6 Benefits Unique to the Giant Magellan Telescope
Extremely large telescopes are the future of ground-based astronomy, each offers unique and complementary capabilities for understanding our place in the Universe
There’s a new class of ground-based telescopes under construction, aptly called “extremely large telescopes,” that astronomers are excited about, and with good reason. These mega telescopes will have massive light-collecting mirrors that are nearly 4x the size of today’s largest telescopes and up to 200x more powerful. This leap in observing capability will revolutionize nearly every aspect of astronomy — from the formation and evolution of objects we can directly see, like planets and galaxies, to cosmology and the things we can’t directly see, like the nature of dark matter and dark energy.
With the next generation of extremely large telescopes on the near horizon, there are six benefits unique to the Giant Magellan Telescope that astronomers are eager to take advantage of:
1. Sharper Images
Adaptive optics removes the blurring caused by Earth’s atmosphere
You may wonder how a ground-based telescope can deliver even sharper images than today’s best space-based telescopes. Bypassing the turbulence of Earth’s atmosphere was a key motivation for space-based telescopes to begin with. The answer is adaptive optics or AO, a serious game changer for the future of astronomy. AO counteracts the natural burring effect of the Earth’s atmosphere using deformable mirrors. While many of the current generation of ground-based telescopes have been retrofitted with this vision-correcting technology, the Giant Magellan Telescope is one of the first to incorporate state-of-the-art AO into its core design. Built directly into the secondary mirrors, the Giant Magellan Telescope uses seven deformable mirrors — each only two millimeters thick and flexible enough to be reshaped up to 2000x per second — to counteract atmospheric turbulence. Depending on the science case, this remarkable technology allows us to produce images 4-16x sharper than the James Webb Space Telescope from the ground.
“Adaptive optics will let us form the sharpest possible images for single objects — like planets — and will boost the resolution by 50% even over the widest field of view of the telescope, which will give GMT the best combination of sensitivity and field of view of any ELT.” — Dr. Rebecca Bernstein, Chief Scientist for the Giant Magellan Telescope
“The inner solar system will become uninhabitable in the future and the fate of humanity is ultimately tied to finding habitable conditions in distant planets. The Giant Magellan Telescope, with its unprecedented ability to map the compositions of distant planets, will be central for this quest. Funding the Giant Magellan Telescope must be a top U.S. priority — to maintain U.S. leadership in science and the quest for a new home for the human species.” — Shardha Jogee, Professor in Astronomy and Associate Dean for Faculty Affairs, College of Natural Sciences at The University of Texas at Austin
2. Maximized Light
Collecting efficiency allows for more light preservation, and more light equals more science
Illustration showing Giant Magellan light path to science instruments, two reflections allow the 25.4-meter telescope to perform with the collecting power of a 30-meter telescope. Credit: Damien Jemison, Giant Magellan Telescope – GMTO Corporation.
The more light a telescope can collect and send to its instruments, the better the science. Collecting the light is the first step, but what a telescope does with all the precious light it collects is just as important. So, let’s talk about light loss, because with each photon lost on the journey to a telescope’s science instruments, the less data that we have to work with. A telescope system must efficiently funnel the light it collects into the telescope’s science instruments otherwise it will require even larger light collecting surfaces to account for waste. Just like water lost from a leaky pipe, a telescope loses photons with each reflection needed to focus the light into the instruments, through the instruments, and then to the final detectors to be analyzed and turned into cold hard science.
“The ELTs will be humanities largest optical telescopes, and the Giant Magellan Telescope’s novel design means we can gather an order of magnitude more light with 6x higher resolution than JWST over a field of view ½ the size of the moon. This unique capability means we can observe more stars and galaxies at a time, a multiplex advantage that makes the Giant Magellan Telescope highly competitive and complementary to its somewhat larger siblings, the E-ELT and TMT.” — Brian Schmidt, Distinguished Professor of Astronomy, Australian National University
At each mirror surface, a modern telescope loses about 15% of light, on average. For the Giant Magellan Telescope, only 2 reflections are required to direct the light it collects into wide field instruments and only 3 reflections are required to direct light to small field instruments. A benefit that’s all thanks to that AO system mentioned earlier, and the fact that the system is built within the telescope’s secondary mirrors. This makes the Giant Magellan Telescope extremely efficient and able to do science with a larger fraction of collected light. In fact, its 25.4-meter optical design performs with the collecting power of a 30-meter telescope!
3. Southern Hemisphere Access for American Astronomers
Chile is an astronomical powerhouse with prime conditions for observing
The Giant Magellan Telescope is being built at Carnegie Science’s Las Campanas Observatory (LCO). Our home at Las Campanas is ideal for astronomy thanks to its dark skies, high altitude, dry climate, and stable atmosphere on the western edge of a continent. The unique qualities of the Atacama Desert make it one of the best places on Earth for astronomical observations. As home to nearly 70% of the world’s current and planned observatories, Chile not only provides legal protection for dark skies but also community and infrastructure support for the astronomical facilities it hosts.
“The Atacama Desert in Chile is undoubtedly the best site in the world to do astronomical observations. Besides having dark and clear skies, with very stable atmospheric conditions that yield the sharpest possible images, the country has a long-term history of welcoming and supporting international astronomy.” — Guillermo Blanc, Associate Director for Strategic Initiatives, Carnegie Science
The Atacama Desert happens to be one the best places on Earth to view the Universe. From this unique spot, there’s a lot to see. The sky above the Earth’s Southern Hemisphere is of particular scientific interest, as it’s a straight shot to the center of our own Milky Way Galaxy and the supermassive black hole residing there. Not to mention the nearest star to our Sun (Proxima Centauri) with its system of seven orbiting planets and several potentially habitable planets, and the closest neighboring galaxies to our own — the Magellanic Clouds.
Because the Giant Magellan Telescope is being built by an American–led international consortium of 15 partners, American astronomers will have access to it and be able to build scientific instruments for it. The Giant Magellan Telescope will leverage the National Science Foundation’s existing astronomical investments in Chile, amplifying their impact for decades to come. For the future of American-led scientific discovery, access to the Southern Hemisphere is not just a benefit, but a necessity.
4. Detailed Wide-Field Science
A combination of high performing field of view, image quality, and light sensitivity offers boosted scientific output
Other ELTs need to take as many as 13x more images to capture the same view of the Universe. With the Many Instrument Fiber System, or MANIFEST, the Giant Magellan Telescope will be able to concurrently observe 100’s of objects and increase the number of targets that can be studied at once. MANIFEST is a multi-object fiber positioning system that allows the telescope to feed light from 100’s of celestial objects simultaneously to its spectrographs. Credit: Damien Jemison, Giant Magellan Telescope – GMTO Corporation.
The aperture of a telescope is not the only important factor to consider for scientific performance. Similar to using a camera lens for a wide-angle photograph, for science that requires observing large numbers of objects across a large area of the sky, a wide field of view is crucial to efficiently collecting that sample. When it comes to a telescope’s field of view — the area that can be seen through an optical device — a wide field of view lets us collect data needed for solving problems like understanding dark matter, constraining dark energy, and studying the formation of galaxies. What sets the Giant Magellan Telescope apart is its unique combination of high performing field of view, image quality, and light sensitivity. When measuring these three qualities, a metric known as “etendue,” things really get exciting. This combination lets us create wide-field images up to 13x larger, 16x faster, and 50% sharper than other extremely large telescopes. Other extremely large telescopes will need to take as many as 13x more images to capture the same view of the Universe for science that requires studying large populations of stars and galaxies.
“The Giant Magellan Telescope is really an all-purpose telescope. It will have an impact in nearly all areas of astronomy research from objects in our solar system to the most distant galaxies and everything in between. Its wide field of view will make it ideal for studying large samples of objects, a key to understanding how objects evolve in time.” — John Mulchaey, President, Carnegie Science
So, what’s the benefit of being able to see detailed views of fainter objects all while capturing more of them in a single image? Bernstein shares that “the speed at which the Giant Magellan Telescope will perform wide-field science will significantly increase our scientific output.” Increased scientific output in turn offers a decreased cost of operations. The telescope’s power for wide field science is truly unmatched, especially for studying faint sources. This can include stars in the halo of our galaxy that together reveal the history of small galaxies, which have fallen into our own, or galaxies at large distances that together tell us how they have evolved over time as a population.
5. Direct Imaging of Earth 2.0
Studying the atmospheres of exoplanets in the reflected light of their parent stars
Time lapse video of HR8799, the first extrasolar planetary system ever directly imaged. Using observations collected over 12 years, Northwestern University astrophysicist Jason Wang assembled this time lapse video of the family of four planets — each more massive than Jupiter — orbiting their star. The video is followed by a simulation of an Earth-like planet detection in the reflected light of their parent star through a coronagraph. This masking technique is similar to blocking the Sun with your hand when viewing a bird overhead. Direct imaging is a game changer for the way we do exoplanet science. Credit: Damien Jemison, Giant Magellan Telescope – GMTO Corporation.
To date, no telescope has ever taken an image of a habitable exoplanet, but with the Giant Magellan Telescope that’s about to change.
You may be wondering what a “habitable” exoplanet is exactly and why we haven’t been able to directly image one. Habitable exoplanets are like our Earth, but they reside outside of our solar system. They support temperate climates that can potentially carry liquid water, a key ingredient for life. In addition, an exoplanet that may support life must be old enough to have cooled down since its formation and have had time for life to evolve. In our galaxy alone it’s estimated that there could be as many as 40 billion “habitable” exoplanets… 40 billion.
The tricky part in imaging Earth 2.0 is that they don’t emit their own light. Their cool temperature puts them just out of visible reach for today’s best telescopes. The only way for us to image these planets is in the reflected light of their parent star — like the way we see the moon from Earth, or the Earth from space. The Giant Magellan Telescope’s unique design will provide not only the sensitivity to detect these illusive planets but also the ability to develop a unique kind of science instrument that will enable an even higher image resolution. At first light, astronomers will be able to use an “extreme AO” coronagraph called GMag AO-X to directly image Earth-like planets in the reflected light of their parent star. Thanks to the combination of the telescope’s unique design and the scientific instruments that it can be paired with, we’ll finally be able to detect and study these faint and rocky cool planets that have been in obscurity.
“The Giant Magellan Telescope will be a major upgrade for our ability to study planets around other stars, especially when we take pictures of them using the in-development instrument GMag AO-X. The big improvement in resolution and sensitivity over today’s telescopes will open the most exciting science case imaginable: looking for life on those planets by focusing on their atmospheres.” — Jared Males, Associate Astronomer, University of Arizona Steward Observatory
“How amazing that we know of thousands of exoplanetary systems with thousands of planets unlike our own. The Giant Magellan Telescope will help us understand how these remarkable worlds formed. We will peer into planetary nurseries and find out how protoplanets are growing, and we will compare the chemical makeups of infant systems to that of mature planets. We will create a window to understanding our own solar system’s history.” — Alycia Weinberger, Associate Director, Earth and Planets Laboratory, Carnegie Science
6. More Science per Dollar
27x more compact than similar types of science instruments without compromising performance
Renderings comparing physical size of similar types of science instruments on ELTs. The Giant Magellan Telescope is 27x more compact than similar ELT science instruments with zero compromise in performance. Credit: Damien Jemison, Giant Magellan Telescope – GMTO Corporation.
The Giant Magellan Telescope offers many performance advantages. In addition to being efficient with the light it collects, it has a very “fast” optical design. In other words, its Gregorian design has a short focal length and so brings light into focus extremely quickly. This results in a compact focal plane that lets the telescope pair with science instruments up to 27x smaller in volume than other extremely large telescopes, all without compromising performance.
“The fast focal ratio of the Giant Magellan Telescope’s optical design is transformative for instrument builders. It allows us to create compact instruments with high light collection efficiency and lower complexity (ergo cost). This efficiency translates into more observations in less time — an invaluable advantage for a discovery-driven field.” — Juliana García-Mejía, Combined Heising-Simons Foundation 51 Pegasi B & Pappalardo Postdoctoral Fellow at MIT, PI of the Tierras Observatory
“The plate scale and layout of the Giant Magellan Telescope’s primary mirrors, i.e., the telescope’s pupil, make it possible to design a high efficiency instrument that may actually outperform instruments on the other ELTs. Furthermore, several currently unexplored techniques that may enhance considerably for the detection of biomarkers in the atmospheres of exoplanets may be tested much more straightforwardly at the Giant Magellan Telescope’s plate scale.” — Andrew Szentgyorgyi, Astrophysicist, Harvard Smithsonian Center for Astrophysics
While the Giant Magellan Telescope is indeed giant, as far as the new class of extremely large telescopes goes, it’s rather compact. And a compact telescope lets us build compact instruments. These smaller instruments can be built faster, with less risk, and more design solutions. A benefit for astronomers when they need to act fast in addressing new scientific opportunities in the decades to come. They’ll even be able to develop and build instruments capable of accessing the telescope’s 20-arcminute full field of view. This will drastically cut down the cost of observing and operation time. Talk about a big bang for your buck.
