A cosmic mystery: Is China building the world’s biggest telescope?

Top American astronomers are hunting for clues about a giant that Beijing isn’t talking about.

There are signs that China is building a giant telescope to explore the universe. Picture: Cfoto/DDP/Zuma Press

Astronomer Robert Kirshner investigates some of the universe’s biggest questions: What happens when a star explodes? Is the universe still expanding?

The Harvard emeritus professor recently added a new mystery to the list: Is China quietly building the world’s biggest telescope? He would like to know, because he leads a rival telescope project in the US.

There are clues. In January, state-owned Nanjing Astronomical Instruments said on social media it had won a $US22m ($33.5m) bid for a dome to surround a 14.6m telescope. In an April post, students visiting a science institute mentioned researchers showing them mirror arrangements for such a telescope. And a top Chinese astronomer told state media he wanted to finish the telescope before he retires.

Yet Chinese officials have not directly acknowledged the observatory, which would threaten American technological leadership and potentially give Beijing a military advantage.

“You would expect, normally, some kind of chest thumping,” Professor Kirshner said.

China’s leading astronomer and his institute, a national research organisation that appears to be in charge of the telescope, did not return requests for comment.

If China is building the big scope: “Why the hell are they doing that?” said Matt Mountain, head of the non-profit organisation that manages observatories, as well as the Hubble and James Webb space telescopes, for the National Aeronautics and Space Administration.

Dr Mountain has two hypotheses. First, astronomical advances benefit both scientific and military purposes, as astrophysicist Neil deGrasse Tyson highlighted in his book, Accessory to War. Huge telescopes can look at military satellites, not just stars and planets.

The James Webb space telescope’s mirror has a 6.4m diameter. Picture: Laura Betz/NASA/AP

The second: Beijing is investing in astronomy to inspire children to enter the sciences – so it can surpass the US in a couple of decades. “Astronomy is an entry-level drug for science, technology, engineering and math,” Dr Mountain said.

By Professor Kirshner’s count, 18 of the 23 astrophysics-focused Nobel prize winners in the past half-century worked in America.

While space telescopes such as the James Webb get more attention, those on the ground still matter. They are easier to service and much bigger, offsetting disadvantages such as light pollution and atmospheric distortions.

Bigger telescopes mean sharper images, making it easier to determine the distance between faraway objects, Professor Kirshner said. Astronomers can then discover more planets orbiting stars in the Goldilocks temperature range that could support life.

The Hubble and Webb space telescopes have mirrors with diameters of about 2.5m and 6.5m, respectively. The four biggest on Earth – one in Spain and three in the US – are all roughly 10m in diameter. Professor Kirshner’s Thirty Meter Telescope group, an international project with US, Canadian, Indian and Japanese institutions, proposes a 30m telescope on Hawaii’s Big Island.

These giant telescopes cost roughly $US1bn to $US2bn, Dr Mountain said, and costs rise with size. They also take years to build.

Professor Kirshner realised it would help make the case in Washington for funding if he could show China was building one too. His best sources have been Chinese-speaking peers who informally confirmed the development of a telescope site on the Tibetan Plateau, in China’s southwest. Dr Mountain says Chilean astronomers told him China was also exploring a southern hemisphere observatory in Chile.

Armed with the information, Professor Kirshner met congressional staffers and National Science Foundation officials.

A 39m European telescope, set to be the world’s biggest, is under construction in Chile. Picture: Rodrigo Arangua/AFP/Getty Images

He ran into a roadblock in May, when President Donald Trump proposed to congress that the NSF’s annual budget be cut to $US4bn from $US9bn. Mr Trump’s science and technology adviser said then that scientific progress had stalled in some fields and more money wouldn’t necessarily mean more scientific impact.

In its budget request, the NSF proposed advancing only the Giant Magellan Telescope, backed by a California-headquartered consortium. At 25.3m wide, the Magellan would be bigger than China’s but smaller than Professor Kirshner’s proposed telescope.

Professor Kirshner got a reprieve in mid-July. A Senate spending committee recommended minimal cuts to the NSF, and said it supported both the Magellan and his Thirty Metre projects.

The Wall Street Journal