27-07-2025
A cosmic mystery: Is China building the world's biggest telescope?
Astronomer Robert Kirshner investigates some of the universe's biggest questions: What happens when a star explodes? Is the universe still expanding?
He 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 U.S.
There are clues. In January, state-owned Nanjing Astronomical Instruments said on social media that it won a $22 million bid for a dome to surround a 48-foot telescope. In an April social-media 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 haven't 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," said Kirshner, a Harvard emeritus professor.
The leading Chinese astronomer and his institute, a national research organization that appears to be in charge of the telescope, didn't return requests for comment for this article.
If China is building the big scope, that raises another question.
'Why the hell are they doing that?" said Matt Mountain, head of the nonprofit organization that manages observatories, as well as the Hubble and James Webb space telescopes, for the National Aeronautics and Space Administration.
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 second hypothesis: Beijing is investing in astronomy to inspire children to enter the sciences—so it can surpass the U.S. in a couple of decades.
'Astronomy is an entry-level drug for science, technology, engineering and math," said Mountain.
American institutes are the New York Yankees of modern astronomy. By Kirshner's count, 18 of the 23 astrophysics-focused Nobel Prize winners in the last half-century worked in the U.S.
While space telescopes such as the James Webb get more attention these days, 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, 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 8 feet and 21 feet, respectively. The four biggest ones currently on Earth—one in Spain and three in the U.S.—are all roughly 33 feet in diameter.
If China completes a 48-foot telescope soon, it would be the world's biggest, unless a delayed 128-foot European telescope in Chile is finished first.
Kirshner's Thirty Meter Telescope group, an international project with U.S., Canadian, Indian and Japanese institutions, proposes a 98-foot telescope on Hawaii's Big Island. Instead of making one massive mirror, which would require mountain transport and the construction of an unfeasibly huge furnace, it would use 492 hexagonal segments, each 4.7 feet wide.
These giant telescopes cost roughly $1 billion to $2 billion, Mountain said, and costs rise with size. They also take years to build.
Drawing on political rather than scientific wisdom, Kirshner realized it would help make the case in Washington for big-telescope funding if he could show China was building one too.
Kirshner's best sources have been Chinese-speaking peers who informally confirmed the development of a telescope site in the Tibetan Plateau, in China's southwest. Mountain says Chilean astronomers told him China was also exploring a Southern Hemisphere observatory in Chile.
Armed with the information, Kirshner met congressional staffers and National Science Foundation officials.
He ran into a roadblock in May, when President Trump proposed to Congress that the NSF's annual budget be cut to $4 billion from $9 billion. Trump's science and technology adviser said then that scientific progress had stalled in some fields and more federal money wouldn't necessarily mean more scientific impact.
In its budget request, the NSF proposed advancing only the Giant Magellan Telescope, which is backed by a California-headquartered consortium. At 83 feet wide, the Magellan would be bigger than China's but smaller than Kirshner's proposed telescope. Like the European telescope, this observatory would be in Chile.
The Magellan's location would leave China with the Northern Hemisphere's biggest telescope. Earth's curvature means each hemisphere offers different views.
Kirshner got a reprieve in mid-July. A Senate spending committee recommended minimal cuts to the NSF, and said it supported both the Magellan project and Kirshner's Thirty Meter Telescope.
Kirshner called on Congress to endorse what he called a 'vigorous response to China's efforts."
Write to Stu Woo at
