Lighting and astronomy

Abstract

The sky is fading. Prime sites for astronomical observatories are rare. A stable, clear, dry atmosphere is crucial. Yet many of the best sites worldwide are slowly losing their view of the most distant astronomical objects as more and more stray light appears in the last microseconds of what may have been a 10-billion-year journey. That intruding light comes from outdoor lighting used for roadways, parking lots, advertising, and decoration and from automobile headlights. It gets into the sky, and ultimately into telescopes, either directly from light fixtures or through reflection off the ground or other surfaces, followed by scattering from molecules and aerosols in the atmosphere. Largely because of that stray light, or sky glow, new giant telescopes are being built in the most remote corners of the planet. Yet even those sites are now threatened by artificial light from communities that may be located hundreds of kilometers away, as shown in figure 1. © 2009 American Institute of Physics.