Podcaster: Richard Drumm
Title: Space Scoop: Reds vs Blues
Organization: 365 Days Of Astronomy
Link : astrosphere.org ; http://unawe.org/kids/unawe1125/
Description: Space scoop, news for children.
Bio: Richard Drumm is President of the Charlottesville Astronomical Society and President of 3D – Drumm Digital Design, a video production company with clients such as Kodak, Xerox and GlaxoSmithKline Pharmaceuticals. He was an observer with the UVa Parallax Program at McCormick Observatory in 1981 & 1982. He has found that his greatest passion in life is public outreach astronomy and he pursues it at every opportunity.
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Transcript:
This is 365 Days of Astronomy. Today we bring you a new episode in our Space Scoop series. This show is produced in collaboration with Universe Awareness, a program that strives to inspire every child with our wonderful cosmos.
Today’s story is:
Reds vs Blues
Space is a colorful place! Take, for example, this beautiful photo of a bright open star cluster surrounded by blue and red clouds of gas. The cluster is called NGC 2100 and is located in the southern constellation of Dorado, the Swordfish.
The way that the colors are neatly separated makes it look like a competition between the reds and the blues. In the red corner, there’s the gas that our Sun is mostly made of: hydrogen gas! And in the blue corner, we have the mighty Os that we need to breathe: oxygen gas!
But why are these gases separated like this? Well, it all comes down to how much the gas is heated by stars – but not by those in the star cluster shown here, it’s actually about 10,000 light years behind the gas clouds.
There’s another star cluster beyond the top-right corner of the picture, which contains hotter and younger stars. This cluster is RMC 136 and is surrounded by a glowing nebula we call NGC 2070, also called the Tarantula Nebula. This is associated with the Large Magellanic Cloud which is an irregular galaxy that is orbiting the Milky Way.
The hot, young stars of RMC 136 are powerful enough to make the oxygen gas that is close to them in the upper part of the picture glow. This glowing is called fluorescence, and is the key to knowing what the universe is made of.
Astronomers use prism-like spectroscopes to break the light from stars and nebulae into the spectrum of colors. Different elements fluoresce in different colors, which are seen as bands of specific colors in the spectrum, much like a bar code. Study the bar code in the spectrum and you can quickly figure out the elements in the glowing cloud.
But farther away from RMC 136, down at the bottom of the picture, the stars can’t heat the oxygen gas that’s there enough to make it shine, so it stays dark.
Only hydrogen is glowing at the bottom of the picture, as it takes less energy to make it shine than it does for oxygen.
So the gases aren’t really separated into two areas. The hydrogen and oxygen gases are actually mixed up, both gasses are present at the top and bottom of the picture, but which gas we see shining brightly depends on how close it is to the hottest stars.
Hey, Here’s A Cool Fact:
The oxygen isn’t fluorescing blue light. The color blue was selected here to make the picture especially pretty for the ESO’s “Hidden Treasures 2010” competition. Red, white & blue make for a pretty picture. Just look at the Pepsi logo or the French flag and you’ll see what I mean.
The oxygen is actually glowing green! This strong emission color is very common in gaseous nebulae. The green glow was discovered in the Cat’s Eye Nebula by astronomer William Huggins in 1864. The source of the green glow, though, was a complete mystery to early astronomers and their spectroscopes.
They initially thought this was a new element and gave it the name Nebulium in the late 1890s. It took until 1927 for astronomer Ira Sprague Bowen to show us that the so-called “forbidden transition lines” of doubly ionized oxygen was the cause of the greenish color.
These greenish transitions are only somewhat forbidden by the selection rules of quantum mechanics. So in the extremely rarefied gas of nebulae they do happen often enough that we can see the nice green glow of oxygen out among the stars!
Thank you for listening to 365 Days of Astronomy!
End of podcast:
365 Days of Astronomy
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The 365 Days of Astronomy Podcast is produced by Astrosphere New Media. Audio post-production by Richard Drumm. Bandwidth donated by libsyn.com and wizzard media. 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. This year we will celebrate more discoveries and stories from the universe. Join us and share your story. Until tomorrow! Goodbye!