From: Nature News Service
Posted: Friday, August 9, 2013
This weekend, as millions of people gaze up at the stars and wait for Perseid meteors to streak across the sky, one would hardly think that these awe-inspiring "shooting stars" are also a source of atmospheric pollution.
However, meteors, like those from this month's Perseid meteor shower, burn up high in the Earth's atmosphere leaving behind gases. "It's a form of natural pollution," says Gemini Observatory's Chad Trujillo who heads up the facility's state-of-the-art adaptive optics (AO) program.
This "pollution" doesn't actually pose a threat to humanity (it's been around for eons and seems to have had no adverse effect), but it's a real boon to astronomers.
"One of the gases left behind by meteors is sodium, which collects in a layer about 60 miles (90 kilometers) above the Earth," says Trujillo (animation: http://www.gemini.edu/node/12050). "The reason astronomers are so fond of this particular pollution layer is because we can make it glow by using a sodium laser to excite this sodium and produce temporary, artificial stars wherever we like. Believe it or not," jokes Trujillo, "there aren't enough stars in the sky for astronomers!"
Astronomers use these artificial stars, called laser guide stars, for AO systems such as the latest technology at the Gemini South telescope in Chile. AO allows scientists to see the universe with unprecedented clarity.
The Perseid meteors are byproducts of Comet 109/Swift-Tuttle, which leaves a trail of dust and ice behind when it passes by Earth's orbit. Each year, however, the Earth passes through the comet's dust- and ice-filled orbit. As it plows through that "debris," its small particles burn up in our atmosphere.
"Perhaps one person's celestial 'pollution' is another's 'natural resource,'" said Maria Womack, an astronomy program officer at the US National Science Foundation (NSF). "It's this sodium layer, provided courtesy of meteors like the Perseids, that astronomers use to get the clearest views and understand the universe better."
To celebrate this "happy marriage" of AO laser-guide-star technology and natural meteor remains in Earth's atmosphere, Gemini Observatory is releasing a spectacular set of images illustrating laser guide stars, including its newest technology, which is part of its GeMS adaptive optics system (GeMS stands for Gemini Multi-conjugate adaptive optics System and is featured in a recent press release at http://www.gemini.edu/120528). The GeMS system uses five separate laser beams to create a "constellation" of laser guide stars (images: http://www.gemini.edu/node/12050), which allows for significantly better corrections than previous generations of AO systems.
"The next generation of large ground-based telescopes will require advanced AO systems like GeMS to work at their full-potential," Trujillo explains, "because as telescopes get bigger they must look through a wider column of air. The wider the column of air, the more turbulence in the air will distort the observed light. Using laser guide stars gives us a reference so we can correct for that turbulence and see things with amazing clarity from the ground."
In addition to Gemini South, a laser guide star system is used at the Gemini North telescope on Mauna Kea in Hawai'i and many major ground-based observatories worldwide.
Enjoy this year's Perseid meteor shower which peaks on the night of August 11-12; astronomers will!
Gemini Observatory, Hilo, Hawai'i
+1 (808) 974-2510, cell: +1 (808) 936-6643
Gemini Observatory, La Serena, Chile
+56 51-2-205-628, cell: +56 (0)9-6919-8294
Gemini Observatory, Hilo, Hawai'i
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The Gemini Observatory is an international collaboration with two identical 8-meter telescopes. The Frederick C. Gillett Gemini Telescope is located on Mauna Kea, Hawai'i (Gemini North) and the other telescope on Cerro Pachón in central Chile (Gemini South); together the twin telescopes provide full coverage over both hemispheres of the sky. The telescopes incorporate technologies that allow large, relatively thin mirrors, under active control, to collect and focus both visible and infrared radiation from space.
The Gemini Observatory provides the astronomical communities in six partner countries with state-of-the-art astronomical facilities that allocate observing time in proportion to each country's contribution. In addition to financial support, each country also contributes significant scientific and technical resources. The national research agencies that form the Gemini partnership include: the U.S. National Science Foundation (NSF); the Canadian National Research Council (NRC); the Brazilian Ministerio da Ciencia, Tecnologia e Inovacao (MCTI); the Australian Research Council (ARC); the Argentinean Ministerio de Ciencia, Tecnologia e Innovacion Productiva; and the Chilean Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT). The Observatory is managed by the Association of Universities for Research in Astronomy, Inc. (AURA) under a cooperative agreement with the NSF. The NSF also serves as the executive agency for the international partnership.
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