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Why astronomers are worried about 2 major telescopes right now
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By Monisha Ravisetti published about 6 hours ago
Scientists may only get to have either the Giant Magellan Telescope or
the Thirty Meter Telescope. The problem? Both are already in the works.

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a chrome dome with a hole in the top and a chrome cube like building
with a gap in its front both shoot orange lasers into the starry sky.
An artist's rendering of the US-ELTP Thirty Meter Telescope (TMT) (left)
and Giant Magellan Telescope (GMT) (right) with their Laser Guide Stars
(LSG) turned on. (Image credit: US-ELTP (TIO/NOIRLab/GMTO))

There's a bit of tension right now in the U.S. astronomy community and,
perhaps unsurprisingly, it has to do with telescopes — extremely large
telescopes, in fact. Here's what's going on.

The National Science Foundation (NSF), a source of public funding that
two powerful next-gen observatories have been banking on for financial
support, is facing pressure to go forward with only one telescope. This
is because last month, the National Science Board — which is basically
an advisory committee for the NSF — recommended that it cap its giant
telescope budget at $1.6 billion. This is a lot of money, but it's just
not enough for both. The board even says the NSF will have until only
May of this year to decide which telescope gets the go-ahead.

Yet, both telescopes are already in the middle of construction, both are
equally important and both are actually supposed to work together to
fulfill a wide-eyed dream for astronomers. Because of how utterly huge
they're meant to be, they're expected to one-up even NASA's $10 billion
James Webb Space Telescope (JWST) in many ways. That's the
gold-mirrored, silvery-shielded trailblazer sitting a million miles from
Earth right now, finding deep space gems so quickly it's normalizing us
to seeing things humanity once couldn't fathom seeing. Imagine something
better.

Related: Scientists bury time capsule to celebrate upcoming Extremely
Large Telescope

"To my knowledge, neither telescope today has a path forward without the
investment by NSF," John O'Meara, chief scientist at the Keck
Observatory, told Space.com. "I've said in other interviews that 'great
vision should drive great budget, not vice versa,' and I believe it here."

One of the big scopes is the Giant Magellan Telescope (GMT). It's taking
shape as you read this in the clear-skied deserts of Chile, and it's
projected to cost something like $2.54 billion as a whole. The other is
called The Thirty Meter Telescope (TMT). That one's location is a bit
more controversial. It's planned to decorate a mountain in Hawaii called
Mauna Kea, but locals have protested the decision because this stunning
volcanic peak that boasts low humidity and gentle winds (perfect
conditions for astronomy) is extremely meaningful in native Hawaiian
culture. It's a fraught situation, as 13 other telescopes already live
in the area and some local people say the facilities are impacting the
natural environment. In terms of cost, however, the projected amount is
just about symmetrical to the GMT's.

"They're expensive," Eric Isaacs, the president of the Carnegie
Institution for Science, which has provided a sizable amount of private
funding for the GMT, told Space.com "Not so much that the NSF couldn't
do it — but they'd have to move things around and decide that's a priority."

A rendering of a metallic dome in a rocky, slightly sandy-looking area.
A large mirror is visible inside the dome.

An artist's illustration of the Thirty Meter Telescope atop the volcanic
peak of Maunakea in Hawaii. (Image credit: Thirty Meter Telescope)
As of now, both telescope crews seem to remain hopeful while waiting for
a decision.

"Our international consortium is fully committed to successfully
completing the $2.54 billion Giant Magellan Telescope," the GMT team
told Space.com.

"We read with great interest the NSB's recommendation to the NSF and are
eager to work with the NSF to advance US leadership in astronomy for the
next generation of astronomers," a spokesperson for the TMT told Space.com.

Isaacs acknowledges there's some natural competition due to the $1.6
billion announcement, but all in all, emphasizes that the teams have a
united front. "We're sticking together," he said. "We were hoping NSF
would come up with anything at this point, and they're really waking up
to this."

Telescope friends
There's a key reason these telescopes are meant to be companions. Each
can find the other's missing pieces; together, they can paint a picture
of the universe in its grand totality.

The GMT is going to be on call for the Southern Hemisphere, while the
TMT will have the Northern Hemisphere. Both also have complementary
expertises. Some things the TMT can do, the GMT won't be as trained on.
But the GMT can pick up where the TMT leaves off in other regards.
Tag-team vibes. In this way, while holding hands and walking through the
cosmos, the telescopes are supposed to be able to execute science our
current robotic eyes on the sky simply can't compete with. How could a
ground-based telescope view things the spaceborne JWST can't, you
wonder? The quick answer is that a telescope on our planet can be bigger
than one in space. For now, at least.

an oval with three sections shaded pink, purple and blue.

The overlapping observing coverage of the US-ELTP provides US
astronomers with unfettered all-sky access from the Giant Magellan
Telescope in the southern hemisphere and the Thirty Meter Telescope in
the northern hemisphere. The timezone separation between the sites would
increase the system’s capabilities for time-domain astrophysics. (Image
credit: US-ELTP (TIO/NOIRLab/GMTO))
The TMT, which just finished polishing the 100th of its 492 total
mirror segments, is planned to have a primary mirror that's (obviously)
30 meters, or 100 feet, in diameter. The GMT will have seven
27.6-foot-wide (8.4 m) mirror segments positioned in a pattern that
resembles a six-petaled daisy to form a single 83.3-foot-wide (25.4 m)
light-collecting surface. The bigger the mirror, the more light you can
get. The more light you can get, the deeper you can see, and the dimmer
objects you can pick up.

"TMT will deliver images that are more than 12 times sharper than the
Hubble Space Telescope and more than four times sharper than those from
JWST," the TMT team said in a release.

"These are the instruments for the next decades," Isaacs said.

seven round mirrors are sourounded by scaffolding.

(Image credit: GMTO Collaboration)
Plus, both ground-based observatories can be adapted over time because
they're physically on our planet. A bunch of astronauts can't exactly
travel a million miles to reach Lagrange Point 2, where the JWST is
situated, to tinker with the machine. The Hubble Space Telescope could
be serviced back in the day because it sits in low Earth orbit — but
even that was enough of a feat to warrant celebration decades later.

Why the U.S. government has a stake in the stars
It's fascinating how the science board's recommendation has sent ripples
down into politics, managing to make headlines about the country's
tricky status as a leader among the stars.

The worry comes from the fact that these telescopes are supposed to
represent a significant leap forward for U.S. astronomy and U.S.
astronomers.

Already, the European Southern Observatory's giant telescope project
(unironically named the Extremely Large Telescope) is walking steadily
to completion; China also has plans for its own enormous bridge to the
stars.

"From our view, the most important thing is, let's at least build one,"
Isaacs said. "If we don't, we're out of the game, and China and the EU
[European Union] are gonna continue on. But we certainly want to
advocate for two at this point, because we think it really keeps us in a
leadership position."

In fact, soon after the board presented its $1.6 billion recommendation,
Congress released its Fiscal Year 2024 funding bill. In this bill,
Congress says it would like the nation to have a "two-observatory
footprint" via the U.S. Extremely Large Telescope (USELT) program,
though funding levels weren't specified. Interestingly, it does mention
that the NSF, in total, will get $9.06 billion to work with. Still, the
NSB's number remains the only one scientists have to contend with as of
yet for the telescope program.

"I think that number, it sends a message," Isaacs said. "I mean, we have
roughly a third of what we need, but we can't build it unless we get NSF
involved because it's just gonna be hard to raise that kind of money,
even from wealthy, private people. It's the same thing with the TMT."

five funny-shaped land-based telescopes stand side by side in a
comparison chart.