The universe’s past, in close-up
If there were a Guinness world record for making telescope mirrors, Dean Ketelsen would likely win it. Colleagues boast that the onetime Iowa farm boy has ground and polished more square footage of optics than any human being alive.
“It used to be a mysterious thing that hunch-backed people in white coats did,” the 55-year-old technician said while taking a break at the University of Arizona’s Steward Observatory Mirror Lab. “Now we use machines to grind the glass. They’ve taken a lot of the black arts out of it.”
Maybe so. But Ketelsen can’t help being as proud as a soccer parent of his latest achievement. Resting behind him in the laboratory under the university’s football stadium was the first of seven huge mirrors being made for the Giant Magellan Telescope.
One of a new generation of super-large, ground-based telescopes being constructed around the world, the Giant Magellan’s 80-foot-diameter light-gathering area will dwarf the largest telescopes in the world.
“It’s just amazing what these new telescopes will resolve,” Ketelsen said.
Not since the 1980s, when the last generation of big telescopes was built, led by the twin 33-foot Keck telescopes on Mauna Kea, Hawaii, has there been such an air of anticipation in the world of astronomy.
The Magellan instrument, powerful though it will be, is the smallest of three monstrous telescopes in various stages of construction around the world.
Together, they will at last pull back the curtain from the universe’s birth chamber, allowing scientists for the first time to study the processes that created today’s mature cosmos of planetary systems, stars, galaxies and galaxy clusters -- all flying apart at breakneck speed.
“We’re going to be able to peer back into the universe’s dark ages, when everything got started,” said Chuck Steidel. Steidel is an astronomy professor at Caltech, which, in combination with the University of California, is planning the Thirty Meter Telescope at Mauna Kea in Hawaii.
Even its 98-foot-diameter light-collecting area will pale before the European Extremely Large Telescope, which will possess a collecting area 138 feet across.
For comparison, consider that the famous telescope on Mt. Wilson, with which Edwin Hubble made some of the greatest scientific discoveries of the 20th century, had a mirror just over 8 feet across.
The official date of “first light” when all three telescopes begin their work is 2018. The real date is a secret because all three are racing to be first.
“Being first matters,” said Gary Sanders, who is designing the Thirty Meter Telescope. “When you open a window, the first to look through it sees the most exciting things.”
Scientists like to refer to big telescopes as time machines, because the farther into space they peer, the more ancient the light they are seeing. Currently, the best time machines we have are the Keck telescopes and a handful of others in that size range, as well as the Hubble Space Telescope. The new telescopes will be anywhere from 10 to 100 times more sensitive than those.
They will scroll the calendar back more than 13 billion years, to the era when the first structures in the universe began forming out of the murky plasma that dominated the first few hundred thousand years after the Big Bang. That era is referred to as the dark ages because the universe, mostly made of hydrogen atoms, was neutral and opaque, without stars.
The next 5 billion to 6 billion years is when the universe developed into the form we know today.“We have an inkling of how that worked, but TMT will allow us to understand the details,” Steidel said.
“We’re going to be able to witness the first galaxies assembling,” said Wendy Freedman, director of the Pasadena-based Carnegie Observatories, which is building the Giant Magellan Telescope in Chile. “We’ll also be able to study the first black holes.”
The new telescopes should also help us find planets outside our solar system. Currently, scientists infer the presence of planets around other stars by, for instance, the way they cause the star’s light to dim when the planet crosses in front of it.
Markus Kissler-Patig, the project scientist for the European telescope, said its giant “light bucket” might see Earth-like planets for the first time, “if the star is close enough.”
Finding such planets is the Holy Grail in planetary science, bringing us a big step closer to finding life elsewhere in the universe.
The new telescopes could also help unravel the biggest mysteries in cosmology today: What is dark matter and dark energy?
The price is right
For years, the Hubble Space Telescope has led the world in astronomical research, filling books with stunning photographs of nebulae and galaxies. So why a new generation of ground-based observatories?
“There isn’t any doubt that if money were no object, you’d build all telescopes to go to space,” Steidel said.
But money is an object. Take, for instance, the James Webb Space Telescope, the successor to Hubble being built by Northrop Grumman Aerospace Systems in Huntington Beach. Scheduled to launch in 2014, the infrared space telescope is expected to cost at least $3.5 billion.
The Giant Magellan Telescope, whose light-gathering surface is nearly four times the diameter of Webb’s 21 feet, will cost about $700 million.
A key technological innovation allowing the giant scopes to compete with Hubble and Webb is adaptive optics, which enable a telescope to screen out the blurring caused by the Earth’s atmosphere.
The system works by shining a laser at a bright star, or by creating a fake star by bouncing the laser off sodium ions high above the Earth.
The instrument measures the amount of distortion in the beam caused by atmospheric turbulence, then relays this information 800 times a second to the telescope, which compensates for it. A muddy, twinkling star suddenly flares up into a diamond-sharp point of light.
Despite the tight economy, all three projects claim to be well on the way. Some $330 million has been committed to the projected $1-billion Thirty Meter Telescope, and Carnegie’s partners have committed $200 million to the Giant Magellan. Kissler-Patig said about 100 million Euros of the total expected cost of 950 million Euros (about $1.5 billion) has been spent designing the European telescope.
To those who ask why three big telescopes, Freedman pointed to the 1980s, when the Keck telescopes were planned. People said there would be no room for others. “In the end, we got 17 telescopes in the 6- to 10-meter range,” she said.
Caltech’s telescope and the European instrument have the same design, using hundreds of small mirrors, each about 4 feet in diameter, to make one giant mirror.
The Giant Magellan Telescope alone is relying on big mirrors. The design calls for six mirrors, each 27.5 feet across, arranged in a circle around a seventh mirror in the center.
The arrangement makes polishing a challenge because each mirror has to be shaped differently.
“Making big mirrors is like Julia Child making a souffle -- success is in the details,” said Peter Wehinger, a staff astronomer at the Steward Observatory.
The lab in Tucson is the only place in the world where big mirrors are being made. And Ketelsen is the acknowledged high priest of the mysterious process. He’s proud that he’s never lost a mirror, though he has come close. When he made his first big mirror, two tons of glass leaked out before he fixed the problem.
The first step is to load 48,000 pounds of glass costing $1.2 million onto a rotating carousel. Then the lid is clamped down on this giant crock pot and the whole mass is cooked for a week at 2,160 degrees. After the glass is melted into the shape of a giant cookie, it is allowed to cool for 12 weeks.
After that, it is moved into the polishing room. That’s where the first of the Giant Magellan Telescope mirrors was resting on a recent afternoon. Even though that mirror was cast in 2005, polishing had yet to begin. Wehinger said it would take eight or nine years to finish the telescope.
For Ketelsen, the Giant Magellan Telescope will be the crowning achievement of his life.
“Being part of this is a real blast,” he said.
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