August 10, 2013
Celestial Pollution From Perseid Meteor Shower
[ Watch the Video: Laser Lights Criss Cross Hawaiian Skies ]
April Flowers for redOrbit.com - Your Universe Online
The annual Perseid Meteor Shower will peak this weekend. As redOrbit’s Lawrence Leblonde reported, scientists are predicting that due to a lack of strong moonlight, this could be one of the most impressive shows in years.
But that isn’t the reason scientists are so happy about the shower. In addition to a fantastic light show every summer, the Perseid shower provides “celestial pollution” which helps astronomers see the universe in greater detail.
Meteors burn up in the Earth’s atmosphere, providing the light show we all enjoy, as well as 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.
These gases have been around for eons, and don’t pose a threat to humanity. However, they are a 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. “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!”
These artificial stars, called laser-guide-stars, are used by astronomers for AO systems such as the latest technology at the Gemini South telescope in Chile – allowing them to see the universe with unprecedented clarity.
The meteors of the Perseid shower are byproducts of Comet 109/Swift-Tuttle. Swift-Tuttle leaves a trail of dust and ice behind when it passes Earth’s orbit. Each year, Earth passes through this debris field and small particles from the field 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. “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.”
The scientists at Gemini Observatory are releasing a spectacular set of images - including its newest technology which is part of its Gemini Multi-conjugate adaptive optics System (GeMS) - illustrating laser guide stars to celebrate this “happy marriage” of AO technology and natural meteor remains. Five separate laser beams are used by the GeMS system to create a “constellation” of laser guide stars. This constellation 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.”
A laser guide star system is used at both Gemini South in Chile, and Gemini North on Mauna Kea in Hawaii, along with many major ground-based observatories worldwide.