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The City Dark

Premiere Date: July 5, 2012

'The City Dark' in Context

Effects of Light on Astronomy

Irving Robbins, a Brooklyn-born astronomer running the last remaining observatory on Staten Island, New York, is a reminder that stars could once be studied in New York City. Now only the brightest objects shine through the light-polluted sky. Robbins says, "I've seen the Milky Way twice — when there were blackouts."




The City Dark introduces Irving Robbins, a Brooklyn-born astronomer running the last remaining observatory on Staten Island, New York. He is a reminder that stars could once be studied in New York City. Now only the brightest objects shine through the light-polluted sky. Robbins says, "I've seen the Milky Way twice — when there were blackouts."

Filmmaker Ian Cheney leaves New York City seeking darker skies and finds his way to Sky Village, a dark-sky haven for astronomers in rural Arizona. The village's denizens come from all walks of life. What draws them together is their need to be close to a dark night sky. Cheney visits a mountaintop in Mauna Kea, Hawaii, considered the best site for professional astronomy in the world. Here, astronomers rely on Pan-STARRS, the world's newest, largest telescope-camera, to detect Earth-killing asteroids, but urban growth in the valley below creates a luminous haze that impedes their work. "It's as though you're looking through fog," says John Tonry of the University of Hawaii.

Beyond the problems of decreased visibility due to urban sky glow, light trespass, glare and clutter, astronomers face another problem caused by light pollution. Not only is the night sky harder to see, but the objects astronomers can see are more difficult to analyze. Astronomers analyze the physical properties that make up stars, galaxies and other objects in the sky through spectroscopy. Spectroscopy is the analysis of the color components of light of an object. For astronomers, this means creating a spectrogram showing the optical spectrum of a given galaxy. The spectrogram allows the astronomer to use these color components of light to figure out the chemical properties and temperatures of the objects they are observing and make determinations about how fast the objects are moving. Spectroscopy has long been considered the most valuable tool in the astronomer's toolbox. As telescopes become larger and more sensitive to refracted light, there is an increasing need for observation in light controlled environments.

Some of the best locations for conducting telescopic observation are high and dry places, such as the Atacama Desert in Chile or the South Pole. Dry locations at high altitudes allow for the least sky noise, or background atmospheric interference caused by atmospheric pollution, humidity and light. Astronomers have been stationed in these remote locations for more than 50 years, but as more and more astronomers leave behind less useful stations and flock to these, many once populated stations are out of commission.

Photo caption: Dark sky reserves, like this one around Mont Megantic in Canada, preserve starry night skies for researchers and amateur stargazers alike.   Credit: Wicked Delicate Films LLC.

Sources:
» Cornell University. "Ask an Astronomer: How Does Light Pollution Affect Astronomers?"
» Fischer, David E. "Going to the Ends of the Earth." Astronomical Society of the Pacific, No. 38, Spring 1997.
» University of Arizona. "What is Spectroscopy?"
» Wright, Gregory. "Astronomy at the South Pole." Optics and Photonics News, Optical Society of America, January 2004.



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