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Mercury, May/June 2002 Table of Contents

Courtesy of the European Southern Observatory.

by Govert Schilling

Italian astronomer Roberto Gilmozzi envisions a 100-meter telescope – an instrument that would make current telescopes seem like opera glasses.

Give him one billion euros, and Roberto Gilmozzi will build you the largest telescope in the world – an instrument that would completely dwarf the current generation of giant telescopes. His telescope would be as high as the Great Pyramid in Egypt, and 10,000 times more sensitive than the 10-meter Keck telescopes in Hawai’i. "Everybody told me I was crazy," says Gilmozzi, "but meanwhile, we have completed the basic design."

Gilmozzi is not a crackpot fantastique. Since October 1999, the Italian astronomer has been Director of the Paranal Observatory in Chile, where the European Southern Observatory (ESO) is completing its Very Large Telescope, an interferometric array of four telescopes, each with a mirror diameter of 8.2 meters. Gilmozzi is confident his dream can be fulfilled. Four years from now, ESO could start constructing the OWL (OverWhelmingly Large) Telescope.

OWL will boast a 100-meter mirror, a gigantic optical device larger than a football field (European or American). The secondary mirror will be larger than a basketball court. The spherically-shaped mirror surface will consist of some 2,000 hexagonal segments, and the telescope construction will also be pieced together from identical building blocks. Despite its enormous size, the giant instrument will weigh a mere 9,000 metric tons. If that sounds heavy, consider the fact that if Keck were scaled up to the same size, it would have a moving weight of 270,000 tons.

Using OWL, astronomers hope to study the very early evolution of the universe, decipher the formation of stars and planets, and prove the existence of Earth-like planets orbiting other stars. OWL will have milliarcsecond resolution and a limiting magnitude of 38 (meaning OWL will be able to detect objects more than 1,500 times fainter than the faintest objects in the Hubble Deep Field). It could easily resolve brown dwarfs in other galaxies, find supernovae out to the visible edge of the universe, and take spectra of extrasolar planets.