If you drove on the winding road up the Chilean Andes, you’d spot the white specks of distant telescopes peppering the hills. Sometime by the end of this decade, one of those specks will tower above the rest, visible even miles away.
Up close, it resembles a rotating luxury apartment complex. Vents taller than a garage door let in air or shut out desert dust. Though the enclosure stands 22 stories tall, it houses no humans. Instead, when the building splits open each night, you’ll see seven of the largest mirrors in the world. Reflected in them is the entire sky – and universe – come alive.
This is the Giant Magellan Telescope (GMT), slated to be one of Earth’s most efficient and powerful telescopes upon completion.
The GMT sprang from an idea in the early 2000s, that science needed to go even bigger, according to John Mulchaey, director of the Carnegie Observatories – including the Las Campanas Observatory in Chile, the telescope’s future home.
“20 years ago, basically people started going, ‘Okay, to really make the next leap in astronomy, we need bigger telescopes,’” Mulchaey says.
Just how big will it go? One mirror alone, 8.4 meters across, fits the James Webb Space Telescope’s primary mirror – with room to spare. All seven create an array 25.4 meters wide, or over 80 feet.
Why it’s so giant is simple: to gather far more light.
“The more light and the sharper an image we get, it translates directly into information,” says Rebecca Bernstein, chief scientist for the Giant Magellan Telescope. Atop the Atacama Desert, the telescope will peer into the cosmos in optical and near infrared light. Operations could start by 2029.
Scientists expect the incoming data and newfound visual clarity will revolutionize how we understand the very fabric of our universe. Bernstein compares the impact to flipping on the lights.
“You have a blackout, and you’re trying to get around your house with one candle – you’re never even gonna find your keys,” she says. “You want to turn on the lights to be able to see more. That’s what collecting more light does for you.”
After that, there’s no spot too dark or distant to see.
Any telescope is like a light bucket, and Bernstein explains, “Light falls like raindrops.”
To see really faint cosmic objects, you’d need a much bigger bucket. Light drops fall upon the GMT as it scans the sky in 360 degree revolutions all night, bouncing off its primary mirrors to hit a group of secondary mirrors above the main body. Those smaller mirrors correct the natural messiness of Earth’s atmospheric turbulence, cleaning up the light before beaming it back through a hole in the centermost primary mirror.
That light is then guided to various scientific instruments sitting below, says Lisa Kewley, director of Harvard and Smithsonian’s Center for Astrophysics – which is currently building instruments including spectrographs. Using these various instruments, scientists could analyze anything from distant galaxies to potential Earths.
(Credit: Giant Magellan Telescope–GMTO Corporation)
It takes a village and at least 17 tons of glass to make one mirror, in a building under the University of Arizona’s football stadium – the Richard F. Caris Mirror Lab.
After constructing an oven and a honeycomb-shaped ceramic mold, lab workers carefully select and load the most perfect chunks of glass into the furnace. It then starts baking, peaking at over 1,000 degrees Celsius, while spinning rapidly. Similar to how swirling a bottle of water pushes liquid up the sides, this motion forces the glass, oozing into the mold, into the parabolic shape needed for the telescope.
The cooling process ultimately takes months. Once the glass is room temperature, workers dismantle the oven and wash out the mirror’s ceramic innards, leaving it hollowed like a beehive.
One of the major challenges is polishing the glass afterwards, according to Buell Jannuzi, director of University of Arizona’s Steward Observatory. The telescope resembles a perfectly symmetrical flower. But the petals themselves aren’t actually symmetrical – one side dips lower, while the other rises higher.
And only the tiniest margin of error is allowed. If one mirror were as big as North America, from coast to coast, Bernstein says the largest bump you’d see would be shorter than an inch.
This is the precision needed to view the universe clearly and why it ultimately takes about four years to prepare one mirror.
That’s all in Arizona, though. To get these precious petals to Chile, they’re carefully loaded atop a flatbed truck. They take a road trip to a shipping port, where they’ll sail down to La Serena, before more trucks lug them up the Pan-American highway to Las Campanas – all with a special police escort.
Read more: How the Mirror Changed Humanity Forever
Think of JWST’s first deep field image – a brilliant conglomeration of galaxies scattered across the early universe like confetti. The GMT would illuminate the whole party, including previously unseen guests and all.
But astronomers won’t only be photographing space.
“The beauty of the [GMT] is also in its spectrographs,” Kewley says. “Not only will we see those clumps of star formations in distant galaxies billions of years ago, but we’ll also be able to measure the chemical elements in those galaxies.”
One of the most enthralling questions this telescope is poised to answer is that of exoplanets – specifically if other habitable, Earth-like planets exist. With it, astronomers could potentially detect gases like oxygen indicating biological origins in exoplanet atmospheres.
The GMT is an international endeavor, one Jannuzi believes reminds us that curiosity and scientific ambition transcend borders.
“Humans all over the world are interested in understanding our universe better and exploring it together,” he says.
And by the time the telescope sees first light, Jannuzi envisions a new generation of fresh graduates and budding scientists who will have the chance to pursue novel ideas.
As for what’s possibly in store? The cosmos is merely the limit.
“If you go back in history and look at astronomy, every time there’s a new telescope, a new leap in technology, you make a leap in your understanding,” Mulchaey says. “To me, the real exciting things for GMT will be the things we know nothing about.”