The United States should commit $1.6 billion to build an “extremely large telescope” that would usher American astronomy into a new era, according to the National Science Board, which advises the National Science Foundation.
In a Feb. 27 statement, 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 were worried about losing ground to their European colleagues in the quest to survey the heavens with bigger, better telescopes.
But which of the two telescopes will be built (and the fate of the dreams and billions of dollars in time and technology already invested) remains an open question. Many astronomers hoped the foundation, which traditionally funds 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 destined 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 so far the international collaborations behind them have raised less than half the projected cost.
In an announcement circulated among astronomers, the board said that funding even one telescope at the $1.6 billion price tag would consume most of the NSF's typical construction budget.
“In addition, the priorities of the astronomy and astrophysics community should be considered in the broader context of high-priority, high-impact projects for the many disciplines NSF supports,” the board said in its statement last week.
Until now, astronomers interested in the result have been careful to note that Congress, as well as the White House and the science foundation, would eventually weigh in.
“This is a marathon, not a sprint,” said Robert Kirshner, director of the International Thirty Meter Telescope Observatory and a former member of the Giant Magellan team. He added that he was hopeful that both telescopes could move forward.
Michael Turner, a cosmologist emeritus at the University of Chicago and former NSF deputy director for mathematical and physical sciences, called the recent development “excellent news for American astronomy and saw “a realistic path forward” for an extremely large telescope.
“Before we know it, the telescope will dazzle us with images of exoplanets and the early universe,” he said. “Should it have happened faster? Of course, but that's history. At full speed, with an eye 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 am very glad that the NSB decided to fund an ELT. I think the worst outcome would have been to not fund any “ELT; That would have been a tragedy! Realistically (and unfortunately), there is no budget for two. But an ELT is critical to the future of American astronomy.”
And she added: “I feel very relieved.”
Robert Shelton, president of the Giant Magellan collaboration, said, “We respect the National Science Board's recommendation to the National Science Foundation and remain committed to working closely with the NSF and the astronomical community to ensure the successful completion” of a telescope. extremely large. “which will enable cutting-edge research and discoveries for years to come.”
But Richard Ellis, an astrophysicist at University College London and one of the early leaders of the Thirty Meter Telescope project, told science“It is a tragedy, given the investment made in both telescopes.”
A telescope's power to see deeper, fainter objects in space is largely determined by the size of its primary mirror. The largest telescopes on Earth are between eight and 10 meters in diameter. Magellan's Giant would group seven eight-meter mirrors to form the equivalent of a 25-meter telescope; The seventh and final mirror was melted last year and workers are ready to pour concrete at the Las Campanas site.
The Thirty Meter would be composed of 492 hexagonal mirror segments, expanding the design of the twin Keck 10-meter telescopes being operated on Mauna Kea by the California Institute of technology and the University of California. (The 100th segment just screened in California, but protests by Native Hawaiians and other critics have prevented any work on the TMT site on Mauna Kea; the project group has been considering an alternative site in the Canary Islands.) None of the telescopes will likely be ready until the 2030s.
Even as the U.S.-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, made up of 798 hexagonal segments, 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 would be the first time in a century that Earth's largest operating telescope is not on American soil.
Both the Giant Magellan and Thirty Meter Telescopes are multinational collaborations based just a few miles apart in Pasadena, California.
NSF support 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 supervision of the National Optical-Infrared Research Laboratory in Tucson, Arizona, that would allow US astronomers to use both telescopes. Astro 2020, a leading panel of the National Academies of Sciences, endorsed the proposal and called it the top priority in terrestrial astronomy for the decade. The panel recommended that the science foundation provide $1.6 billion to buy part ownership of one or both telescopes.
But the costs of these telescopes have 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 turn slowly.
“That process takes three to five years,” said Linnea Avallone, director of NSF's research facilities. “We've been engaged for just over a year. I don't think we're dragging our feet; I don't think we're not being aggressive.” She added that the foundation was being “very good stewards of taxpayer money.”
Did you see a risk in the United States not funding its own Extremely Large Telescope?
“That's a good question, best answered by astronomers,” Dr. Avallone said.
