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International Technology : To World's Astronomers, Northern Chile Is Heaven : Giant new telescopes will make it the best place on Earth to view the universe. Europeans are leading the effort.


CERRO TOLOLO, Chile — Hundreds of astronomers come to northern Chile each year seeking to unravel the riddles of the universe. Arlin Crotts, from Columbia University, was here hoping to add to humankind's sketchy knowledge of how stars are born in turbulent clouds of galactic gas.

As a visiting astronomer at Cerro Tololo Inter-American Observatory, Crotts was using a telescope with a light-gathering mirror four meters (13.1 feet) in diameter, now the largest in the Southern Hemisphere and one of the biggest in the world. He said he was focusing on the Large Magellanic Cloud, a gaseous galaxy being ripped asunder by tidal forces that arise from the gravitational pull of the nearby Milky Way.

"So in the process of being torn apart, this gas is running into itself, being compressed, being shocked by collisions," he explained. "And when you compress gas, you form stars--although that process is a little mysterious."

Crotts, 34, puts little expression in his beard-fringed face, but when he talks about cosmic mysteries, his words twinkle with enthusiasm--as they do when he talks about northern Chile. This area, with three international observatories and two dozen telescopes, is a mecca for astronomers.

"When you combine all these telescopes, it's got to have more square meters than anywhere else," Crotts said.

From lofty peaks like Cerro Tololo, the telescopes look through crystalline desert skies that are cloudless 300 nights a year or more. To take advantage of these excellent conditions, more and better telescopes are being planned. When the next generation of super-telescopes is in place, experts say, northern Chile will have the most favorable combination of equipment and conditions on Earth for optical astronomy.

For example, European countries are preparing to build a new Chilean observatory that will boast a battery of four giant telescopes, each with a mirror measuring 8.2 meters (26.9 feet) in diameter. They will be linked electronically, yielding far greater power than any other system in the world.

"I think northern Chile is going to be the premier site in world astronomy," said Stephen Heathcote. "When these telescopes are built, it very definitely will be."

Heathcote, a staff astronomer at Cerro Tololo, said northern Chile's only rival in astronomical equipment and visual conditions is Mauna Kea, which at 13,796 feet is Hawaii's highest peak. (By comparison, the Cerro Tololo observatory is 7,220 feet above sea level.)

Four big new telescopes, including two with multiple-mirror assemblies equivalent to 10-meter circular mirrors, are to be installed at Mauna Kea by the end of the century. But no instruments there will be as powerful as Europe's planned battery in Chile. And Heathcote said that Mauna Kea, which gets "clouded out" much more frequently than northern Chile, is running out of space for more new telescopes.

There is no shortage of good sites in northern Chile. Its three existing international observatories are on different mountains less than a two-hour drive from La Serena, a pleasant provincial capital and beach resort 250 miles north of Santiago, the national capital.

* Cerro Tololo observatory was built in 1963 by the U.S. government's National Science Foundation and is operated by an association of American universities. In addition to its prestigious 4-meter telescope, Tololo has five others with smaller mirrors.

* Las Campanas, an observatory run by the Carnegie Institute, is the smallest of the three observatories. It has three telescopes, including a highly rated 2.5-meter (8.2-foot) instrument that has the widest field of view of any large telescope in the world.

* La Silla, the European Southern Observatory, is operated by governments of Western Europe. It has 14 telescopes, including the 3.5-meter (11.6-foot) New Technology Telescope, or NTT, the most advanced of its kind.

With the 4-year-old NTT, the Europeans have taken a technological leap ahead of the American observatories here. Its "thin meniscus" mirror (the term describes a shape that is concave on one side and convex on the other) is mounted on dozens of computerized levers, or "actuators," that automatically make minute adjustments in the reflecting surface to correct distortions caused by gravity as the Earth and the telescope turn. The system, called "active optics," gives the NTT's images a sharpness that other telescopes rarely achieve.

Active optics was made possible by high-powered computers, which are needed to quickly calculate and correct mirror distortions.

Like the NTT, the four new 8.2-meter telescopes planned by European astronomers will have thin meniscus mirrors and active optics. Europe is building the new observatory on a barren peak named Paranal near the city of Antofagasta.

The Paranal complex, called the Very Large Telescope or VLT, is expected to be completed by the end of this decade or the beginning of the next. Hardware alone will cost an estimated $250 million.

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