This giant telescope could discover habitable exoplanets and secrets of our universe — if it gets its funding

The Giant Magellan Telescope project is gearing up for a crucial 12–24 months, with their final design phase underway as the team behind the project seek further funding to make the dream of the 25.4-meter (83 feet) multi-mirror telescope a reality.

The Giant Magellan Telescope (GMT) Consortium of 16 universities and research institutions held their first ever summit on April 14th. The summit acted as a way to update academics, the media and the public on how design and construction of the telescope is proceeding following the National Science Foundation (NSF) officially advancing the project to its final design phase in the summer of 2025.

"This is one of the final steps that the project must take before it can be considered for federal funding," Daniel Jaffe, who is the President of the GMT Consortium and a former head of astronomy at the University of Texas, Austin, said during the summit. "Over the past five years the telescope has passed every independent, federally required review. Now my immediate focus is in successfully completing the NSF's final design phase by mid-2027. Pending approval by the NSF and Congress, the Giant Magellan Telescope will enter the beginning of full-scale construction in the fiscal year 2028."

The GMT is one of three telescopes roughly in the thirty-meter (~98 feet) class that should come online in the 2030s. The Extremely Large Telescope (ELT) being built by the European Southern Observatory in Chile is already under full-scale construction and its 39-meter (128 feet) should be the first to enter service in 2029.

Complications

For the GMT and another huge next-gen telescope, called the Thirty Meter Telescope (TMT), the situation is more complex. Both are American telescopes being funded, at least in part, by the NSF. However, in 2024, the NSF had its giant-telescope budget capped at $1.6 billion, which is not enough to fully fund both observatories. This has sent both projects looking towards private and overseas donations.

Jaffe revealed that more than a billion dollars has so far been invested into the GMT project by its partners.

"These contributions, largely made possible by donors and supporters around the world, have enabled 40% of the telescope's components to be in active fabrication and assembly," said Jaffe.

On the Las Campanas mountain top, 7,870 feet (2,400 meters) above sea level in Chile's Atacama desert, which enjoys a darker, drier and more stable night sky than almost anywhere else in the world, the GMT's foundations have already been dug, and roads, utilities and support structures put in place. In Rockford, Illinois, engineers at Ingersoll Machine Tools are constructing the huge mount that will hold the seven 8.4-meter primary mirrors, the seven 1-meter secondary mirrors, and the science instruments. The mount, when finished, will stand 128 feet (39 meters) tall (coincidentally the size of the ELT's entire mirror) and weigh 2,600 tons. It's so large that the company had to construct a special 40,000 square foot (3,700 square meter) manufacturing and assembly bay just to house it.

The mirrors, meanwhile, form a unique optical design. Both the ELT and TMT are going with one huge mirror formed out of many segments joined together, but as mentioned in the preceding paragraph the GMT's primary reflecting surface is made up of seven individual large mirrors, each a little larger in size than the mirror on the Subaru Telescope in Hawaii, for example. In fact, they are the largest single telescope mirrors ever made. By contrast, the primary mirrors on the W.M. Keck 10-meter telescopes are made of segments rather than one solid single mirror.

This design, said GMT's Chief Scientist Rebecca Bernstein, has several advantages, not least how it helps the telescope's adaptive optics.

Adaptive optics describes how telescope mirrors can make minute changes in their shape to counteract the twinkling of stars by the atmosphere.

The GMT is essentially a huge version of the reflector telescope that you might use in your backyard. In the case of amateur telescopes, the light bounces off the primary mirror and is reflected by a smaller secondary mirror to a focal point at the eyepiece. In the case of the GMT, the seven primary mirrors are mirrored, pardon the pun, by seven smaller secondary mirrors that are deformable.

"They are a game changer," said Bernstein. "The secondary mirrors are complex structures, 2mm thick and 1 meter in diameter. Attached to the back of each mirror are about 700 tiny magnets that are pushed and pulled by electromagnetic coils to enable the mirrors to change their shape thousands of times per second to remove the atmospheric jitter."

Those seven primary mirrors, operating in unison alongside the secondary mirrors and adaptive optics, will bring new eyes onto the universe. Exoplanets in the habitable zone of distant stars are a key target. A coronagraph will block the light of a star, isolating the light of any planets around that star, allowing spectroscopic measurements of that planet's light by an instrument called the GMT-Consortium Large Earth finder (G-CLEF) with which to search for biosignatures in the planet's atmosphere.

At the other end of the scale, entire galaxies in the distant universe will come under scrutiny.

"We know that galaxies, and the stars and planets within them, form from vast clouds of gas drawn together by gravity," said Gwen Rudie, who is an astronomer at the Carnegie Institution of Science in California. As massive stars go supernova they drive that gas back out again, leading to a cycle of gas falling in, forming stars and then being blown away again.

"This cycle is not yet understood because the gas has been too challenging to see," said Rudie. "The GMT will let us study galaxies at tremendous distances, which means peering back in time 10 or 11 billion years ago when galaxies were forming stars the fastest. It will revolutionize our understanding by creating the first maps of gas surrounding individual galaxies. We'll be able to peer into the hearts of these young galaxies to connect the sites of star-birth and star-death directly to these gas flows."

However, as excited as Rudie is about the potential for these observations, she is even more excited about the unexpected things that the GMT might find.

"I believe the most remarkable discoveries that the GMT will make will be the ones that we haven't even imagined yet," said Rudie. "There's no telling what we'll find."

However, all this potential will be lost if design and construction on the GMT isn't completed. Even with federal funding hopefully granted by the U.S. Congress, it won't be enough, and Jaffe says that the project is looking to enlarge the current 16-strong consortium and encourage even further private investment to fund the estimated total of over $2 billion to build and operate the telescope.

"This will bring in more resources and added brain-power to drive discovery, leading to science observations in the 2030s," said Jaffe.

With luck, all three giant telescopes will be fully funded, constructed and in operation by the mid-2030s. Between them, and working with other established observatories such as Rubin and the James Webb Space Telescope, they promise to transform our understanding of stars, galaxies and the potential for life beyond Earth.