MICHELE NORRIS, host:
Here's a story about space that does not involve the shuttle. Over the last 20 years a generation of big telescopes has allowed astronomers to discover planets and galaxies far, far away. But those telescopes are nothing compared to what's coming. Mirrors for what will be the world's largest telescope are now being cast in a unique facility in Arizona. NPR's Ted Robbins paid a visit.
TED ROBBINS reporting:
Underneath the east bleachers of the University of Arizona football stadium in Tucson is a sort of merry-go-round, but you wouldn't want to ride it. It's a huge, two-story, rotating furnace with 20 tons of molten glass inside.
Mr. STEVE MILLER (Manager, Steward Observatory Mirror Lab): The maximum casting temperature here will be about 1,180 degrees Celsius.
ROBBINS: In Fahrenheit, that's...
Mr. MILLER: Oh, gee, almost--about twice, 2,200 something, yeah.
ROBBINS: Steve Miller manages the Steward Observatory Mirror Lab, the only place in the world using this method to build mirrors this large: 8.4 meters, or 27 feet. The rotating furnace naturally creates a concave mirror, a bowl, that can effectively gather and focus light.
Mr. MILLER: It's the centrifugal force that throws the glass up against the sides. You could demonstrate this on a carousel in a microwave oven. You know, you could put a bowl of water in there and rotate it around. You can see that the forces will send it out.
ROBBINS: Another unique feature of this process: As the glass melts, it flows around ceramic forms inside the furnace, creating a mirror a few inches thick on top of a glass honeycomb. That makes it just one-fifth the weight of a solid mirror. The process is risky. Scott DeRigne is an oven pilot in charge of the furnace rotation.
Mr. SCOTT DeRIGNE (Oven Pilot): If it's too fast, we end up with too much glass at the outside of the mirror and too little in the middle, or if it's too slow, just the opposite; too much in the middle and too little at the outside.
ROBBINS: The whole thing could collapse into an $8 million blob. That's never happened, but the possibility is enough to keep DeRigne obsessively listening to the rotating motor during the three-day period of highest heat.
Mr. DeRIGNE: So you want to go downstairs and hear the noise that keeps me awake for three days?
(Soundbite of motor)
Mr. DeRIGNE: But I hear this repetitious circling of that one whiny motor, and it's just music to my ears, OK?
(Soundbite of motor)
ROBBINS: Cooling the furnace will take almost three months. Then the mirror will move to another room for polishing to within a billionth of a meter accuracy. That takes about a year. Eventually the mirror will join six other mirrors surrounding a seventh central mirror to become the Giant Magellan Telescope on a mountaintop in Chile. University of Arizona astronomer Roger Angel says it'll look sort of like a six-petaled flower.
Mr. ROGER ANGEL (Astronomer, University of Arizona): The petals are all circular, and they're nearly touching so that, you know, most of this whole 24 meters is covered with the reflecting glass.
ROBBINS: Twenty-four meters is about 78 feet across; that's more than twice the size of the largest existing telescope. The Giant Magellan will be so large and its optics so precise that it will have 10 times the resolution of the Hubble Space Telescope. In human terms, you'd be able to see a man on the moon. But astronomers will look farther, hoping to directly observe some of the dozens of planets spotted orbiting other stars. Wendy Freedman is director of the Carnegie Observatories and head of the consortium sponsoring the Giant Magellan Scope.
Ms. WENDY FREEDMAN (Director, Carnegie Observatories): With a telescope this size, you can spread the light out into its components in a spectrum and actually look at the atmospheres of these planets and determine what they're composed of and learn about planets in worlds far away from our own. So it's a very exciting opportunity.
ROBBINS: So far the consortium has raised only part of the telescope's $500 million price tag. And there's competition from the 30-meter California Extremely Large Telescope, and--yes, this is its name--the 100-meter European Overwhelmingly Large Telescope. But those are in the planning stages. The Giant Magellan Telescope is the first to begin construction. It's due to see first light in 2016. Ted Robbins, NPR News, Tucson.
ROBERT SIEGEL (Host): This is NPR, National Public Radio.
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