Back Through Time : Giant Telescopes Afford Look at Beginning of Universe
High atop this dormant volcano, nearly three miles above the warm waters of the Pacific Ocean, scientists are building the most powerful telescopes in the world, massive instruments that will allow them to peer back through nature’s time machine to the beginning of the universe.
Giant strides in the understanding of the evolution of the cosmos are expected to be made here with telescopes so powerful they will produce images of objects so far away that their light is just now reaching Earth after traveling all the way from the fringes of the universe. If there is anything beyond that, and most scientists doubt that there is, humans may never know because light from more distant objects would not have reached here in the 15-to-20-billion-year history of the observable universe.
“We hope to see the real creation and the evolution of the universe as we see it today,” said astronomer Don Hall, whose domain includes this mountain, destined to become the premier astronomical facility in the world.
No Idle Fantasy
Hall’s dream is no idle fantasy.
The huge telescopes here, and those that will soon join them, “will be the workhorses for the next 50 years,” a time that should bring the answers to many of the questions that have bedeviled scientists for centuries. For here on this mountain, rising above the youngest and largest island in the Hawaiian chain, light years away from the balmly beaches of Waikiki, nature has given scientists a most extraordinary treasure.
Work is nearing completion on the dome that will house the largest telescope ever built, a 10-meter giant so powerful it could capture the light from a single candle on the surface of the moon. And the pastel cinder cones that dot the summit like snowcapped fingertips pointing toward the heavens are themselves capped with some of the most sophisticated telescopes in the world today. More are in the works, ensuring that this mountaintop will almost certainly dominate astronomy in the years ahead.
“Mauna Kea has conditions that are not duplicated at any other site in the world,” said Hall, who is director of the University of Hawaii’s Institute for Astronomy.
Because of a wide range of factors, the images captured in the big scopes here are simply sharper and clearer than those that can be acquired anyplace else, Hall and many other astronomers contend.
Advantages of Site
The clarity of the images is due partly to the simple fact that the mountain is so high, at nearly 14,000 feet. The Earth’s atmosphere absorbs light in some of the most important wavelengths that scientists want to study, but that problem is reduced somewhat at this altitude, thus permitting the United Kingdom, The Netherlands, the U.S. National Aeronautics and Space Administration and Caltech to build some telescopes here that would not work in less desirable locations. They have come here partly because such nuisances as city lights have driven them away from other locations, and partly because Hawaii has mounted an aggressive campaign to become the world center of astronomy.
One crucial factor in the success of an observatory is the dryness of the air. Although located on an island, the air above this peak contains only a small fraction of the water vapor found at sea level.
And atmospheric conditions similar to those that trap smog in the Los Angeles Basin keep it that way.
“At 7,000 to 9,000 feet altitude, there is a very strong inversion layer,” Hall said. “It acts as a barrier which tropical moisture cannot penetrate. That traps moisture below.”
It turns out that islands are ideal for observatories because the absence of a continental land mass reduces convection which would lift moisture to higher altitudes.
‘Quality of Images’
“It’s as though you had a platform at 14,000 feet,” Hall added. “The most crucial thing is the quality of the images.”
The proof of that lies in the fact that Caltech and UC Berkeley chose this spot to build the $87-million Keck Telescope. With the equivalent of a 10-meter mirror--twice the diameter of the famed Hale Telescope on Palomar Mountain in Southern California and four times as powerful--Keck will be the most potent telescope in the world. And for several years, until even more powerful telescopes come on line here, it will capture more light from distant objects than any other telescope can match, even the $1.2-billion Hubble Space Telescope that is to be launched soon after the space shuttle begins flying again.
Keck’s huge dome, as tall as an 11-story building, is nearing completion here. Sometime in 1991, after a yearlong trial run for calibration and adjustments, the 36 hexagonal mirrors that are to act in concert as a single mirror should begin their reign as the largest telescope in the world, far larger than scientists had thought possible only a few years ago.
The most critical part of any great telescope is the mirror that must capture light from objects billions of light years away and focus that light on instruments that will analyze it and produce electronic images.
Large Scopes’ Problems
As recently as the early 1970s, it appeared that mirrors larger than the 200-inch reflector at Palomar would not be practical because anything larger would be too difficult to manufacture, too heavy to mount in a telescope that must track distant targets perfectly for hour after hour, and too susceptible to deformation caused by temperature changes and gravity. Many scientists suspect that the Soviet Union, which now boasts the largest telescope in the world--six meters--learned that the hard way. There has been very little scientific data published from research using that giant scope, suggesting that its performance has been disappointing.
But in recent years scientists have come up with efficient ways of making mirrors on a grand scale. The University of Arizona, for example, has pioneered the concept of using a spinning furnace to create giant, nearly perfect ceramic blanks that can be coated and used as mirrors. As the spinning furnace cools, the molten material hardens in the desired shape.
Japan hopes to build a 7.5-meter telescope using that technology, and a site for that facility has already been picked here. If final financing is approved as expected, that telescope will become the Japanese government’s first major facility built outside of Japan, except for diplomatic offices, Hall said.
The Keck telescope is part of a new breed of super-scopes that will use multiple mirrors to do the work of one. Keck will use 36 mirrors, each about 6 feet across, but the technological challenges are substantial. To work, each mirror must be identical to all the others, or it will be impossible to focus them as a single unit. And each must be operable with such precision that they can act as one, so it must be possible to align them within an accuracy of one-millionth of an inch.
One advantage of using 36 mirrors is that they are small enough to be much lighter, and weight is a critical factor when it comes to moving a giant telescope. The mirror blanks are being ground and polished in Germany, and shipped to Itek Optical Systems in Massachusetts where they are being cut into their hexagonal shape. One enormous hurdle appears to have been surmounted in recent weeks. Scientists have been concerned that the mirrors might deform after they are cut into hexagons, but several blanks have been cut and preliminary results indicate that it will not be a problem, according to Keck officials.
Multiple-Mirror Concept
Like the Keck, the 15-meter National New Technology Telescope which the federally funded National Optical Astronomy Observatories plans to build here, will also use the multiple-mirror concept. Four mirrors will be mounted together like a four-barrel shotgun, and officials hope to have it operational sometime in the next decade. If they are successful, it will supplant Keck as the world’s largest telescope.
Few visionaries thought that telescopes of that size were even remotely possible only a few years ago.
“It’s mind boggling,” astronomer Brent Tully said recently as he fought his four-wheel-drive vehicle along the torturous dirt road to the summit of Mauna Kea.
And the fact that so many of those facilities are destined to come here is no accident, he noted. “This is easily the best site in the world.”
That fact has been recognized by scientists all over the globe, although some contend that close rivals exist in the Southern Hemisphere, most notably in the Canary Islands.
The University of Hawaii, which acts as landlord for the state-owned summit, has actively sought international partners, and with considerable success. The largest telescope now operating on the mountain is owned by the United Kingdom, and it is a 3.8-meter giant. The second largest, measuring 3.6 meters, is owned by Canada and France.
In exchange for providing and maintaining the site, the University of Hawaii gets a minority ownership in all facilities, thus giving astronomers with the university an extraordinary opportunity to use any of the six observatories now on the mountain, and any of those that will come later.
Extraordinary Conditions
All of that is made possible by the extraordinary conditions at Mauna Kea, according to Hall.
That is especially important to astronomers who want to study stars in their formative stages, and the high quality of “seeing” at Mauna Kea has permitted them to begin exploring the last of the wave bands still possible from ground-based instruments.
The United Kingdom and The Netherlands recently completed the James Clerk Maxwell Telescope, which uses a 15-meter radar antenna to study gas in the dense clouds from which stars form. Similarly, Caltech’s 10-meter Kresge Telescope, also called a submillimeter telescope because of the wavelength at which it operates, recently began studying emissions from space in the far-infrared spectrum.
“This is a new area not explored until now,” astronomer Walter Steiger said recently as he stood outside Caltech’s Kresge Telescope.
“We are looking primarily at molecular clouds” in space, he said. “Optical telescopes cannot penetrate those clouds.”
The Kresge will help astronomers determine which molecules are present, and in what quantities, when stars form.
“We want to understand the processes,” Steiger said.
Air Makes Site Ideal
Several telescopes at Mauna Kea can study infrared emissions from space, another profound advantage of Mauna Kea. Moisture absorbs infrared, and the dry air above the mountain makes the site ideal for infrared research.
NASA, for example, has a 3-meter infrared telescope here that is so powerful it can measure the heat from the tiny moons of Uranus, although they are 2 billion miles away and have temperatures of about 300 degrees below zero.
Initial planning for Mauna Kea called for 13 observatories on the summit, and with six completed and the seventh well under way that goal probably will be reached much sooner than had been expected, Hall said. Several other projects, which he declined to specify, are in the works.
That should keep astronomers coming to the mountaintop for decades, but in the years ahead, those trips may become fewer and fewer. Automation is most likely the next major innovation in astronomy, Hall said, and that should make it possible for astronomers in places such as Europe or Southern California to operate telescopes atop Mauna Kea remotely just as though they were sitting in the control room on top of the mountain.
That might be a little less fun, but it would remove some of the frustration that comes when an astronomer who has waited for months arrives at the mountain only to learn that the occasional 100-m.p.h. winds have forced officials to shut down the observatory.
Would Be More Flexible
Remote capabilities would make the telescopes far more flexible because time could be assigned on the basis of observing conditions.
“Flexibility would allow you to match conditions with projects,” Hall said.
Every now and then, any astronomer will tell you, everything happens to fall into place and the viewing is just like magic.
“When one of those nights comes along, when it is so good it just knocks your socks off,” viewing time could suddenly be shifted to projects that would benefit the most from such extraordinary conditions, Hall said. That would include such things as the study of the most distant objects in the universe, those faint remnants of a past so far away that their light is just now reaching the Earth, revealing them as they were then, when they were so very young.
