Biggest Telescope Takes a Gander

AMSTERDAM--The world's largest optical telescope is wowing astronomers even before it is finished. At a press conference here today, the European Southern Observatory (ESO) unveiled the first images from the Very Large Telescope (VLT), which will consist of four identical 8.2-meter telescopes that can operate in tandem (Science, 1 May, p. 670). Currently, only the first telescope is finished; the others will be completed in the next 3 years.

The test observations were hampered by clouds (very rare at Cerro Paranal, which experiences 350 clear nights per year) and a moderate earthquake. "Fortunately, the earthquake protection system worked very well and put the delicate mirror in safe mode to prevent damage," says ESO astronomer Lex Kaper, a member of the First Light team. But even at this stage, the VLT was able to probe the sky in sharper detail than any other ground-based telescope, ESO astronomers said.

The VLT images reveal subtle wisps of gas in the outer regions of a planetary nebula called the Butterfly Nebula (NGC 6302) and faint jets and bow shocks in the Eta Carinae Nebula, along with details of galaxies and star clusters. "Already, we are reaching and exceeding the specifications that we expected to reach within 3 years," says Kaper. The VLT's active mirror support system helps explain its eye for detail. Computerized actuators at the back of the mirror--150 of them--control its shape, compensating for slight distortions due to temperature changes, wind load, and gravity.

When the other three telescopes are finished in 2001, the Very Large Telescope will be able to reveal objects of unprecedented faintness in the distant universe. Says Leiden University cosmologist George Miley: "The VLT will enable us to unravel the formation history of galaxies. Astronomers will become the ultimate historians and archaeologists [of the cosmos]."