Date: October 27, 2011

Title: Space Dust

Podcaster: Jackie Villadsen

Link: Jackie’s blog: http://jackie-goes-to-space.blogspot.com/

Description: There’s a very important part of outer space that we don’t hear very much about: dust. Space dust consists of small grains of carbon and metal floating in space that play a big role in our Galaxy in spite of their small size. An important example: our planet Earth is built out of space dust.

Bio: Jackie Villadsen is a second-year graduate student in astronomy at the California Institute of Technology.

Sponsor:This episode of “365 Days of Astronomy” has been sponsored by AARTScope.blogspot.com, helping create the sense of anticipation and discovery that keep us asking questions”

Transcript:

Stars are the dragons of the Universe. Their massive fiery bellies boil with an inconceivable heat. This heat comes from nuclear reactions. When we set off a nuclear bomb on Earth (which is a very unfortunate and unnatural process), we create for just a tiny moment and in a tiny space the high temperatures needed to fuse together four hydrogen atoms and make helium. By comparison, this process of fusion chugs along constantly, and completely naturally, in the belly of the Sun for 10 billion years! Imagine 10 billion years of continuous nuclear bombs… how strong that is!

Our Sun is a fairly small dragon. She sleeps curled up in the center of the solar system, digesting her meal of hydrogen atoms. Since she is so small, once she finishes turning her hydrogen in helium, the temperatures in her belly won’t be hot enough to turn helium into heavier elements like carbon. But there are lots of bigger, hotter stars lurking out there in the galaxy. When those stars finish burning hydrogen into helium, their hunger is not satisfied, and they digest helium into carbon and nitrogen and oxygen. The biggest stars even go on to make metals, like silicon and iron.

Eventually, a star reaches a point where it can no longer digest the heavy elements in its belly. This is when our sleeping dragon wakes up. Realizing that she has a hot lump of rock in her stomach, she roars in pain, vomiting flames into the sky. Small stars just shed their outer layers of gas like an old snakeskin and then settle down and crystallize into a giant diamond. These unbelievable stellar remnants are known as “white dwarf stars.”

The larger stars bring themselves to a much more violent end. When they have digested their initial supply of hydrogen all the way into iron, and find an undigestable lump of rock in their belly, they explode. Our dragon goes supernova: she falls in on herself, violently spewing flames in all directions as she collapses into a neutron star or a black hole. These flames contain a very precious treasure: the elements produced in the dragon’s belly over the course of her lifetime. As the dragon dies, part of her hoard of treasure is recycled back into the Universe.

After the Big Bang, we pretty much had only three elements: hydrogen, helium, and a tiny tiny amount of lithium. That’s element #1, element #2, and element #3. But think about what our earth is made of, what humans are made of. Our earth involves a ton of metals. We have an iron core. Our bodies involve lots of carbon and nitrogen and oxygen. Our oceans consist of H20 – hydrogen and oxygen. Where do we get carbon and oxygen and nitrogen and iron and everything else we need for our own existence? The answer is the stars. Without the elements produced in the bellies of the stars, we could not exist.

How do the elements ejected by dying stars end up in us? Stars don’t spit out pre-packaged Earths. Imagine the directions on the package: “Just add water, will re-hydrate within 3-5 minutes.” Instead, the stars spit out hot, hot gas, full of metals. As the gas cools, the atoms combine to form molecules, and then the molecules combine to form dust grains. The fiery breath leaves the dragon’s scaly lips and then it cools, turns to ash and drifts away through space.

This space dust is not the same dust we see floating in a shaft of sunlight in our living room and coating our old VHS collection. This is not couch fluff or human skin or cracker crumbs. Instead, these dust grains are little nuggets of metal, transporting the elements we need for life. One common kind of dust grain is made out of carbon, in a form known as graphite, just like the tips of our pencils. Another common type of dust grain is made with silicon atoms – the same element we need for the microchips in our computers. Little pencil tips and little microchips, so small they’re invisible, floating through space.

How do these dust grains turn into us? When you get a lot of gas and dust in one place, its gravity can become strong enough that the cloud of dust and gas collapses under its own weight. When this happens, you normally end up with a flat disk of dust and gas, like a dinner plate. The center of the dinner plate will become a star, eating up most of the dust and gas from the disk. The leftovers become the planets, and eventually become us. In the disk of gas and dust, there are so many dust grains, and they’re all very excited, running every which way. With all these confused and excited dust grains running around, they end up running into each other. And sometimes – not all the time, but sometimes – when they run into each other, they stick. Imagine if two people ran into each other in a busy airport – SMACK! – and then they were stuck for life. Then they run into someone else, and stick to that third person. And maybe another ball of stuck people is forming on the other side of the airport. Eventually you get enough big balls of people that the balls of people start running into each other, and sticking. You get bigger and bigger balls until everyone in the airport – the flight attendants, the TSA security guards, the guy running the Barnes and Noble stand, the tourists in Hawaiian shirts – everyone is stuck in one big ball. That’s how a planet forms. All the crazy little dust grains run around and get stuck to each other until they become bigger dust grains, then rocks, then mini-planets, and finally Earth.

So take a moment right now to look at the back of your hand. Pinch yourself. The skin you are holding between your fingers, the fine little hairs on that skin, the red blood cells coursing through the veins, all of those are made of star dust.

End of podcast:

365 Days of Astronomy
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