Over a month ago, I signed myself up to do a podcast for 365 Days of Astronomy. My podcast will be up on their web site this Thursday. A month and a half seemed like a good long time to record a 5-10 minute talk about some subject in astronomy. Suddenly, it's half a week and that doesn't seem so long. I decided to talk about dust (my research) because it is a really cool topic in astronomy that is broadly neglected. Even astronomers often seem to just consider dust a nuisance. I decided to free-write about space dust in my blog, and hopefully it'll give me ideas about what to put in the podcast.
Stars are the dragons of the Universe. Their massive fiery bellies boil with an inconceivable heat. When we set off a nuclear hydrogen bomb on Earth (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 metallic elements 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 hot 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 (a molten 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. "Just add water, will re-hydrate within 3-5 minutes." Instead, they 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.
Okay, that's enough for now. I read it out loud and that took about 6 minutes. I need to do some fact checking and then add a bit more info about dust, since I barely got to the subject of dust. I think it's okay if my podcast mostly doesn't end up being about dust. I wonder if it's too metaphorical? Nah, I like metaphors :) I tend to think in analogies, a fact that fellow grad student Sirio finds hilarious. When he imitates me talking about electromagnetism (the force that holds together the electrons and the protons in an atom), he says "Mr. Proton and Mr. Electron meet up and shake hands." I kinda like that analogy so I decided to keep it.
Beautifully expressed, as always.
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