… I meant, Stardust “@” Home

By Phil Plait | January 15, 2006 10:45 pm

‘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.

CATEGORIZED UNDER: Astronomy, Cool stuff, Science

Comments (33)

  1. Very cool picture (even though you broke it 😛 ).

  2. Katie Berryhill

    Hey, Phil…be careful when you break it, inhaling fibers can be worse than getting it in your skin. That was part of the advice I got when I got my piece from JPL (perk of the Solar System Ambassador program).

  3. ooh! that stuff (aerogel) is fun to play with and show off. we had some where i used to work, and people never really appreciated it until they actually held it.

  4. KingNor

    what did it soudn like when you droped it? did it shatter like glass or just kinda fall apart?

    how sturdy is it? can you easily crush it (i would ass-you-me so but who knows, since you say its really really weird.

    if you were to toss it up, would it kinda hang like a blown up balloon or does it drop like a rock?

    hehe thanks, i coudln’t manage a whole 20 questions on my own.

  5. Cindy

    Already signed up to search, although it was Katie above who prompted me.

    Cool looking stuff. Glad Stardust landed safely.

  6. Roy Batty

    I’ve pre-signed too!
    How expensive is that stuff? I want some :-)

  7. RAF

    The BA said…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.

    Would the sound be “comparable” to the sound of chalk “skreeching” on a chalkboard? Was it the kind of sound that you could “feel” in your teeth?

    I really don’t know “where” I’m going with this line of reasoning…Just trying to better understand the “sound”. :)

  8. PK

    When I was at JPL, one of the stories in ethics training was that somebody got the sack for putting (stolen) aerogel on ebay…

  9. !


    I want some…

  10. TJ

    I’ve registered for the virtual microscope! Of course, I’m probably number 15,898 or so, but I’ll still do it if I can. It’d be good to have something worthwhile to do on the computer rather than geek out on computer games.

    Aerogel is cool!

    Only 10 days until TAM4!

  11. How could you? Butterfinger Astronomer!

    I’m not sure what I would need Aerogel for, I still want some.

  12. Marlayna

    Where can I get some of this stuff? 😀

    I’d love to help with the research, but chemistry is not my forte :(

  13. hale_bopp

    I don’t have any aerogel, but I do have a Space Shuttle thermal tile…that is pretty cool also to play with. I don’t know if they still do, but NASA had a program where they gave them to teachers (I am sorry…they gave them out on a 99 year loan to teachers, so in 2098, I am in trouble!)


  14. Dee Jay

    Interesting stuff. I wonder if you could get the density down to air level in a solid? I think the best weird out would be to let go of a brick and watch it sort of drift around as though in a fluid.

  15. BJN

    I laughed upon reading a newspaper article that described comet particles pentrating aerogel as “shooting peas into jello”. Howard Burkus at NPR repeated the same shooting peas bit in his radio report on Stardust’s return. Aerogel sounds like pretty crunchy jello — and who shoots peas into jello? Are these cooked, dried or frozen peas? What’s the objective of shooting jello? (I do grasp the value of jello-shooters.) Is it a sport or part of a recipe? Did this analogy originate at NASA?

  16. kit

    ha-ha-ha-ha. Peas in jello. Do the need 60000 people to help eat all the jello shot by peas?

    anyway, how chep is “relatively” cheap. I’m just wondering if there are any commercial use for the aerogel. I want to insulate my house with this stuff :). On the other hand reading of all those splinters in the skin and lungs sounds like not very consumer-friendly product.

  17. Aerogel was developed at Lawrence Livermore National Lab (less than two miles from where I was standing when I saw Stardust reenter as I described in my post in the previous entry). It is an expanded silcon compound of some nature. I don’t know the actual manufacturing method, but I know they take a silicon solution and make it “foam up” with incredibly tiny cells. After you bake out the solvent, the microcell structure is left behind.

    The sound you are trying to describe, Phil, is like a “scree”. The closest anaogy I can come up with is the sound of a piece of room-temperature metal being dragged across a block of dry ice.

    If you’re ever in the San Francisco Bay Area, and can manage a trip to Livermore, the Lab’s Visitors’ Center has some small chunks they’ll give you if you ask. You have to ask, though, and they won’t give you any if you’re part of a large group (say more than a half dozen) since they don’t have very much of it.

    To answer some of the other questions, yes, it will crumble back to silicon powder with the slightest squeeze. And yes, Dee Jay, the density is close enough to air at STP that, supposedly, if you heat it up it will float in air (I have yet to confirm this, though).

    Here’s a link to the JPL site that talks about it: http://t2stardust.jpl.nasa.r3h.net/tech/aerogel.html

    I noticed that they’ve updated the text a little. It used to give the impression that JPL invented aerogel. I’m sure someone must have complained becuase it now says it was “prepared and flight qualified at JPL”, although there’s still no mention of Livermore Lab.

    – Jack

  18. CR

    Interesting pic of the aerogel-in-the-tongs, but for some strange reason, the pic compelled me to buy the Bad Astronomy book…

  19. Stuart Greig

    Lots of this on sale on ebay, cost varies from $20 to $80 depanding on how much you want. This is for very small amounts though, good just for looking at (amaze your friends! etc).

    Also searching ebay found some hifi speakers with “aerogel cores”, not sure if its the same stuff or not but a if it is a good example of practical spin off technology, although not exactly save the planet stuff.

  20. To CR: yeah, Butterfingers are using subliminal messages in his photos 😉

  21. SFwriter

    Hey Phil…

    When you said “A cubic meter of water weighs a ton, by the way.”, didn’t you mean “tonne”…?

  22. Nigel Depledge

    Katie Berryhill said:
    “Hey, Phil…be careful when you break it, inhaling fibers can be worse than getting it in your skin.”

    Quite right. Pay attention, all you who are clamouring to acquire aerogel. Silicosis is not at all funny – it resembles a form of lung cancer, so you really don’t want to inhale silicon (di)oxide fibres.

  23. silence

    People who are looking for aerogel samples to fool around with might want to look at this list of aerogel suppliers.

  24. funestis

    As I know aerogel for now is commercially used for manufacturing of capacitors and for insulation,

  25. ChrisJ

    Actually, aerogel was invented a long time ago, but not by either JPL or Lawrence Berkeley (who has a really nice site with a lot of details including history at http://eetd.lbl.gov/ECS/aerogels/satoc.htm ) although both places have worked on it.

    Remember that this stuff is about 95% void volume – that is, only about 5% of the volume is silica – the rest is empty space, typically filled with air. It is an open-cell material so you can remove the air and it becomes an even better insulator.

    It is a really good thermal insulator but it is hard to use as insulation because it is so fragile. There are people at NASA Glenn (where I’m from) and the University of Missouri that have developed a much stronger version. As usual, there is no free lunch, so you sacrifice some of the desirable properties a little to get the strength increase, although in this case you gain strength much faster than you increase density.

  26. Blakut

    I preregistered myself, i can’t wait to begin..!

    “It is a really good thermal insulator but it is hard to use as insulation because it is so fragile.”

    You could use smaller chunks of aerogel placed in a soft er (and fuzzy) material in order to obtain a good insulator.

  27. Jay Dogg

    can you mold the aerogel or is it totally rigid and will break if bent?

  28. ChrisJ

    You can mold aerogel AND it is rigid and will break if bent. Most aerogels are rigid and will break when you try to bend them. There are a few flexible ones that have been reinforced with a flexible polymer but their flexibility is probably goverened by the polymer rather than the silica backbone.

    Aerogels are made by a sol gel process, which means that the components start out in liquid form and then the react to form the solid. If you pour the sol into a mold it takes the shape of the mold as it gels. The resulting piece isn’t flexible but it is in the shape of the mold.

    You can make any arbitrary shape that you want as long as you can get it out of the mold. Of course, if you get it too thick you’ll have a hard time getting it processed. Liquids don’t flow through the gel so washing the unused reactants out is done by immersing the gel in solvent and allowing diffusion to pull stuff out of the gel. If you make too thick of a piece it takes forever to wash.

  29. Fesstizio

    he he he ! that stuff is frekin sweet one qustion (I got this info of Nova) if it can stop things going 6 times that is right 6 times faster then a bullet why arnt we using this stuff to make a body armor for our soilders or something like that. it is light enough and if you coat it with something to keep it from shattering you got something good going here.

  30. Anuj

    If the aerogel was unable to absorb the impact from being dropped onto a patio floor, I don’t think it will be able to absorb the impact from a bullet.

  31. Could areogel be filled with helium? I am looking to construct Skycity in the near future. Actually a just hotel and restaurant at the mid-point to serve passengers on the space elevator.

  32. Gary Ansorge

    31. Nomad

    I don’t know the porosity of aerogel but Mylar balloons retain helium for a week or more AND it’s a whole lot tougher than aerogels.

    Of course, one COULD use H2 for your lifting gas if it could pass FAA safety rules.

    I saw some calculations that indicated a geodesic dome a half mile in diameter could be self lifting from the hot air created by sunlight shining thru the panels. Its volume increases far faster than the weight of the construction material.

    GAry 7

  33. Gary

    Fesstizio: If you’re thinking of the particles caught in aerogel in the Stardust spacecraft, those were way smaller than bullets, so they didn’t have as much momentum. A bullet would shatter aerogel easily, but a piece of space dust, despite moving faster than the bullet, would get caught in the aerogel.


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