Astronomers recently held groundbreakings for three huge telescopes in five months, the first of which should begin observations by 2021. The scopes’ light-collecting mirrors—each 80 to 126 feet across—will dwarf those at the W.M. Keck Observatory, whose twin 33-foot mirrors are the benchmark today.

In some ways, three groundbreakings in five months isn’t as surprising as it may seem: Over the past century, design leaps have occurred roughly every 30 years, so this crop is right on schedule. Gary Sanders, project manager for the new Thirty Meter Telescope, explains that three decades is simply the time it takes technology to advance enough to warrant new facilities. Upgraded capabilities come at a price; the observatories will cost more than $1 billion apiece and likely direct resources away from existing facilities, such as Keck. But Sanders is confident that astronomers will make good use of them. “There are only 365 nights in a year,” he says, “and a lot of questions to answer.”

“With each generation of new telescopes, we open up new things we never anticipated. It’s the serendipity that really drives the science.”

—Debra Elmegreen, astronomy professor at Vassar College and former president of the American Astronomical Society

Eyes On The Skies

The size of a telescope’s primary mirror—the glass that concentrates light from the sky onto the detector—determines its observing power. Bigger mirrors make for finer-detailed images. Here’s how the next generation of mirrors stack up against Keck I and II.

 

From left to right: Keck I and II, 33 feet; Giant Magellan Telescope, 80 feet; Thirty Meter Telescope, 98 feet; European Extremely Large Telescope, 126 feet.

Mirrors That Erase The Atmosphere

Adaptive optics (AO) systems—which compensate for the blurring effects of the atmosphere—were tacked on to the current generation of big telescopes years after they were built. In the new machines, AO is a standard feature. About 800 times per second, actuators adjust the curvature of a mirror in the telescope’s light path by a few microns. Luc Simard, the TMT’s lead instrumentalist, says AO will allow these observatories to take pictures 10 times clearer than Hubble, whose price tag was four times more than these billion-dollar scopes.