INCOMING!: метеорита в Челябинске, Russian Meteor - February 2013 Options

[Eyesonmars]

I found it interesting that a number of witnesses mentioned feeling the radiant heat of the fireball. A little bigger and we would have had some objects charred on the ground beneath the fireball. How much bigger ?? Even so, the shock wave would have probably extinguished any fires. Much like what happened at Tunguska.

[nprev]

Do you have any references for the heat perceptions? I would be quite surprised by that given the altitude of the detonation plus slant range(s).

[Bill Harris]

Thunder rumbles aren't generally echoes, just the delayed arrival of the shock wave from points along the strike...

That is what I had concluded and was going to post here. And remember although the contrail looks like it is just up on the ceiling, it is many miles long and every part of it has a different range in miles and therefore arrival times. And when the object disintegrated, there were thousands of fragments released, each making their own shock wave.

And the videos confirm the conceptual model of the object disintegrating. As it entered ( I keep wanting to say "reentry") it was solid and made a compact plasma sheath perhaps 30 meters diameter. The smoke trail is ablated silicates that have condensed. When the object ruptures it immediately creates thousands of fragments ranging size from boulders to dust, each with it's own aerodynamic characteristics and trajectory and the surface:volume ratio increases rapidly and so does the amount of material being ablated. The plasma sheath rapidly expands due to the unconstrained fragments and the increase in the volume of plasma from vaporized silicates and whatever volatiles were entrained in the rock.

Whew. It's mind-boggling.

--Bill

[tasp]

I noticed in the different clips shown the degree of camera saturation varied quite a bit. Some of the slower responding imagers totally whited out, and others seemed to have AGC circuits that tried to follow the illumination level.

I was wondering if any photo analysis has been done yet to determine a decel rate along the path for the rock. It would be interesting to have some idea what it withstood before the fragmenting started.

And maybe decel, heating, and turbulence weren't the only effects on it, maybe it was aerodynamically asymmetrical and the slipstream was starting to spin it up some ?

[Mongo]

Do you have any references for the heat perceptions? I would be quite surprised by that given the altitude of the detonation plus slant range(s).

I don't have links myself, but I do recall reading reports that mentioned that people felt heat coming through the windows. One person mentioned that curiosity over this unusual heat was what attracted them outside before the shockwave hit. If the fireball was indeed as bright as the sun or brighter, as seems to be the case, then the infrared radiation should be roughly in proportion, so I would not be surprised if there was a short burst of heat when the main explosion happened.

[Bill Harris]

Do we have any scale information on the cameras used to photograph the Russian bolide? Do we have any idea of the physical dimensions of the dust trail/debris trail (I don't think it's technically a contrail) I've looked at a lot of photographs and videos and I can't get a handle on how to scale the trail. My TLAR sense tells me that it's huge.

--Bill

[walfy]

...I've looked at a lot of photographs and videos and I can't get a handle on how to scale the trail. My TLAR sense tells me that it's huge.

Check out this page for its scale: http://attivissimo.blogspot.ch/2013/02/rus...-in-google.html
I attempted to scale it here.

For what it's worth, I did a quick extraction of 6 sonic boom soundtracks of the meteor from YouTube to see if I could find some similarity between them, at least in the timing of the biggest booms. But nothing stood out as a clear match between any two of them, except for the initial boom, of course! Maybe if a bit more time were spent some similarities could be extracted. But no similarity in the timing and sequence of the booms stands out between any of them with a quick listening or when looking at first 11 seconds of their waveforms:



Of course, there's some glass shattering or car alarms at the beginning of some of them, but some were taken with minimal background noise with the booms standing out. But no pattern. It sounds really different from each location. When all soundtracks play at once, it's a calamity – for the ears!

Something that does stand out is that recordings made closest to the vapor trail almost sound like gunfire or quick and snappy fireworks booms; more distant ones sounded like thunder, "muffled" but still loud.

[walfy]

ONe more thought for the night: it would be a great study to survey glass breakage under this meteor. I suspect that fewer panes shattered directly below it then to the surrounding immediate vicinity, similar to the trees that still stood under the central blast of Tunguska years ago.

[FordPrefect]

Some interesting photos on this photographers blog, who just happened to be outside to do nature photography:


Link

In that photo and the following, it really looks like there are fireball/explosion-like segments visible inside the train still glowing?


Link

And an air-to-air image of the train. See the colour variation on the nearer (left) part of the train? It changes from brownish to blueish hues, indications of different materials being vaporized during its "melt off" process?


Link

[Paolo]

As you can see - they're planning to observe it for several days.

I had googled that. I was just expecting that, given the media hype, they would be releasing early results in quasi-real time like they did with Toutatis last December

[ugordan]

When the object ruptures it immediately creates thousands of fragments ranging size from boulders to dust, each with it's own aerodynamic characteristics and trajectory and the surface:volume ratio increases rapidly and so does the amount of material being ablated.

This is the explanation I subscribe to as well. Each of those separate fragments would see a significantly different deceleration depending on its ballistic coefficient so the fragment train would quickly spread out in along-track direction, creating all those distinct, subsequent booms.

[Mongo]

For what it's worth, I did a quick extraction of 6 sonic boom soundtracks of the meteor from YouTube to see if I could find some similarity between them, at least in the timing of the biggest booms. But nothing stood out as a clear match between any two of them, except for the initial boom, of course! Maybe if a bit more time were spent some similarities could be extracted. But no similarity in the timing and sequence of the booms stands out between any of them with a quick listening or when looking at first 11 seconds of their waveforms:

This does not surprise me. Each individual explosion would have happened at a different location in the air, and hence would be a different distance from the listener, with the distance to each explosion varying with the listener's location. A given shock wave would change its time of arrival relative to that produced by a different explosion, even changing from being earlier to being later than the second shock wave, depending on the location of the listener. So the sequence of bangs and booms would be different at each location on the ground.

[dvandorn]

...Each of those separate fragments would see a significantly different deceleration depending on its ballistic coefficient so the fragment train would quickly spread out in along-track direction, creating all those distinct, subsequent booms.

Exactly the point I made. The multiple booms were sonic booms created by the fragments of the original impactor after the initial explosion.

-the other Doug

[Bill Harris]

...it really looks like there are fireball/explosion-like segments visible inside the train still glowing?

Yes! I noticed those "redder" areas in the initial videos and attributed them to redder light where the blue had been scattered by very small particles (a "sunset effect"). But later-presented and better quality photos do indeed show that the red is incandescent-- I was not expecting the heat to be retained that long, but it's only a very few seconds after the fireball had passed.

--Bill

[ugordan]

This video shows nicely that incandescence nicely.