Mega-Telescope Rises in Chile

EIGHT European countries are cooperating in the construction of the world's largest telescope, which they say will have "a profound impact" on the science of cosmology - the study of the structure and evolution of the universe.

The instrument, known simply as the VLT - Very Large Telescope - "will allow observation of the faintest and remotest parts of the known universe," according to Daniel Hofstadt, technical manager at the European Southern Observatory (ESO) at La Silla in Chile's arid north.

The VLT, scheduled to be in partial operation by 1996 and complete by 2000, will be built on what scientists think is the driest spot on earth, a 2,664-meter (8,700-foot) peak at Cerro Paranal in Chile's Atacama Desert.

Lack of moisture and the absence of interfering light sources convinced researchers that Cerro Paranal is a better location than La Silla itself, where ESO already operates 14 telescopes.

Although ESO scientists insist that they maintain a "friendly" rivalry with US astronomers (who operate another observatory nearby), the European governments putting up the 382 million deutsche marks (about $187 million) for the project may have a more competitive view.

European scientists will be "second to none" in space exploration with the completion of this "astronomer's dream," reads an ESO news release. Another says the VLT's images will be almost as sharp "as if it were in space," as is the US-built orbiting Hubble telescope.

Hofstadt says the Hubble has advantages because it is outside the earth's ultraviolet-ray barrier and other distorting influences. But the size of the VLT will give it distinct capabilities. It will look for planets around nearby stars, study stars born in interstellar clouds, and probe the innermost regions of the active galaxies.

Experts say the new technology will undoubtedly lead to "wholly unexpected discoveries."

Such surprises are already fairly common, as a recent visit to La Silla revealed. A German team visiting to update 10-year-old data on a particular star found it losing mass and heating up, contrary to expectations.

"That's not supposed to happen, according to the theories," said astronomer Klaus Teschner, on the ride down the mountain.

Scientists from member countries (Germany, France, Belgium, The Netherlands, Sweden, Italy, Denmark, and Switzerland) apply competitively to use "observing time" at the ESO.

European astronomers are excited about the new discoveries the VLT will likely bring. "Seeing deeper into the universe as we will with the VLT," says Belgian astronomer Cristoffel Waelkens at La Silla, "puts us in touch with an earlier period in the creation of the universe.

"These extremely critical observations will enable us to see galaxies forming and pinpoint all kinds of theories with much more detail," says Dr. Waelkens, a professor at Louvain University.

The VLT will have four separate telescopes that are each 8.2 meters in diameter (26.8 feet). When the images from the four telescopes are combined, the total light-gathering power of the apparatus will be the equivalent of a 16-meter (52.5-foot) telescope. Larger telescopes like the VLT penetrate farther into the universe, because they can collect more light and other radiation.

Fabricating such a huge piece of glass is a technological challenge in itself. The ESO has contracted with the Schott Glassworks of Mainz, Germany, to build the razor-thin mirrors out of Zerodur, a glass-ceramic material. Schott is building special rotating molds for the four concave disks. Polishing alone will take six months after casting.

The VLT will contain 200 computer-controlled panels built under each mirror to allow an operator to make tiny adjustments for distortions. This technology has already been incorporated and tested by ESO on an earlier model.

The VLT will be satellite-linked to Europe, so that an astronomer at ESO headquarters in Munich can work with its data just as well as an on-site scientist in Chile.

Not all the technological advances are received with enthusiasm by the astronomers themselves. Doing their field research via satellite from a European office doesn't appeal to some.

"You come to Chile, you go up the mountain, you look at the stars," says Mr. Teschner. "Sitting at a computer terminal in Munich, it's not the same."

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