Question regarding expected speed of impact of Stardust

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Question regarding expected speed of impact of Stardust

Post by GuruBuckaroo »

The question I'm asking is about the speed of expected 'real' stardust impacts as compared to the speed (and, well, size) of the Mir calibration movies.

Basically, where I'm going is this: On all of the calibration movies, you can see a 'speck' just above where the visible track starts. I assume this is the impact hole, or some other artifact caused by the impact. I've yet to see a well-defined impact track (as shown in the calibration movies) in a 'real' focus movie, but I, and several others who concur with my hits, have seen plenty of these specks - tiny black spots well below the surface. The update post recently listing candidtate tracks claims those may just be inclusions in the aerogel - but if the true stardust is moving faster than the 'calibration' dust, then the actual track may be starting well below the specks so many many have identified. My point is that the 'classic' track signature may not be visible simply because it is too deep, below the area of the focus movie.

The other half of this question, then, becomes about the expected size of the particles. If the particles are much smaller than those of the known calibration movies, then the specks themselves may be the stardust - and may not leave a classic track due to the size.

In short, I've yet to see a 'classic' track in a 'real' focus movie, and yet to see a 'speck' in a 'calibration' movie - except as a precurser to a track. If both of my assumptions are wrong (faster, smaller particles of 'real' stardust), then perhaps those features we were taught to identify as fragments of aerogel are the real particles.

Of course, I suppose none of this can be really answered until they start sticking needles into aerogel to collect potential samples. Comments?
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Post by Wolter »

Well issues about differences between calibration and real have been discussed on several other threads yet. Just search the forum about it.
On the stardust site you can find info about what is expected about interstellar dust.

The current tutorial and calib. movies are the best guess on what is expected about what we can see. But then again: expect the unexpected.

The specs you are refering about are under investigation by the team and we just have to wait for their verdict on it. Until then..

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Post by JOC »

Further to Wolter's pointer, the particular section on expected particle sizes present in the interstellar(IS) dust stream is at: ... #interdust

For an idea of what a real IS track might eventually look like, I think a good guide is to picture variations on the following track(whatever it is), if it had entered the aerogel at more head-on of an angle(ie less sideways), and then imagine if it was sometimes bigger(wider or bulbous), sometimes smaller, sometimes carrot-shaped(=tapering in as the depth increases), with a visible surface hole, or maybe not, etc, etc, every variation you can imagine.... ... =8153179V1

Add to that, the fact that some of the movies are darker(more poorly lit), more obscured with surface debris, or poorly focused, etc, etc and we can begin to see why the Stardust team themselves can't predict precisely the one, true vision of what we should look for.

[NB it seems, in particular, that we might get several different types and they might all be interstellar dust tracks... just of different size dust and/or different material]

[PS the likely relative speed of impact into the aerogel was quoted as 20km/s and that's the speed that was used in the simulated tests - the MIR samples were additional to those tests, and if the speed was different(prob was lower) then I presume any images used from MIR were modified to correspond with the test images][of course, my expectations and reality might not necessarily agree, naturally... Caveat emptor; your mileage may vary; batteries not included; etc, etc ;-)]
Twinkle, twinkle, little dust!
How I wonder which to trust!
From stars above the world you fell!
Buried like treasure in aerogel.

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