The aperture on the planned Chinese telescope would have a massive diameter of more than eight metres. That's several times larger than most solar telescopes used by professional astronomers, and about five times larger than the world's current biggest solar telescope.
The second-biggest one now being planned - the Advanced Technology Solar Telescope - will be located in Hawaii by about 2016, with an aperture diameter of a little over four metres.
However, China's plans to construct a solar telescope of such magnitude brings immense challenges, one of the most formidable being heat. Unlike telescopes that are aimed at far more distant celestial objects, such as other stars, planets and galaxies, solar telescopes aimed at our sun are at risk of being fried by the magnified rays.
The energy collected by a reflective surface with a diameter of eight metres could melt most metals, Liu said.
Though solar astronomers rarely try to capture the entire sun in one viewing - opting instead to focus on areas as small as 20 square kilometres, one at a time, and then putting them all together - the heat can still raise the temperature on the telescope's delicate light sensor to more than 100 degrees Celsius.
"It can be so hot that air close to the sensor heats up enough to cause turbulence that ruins an image," Liu said.
All existing solar telescopes on the mainland keep their light sensors in an air-tight enclosure in which heat can quickly build up and not easily escape. If something goes wrong in the chamber, it could mean weeks, if not months, of troublesome maintenance involving the opening and sealing of the chamber.
But many scientists have questioned the feasibility of creating such a massive solar telescope. And finding a lens manufacturer able to meet the astronomers' specifications could also be difficult.
Astronomers at Purple Mountain Observatory in Nanjing have proposed a multiple-mirror design, but that would also be met with technical challenges, such as how to piece together hundreds of mirrors to make them work as one with minimal distortion to the images.
Liu said he missed his days working in the United States years ago. Unlike China, which puts most of its resources into a few very large projects, the US builds about 20 smaller but highly advanced solar telescopes almost every decade, keeping them up-to-date - and they often produce exciting results.
"When I worked in observatories in Hawaii, I would drive a few kilometres to the hilltop and work for a few hours. Then I could come down to the beach and scuba dive. I'd be grateful to just be alive [if I were working] in Tibet," he said.
However, politicians aside, not every one in Liu's field shares his apprehension about putting the telescope in Tibet.
Dr Zhang Mei, a researcher with the National Observatory in Beijing, said she was indifferent about the telescope's location, as long as it could produce the best images possible.
"I don't think I will man the telescope," she said. "Most of the work, I hope, will be done by remote control. We should be able to sit in our office in Beijing and get first-hand results."
Dr Zhang Hongqi, also a researcher with the National Observatory, said he favoured Tibet because of its pristine sky. He also said the final decision on where to place the telescope would be made by scientists, not politicians, contrary to what Liu believes.
"To make unprecedented discoveries, we may need to make unprecedented personal sacrifices," Zhang said.


Staring at the sun from the roof of the world

Two powerful Nasa telescopes atop a Hawaiian volcano. Photo: Reuters

Birds fly over Bam Co Lake in a lonely corner of Tibet. Photo: Xinhua

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China

Proposal to put China's US$80m sun-gazing telescope in Tibet's highlands - known as hell for astronomers - triggers political and scientific debate


Staring at the sun from the roof of the world

.css-1c6uqr6{color:inherit;font-weight:inherit;font-size:inherit;font-family:inherit;line-height:inherit;overflow-wrap:break-word;}Proposal to put China's US$80m sun-gazing telescope in Tibet's highlands - known as hell for astronomers - triggers political and scientific debate

Proposal to put China's US$80m sun-gazing telescope in Tibet's highlands - known as hell for astronomers - triggers political and scientific debate