Our view from Earth has always been pretty good, aside from clouds and glare. It was transformed by telescopes in the 1600s, though, and has improved wildly ever since. From X-ray telescopes to the atmosphere-bypassing Hubble Space Telescope, it's hard to even believe what we can see now.
And despite all they've done, telescopes are just getting started. Astronomy is on the verge of another Hubble-like disruption, thanks to a new breed of mega-telescopes that use huge mirrors, adaptive optics and other tricks to peer deeper into the sky — and further back in time — than ever before. These billion-dollar projects have been in the works for years, from hulks like Hawaii's controversial Thirty Meter Telescope to the James Webb Space Telescope, Hubble's highly anticipated successor.
Today's largest ground-based telescopes use mirrors 10 meters (32.8 feet) in diameter, but Hubble's 2.4-meter mirror steals the show because it's above the atmosphere, which distorts light for observers on Earth's surface. And the next generation of telescopes will outshine them all, with even more enormous mirrors as well as better adaptive optics — a method of using flexible, computer-controlled mirrors to adjust for atmospheric distortion in real time. The Giant Magellan Telescope in Chile will be 10 times more powerful than Hubble, for example, while the European Extremely Large Telescope will gather more light than all existing 10-meter telescopes on Earth combined.
Most of these telescopes won't be operational until the 2020s, and some have faced setbacks that could delay or even derail their development. But if any really do become as revolutionary as Hubble was in 1990, we better start preparing our minds now. So, without further ado, here are a few up-and-coming telescopes you'll probably hear a lot about in the next few decades:
1. European Extremely Large Telescope (Chile)
The European Extremely Large Telescope will be the largest telescope on Earth once it's completed. (Image: L. Calçada/ESO)
Chile's Atacama Desert is the driest place on Earth, almost completely lacking the precipitation, vegetation and light pollution that can muddle skies elsewhere.
Already home to the European Southern Observatory's La Silla and Paranal observatories — the latter of which includes its world-renowned Very Large Telescope — and several radio astronomy projects, the Atacama will soon also host the European Extremely Large Telescope, or E-ELT. Construction on this aptly named behemoth began in June 2014, when workers blasted away some flat space atop Cerro Armazones, a 10,000-foot mountain in the northern Chilean desert. Construction on the telescope and the dome began in May 2017.
Projected to start operation in 2024, the E-ELT will be the largest telescope on Earth, boasting a main mirror that stretches 39 meters across. Its mirror will be composed of many segments — in this case 798 hexagons measuring 1.4 meters each. It will collect 13 times more light than today's telescopes, helping it scour the skies for hints of exoplanets, dark energy and other elusive mysteries. "On top of this," the ESO adds, "astronomers are also planning for the unexpected — new and unforeseeable questions will surely arise from the new discoveries made with the E-ELT."
2. Giant Magellan Telescope (Chile)
The Giant Magellan Telescope will scan the skies for alien life on distant worlds. (Image: Giant Magellan Telescope)
Another addition to Chile's impressive telescope collection is the Giant Magellan Telescope, planned for Las Campanas Observatory in the southern Atacama. The GMT's unique design features "seven of today's largest stiff monolith mirrors," according to the Giant Magellan Telescope Organization. These will reflect light onto seven smaller, flexible secondary mirrors, then back to a central primary mirror and finally to advanced imaging cameras, where the light can be analyzed.
"Under each secondary mirror surface, there are hundreds of actuators that will constantly adjust the mirrors to counteract atmospheric turbulence," the GMTO explains. "These actuators, controlled by advanced computers, will transform twinkling stars into clear, steady points of light. It is in this way that the GMT will offer images that are 10 times sharper than the Hubble Space Telescope."
As with many next-generation telescopes, the GMT is setting its sights on our most vexing questions about the universe. Scientists will use it to search for alien life on exoplanets, for instance, and to study how the first galaxies formed, why there's so much dark matter and dark energy, and what the universe will be like a few trillion years from now. Its target for opening, or "first light," is 2023.
3. Thirty Meter Telescope (Hawaii)
In addition to working alongside the James Webb Space Telescope, the Thirty Meter Telescope would be on the lookout for dark matter. (Image: Thirty Meter Telescope)
The Thirty Meter Telescope's name speaks for itself. Its mirror would be triple the diameter of any telescope in use today, letting scientists see light from farther and fainter objects than ever before. Beyond studying the birth of planets, stars and galaxies, it would also serve other purposes like shedding light on dark matter and dark energy, revealing connections between galaxies and black holes, discovering exoplanets, and searching for alien life.
The TMT project has been in the works since the 1990s, envisioned as a "powerful complement to the James Webb Space Telescope in tracing the evolution of galaxies and the formation of stars and planets." It would join 12 other giant telescopes already perched atop Mauna Kea, the tallest mountain on Earth from base to peak and a mecca for astronomers around the world. The TMT received final approval and broke ground in 2014, but work was soon halted due to protests opposing the telescope's placement on Mauna Kea.
TMT has offended many Native Hawaiians, who oppose further construction of large telescopes on a mountain that is considered sacred. Hawaii's supreme court ruled TMT's construction permit invalid in late 2015, arguing the state didn't let critics voice their grievances at a hearing before it was granted. The state's Board of Land and Natural Resources then voted to approve the construction permit in September 2017, although that ruling is reportedly being appealed.
4. Large Synoptic Survey Telescope (Chile)
The Large Synoptic Survey Telescope will have a camera about the size of a small car. (Image: Large Synoptic Survey Telescope Corporation)
Larger mirrors aren't the only key to building a game-changing telescope. The Large Synoptic Survey Telescope will measure just 8.4 meters in diameter (which is still pretty huge), but what it lacks in size it makes up for with scope and speed. As a survey telescope, it's designed to scan the entire night sky rather than focus on individual targets — only it will do so every few nights, using Earth's largest digital camera to record colorful, time-lapse movies of the sky in action.
That 3.2 billion-pixel camera, about the size of a small car, will also be able to capture an extremely wide field of view, taking images that cover 49 times the area of Earth's moon in a single exposure. This will add a "qualitatively new capability in astronomy," according to the LSST Corporation, which is building the telescope along with the U.S. Energy Department and National Science Foundation.
"The LSST will provide unprecedented three-dimensional maps of the mass distribution in the universe," the developers add — maps that could shed light on the mysterious dark energy that drives the universe's accelerating expansion. It will also produce a full census of our own solar system, including potentially hazardous asteroids as small as 100 meters. First light is scheduled for 2022.
5. James Webb Space Telescope
Three times the size of Hubble, the James Webb Space Telescope should be able to gaze deeper into ancient space. (Image: Northrop Grumman/NASA)
NASA's James Webb Space Telescope has big shoes to fill. Designed to succeed Hubble and the Spitzer Space Telescope, it has generated high expectations — and expenses — during nearly 20 years of planning. Cost overruns pushed the launch date back to 2018, then testing and integration delayed it further until 2020. The price tag soared past its $5 billion budget in 2011, nearly leading Congress to nix its funding. It survived, and is now limited to an $8 billion cap set by Congress.
As with Hubble and Spitzer, JWST's main strength comes from being in space. But it's also three times the size of Hubble, letting it carry a 6.5-meter primary mirror that unfolds to reach full size. That should help it top even Hubble's images, providing longer wavelength coverage and higher sensitivity. "The longer wavelengths enable the Webb telescope to look much closer to the beginning of time and to hunt for the unobserved formation of the first galaxies," NASA explains, "as well as to look inside dust clouds where stars and planetary systems are forming today."
Hubble is expected to remain in orbit until at least 2027, and possibly longer, so there's a good chance it will still be at work when JWST arrives on the job in a few years. (Spitzer, an infrared telescope launched in 2003, was designed to last 2.5 years but may keep working until "late in this decade.")
The JWST isn't the only exciting new space telescope on NASA's plate. The agency also acquired two repurposed spy telescopes from the U.S. National Reconnaissance Office (NRO) in 2012, each of which has a 2.4-meter primary mirror along with a secondary mirror to enhance image sharpness. Either of these repurposed telescopes could be more powerful than Hubble, according to NASA, which has been planning to use one for a mission to study dark energy from orbit.
That mission, titled WFIRST (for "Wide-Field Infrared Survey Telescope"), was originally going to use a telescope with mirrors between 1.3 and 1.5 meters in diameter. The NRO spy telescope will offer big improvements over that, NASA says, potentially yielding "Hubble-quality imaging over an area of sky 100 times larger than Hubble."
WFIRST is designed to settle fundamental questions about the nature of dark energy, which makes up roughly 68 percent of the universe yet still defies our attempts to understand what it is. It could reveal all kinds of new information about the evolution of the universe, but as with most high-powered telescopes, this one is a multi-tasker. Beyond demystifying dark energy, WFIRST would also join the rapidly growing quest to discover new exoplanets and even entire galaxies.
"A picture from Hubble is a nice poster on the wall, while a WFIRST image will cover the entire wall of your house," team member David Spergel said in a 2017 statement. WFIRST was scheduled to launch in the mid-2020s, although a shadow now hangs over the entire project due to NASA budget cuts proposed by the Trump administration. The issue is still in the hands of Congress, and many astronomers have warned that cancelling WFIRST would be a mistake.
"The cancellation of WFIRST would set a dangerous precedent and severely weaken a decadal-survey process that has established collective scientific priorities for a world-leading program for a half century," said Kevin B. Marvel, executive officer for the American Astronomical Society, in a statement. "Such a move would also sacrifice U.S. leadership in space-based dark energy, exoplanet and survey astrophysics. We cannot allow such drastic damage to the field of astronomy, the impacts of which would be felt for more than a generation."
7. Five-hundred-meter Aperture Spherical Telescope (China)
China recently opened a giant radio telescope with the Five-hundred-meter Aperture Spherical Telescope (FAST) project, located in Guizhou province. With a reflector diameter roughly the size of 30 football fields, FAST is almost twice as large as its cousin, the Arecibo Observatory in Puerto Rico. While both FAST and Arecibo are massive radio telescopes, FAST can shift its reflectors, of which there are 4,450, to different directions to better investigate the stars. Arecibo's reflectors, in contrast, are fixed in their positions and rely on a suspended receiver. The $180 million telescope will seek out gravitational waves, pulsars and, of course, signs of alien life.
FAST was not without controversy, though. The Chinese government moved 9,000 people who were living within a 3-mile radius of the telescope site. Residents were given roughly $1,800 to aid their efforts to find new homes. The goal of the move, according to government officials, was to "create a sound electromagnetic wave environment" for the telescope to operate.
China also recently approved another, even larger radio telescope, the Chinese Academy of Science announced in January 2018. It's scheduled to open in 2023.
8. ExTrA project (Chile)
Its three telescopes may be small compared with some of the giants in this list, but France's new ExTrA ("Exoplanets in Transits and their Atmospheres") project could still be a huge deal in the search for habitable planets. It uses three 0.6-meter telescopes, located at the ESO's La Silla Observatory in Chile, to regularly monitor red dwarf stars. They collect light from a target star and from four comparison stars, then feed the light through optical fibers into a near-infrared spectrograph.
This is a novel approach, according to the ESO, and helps to correct the disruptive effect of Earth's atmosphere, as well as errors from instruments or detectors. The telescopes are meant to reveal any slight dips in brightness from a star, which is a possible sign that star is being orbited by a planet. They're focused on a specific type of small, bright star known as an M dwarf, which are common in the Milky Way. M dwarf systems are also expected to be good habitats for Earth-sized planets, the ESO notes, and thus good places to look for potentially habitable worlds.
On top of searching, the telescopes can also study the properties of any exoplanets they find, offering details about what it might be like in their atmospheres or on the surface. "With ExTrA, we can also address some fundamental questions about planets in our galaxy," team member Jose-Manuel Almenara says in a statement. "We hope to explore how common these planets are, the behavior of multi-planet systems, and the sorts of environments that lead to their formation."
Editor's note: This story has been updated with new information since it was originally published in August 2014.