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midtskogen
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16 Dec 2016 03:08

Let's continue the thread in the old forum.

A new asteroid impact simulation
But it's odd that the video does not mention another, extremely important factor: impact speed, which is much more important than size for the total energy involved, unless the airburst scenario really is higher speed.
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16 Dec 2016 14:39

That does seem odd, but the way their simulations work is to follow the transfers of energy during the impact -- both through atmosphere and water, so all that varying impact speed does is scale the total energy by the square of the speed.  (And as you intuited, it also plays into whether it reaches the surface or airbursts).  The factors of speed, size, composition, and entry angle all play together as to what the impact looks like, but their presentation focuses on the differences in water jet and wave formation based on energy and impact vs. airburst.

I thought it was surprising to see how part of the pressure wave, and water vapor with it, quickly propagates backwards, since the asteroid's entry path cleared out a channel of low pressure in the atmosphere. 

It's also terrifying to imagine a water jet that is several kilometers high. =o
 
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16 Dec 2016 23:45

My intuition tells me that this is complex and that the heat plays a major role her, but whether a doubling of speed can be exchanged for a quadrupling of mass at this scale with little difference in effect, I don't know.  Yes, the water jet is terrifying.

On a much smaller scale, I made a video summarising the findings after the fireball off the coast of Norway last week.
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28 Feb 2017 12:45

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28 Feb 2017 13:15

That is quite awesome 
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01 Mar 2017 06:55

Since we are talking about asteroids, 99942 Apophis is on of the more interesting asteroids, as it was calculated a long time ago that it had a 2.7 % probability to hit Earth, which was later confirmed to be a very small probability ;)

Also, 16 Psyche is quite a interesting asteroid too, as it was probably involved in a massive collision which devastated it, causing it to probably be literally a big blob of mostly iron and nickel.
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15 Mar 2017 04:21

I got this image last night:
► Show Spoiler

Visible for about 6.5 seconds (video).  Slow moving meteor (12 km/s) reaching an altitude of 34 km.
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26 Mar 2017 15:49

Added a small piece of Libyan Desert Glass to the collection of meteorite-related things.  

► Show Spoiler


This is an impact-generated glass formed by the melting of sandstone under the extreme heat of the fireball, similarly to the "Trinitite" at the first atomic bomb detonation.  A few rare pieces include streaks of iron which was found to be of meteoric origin, and study of the glass and surrounding geology further support the impact-origin of the substance, although the crater itself has not been found (likely eroded and buried under the sand).  The impact probably occurred about 25-30 million years ago.
 
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21 Apr 2017 06:10

A nice fireball photographed last night by our meteor network:
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The entry speed was 12.8 km/s and terminal height (against a twilight sky) of 33.1 km.  This makes it a meteorite candidate.  It fell over southern Sweden.  It was only moderately bright, though, so the entry mass was likely not very high.
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midtskogen
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21 Apr 2017 06:11

midtskogen wrote:
A nice fireball photographed last night by our meteor network:
► Show Spoiler

The entry speed was 12.8 km/s and the terminal height (against a twilight sky) was 33.1 km.  This makes it a meteorite candidate.  It fell over southern Sweden.  It was only moderately bright, though, so the entry mass was likely not very high.
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25 May 2017 14:23

Another nice meteor recorded shortly after true midnight last night: Seen from Harestua near Oslo.  It appeared above the northern horizon and crossed nearly the entire sky disappearing towards the southeast.
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25 May 2017 15:40

Slow, but doesn't seem really persistent, wow!
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25 May 2017 23:26

Entry speed: 21 km/s. Entry angle: 6.7 degrees.
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26 May 2017 20:05

Almost an Earth-grazer!
 
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midtskogen
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23 Jun 2017 13:39


Supposedly shot a few days ago near Barybino, Moscow oblast.  Little info to be found so far.  An article, mostly nonsense, here.
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