National Geographic
Menu

Counting Stars at the Saguaro National Park BioBlitz

Two hikers taking SQM measurements of the night sky on a trail in Saguaro National Park East. Photo courtesy Jeremy White, National Park Service

 

By Sean O’Connor

Artificial lights flood the night sky, making the urban and suburban lives that so many of us live a little brighter, but not necessarily for the better.

Light pollution also drowns out the sea of stars shining through our atmosphere. Who doesn’t love to look up at the night sky and see a palette full of bright, shining, stars? How many of us perhaps have never experienced this at all because of where we live?

But our human desire to experience the unadulterated night sky isn’t the only reason to care about the brightness of lights at night. There are also animal species that can be negatively affected by these glowing bulbs. That is why the GLOBE at Night program coordinated a Tucson-wide night sky inventory during the 2011 National Geographic BioBlitz in Saguaro National Park.

Connie Walker of the National Optical Astronomy Observatory helped coordinate the inventory event. To measure the night sky brightness, a type of instrument called sky quality meters were used by all the groups of people who hiked across various trails in both parks as well as drove across four major streets of Tucson, Walker explained. “Some drivers took measurements through their moon roofs. During the daytime participants in the BioBlitz event catalogued over 850 species of animals and plants. The night sky inventory data will be used to compare with these species,” Walker said.

According to Walker, one such comparison studies how light pollution impacts lesser long-nosed bats in the Tucson city area to see whether or not light pollution is affecting their foraging habits. Preliminary results show that the bats seem to preferentially travel in the darker areas of Tucson to get from roosts in Saguaro National Park East to foraging areas.

Overall, the night sky inventory during BioBlitz 2011 in Tucson  “was a tremendous success,” says Walker. Values ranged from a stellar magnitude of 2 at the center of town to 6 at the far edges of the national park.

Results show that the skies are tremendously dark at Happy Valley Saddle in the Rincon Mountains (in the more remote East district of Saguaro National Park). A limiting stellar magnitude of 7 (e.g., the faintest star you can see) at Happy Valley means that the night sky is basically unpolluted. You can see thousands of stars there as opposed to downtown Tucson, where you see less than 50 with a limiting stellar magnitude of 2.

 

In the map above, the lighter the dots, the brighter the night sky. The darker the dots, the darker the night sky. Map courtesy of Mark Newhouse and Dave Bell, NOAO

This practice of measuring stellar magnitude, or the brightness of stars or other celestial bodies from Earth, dates back to a period when light pollution was not an issue at all, over 2,000 years ago, even before the time of the astronomer and geographer, Ptolemy.

The GLOBE at Night program is an international citizen-science campaign to raise public awareness of the impact of light pollution by inviting citizen-scientists to measure their night sky brightness and submit their observations to a website from a computer or smart phone.

According to the GLOBE at Night website, “light pollution threatens not only our “right to starlight, but can affect energy consumption, wildlife and health.”

The GLOBE at Night campaign has run for two weeks each winter/spring for the last six years. People in 115 countries have contributed 66,000 measurements. The night sky inventory in Tucson was coordinated by the NOAO Education and Public Outreach group in collaboration with the International Dark-Sky Association and the National Park Service’s Night Sky Team.

Join the GLOBE at Night program as citizen scientists in 2012 on the following dates: January 14-23, February 12-21, March 13-22, April 11-20.

Sean O’Connor is the project coordinator of educational mapping for National Geographic Education. When he’s not creating maps or advising his colleagues on mapping issues, he enjoys researching history, canoeing and kayaking, and exploring the world around him. In his work at NG, Sean has helped to develop the National Geographic FieldScope tool and launch a new suite of dynamic, on-line mapping tools for students and teachers.

Comments

  1. [...] our view of the night sky and can have other negative impacts on natural ecosystems. Check out this post from our 2011 BioBlitz in Arizona about a citizen science program that has participants measuring [...]