Light Pollution in Central and Southern Arizona

Abstract

Since the advent of artificial illumination, humans have inadvertently brightened more space than they intended. Throughout the centuries, we have “lit up the night as if it were an unoccupied country, when nothing could be further from the truth." The phenomenon of light falling where it is neither wanted nor needed is known as light pollution.3 An unshielded light bulb produces excess illumination, and light spills into the sky and onto surrounding properties. It is estimated that the United States alone projects over $4.5 billion worth of excess light into the sky every year. While outdoor lighting is essential for businesses and residences alike, light pollution adversely affects the astronomy community. Arizona is home to eighteen telescopes and *1030 optic research facilities,6 which brought $252.8 million into the state in 2006. However, the cosmos is less visible now than it was several decades ago. It is not that the stars are dimmer; “rather, the Earth has become vastly brighter,” so that celestial objects are more difficult to see. The atmosphere is now less transparent and more reflective, with the stars looking washed-out as a result of sky glow. Arizona’s efforts in combatting light pollution began in in the 1970s, when astronomers working at the Kitt Peak National Observatory11 noticed a decrease in astronomical visibility of the night sky.12 This observation corresponded with the growth of the Tucson metropolitan area and its sky glow.13 Astronomers and academics persuaded local city and county officials to enact ordinances governing the brightness and intensity of external lighting. As a result of these efforts, the visibility of the sky in southern Arizona has held steady at 1970 levels. However, new state legislative actions such as permissions for electronic light-up billboards threaten to reverse this progress. In the coming decades, Arizona’s skies--and the lucrative astronomy industry that depends on them--are in danger because of the rapid and unchecked growth of the Phoenix area.