Measuring Light Pollution - The GLOBE at Night campaign
GLOBE at Night is a fun, international public science event that encourages everyone, to measure the darkness of their local skies and contribute their observations online to a world map. The event is part of the wider “Dark Skies Awareness” IYA2009 cornerstone project, and measures the sky darkness by counting the number of stars in a given part of the sky as seen from the observer's location.
About 1 out of 10 people worldwide have never seen 90% of the stars in our night sky. This figure will get worse with the increase in number of people living on earth and the corresponding increase in inappropriate and unshielded outdoor lighting. The effect of this light pollution is to diminish the number of stars people can see, and poses a serious threat to astronomical research. Besides its impact on astronomy, new research shows that light pollution also adversely affect insect and animal life and negatively impacts on human health and immune function. It is also a symptom of unnecessary light wastage and thus energy wastage.
S.A. Astronomical Observatory will engage some learners from different schools around Cape Town where they will participate in the Globe at Night star counting exercise, and invite other schools and the general public to participate in this worldwide event. The star counting will focus on the constellation Orion, one of the most prominent constellations in the evening sky. Below is a picture taken of the constellation as seen from the South African Astronomical Observatory in Cape Town. According to the indigenous Namaquas the red star Betelgeuse, just right of centre in the picture, (outlining the shoulder of Orion) is a lion while the arc of three whitish stars above to the left of it (forming Orion's belt) depicts three zebras.
Constellation of Orion as seen from Cape Town. Courtesy of Dr Steve Potter of the S.A. Astronomical Observatory.
The campaign will run from 16 to 28 March, and during this time people in locations all around the world will count the number of stars seen in and around Orion, with the aid of magnitude charts. The less stars one see the worse the light pollution is in your location, assuming no bad weather. Each of these people will then submit their results electronically to a database, contributing to the measurement of the current light pollution seen around the world.
South Africa is currently registered as one of the 110 GLOBE countries, and any one who lives and works in one of these countries can take part in the campaign.
More information on the Globe at Night event and the results from previous years can be found at http://www.globe.gov/GaN. A special activity packet with a step by step guide is available, showing you how to do the star counting activity following the Five Easy Star-Hunting Steps:
1) Find your latitude and longitude.
2) Find Orion by going outside an hour after sunset (about 7-10pm local time).
3) Match your nighttime sky to one of the magnitude charts.
4) Report your observation.
5) Compare your observation to thousands around the world.
The general activity pack can be found at http://www.globe.gov/GaN/observe.html and the special pack for teachers can be found at http://www.globe.gov/GaN/observe_teacher.html.
The result of the GLOBE at Night campaign 2008 is shown below. Note that the fainter the limiting magnitude (i.e. bigger number) the darker the sky and the more stars one will be able to count.
GLOBE at Night results for 2008. Note the bigger the limiting magnitude, the darker the night sky and the more stars one will be able to count. Image credit: GLOBE Program and NOAO/AURA/NSF.
If you plan to take part in this global event, we would love to hear from you! You can contact Dr Enrico Olivier from the South African Astronomical Observatory at (021) 460 9313 or at olivier(at)saao.ac.za. Happy star counting!!