This autumn, the main thing astronomers in part of the Washington area will see through their telescopes is irony. Discovery Communications, the parent company of the cable television channel specializing in science-orientated programmes and which sells telescopes in its shops, is planning to build a new global headquarters—with an illuminating twist.

The intended site is at Silver Spring, Maryland, not far from the Washington headquarters of the US space agency NASA. And the most prominent feature of the new building will be a 300-foot tower shooting a powerful beam of light into the night sky.

That is intolerable, say the area's astronomers, who are increasingly sensitive to the issue of ‘light pollution’, and are bemused that Discovery does not seem to be. “Isn't part of their charter to promote science and protect the environment?” asks Bob Gent, public affairs officer for the International Dark-sky Association (IDA). “Yet here they are destroying the night sky and ruining astronomy.”

The night sky above the US capital is steadily deteriorating, as it is over most major cities around the world. “Light pollution in Washington is becoming more of a topic of concern for everyone,” says John Settle, president of the Greenbelt Astronomy Club, an amateur group in Greenbelt, Maryland, which is near Silver Spring. “This is probably the second most polluted area [in the United States] after New York City, and this light will only degrade the quality of life for everyone around here. Its only purpose seems to be an ostentatious display of corporate power,” he says.

Settle says that in the Greenbelt area, which is also home to an astronomy club composed of employees at NASA's Goddard Space Flight Center, star-gazers can see only second-magnitude stars. Spotting fifth- or sixth-magnitude stars, he says, needs more than an hour's drive.

There is no major astronomical research left in the Washington area, and the US Naval Observatory moved its heavy equipment and operations to Arizona more than 40 years ago.

Geoff Chester, the observatory's spokesman, questions the reason for the planned tower light: “Why would anyone want to waste photons for something that's just going to light up the bellies of airplanes?” However, he doubts whether it will have much impact on the observatory's small-scale work.

But Gent says he has heard numerous complaints, not only from amateur astronomy clubs. “The American Astronomical Society has contacted me. So has the University of Maryland astronomy department,” he says.

David Leavy, spokesman for Discovery Communications, says he is unaware of any complaints except for one letter from the IDA. But he admits that a recent article in a local paper about the plans for the building has made the company sensitive to the concerns.

So far, he says, no changes have been made to the design. “But as we go forward we'll be consulting with the organizations to make sure this structure is something… that will be environmentally sound and will not cause any celestial inconvenience.” Rest assured, says Gent, the IDA will be watching.