Twice The Stardust?

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O'Henry
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Joined: Thu Aug 05, 2010 6:44 am

Twice The Stardust?

Post by O'Henry »

As a new member to the Stardust public team effort, I have a small question: I notice that in the "Stardust Search Tutorial: Views 2 and 3" appear to contain double stardust particles but only, possibly, single tracks (although one of them seems to provide a double track). Anyone else notice this? And, if anyone sees what I an referring to, I wonder if there might be a simple explanation for this apparent visual anomaly? Thanks.
DanZ
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Re: Twice The Stardust?

Post by DanZ »

Hi O'Henry and welcome aboard! I think if you read all the posts in the thread here, you'll get the details you need.

But let me know if you need more.

Cheers,

Dan
O'Henry
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Joined: Thu Aug 05, 2010 6:44 am

Re: Twice The Stardust?

Post by O'Henry »

Hi DanZ thanks for the reply and the welcome. It makes perfect sense, I suppose, that the particles may and can have a snowplow effect when when encountering the aerogel. Surprising it doesn't happen more frequently. Must admit, however, that seeing the track you've referenced, the I1043,1,30 Track image, and the way the particle track appears to curve it's way down to it's final resting place, suggests a new question: is the I1043,1,30 Track image really curving downward or is that something of an optical illusion? Am I correct in assuming that the light source for the photomicrographs is directly overhead, perpendicular to the lens of the microscope, camera and the array of aerogel tiles? Maybe some of the particles are spinning, like english on a cue ball, as they are captured by the aerogel? Should I be looking for more rare curved tracks in addition to the rare double particled tracks? Thanks, again.
DanZ
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Re: Twice The Stardust?

Post by DanZ »

Almost all of the tracks I've seen so far (including most of the candidates) look a little wobbly, but overall, fairly straight at first glance. Some also appear to have an "offshoot" track toward the end, with Track 29 being a great example, and to some degree Orion and Sirius. But overall I would say look for what "look like tracks" (if that makes sense) and not necessarily curves. It's only this different angle view of track 30 that shows a slight arching curve (be sure to ignore the swooping dark black line), but this is not what you would see in the Virtual Microscope. On the other hand, you ask some good questions. Let me check with the scientists and see what they think. Stay tuned.

Dan
DanZ
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Re: Twice The Stardust?

Post by DanZ »

Okay O'Henry, here's your answer straight from Anna Butterworth who did the analysis:

You're looking at an x-ray absorption image from the scanning transmission x-ray microscope at Advanced Light Source synchrotron (ALS) at Lawrence Berkeley National Laboratory. The sample is placed perpendicular, between the x-ray beam source and the detector and I used 708 eV (an energy used for mapping absorption due to iron). Mapping x-ray absorption essentially gives you a map of density variation, which is why you see the track a little lighter.

The curvature in this image is real, and it is due to slightly buckling the aerogel of the picokeystone when it was mounted. The optical image of the track before it was mounted was perfectly straight.


So, seems you shouldn't worry about the curve.

Cheers,

Dan
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