… I meant, Stardust “@” Home

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Jan 15, 2006
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'What is this stuff?

It's called aerogel, and it's an extremely lightweight form of silicon dioxide. It's heat-resistant, relatively cheap to make, and can be used, say, to capture particles ejected off of a comet if you happen to be swooping down really close to one.

Hey, didn't NASA just do that?

Very astute of you. Yes, they did, and the aerogel was used to snag some of the stuff that comets are made of. The particles from the comet slammed into the aerogel held out by the Stardust probe as it swept by the comet, were gently decelerated by the weird nature of the gel, and came to a stop inside the foam. Now that Stardust has returned to Earth, scientists can investigate the guts of a comet inside the comfort of their own lab, assuming their lab is comfortable.

Thousands of comet bits hit the aerogel, and you'd think scientists would be happy with that. You obviously don't know many scientists! It's been calculated that hidden among those particles are a handful (well, that's not a useful word, unless it's a bacterium's hand) of truly interstellar dust grains; particles from distant stars that happen to be floating around in the solar system. They've calculated that there may be about 50 dust grains in the aerogel. Yes, 50. Total. That ain't many. Scientists would dearly love to study them. But how to find them?

That's where you come in. Stardust scientists have created a "virtual microscope", an automated microscope that will scan the aerogel taking images. It would take one person 30,000 hours to look at all the images... or 3000 people ten hours. So why not let thousands of people take a poke at the images?

The Stardust team has decided to do just that. They will train volunteers to go over the images, looking for the interstellar interlopers. This project will start in March, and they'll be looking for volunteers. I bet more than a few BABloggers will join up. If you do, let 'em know I sent you!

Hmmm, I'm not done here just yet. I want to talk a bit more about aerogel. It has been certified as the lightest weight solid by Guinness, which I always thought was a beer company. At 3 milligrams/cc, aerogel is pretty thin stuff; water is over 300 times denser. A cubic meter of aerogel would only weigh 3 kilograms, less than, for example, my cat. A cubic meter of water weighs a ton, by the way.

I wound up with some aerogel when a Bad Astronomy fan who happened to have access to some sent me a small sample many years ago, shortly after the Stardust launch. It's is really, really weird stuff. The piece he sent was a 6 x 8 x 1 centimeter slab, so it weighs about 144 milligrams, or 0.144 grams. I cannot convey to you how odd it is to hold something that you know is there, but you really cannot feel its weight. The stuff really is like solid smoke.

Here is another picture I took:

This picture was taken a few seconds after I dropped the slab on my back patio, shattering it. I'm a clod sometimes (in my favor, the stuff is extremely friable). Still, take a look at the way it looks blue, but it casts a red shadow. More weirdness. The gel evidently scatters blue light, letting red through, just like our air does, which is why the sky is blue, and sunsets red.

I was able to scoop up most of the chunks (being very careful; I've been warned it's crumbly and can leave micro-splinters in the skin) and salvage them. Another really weird thing: when I grabbed them with the tongs, they made a really strange sound, like a high-pitched ringing or scraping. I can't really describe it. This stuff is just plain bizarre, and very cool. I'll have to figure out some way to display it in my house -- but I'll also have to find some way to store it so it's safe from me.