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Not Just Pretty, Perseid Meteors Hold Key to Clear View of the Heavens

The views expressed are those of the author and are not necessarily those of Scientific American.


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A Perseid meteor streaks across the sky over the Very Large Telescope in Chile. Credit: ESO/S. Guisard

A Perseid meteor streaks across the sky over the Very Large Telescope in Chile. Credit: ESO/S. Guisard

The Perseids meteor shower, which peaks August 11-12, isn’t just a dazzling celestial show. The annual event also supplies our atmosphere with an essential ingredient for groundbreaking astronomical research.

Our atmosphere is turbulent. The turbulence is what makes stars twinkle. Although twinkling stars are lovely to look at, they are a bit of a nuisance to astronomers. All that dancing and shimmering obscures the fine detail in planets, nebulae and galaxies. If only they could steady the atmosphere, they could learn so much more about the cosmos. But because the sky refuses to be tamed, scientists do the next best thing: they make their telescope mirrors change shape in tune to the moving atmosphere. This is where the Perseids come in.

During the Perseids, our planet runs into the debris trail of Comet Swift-Tuttle, a ball of ice that orbits the sun every 130 years and last visited the inner solar system in 1992. Every time the comet returns, it sheds flakes of ice and dust. And every year, Earth passes through cometary dandruff. Each comet chunk slams into the upper atmosphere at nearly 60 kilometers per second and flares as a meteor or “shooting star.”

A sodium laser fires from the Gemini South telescope in Chile. Credit: Gemini Observatory/AURA

Every impact shaves a bit of sodium off the meteors. Some of the sodium atoms float in a layer roughly 90 kilometers above Earth’s surface. By firing a telescope-mounted laser into the sky, astronomers can make a spot of the sodium glow. The glowing spot looks like an artificial star. Because astronomers know exactly what a glowing spot should look like, they can then rapidly deform small mirrors in the telescope—sometimes at over a thousand times a second—until the spot appears nice and round. Thus calibrated, the telescope can reveal a far clearer picture of the celestial object of interest than might otherwise be obtained In effect the technique removes the confounding atmosphere. Because the telescope continuously adapts to the changing atmosphere, astronomers call this technique “adaptive optics.”

Adaptive optics systems bring everything from nearby moons to distant galaxy clusters into sharper focus. Astronomers use them to observe stars orbiting the supermassive black hole at the core of our galaxy roughly 28,000 light-years away. By watching stars whip around the galactic center for over a decade, researchers were able to figure out that the black hole weighs the same as 4 million suns. And by combining adaptive optics with a tool to block out starlight, astronomers can take pictures of planets orbiting distant stars in our galaxy—all because of the sodium that meteors bring.

The Perseids will reach full swing–with nearly 100 meteors per hour streaking across the sky–on the night of August 11. The best time to watch is after midnight well away from city lights. With no moon to spoil the view, this year’s show should be a good one. Every meteor you see will be a tiny piece of a comet, a remnant from the birth of our solar system. Each one leaves behind a bit of itself that lets astronomers push the boundaries of our knowledge of the cosmos.

Christopher Crockett About the Author: Christopher is a AAAS Mass Media Fellow and intern for Scientific American. In a previous life he was an astronomer and spent the last several years looking for planets. Follow on Twitter @@CosmicThespian.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. bsoetoro 11:24 am 08/10/2013

    I’m betting that one o Obummers sons figured all dis out !!!

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  2. 2. shjsmni 5:16 pm 08/10/2013

    @ bsoetoro: It makes my squishy lib heart sing with joy when a knuckle-dragging hater like you disses the President for no reason at all. You are going to be soooooo miserable for, well, the rest of your miserable life, because the demographics favoring us libs are going to wash your kind out of Congress over the next decade. But you’ll still be free to hate, and continue to view the world from the perch of mythology pushed by the Koch brothers and the likes of Karl Rove. So just keep on being who you are. Don’t compromise. Stay pure. Don’t expand the Republican tent. In fact, shrink it further, so that only old, rich, white guys fit inside, along with their sad, tragic toadies like you, who have drunk the Kool-Aid and vote against their economic best interests. You rock, Fred Flintone!

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  3. 3. popseal 10:33 pm 08/10/2013

    Assigned to a completely darkened corner of the Pakistan desert on a clear winter’s night, I saw from my post the Milky Way as a wide gray band of ‘mist’ stretched across the sky. Using a night vision devise, the sky was so full of light I couldn’t find the Big Dipper for the abundance of now visible stars. Then in the awe of the beauty, I had the strangest feeling that God was laughing. So I laughed with Him.
    Later another watchman and I counted orbiting satellites, seeing five of them twinkle as they ran their man directed course overhead. Through the morning dust my eyes were protected from the sun as I could see ‘spots’ on the sun with the 10X binoculars. The heavens really do “…declare His handiwork”.

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  4. 4. onapthanh 10:03 am 08/11/2013

    I thought that by using a night vision devise, the sky was so full of light I couldn’t find the Big Dipper for the abundance of now visible stars. Then in the awe of the beauty, I had the strangest feeling that God was laughing@ http://onaprsc.com.vn

    Link to this
  5. 5. onapthanh 10:04 am 08/11/2013

    To be free to hate, and continue to view the world from the perch of mythology pushed by the Koch brothers and the likes of Karl Rove. So just keep on being who you are@ http://onaplioa.com.vn

    Link to this

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