ASTRONOMERS CELEBRATE “CELESTIAL POLLUTION” FROM PERSEID METEOR SHOWERby xzhang
Close up of the Gemini South (GeMS)
laser which splits into 5 points to create a 'constellation' of guide stars for
improved corrections over a larger patch of sky. The points at the end of the
laser "columns" are where the laser light excites sodium atoms about
90 kilometers overhead and produces laser guide stars used for adaptive optics.
The visibility of the laser "columns" beneath the laser guide star
"constellation" is due to scattering of the laser's light by dust and
moisture in the lower atmosphere.
Credit: Gemini Observatory/AURA
The Gemini South GeMS laser propagates into the night sky as the Milky Way rises during GeMS/GSAOI System Verification observations.
Credit: Gemini Observatory/AURA
This image of the Orion Nebula Bullets
regions exemplifies the dramatic clarity (high resolution) that is achieved
with the GeMS adaptive optics system at the Gemini South telescope in Chile. In
this image, strong winds from violent explosions associated with a region of
star birth behind the Orion Nebula expel bullets of gas that created this
spectacular system of molecular hydrogen wakes. Researchers and Principal
Investigators John Bally and Adam Ginsberg of the University of Colorado used
GeMS data to determine the intensity of the blast and the nature of the
bullets. “Are they dense fragments of circumstellar disks? Could they be
ejected protoplanets? Or are they portions of the prestellar core from which
massive stars form?” Bally asks. “The Sub-arcsecond resolution provided by GeMS
is needed to resolve these shocks and to search for the compact, high-density
knots responsible for these wakes.”
Gemini Observatory Press Release
For release on August 9, 2013
Publication-quality images and HD video available at: http://www.gemini.edu/node/12052
“Celestial Pollution” from meteors like this weekend’s Perseid Meteor Shower sprinkle sodium high up in our atmosphere and give astronomers what they need to see the universe in much greater detail.
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 (see animation). “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,” it’s 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: www.gemini.edu/node/12028). The GeMS system uses five separate laser beams to create a “constellation” of laser guide stars, (see top figure) 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 (see images) 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!