How Much Light Pollution is Out There?

Here's your mission, should you choose to accept it: Look up in the sky after dark and count the stars you see.

As part of a worldwide push to gauge how much light pollution is out there, a scientific organization is asking people to look for specific constellations during the next two weeks and share observations on the Internet.

You probably won't be able to see the Milky Way from your San Jose backyard, experts say - but this area is still better off than some when it comes to the artificial lighting that illuminates the sky and interferes with stargazing. It isn't as bright as Los Angeles, isn't as gaudy as Las Vegas, and is home to the Lick Observatory - which has worked closely with San Jose officials to ensure special streetlights are used here.

The stargazing effort, dubbed the Great World Wide Star Count, is open to anyone who has access to a computer and the World Wide Web. And while scientists hope it will help them map light pollution on a global scale, they do have another motive.

"We want people to go outside and look up, to appreciate the night sky," said Dennis Ward, an educational technologist and astronomer with the University Corporation for Atmospheric Research in Boulder, Colo. The consortium of universities is organizing the event along with planetariums and scientific societies across the country.

Under perfect conditions - no moon, a clear sky and minimal light pollution - a stargazer should be able to see as many as 14,000 stars, Ward said. But in many major cities, where used car lots, shopping malls and football stadiums illuminate the night, often fewer than 150 are visible.

"It's pretty bad," said Ben Burress, staff astronomer at Chabot Space & Science Center in Oakland. "People who live in cities tend to not think about the nighttime sky very much because they can't see it very well," he said. "You can't just walk outside and see something really enthralling."

That's a shame - and probably a major deterrent to kids developing an interest in the sciences these days, said Bob Gent president of the board of directors of the International Dark-Sky Association in Tucson, Ariz. When Gent was a young boy growing up in Phoenix, he could view a sky filled with thousands of objects, including his favorite, the Milky Way.

Seeing the constellations made him curious about the universe and our solar system, and instilled in him a respect for the outdoors.

"I became an astronomer for life by the time I was 5 years old," he said. "But now we've lost the heritage of dark skies in these big cities."

Light pollution has become a growing problem around the globe, fueled by urban sprawl and a growing population. Satellite images show much of the U.S. eastern seaboard is socked in by light pollution, as well as most large cities across the rest of the country.

Among the problems caused by light pollution: Bright lights have interrupted the migratory patterns of birds and disoriented baby marine turtles. As a result, dozens of communities across the country have begun to enact ordinances aimed at reducing the glare.

"It's not just astronomy impacted," Gent said. "It's a wildlife issue. It's the loss of the inspiration of the night sky. It's all those - while we're wasting energy."

When it comes to lighting, many city governments and private corporations have kept safety issues - and good business - squarely in mind, opting to keep streets, parking lots and store displays well-lit. While dark-sky advocates aren't calling for blackened city scapes, they do point out that some lighting is purely ornamental and unnecessary - think Las Vegas.

Despite the fact that the Bay Area has been densely populated for decades, it wasn't that long ago that you could drive a little ways and get a magnificent view of the sky, said Marni Berendsen, education project coordinator for the San Francisco-based Astronomical Society of the Pacific. During the early 1990s, for example, Berendsen would go to Mt. Diablo near Walnut Creek to see the Milky Way.

No longer.

"As the years go by and more and more houses are built at the base of the mountain," she said, "we're really starting to lose our dark sky up there."

San Jose is one community that has made great strides to reduce its light pollution - at least the kind that can obstruct observatory instruments. Of the city's 60,293 streetlights, an estimated 51,341 are low-pressure sodium lights, energy savers that give off a yellowish hue. They produce a light that researchers at the Lick Observatory can easily filter out.

"They've really gone out of their way to help the observatory," said Burt Jones, assistant director of Lick. "Most cities are not like that."

Organizers of the Great World Wide Star Count wish more communities would take similar steps to turn down the lights. If their event becomes an annual one as they envision, scientists will be able to compare data from year to year and map the light-pollution changes. They hope their event will raise awareness of the issue, while shedding light on how poor the stargazing is from some urban centers.

"That's one of our goals," Ward said, "to make people understand there could be so much more."