Word: mirror
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...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...
...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...
...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...
...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...
...ultraviolet, for example, and some wavelengths of infrared--can't penetrate the atmosphere at all. Moreover, telescopes radiate infrared light of their own, which contaminates celestial images. That's why NASA's plan to launch a Next Generation Space Telescope by 2009 still makes sense. With an 8-m mirror of its own, NGST will be able to see distant galaxies, for example, that no earthly telescope could ever see through the glare of its own heat...