Despite giant new observatories and fancy satellites, scientists find their view of the cosmos increasingly obscured by the by-products of a technological society. At a recent meeting of the International Astronomical Union in Vienna, researchers singled out some particularly galling modern pollutants:
Space Junk The Department of Defense tracks 8,500 objects in orbit around Earth, including dead satellites and bits of expended rocket stages. Orbiting debris threatens commercial and scientific satellites alike. Even telescopes on the ground could be affected. "Iridium communication satellites are shiny and flat. If a telescope catches sunlight glinting off one of them, it can burn out a detector," says Patrick Crane, an astronomer at Interferometrics in Chantilly, Virginia.
Light Pollution Stray light from street lamps wastes energy and robs city dwellers of the night sky's beauty. Astronomers at Mount Palomar, near San Diego, have worked with local officials to find mutually beneficial solutions. Mount Wilson Observatory, near Los Angeles, has all but given up deep-sky astronomy.
Interference From Electronic Devices Cell phones, pagers, and other wireless gadgets are broadcasting their signals at some of the frequencies that most interest radio astronomers--and companies are always looking to expand into new parts of the radio band.
Advertising There are serious proposals for placing conspicuous billboards, mirrors, and solar power stations in Earth orbit. The first attempt at such a project, a Russian mirror that would work as a huge spotlight, failed last winter.