[meteorite-list] Dark mass in front of Cherbakul bolide + raining meteorites‏

From: Jodie Reynolds <spacerocks_at_meteoritecentral.com>
Date: Sat, 23 Feb 2013 16:16:52 -0800
Message-ID: <1437219553.20130223161652_at_spaceballoon.org>

Hello Vincent and list,

I haven't gone and processed that video myself, but just skimming
your enhancement, my first blush is a nice image of the Bow
Wave ("shock cone") and boundary layer. Given the tremendous compression there's never
going to be a clean air image anywhere near that thing, viscous
effects and wave drag will assure us that.

Aerodynamics and compressibility aren't really my area of expertise,
I'm optical physics, but I'll bet there's enough rough numbers out
there to model what you're observing. OpenFOAM has a very good
compressible flow solver, then feed that to the fantastic Paraview.

http://www.openfoam.com/features/paraview.php
http://www.paraview.org/



Saturday, February 23, 2013, 3:27:48 PM, you wrote:



> Hi Murray,

> Thank you for your comments.

> The photos comes from this video: http://youtu.be/PHf20NVZSV4 (The
> bolide is visible at 4:35, deflagrations at 7:01)

> I have updated my galery with several photos from the bolide, there
> is 1/10 s between each image.
> http://www.flickr.com/photos/93493758 at N04/

> The first image posted early today was focalized on the head of bolide up to 800X magnification.

> I agree with the suggestion of Chris, who's consider an
> atmospheric effect related to the supersonic shockwave or
> compression zone. I don't think that is an artifact from camera or
> from the car windshield. It would be possible that's an electronic
> effect from pixel saturation, but why others images don't show it?

> This is the first time that I see this kind of effect in a fireball.

> Cheers

> Vincent


> ----------------------------------------
>> Date: Sat, 23 Feb 2013 14:47:56 -0700
>> From: murray.paulson at gmail.com
>> To: meteorh3_6 at hotmail.com; meteorite-list at meteoritecentral.com
>> Subject: Re: [meteorite-list] (sans objet)
>>
>> HI VIncent:
>>
>> First off, the meteor would not be dark, rather it would be white hot.
>> The dark spot is probably a camera contrast artifact. But I thought
>> that it would be interesting to do some calculations on the object.
>>
>> Some quick back of the Excel envelope calculations.
>>
>> I am not sure which video you are using for this analysis, but lets
>> assume that it is not a telephoto close up, and is a wide field focal
>> length, say 50 degrees. This would go along with cell phone cameras
>> and dash cameras and is just a guess. If the video was 640 pixels
>> wide, (compressed for Youtube) and we place the meteor at 30 km
>> distance then each pixel in the image is
>>
>> video width 50 degrees
>> 640 pixels
>> 0.078125 deg/pixel
>> 0.001363538 radians
>> assume a distance of 30 km
>> 40.9 meters/pixel
>>
>> Now the dark object seems to take up several pixels, so lets assume 3
>> pixels width. This would give us an object size of 120 meters, which
>> is closer to the size of the asteroid that was passing between the
>> earth and the moon on the same day.
>>
>> If I go the other way and place a 15 meter object at 30 km, the math give us
>>
>> 15 m
>> assume at 30 km
>> 0.0005 radian angular width or
>> 0.0286 degree
>> 1.72 minutes of arc
>> 0.37 pixel
>>
>> With the same camera, we would have the body size as 1/3 of a pixel.
>>
>> Now, the video may have been zoomed in, and so you can scale these
>> numbers by the ratio of the true field divided by the 50 degree guess.
>>
>> Cheers.
>>
>> Murray
>>
>> On Sat, Feb 23, 2013 at 9:39 AM, Vincent . <meteorh3_6 at hotmail.com> wrote:
>>>
>>> Dear all,
>>>
>>> When a very big bolide is observed, some witnesses explain the observation of "the" meteorite parent, just in front of bolide.
>>>
>>> I wanted to check this very unknow phenomen.
>>>
>>> I decomposed some video from Chelyabinsk bolide. One of them shows a dark mass in front of the bolide!!! It seem rotating. The dark mass is visible during approx 1/2 second. Some details are visible 3/10 second later during 2/10 seconds.
>>>
>>> With an exciting surprise, the end of path, 1 second later show the fragmentation of two medium mass. One of them create a veritable "plume" in the sky. Perhaps the beginning of a rain meteorite?
>>>
>>> If this is really the explosion of a meteroite mass in sky and/or the real "asteroid" falling in the atmosphere, then that's is the first time that the phenomen is recorded! I'll be very happy to have it discovered.
>>>
>>> Photos are visible ==> http://www.flickr.com/photos/93493758 at N04/ Enjoy!!
>>>
>>>
>>> Kind regards
>>>
>>> Vincent
>>>
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-- 
Best regards,
 Jodie                            mailto:spacerocks at spaceballoon.org

Received on Sat 23 Feb 2013 07:16:52 PM PST