© Charles Chandler

 

Video data were also collected at Chelyabinsk, one of the best of which was this one, taken by a dash-cam at the intersection of Beyvelya and Professora Blagikh streets (55° 13' 16" N, 61° 17' 45" E). The clock on the dash-cam wasn't correctly set, since its time-stamp starts at 2012-12-31, 18:30:40, though the event actually occurred on 2013-02-15. Regardless, the time-stamps are referenced in Figure 1 to more surely identify the frames in question. The video has a resolution of 480 × 360 pixels, at 30 frames per second, with good color depth.

 

The video captured several flashes of light, and the smoke trails left by the bolide, giving us a lot more information about the distinctive processes at work. Figure 1 shows 2 frames per second, over the relevant 16 second span. The largest flash occurred in frame 630. Determining the actual location of the bolide relative to the characteristics of the trail it left cannot be done just from that frame, since it was almost completely saturated. So the position was interpolated from previous and successive frames.

1. The selected frames were aligned horizontally by a common reference point (i.e., the leftmost of two smokestacks, visible in frame 346).
2. A high-contrast copy of the aligned frames was generated on which to do the photogrammetry.
3. The green curve passes through the observable locations of the bolide. If the bolide was traveling at a consistent speed, the positions should have all fallen on a straight line. But it was surely decelerating. Moreover, the video was taken from a moving car; the car went around a turn; and the dash-cam had a fish-eye lens, distorting the geometry. Regardless, the curve is smooth enough that additional mathematical analysis isn't necessary for a reasonable interpolation.
4. At the end of the sequence (i.e., frame 754), a trail of highly active plasma is still glowing brightly. The blue curves project the location of this plasma back to frame 630.
5. In frame 630, the red dashed line denotes the path of the bolide, based on its vertical position in previous and successive frames.
6. The intersection of the red dashed line and the green line is the location of the bolide in that frame.
7. This shows that the brightest flash occurred when the bolide was at the end of the thickest portion of the plasma trail.

We can also note that the bolide flared up again (i.e., frame 660), leaving a smaller trail of glowing plasma. But the color shift in frame 673 is suggestive of a lens flare, meaning that the brighter flash occurred once again when the bolide was done expelling plasma. So it wasn't that the brightest flashes created the trails of glowing plasma. Rather, the brightest flashes were events that terminated the process that was expelling the plasma.

 

 

Figure 1. Photogrammetry of the Chelyabinsk bollide.

 

 

These data can then be correlated with still images taken a couple of minutes later.

 

 

Figure 2. The bolide's trail shortly after its passing. (AP Photo/Chelyabinsk.ru)

 

 

This is interesting because the large step-down at frame 630 shows no evidence of an explosion, nor does the end of the trail at frame 673. This suggests that there was a physical separation between the flash and the smoke-producing process. If the bolide disintegrated due to Coulomb forces inside an ionized bow shock, the flashes were at the edge of the bow shock. This would not have disrupted the smoke coming off the bolide itself. (See Figure 3 and Figure 4.)

 

We should also acknowledge that any net charge is around the outside of an object. For this reason, a Coulomb explosion can reduce the mass of an object, without thoroughly destroying it. Obviously, this bolide maintained its general form and processes through the largest flash, which is consistent with a Coulomb explosion, and not with disintegration due to internal hydrostatic pressure.