The United States should commit $1.6 billion to build an “extremely large telescope” that will take American astronomy into a new era, according to the National Science Council, which advises the National Science Foundation.
In a statement on February 27, the board gave the foundation until May to decide how to choose between two competing proposals for the telescope. The announcement came as a relief to American astronomers, who worry that their European colleagues are losing ground in trying to survey the heavens with bigger and better telescopes.
But which of the two telescopes will be built — and the fate of the dreams and the billions of dollars worth of time and technology already invested — remains an open question. Many astronomers hoped the foundation, the traditional funder of national observatories, would find a way to invest in both projects.
The two projects are the Giant Magellan Telescope at Las Campanas in Chile and the Thirty Meter Telescope, possibly intended for Mauna Kea on the island of Hawaii, also known as the Big Island. Both would be larger and more powerful than any telescope currently on Earth or in space. Each is expected to cost about $3 billion or more, and less than half of the projected cost has so far been raised by the international partnerships that support it.
In a statement circulated among astronomers, the board said funding even one telescope at $1.6 billion would take up most of NSF’s typical construction budget.
“Furthermore, the priorities of the astronomy and astrophysics community must be considered in the larger context of the high-priority, high-impact projects for the many disciplines that NSF supports,” the board said in its statement last week.
So far, astronomers involved in the outcome have been careful to note that Congress, as well as the White House and the scientific establishment, would ultimately all have their say.
“This is a marathon, not a sprint,” said Robert Kirchner, director of the International Thirty-Meter Observatory and a former member of the Giant Magellan team. He added that he was optimistic that both telescopes could proceed.
Michael Turner, cosmologist emeritus at the University of Chicago and former assistant director of physics and astronomy for the NSF, called the recent development “excellent news for American astronomy” and saw “a realistic path forward” for an extremely large telescope.
“Before you know it, the telescope will be dazzling us with images of exoplanets and the early universe,” he said. “Should it have happened sooner? Of course, but that’s history. Full speed ahead, eyes on the future!”
Wendy Freedman, a cosmologist at the University of Chicago who led the Giant Magellan project in its first decade, said in an email: “I’m very happy that NSB has decided to fund an ELT, I think the worst outcome would not be to fund any ELT not at all? it would be a tragedy! Realistically (and unfortunately), there is no budget for two. But an ELT is critical to the future of US astronomy.”
She added: “So I’m very relieved.”
Robert Shelton, president of the Giant Magellan collaboration, said: “We respect the National Science Council’s recommendation to the National Science Foundation and remain committed to working closely with NSF and the astronomical community to ensure the successful implementation” of an extremely large telescope. “which will enable cutting-edge research and discoveries for years to come.”
But Richard Ellis, an astrophysicist at University College London who was one of the early leaders of the Thirty Meter Telescope project, told Science, “It’s a tragedy, given the investment that went into both telescopes.”
A telescope’s power to see deeper and fainter objects in space is largely determined by the size of its primary mirror. The largest telescopes on Earth are eight to 10 meters in diameter. The Giant Magellan will group together seven eight-meter mirrors to make the equivalent of a 25-meter telescope. The seventh and final mirror was cast last year and workers are ready to pour concrete at the Las Campanas site.
Thirty Meter will consist of 492 hexagonal mirror sections, scaling up the design of the twin 10-meter Keck telescopes operated on Mauna Kea by the California Institute of Technology and the University of California. (The 100th segment just aired in California, but protests by Native Hawaiians and other critics prevented any work at the TMT site on Mauna Kea; the project team was considering an alternative site in the Canary Islands.) No telescope is likely to be ready by 2030.
Even as the American-led effort moves forward, the European Southern Observatory is building an extremely large telescope — called the Extremely Large Telescope — at the Paranal Observatory in Chile. Its main mirror, consisting of 798 hexagonal sections, will be the largest and most powerful of all — 39 meters in diameter. It will also be the first among competitors to be completed. European astronomers plan to begin using it in 2028. If the effort is successful, it will be the first time in a century that the largest operating telescope on Earth is not on American soil.
Both the Giant Magellan and Thirty Meter telescopes are multinational collaborations based a few miles apart in Pasadena, California.
Support from the NSF has been a point of contention between the two groups since their inception 20 years ago.
In 2019, the two groups agreed to join forces to create a US ELT program, under the National Optical Infrared Research Laboratory in Tucson, Ariz., that would allow US astronomers to use both telescopes. Astro 2020, a blue-ribbon panel of the National Academies of Sciences, endorsed the proposal, calling it the top priority in terrestrial astronomy for the decade. The panel recommended the science foundation chip in $1.6 billion to buy partial ownership in one or both telescopes.
But the cost of those telescopes has continued to rise, and $1.6 billion doesn’t go as far as it once did. And the wheels of the scientific community and the federal government are turning slowly.
“This process takes three to five years,” said Linnea Avallone, head of research facilities at NSF. I don’t think we’re dragging our feet. I don’t think we’re not aggressive. He added that the foundation was “very good stewards of taxpayers’ money.”
Did he see the danger for the United States in not funding an extremely large telescope of its own?
“That’s a good question, better answered by astronomers,” Dr Avallone said.
