Astronomers Encourage Cities to Shield Outdoor Lighting

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Astronomers Encourage Cities to Shield Outdoor Lighting

Our home galaxy, the Milky Way -- that iconic stream of stars coursing across the night sky -- cannot be seen by one-third of humanity and 80 percent of Americans. As the artificial glow from towns and cities increases every year, and starry nights become unfamiliar to many, astronomers and dark-sky advocates are pushing to reduce light pollution -- starting with changes to outdoor lighting.outdoor lights

The American Astronomical Society passed a resolution at their annual meeting in Grapevine, Texas this month, “affirming that access to a dark night sky is a universal human right, making quality outdoor lighting a worldwide imperative.”

The organization also endorsed a set of recommendations for outdoor lighting. In short, “shield the light, dim it, and use redder, warmer colors,” said Lori Allen, director of the Kitt Peak National Observatory in Arizona.Light pollution from street lights, lit billboards and other outdoor light fixtures affects many people and wildlife species, nocturnal and diurnal alike. “It has huge effects on public health, the environment and certainly for astronomy,” said James Lowenthal, an astronomer at Smith College in Northampton, Massachusetts. Astronomers at observatories can see the effects of light glow from a city hundreds of miles away, to their dismay.

Many cities transformed their outdoor lighting following the recent revolution in light-emitting diodes, or LEDs. Blue LEDs earned three engineers the Nobel Prize in physics in 2014, since blue was the last color needed to make white LEDs. The new lights are now ubiquitous in smartphones, computer screens and energy-efficient light bulbs.

Nevertheless, these blue-white LEDs turned out to be worse for light pollution than the orange high-pressure sodium lights they replaced. Blue light at night can disrupt people's sleep cycles by suppressing melatonin, a hormone that normally helps people sleep, more than other colors of light, said Martin Aubé, a physicist at University of Sherbrooke in Québec, Canada. Blue light also obscures people's view of the night sky more than reddish lights.