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TheSpaceWriter_2Date: September 10, 2009

Title: Singing the Ultraviolet Blues

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Podcaster: Carolyn Collins Petersen

Organization: Loch Ness Productions
http://www.lochnessproductions.com/index2.html

MUSIC CREDITS: “Deep Blue” from Geodesium Fourth Universe “The Ocean of Space” from Geodesium West of the Galaxy. http://www.geodesium.com.

Description: ltraviolet light is the bane of sunbathers, but for astronomers, it opens up new windows on energetic processes in the cosmos. Come sing the ultraviolet blues with Carolyn Collins Petersen, TheSpacewriter.

Bio: Carolyn Collins Petersen is a science writer and show producer for Loch Ness Productions, a company that creates astronomy documentaries and other materials. She works with planetariums, science centers, and observatories on products that explain astronomy and space science to the public. Her most recent projects were the Griffith Observatory astronomy exhibits in Los Angeles and the California’s Altered State climate change exhibits for San Francisco’s California Academy of Sciences. She has co-authored several astronomy books, written many astronomy articles, and is currently working on a new documentary show for fulldome theaters, a vodcast series for MIT’s Haystack Observatory, and a podcast series for the Astronomical Society of the Pacific.

Special thanks to Dr. Marty Snow, CU-LASP, and Mark C. Petersen, for their comments and suggestions for this script.

Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by Loch Ness Productions, a unique multimedia production company, specializing in cosmically creative content and space music for planetariums and fulldome theaters world wide. Loch Ness Productions also works with exhibit designers, observatories, space institutes, and publishers to bring a love of astronomy, earth science, and space science to audiences everywhere. On the web at www.lochnessproductions.com.

Transcript:

Hello. I’m Carolyn Collins Petersen, TheSpacewriter, and I’ve got ultraviolet on my mind.

Ultraviolet light is part of the electromagnetic spectrum – which is the full range of light that is radiated or reflected from objects in the Universe. Obviously, our eyes detect the optical range, also referred to as the visible. That contains all the colors we can see, from red through violet. Beyond the visible are the parts we don’t see – x-ray, gamma-ray, microwave, radio, infrared, and ultraviolet.

Now, even if we can’t see all of the spectrum, our bodies can detect some of it in other ways. Let’s explore that idea.

Imagine you’re stretched out, relaxing in the sunlight – maybe you’re on summer vacation at the beach. The Sun’s kind of bright, so you’ve got your sunglasses on, and you’ve put on lots of sunblock to keep you from getting sunburned. Ahhhhh… the warmth of the Sun feels so good on your skin. You drift off to sleep, listening to the sound of the waves lapping up on the beach just a few yards away. What a way to relax… sun, surf, and sand.

What you’re really doing is having an interaction with radiation from the Sun. It involves three parts of the electromagnetic spectrum: visible, infrared, and ultraviolet. You’re screening out some of the visible light with your sunglasses; you’re feeling the infrared on your skin as a warm glow; and… sadly, the ultraviolet rays that managed to get through the atmosphere are doing a number on the parts of your skin where you didn’t quite get enough sunblock on. Those wavelengths of light just past indigo on the spectrum are going to have YOU reaching for the burn ointment and singin’ the ultraviolet blues.

Astronomers sing a different tune – a happy tune – about ultraviolet light, because it gives them a window onto some very hot, active objects and processes in the Universe.

For example – when galaxies interact with each other, the resulting stupendous collisions send shockwaves through clouds of dust and gas in each galaxy. That compresses the clouds, causes them to coalesce, and eventually they form stars.

Once those hot stellar newborns begin to shine, they give off massive amounts of ultraviolet radiation (often referred to as UV.) And, they’re not just born a few at a time – those new stars created in the wake of a galaxy collision come in batches. In addition, nearby interstellar gas clouds get heated by the radiation pouring off the neighboring hot young stars. If the clouds are heated up enough – say hotter than the surface of the Sun – they give off ultraviolet radiation. If an astronomer finds a cloud of gas radiating in both the ultraviolet and infrared, then it’s a sure bet there’s something hotter nearby.

And that cosmic heating element doesn’t have to be newborn stars, either. Supernova explosions can give off ultraviolet light. So can the hot stars at the centers of planetary nebulae. Astronomers also detect some UV radiation given off as matter swirls in the accretion disk around a black hole and is heated by friction and strong magnetic fields.

There are a number of fascinating studies that astronomers do using ultraviolet light from distant stars and quasars as a probe of the interstellar medium – that stuff between the stars. Here’s how that works. As that light travels through space, chemical elements absorb some of it. If you break the ultraviolet light up into its component wavelengths – what astronomers call “taking a spectrum” – the wavelength bands where the elements are absorbing the UV will look dark. Each chemical element has a characteristic set of dark lines, called its absorption spectrum. So, UV – or, actually the UV dropouts in a spectrum – can tell astronomers a lot about what’s out there floating in space between the stars and even between galaxies.

Right here in the solar system, the gases streaming away from comet tails are energized by interaction with the solar wind, and that gives off ultraviolet light. So do auroral displays on Earth, Jupiter, and Saturn. And, of course, as you have probably figured out by now, the Sun is a prodigious ultraviolet emitter.

Now, much of the ultraviolet radiation in the Universe that astronomers study is more energetic than the UV that punches through Earth’s atmosphere to give you a sunburn. The radiation coming from supernova explosions and starbirth knots and white dwarfs and other active, hot objects gets absorbed by our thick blanket of air. To detect those wavelengths of UV light, astronomers need space-based observatories like Hubble Space Telescope or the Far Ultraviolet Spectrograph Explorer that charted the ultraviolet Universe for several years.

There have also been a number of observatories with ultraviolet-sensitive instruments lofted into long-term orbit, plus a collection of sounding rockets and the Space Shuttle, all carrying UV-sensitive instruments into space.

So, the next time you’re lying out there on the beach, soaking up infrared and avoiding ultraviolet rays (as you should,) think about the UV radiation that astronomers study. It’s giving them a whole other look at the Universe and revealing a lot about energetic cosmic processes.

If you’d like to learn more about ultraviolet astronomy, point your browser to www.thespacewriter.com/wp and click on the 365 Days of Astronomy tab. You’ll find a wealth of information and links about this fascinating branch of science. Thanks for listening!

End of podcast:

365 Days of Astronomy
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The 365 Days of Astronomy Podcast is produced by the New Media Working Group of the International Year of Astronomy 2009. Audio post-production by Preston Gibson. Bandwidth donated by libsyn.com and wizzard media. Web design by Clockwork Active Media Systems. You may reproduce and distribute this audio for non-commercial purposes. Please consider supporting the podcast with a few dollars (or Euros!). Visit us on the web at 365DaysOfAstronomy.org or email us at info@365DaysOfAstronomy.org. Until tomorrow…goodbye.