• An artist concept of TMT at night, with the laser guide star system illuminated.
    Credit: Courtesy TMT Observatory Corporation

TMT Groundbreaking Launches New Era of Discovery

Construction officially has begun near the summit of Hawaii's Mauna Kea on what will be the largest telescope on the planet: the Thirty Meter Telescope (TMT).

"It is both exhilarating and intimidating to have reached this point," says Tom Soifer, professor of physics and Kent and Joyce Kresa Leadership Chair of the Division of Physics, Mathematics and Astronomy at Caltech. "It is exhilarating because of the enormous amount of effort it has taken us to get here and because, now that we are at the groundbreaking, TMT—and the scientific opportunities it brings—becomes much more real. It is intimidating because we've only just begun the work."

TMT, which is scheduled to begin observations in the early 2020s, will join the family of observatories already on Mauna Kea, including Caltech's twin 10-meter telescopes at the W. M. Keck Observatory, the current record-holder for the largest optical and infrared telescope in the world.

At 10 to 100 times more sensitive than Keck—depending on the type of observation—TMT is designed to tackle the most challenging questions of the cosmos, such as whether there is life on planets beyond the solar system, the nature of dark energy and dark matter, and the formation and evolution of galaxies.

Wide-angle view of 200-inch Hale Telescope
Credit: Scott Kardel

Caltech has played a leading role in the conception, design, and construction of the TMT, the latest (and greatest) of the Institute's pioneering efforts to build the most powerful observatories in the world. In the early 20th century, astronomer George Ellery Hale, one of the founders of Caltech, spearheaded the construction of the 200-inch telescope at Palomar Observatory, which stood as the largest telescope for 45 years until 1993 when Caltech and the University of California built the W. M. Keck Observatory. The Hale Telescope, as it became known, helped astronomers measure the expansion of the universe and discover exotic, bright objects called quasars, among numerous other achievements.

The twin 10-meter Keck telescope domes on Mauna Kea, Hawaii
Credit: Rick Peterson/WMKO

Caltech was also instrumental in the design and construction of Keck, which has become the preeminent optical and infrared observatory in the world. Over the last two decades, astronomers from around the globe—including many at Caltech—have used the twin Keck telescopes to detect planets beyond the solar system and peer into other planetary systems; probe the black hole at the center of the Milky Way galaxy; learn how the universe has evolved since the Big Bang, how galaxies form, and how stars are born; and to study dark matter, the mysterious stuff that makes up most of the universe's mass, and dark energy, the enigmatic force that's expanding the universe at an ever-faster rate.

The design of TMT and its instruments are based on Keck—only bigger, faster, and better. For example, each Keck telescope comprises 36 hexagonal mirror segments, which together act as a 10-meter-wide mirror. TMT, on the other hand, will have 492 segments that function as a 30-meter-wide mirror.

With such light-gathering ability, state-of-the-art instruments, and a first-ever fully integrated adaptive optics system to cancel out the blurring effects of the atmosphere, TMT will be able to see farther and more clearly than Keck or any other telescope at the same optical and infrared wavelengths.

For example, it will capture unprecedented images of planets beyond our solar system, revealing their atmospheres and environments in detail, and bring astronomers closer to answering the question of whether there is life elsewhere in the universe.

TMT will study how galaxies form and evolve, and how they're distributed across the universe. By exploring the large-scale structure of the universe and how it has changed over time, astronomers can probe dark energy and dark matter, as-yet invisible stuff that seems to interact only gravitationally with ordinary matter like stars. Both comprise the vast majority of the matter and energy in the universe and remain one of the most confounding questions in science.

The telescope will peer back in time to observe the first galaxies that came into existence 13 billion years ago, unveiling an era of cosmic history just beyond the reach of current telescopes.

TMT will study black holes that are millions to billions of times as massive as the sun and reside at the center of distant galaxies. It will also examine enormous explosions known as gamma-ray bursts, which are the most powerful events in the universe.

But what has many astronomers the most excited is not the expected discoveries, but the surprises that await, says Ed Stone, Caltech's David Morrisroe Professor of Physics and executive director of the TMT International Observatory, an international partnership that includes Caltech, the National Astronomical Observatories of the Chinese Academy of Sciences, the National Institutes of Natural Sciences in Japan, and the University of California. "It's not just about understanding better what you already know but learning what you didn't even know was out there," he says.

These future discoveries, Soifer adds, would not be possible were it not for the vision and continuing support of Caltech's collaborators and partners. "Gordon and Betty Moore and the Moore Foundation have been essential to getting TMT where we are today," Soifer says. That support began with a gift of $140 million to Caltech and the University of California to develop the early concept of a telescope larger than Keck. "The foundation has continued to provide the critical support that has allowed the project to continue," he says. "TMT is a testament to the Moore Foundation, our ingenuity, and the spirit of exploration."

Written by Marcus Woo