First interstellar candidate extracted from Stardust interstellar tray

Last Friday afternoon we extracted the first interstellar candidate from the Stardust interstellar tray. It is the one first identified by magickestrel on the candidates page. (Does anyone know how to contact him? I invited him by e-mail to name this feature back in October, but got no response.) 355 other dusters also identified this feature.

This is Dave Frank in the Cosmic Dust Lab at Johnson Space Center, with the cut picokeystone nearly ready for extraction from the tray. The candidate is the little dot in the upper center of the picokeystone.

This is a low-magnification image of the picokeystone after extraction, viewed from the side, with picoblocks still attached.

I’ve talked before about how much we would learn about these features by extracting them, because we have been forced to do Stardust@home imagery in the worst possible conditions. We learned this lesson from the cometary side of Stardust, and now we know for sure how true it is on the interstellar side as well. Compare this high-magnification (50x objective) image that you see in the VM on the candidates page to this:

Wow! In my view, this is very likely to be a real track. It is consistent in trajectory and morphology with an interstellar origin. The track length is on order 20 microns, and it is flared, consistent with a high-speed impact. It may even have a surviving terminal particle. If it turns out to be real, there is another piece of good news — it appears that the trajectory can probably be reconstructed reasonably accurately. We have tried to look at it at 90 degrees to this view, but cannot image it in that direction. Synchrotron imaging of the track may be very important for trajectory reconstruction. The amazing thing is that this image was taken through cut picoblocks, which we are not removing, at least for now (this is because of a problem that we had with an earlier picokeystone when removing the picoblocks).

We emphasize that although this looks promising, we won’t know whether this is interstellar without a lot more analysis, and probably also extraction of many more candidates.

This goes to Alexandre Simionovici at ESRF in Grenoble for synchrotron x-ray microprobe analysis today, along with three off-normal tracks.

Stardust@home dusters identified this track. Without the Stardust@home project, this would not have happened. Hats off to you!