Organization:365 Days Of Astronomy
Description: Space scoop, news for children.
When the Solar System was formed, there were lots of spare pieces left over. These spare pieces are called asteroids and comets.
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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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This is the 365 Days of Astronomy Podcast. 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.
Searching for Star-making Materials in Our Dusty Old Universe
The Universe is 13.82 billion years old. When you look at the band of light that we call the Milky Way in the night sky there are dark lanes splitting the soft white of the band of light. The dark lane is a band of dust or dust lane.
But the dust in space is very different from the stuff you might find under my bed. That dust is fragments of cotton fibers & shed skin cells.
Cosmic dust is made of tiny particles of, well, (inhales deeply) oxygen. Also carbon, iron, the whole periodic table of the elements!
These particles are much smaller than the width of a human hair, floating around like so much smoke in the space between stars.
Astronomers used to consider cosmic dust a nuisance. It blocks the light from objects in space, making the Universe appear very dark and hiding lots of interesting, faint things like distant galaxies.
But they say every dusty cloud has a silver lining. When astronomers started to use special IR cameras to look at space in the infrared, they discovered that they could see the dust shining. It was glowing because it had a temperature. And the IR color was a direct indicator of that temperature.
This is lucky for us because there are several very important reasons to study it.
This dust is the material that makes up pizza, beer, shrimp cocktail, humans, rocky planets and other stars! You know. All the good stuff!
Cosmic dust is made around stars, along with lots of molecules. “What’s a molecule?” some of you might ask. This is stuff that contains two or more atoms, and often the atoms are from different elements.
There are some molecules in our Sun. Some of them are magnesium monohydride, calcium monohydride, iron I hydride, chromium hydride, sodium hydride, hydroxyl radicals, vanadium monoxide, and titanium monoxide.
Some big stars end their lives in a particularly spectacular fashion – an explosion bright enough to outshine billions of stars. A supernova. Today we’ll be talking about the core collapse type of supernova.
The stars that make these supernovae are heavier than our Sun, maybe 10 times as massive or even more. As the star shines, it fuses hydrogen into helium, then helium into carbon and on up the periodic table till it gets to iron.
Then it’s like the foundation is kicked out from under it. It can’t fuse iron into anything heavier. That’s the end of the road for the star.
When a star becomes a supernova, it’s a colossal, titanic and downright humongous explosion. First, though, there’s a collapse and then there’s the explosion.
And when the collapse happens all the elements that the star had been building for millions of years, elements up to iron, are kind of melted down.
When this happens, all those dusty molecules in the star’s atmosphere are destroyed right along with the atomic elements.
Then the explosion happens, and in a process called explosive nucleosynthesis the melted down bits are rebuilt into all the elements, even those heavier than iron, and there are LOTS of them! Important stuff, like copper, silver, gold, lead & uranium!
But it’s so hot in the supernova that it takes a couple hundred days for things to cool down enough for molecules to form again from the ejecta.
Astronomers discovered tiny little dust grains and molecules inside a supernova remnant or SNR a few months ago. For the first time they found HCO+, the formyl cation and SO, sulfur monoxide, in the inner parts of an SNR. They’d detected other molecules before, but this was the first time for these particular ones.
The star they were studying exploded in the Large Magellanic Cloud, or LMC, in 1987. It’s called SN 1987A. As the gas expands away from where the star was, it cools and the atoms formed in the explosion can join together and form molecules.
The LMC is a satellite galaxy of the Milky Way and is 163,000 light years away. It’s visible from the Southern Hemisphere and is invisible to us northerners.
So it didn’t really explode in 1987, but 163,000 years before then. But we couldn’t see the explosion till then because we had to wait for the light to get here. We’ll just say it happened in 1987 so it makes sense, ok?
Anyway, where was I? Oh yeah.
Since then the remains have cooled down enough that new molecules are able to form from out of the many elements created in the supernova. The result is a kind of rich, dust factory, a soup of elements that are keen to link up into various molecules.
This is good news for us, because like a phoenix rising from the ashes, the dead star has helped to create new stars, planets and maybe some day life forms like that shrimp cocktail!
The astronomers were using ALMA, that awesome radio telescope array in Chile’s Atacama desert. That scope was used because these molecules emit the radio wavelengths that ALMA specializes in.
To see what all this looks like, here’s a link to an amazing animation from Dr. Remy Indebetouw and my other friends at the NRAO:
That dark red bit in the middle at the end of the video clip is where this latest detection of molecules is happening.
Hey, Here’s A Cool Fact:
The interesting bit that they found was in the ratios of various isotopes of the elements in the molecules. These ratios are consistent with supernova explosion models that show that sometimes the explosions are inefficient and that mixing of the onion layer-like structure of the progenitor star happens during the explosion.
The outer layer of the star’s atmosphere has plenty hydrogen. Deeper layers of the star where there is carbon & oxygen are blasted out through the outer layer of hydrogen and the chaotic turbulence causes them to mix with the hydrogen. This enables the HCO+ molecule to form.
And deeper still are layers of silicon & sulfur that get blasted outward and get mixed with the outer oxygen layer, forming SiO, silicon monoxide and preventing SiS or silicon monosulfide from forming.
Cool, huh? Well, ok, hot actually…
Thank you for listening to the 365 Days of Astronomy Podcast!
End of podcast:
365 Days of Astronomy
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!