Beyond Hubble

PHOTO COMPOSITE BY THE GEMINI OBSERVATORY
ALMOST HEAVEN: The dome of Gemini North sits perched under a brilliantly clear sky 14,000 ft. above sea level on Hawaii's Mauna Kea

The sun is setting over the luxury resorts of Kona, on Hawaii's Big Island. Warm tropical breezes waft lazily through the palms. Honeymooning couples sip mai tais by the pool as waves break gently on white sand.

Just 30 miles inland, conditions aren't quite so pleasant. The sunset is every bit as gorgeous from here, at the summit of the long-dormant volcano Mauna Kea, but temperatures hover around 38[Degrees]F, with a windchill that dips well below freezing. At an altitude of nearly 14,000 ft., the atmosphere carries barely half the oxygen it does at sea level, so the slightest exertion can leave visitors gasping. Those who travel to the summit without getting properly acclimated risk altitude sickness and even death.

But with night skies that rank among the clearest and darkest on Earth, Mauna Kea offers an unsurpassed view of the heavens--and that's why, despite the harsh conditions, astronomers can't wait to visit. Stargazers come here from around the world to answer some of the deepest mysteries of the cosmos: When in the depths of time did galaxies first flare into existence, and what made it happen? What is the elusive dark matter whose mass dominates the universe? How many stars have planets--and do those alien worlds harbor intelligent life?

These questions and more have tantalized astronomers for decades--and Mauna Kea is one of the few places where answers may finally be found. The mountain is dotted with white and silver observatory domes, sprouting like oversize mushrooms from the barren, rocky rubble that was once molten lava and, much later, a holy place of the native Hawaiian people. And although it's not obvious to the casual visitor, these domes conceal stargazing machines of unprecedented power.

For nearly a half-century, starting in 1949, the world's most powerful research-quality telescope was the Hale, on Palomar Mountain, in California. Its mirror, 5 m (17 ft.) in diameter, focused more faint starlight than anything else on the planet. But in the past few years, the Hale has been humbled. Here on Mauna Kea alone sit the Subaru telescope (no relation to the car), with a mirror more than 8 m (27 ft.) across; the Gemini North telescope, also topping 8 m; and the kings of the mountain, the twin Keck telescopes, whose light-gathering surfaces are an astonishing 10 m--33 ft.--in diameter.

The story is the same all over the world. In the high Andes of northern Chile, five more 8-m-class telescopes are either finished or nearing completion, while peaks in Arizona, Texas and South Africa too boast scopes more powerful than anything known to science just a decade ago.

That's not all. While each of these instruments trumps the Hale in light-gathering power, many are poised to outshine even the Hubble Space Telescope, which has been delivering astonishing snapshots of deepest space since it was refurbished in 1993. The orbiting observatory's nearly 2.5-m (8-ft.) mirror isn't all that powerful, but since it floats above Earth's constantly roiling atmosphere, the Hubble has been unrivaled in the sharpness of its images. No more. Using an ingenious technological trick to eliminate atmospheric blur, most of the new telescopes will soon achieve Hubble-quality focus--and even beat it under the right conditions.

This is a breakthrough of astronomical proportions. Whereas for years scientists have had only one Hubble-quality telescope, they will soon have access to more than a dozen. "What's been happening in the telescope game," says John Huchra, a veteran observer and a professor at the Harvard-Smithsonian Center for Astrophysics, "is incredible."

It has also been a long time coming. Impressive as the Hale telescope was for its day, it represented a technological dead end. The Hale, like its smaller predecessors, was powered by a mirror that's essentially a huge hockey puck of glass ground into a concave, light-focusing curve on one face and coated with reflective metal. To keep from sagging under its own weight and distorting the curve, the mirror had to be a bulky 26 in. thick, and it weighed 20 tons. That enormous heft called for an even more massive support structure to hold the whole thing up while at the same time adjusting constantly to counteract the effect of Earth's rotation. Scaling the design up any further would have been absurdly expensive.

During the 1960s, astronomers' lust for light was temporarily satisfied by the development of electronic light detectors. Because these detectors are up to 100 times as sensitive as photographic plates--the standard recording medium since the turn of the 20th century--every telescope on Earth saw its power boosted a hundredfold essentially overnight. That kept the scientists happy only for a while, however, and everyone agreed that telescopes needed some sort of radical new design. Unfortunately, says Matt Mountain, director of the Gemini Observatory, "nobody knew how to make the conceptual leap."

By the early '80s, though, telescope designers were leaping all over the place. University of Arizona astronomer Roger Angel's solution to the sagging-glass problem was to cast huge mirrors that are mostly hollow, with a honeycomb-like structure inside to guarantee stiffness. University of California at Santa Cruz astronomer Jerry Nelson opted instead to create a mirror not from a single huge slab of glass but from 36 smaller sheets that would, under a computer's control, act as one. And in Europe, design teams came up with yet another idea, the exact opposite of Angel's: instead of making the mirror hollow to save weight, let it be thin--about 8 in. thick for an 8-m mirror, in contrast to the 5-m Hale's 26 in.--and counteract the resulting floppiness with computer-controlled supports that continually readjust its shape.