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

[jasedm]

Wow!!

That's amazing. Inevitable comparisons to Tunguska will be made, but very fortunate this wasn't of that magnitude. Hope all ok

Jase

[ElkGroveDan]

With all those videos there's no doubt an exact and precise trajectory can be computed and I would assume a possible range of orbits extrapolated.

[Gladstoner]

.

[dvandorn]

I can certainly see how there was a pretty big explosion in the air, there is a rather extreme pulse of light and then the contrail sort of vanishes. But -- a 500 megaton explosion only 18 km up, over a populated town, and all we had from that was a bunch of broken glass? I mean, that's more powerful of an explosion than the Tsar Bomba, the largest thermonuclear explosion that has ever been accomplished, and that explosion caused the clouds to move at hundreds of miles an hour away from the blast at distances of 20 to 30 miles. I sure don't see that kind of immense airburst in the videos of the bolide....

-the other Doug


Edit:
oops -- just reviewed the figures, and either I misread the megatonnage the first time through or Mongo adjusted his figures. Still, a 5 MT bomb packs an awfully big punch...

[Gladstoner]

.

[dvandorn]

FYI, NASA TV is running live coverage of the closest approach of DA14 2012 from JPL, with some live feeds from telescopes in Australia, where the asteroid is currently traversing the sky.

-the other Doug

[Mongo]

Apparently, due to Russian laws pertaining to insurance claims, many cars in Russia have dashboard cams (do the Youtube search 'Russia dash cam' ). This means that many more videos of the bolide should be coming out in the days and weeks ahead.

I am waiting for a video that includes both the main flash and the arrival of the shock wave. That would allow us to estimate the distance and height above the ground of the detonation, and hence the minimum energy needed to cause at least 1 kPa of overpressure. I am betting it will be a figure in the low megaton range. A low kiloton-range explosion is already excluded in my opinion. The interval between explosion and shock wave hitting would have been too short, in the 20-30 second range, which I believe is already ruled out from the existing videos.

[dvandorn]

Oh, cool -- the JPL visualizations manager is showing DA14 on Eyes on the Solar System.

-the other Doug

[TheAnt]

Apparently, due to Russian laws pertaining to insurance claims, many cars in Russia have dashboard cams (do the Youtube search 'Russia dash cam' ). This means that many more videos of the bolide should be coming out in the days and weeks ahead.

Yes, this one is a dashcam vid of the event.

[ugordan]

Still, a 5 MT bomb packs an awfully big punch...

Tunguska was in recent years re-estimated to have been around something like that. This clearly had to be less. How much less depends on the actual altitude of the "airburst". At 10 km, a Hiroshima-type burst seems plausible to me. To be in the megaton range, it would have had to be significantly higher up, otherwise I'd expect much more extensive damage below. But these are all just my W.A.G.s...

NASA is estimating this to be around a 15 meter object and they're calling this one the biggest one after Tunguska. Doesn't say what their estimates are based on.

[Mongo]

NASA is estimating this to be around a 15 meter object and they're calling this one the biggest one after Tunguska. Doesn't say what their estimates are based on.

The impact effects website gives the following results for a 15m object with density adjusted to produce a 1 kPa overpressure at a realistic distance given the videos. Total mass would be about 13,000 tonnes for an energy release of 830 KT.

Your Inputs:
Distance from Impact: 15.00 km ( = 9.32 miles )
Projectile diameter: 15.00 meters ( = 49.20 feet )
Projectile Density: 7200 kg/m3
Impact Velocity: 30.00 km per second ( = 18.60 miles per second )

Energy:
Energy before atmospheric entry: 5.73 x 10^15 Joules = 1.37 MegaTons TNT
The average interval between impacts of this size somewhere on Earth is 140.0 years

Major Global Changes:
The Earth is not strongly disturbed by the impact and loses negligible mass.
The impact does not make a noticeable change in the tilt of Earth's axis (< 5 hundreths of a degree).
The impact does not shift the Earth's orbit noticeably.

Atmospheric Entry:
The projectile begins to breakup at an altitude of 28500 meters = 93400 ft
The projectile bursts into a cloud of fragments at an altitude of 16200 meters = 53100 ft
The residual velocity of the projectile fragments after the burst is 18.8 km/s = 11.7 miles/s
The energy of the airburst is 3.47 x 10^15 Joules = 0.83 MegaTons
Large fragments strike the surface and may create a crater strewn field. A more careful treatment of atmospheric entry is required to accurately estimate the size-frequency distribution of meteoroid fragments and predict the number and size of craters formed.

Air Blast:
The air blast will arrive approximately 1.11 minutes after impact.
Peak Overpressure: 1050 Pa = 0.0105 bars = 0.149 psi
Max wind velocity: 2.47 m/s = 5.52 mph
Sound Intensity: 60 dB (Loud as heavy traffic)

[ugordan]

The interval between explosion and shock wave hitting would have been too short, in the 20-30 second range, which I believe is already ruled out from the existing videos.

This video in particular shows a very long delay between start of filming and shock arrival, but it's obvious from the viewing angle that it's a ways off from the groundtrack so a minimum slant distance (here at least 23 km) is all we can infer. It does also show an unseen building smoking, perhaps it's the collapsed roof of the zinc factory. That amount of damage at that kind of range seems to support a high kiloton range. However, it's dangerous to infer too much from blast effects at these ranges as they start to depend upon meteorological conditions - inversion layers in the atmosphere, etc.

If the burst was at 20-ish km, I personally would place a bet at around 1 MT.

[ugordan]

This just in, via NASASpaceflight.com: a full length video from the flash to the sound. Whopping 2m 21 sec delay! Bolide starts at around 4:30 in the video.

This sucker was big!

[Mongo]

This just in, via NASASpaceflight.com: a full length video from the flash to the sound. Whopping 2m 21 sec delay! Bolide starts at around 4:30 in the video.

This sucker was big!

Holy Cow! Even at that distance, it broke windows! Assuming an overpressure in that video of 0.95 kPA, the overpressure at the distance of the closer videos (with the explosion at about a 45 degree elevation from the horizon) would be about 1.18 kPa, which might be enough to cause the documented damage at the zinc factory, assuming that it was poorly constructed and maintained. So around 1.33 MT at minimum, it could be greater than that.

Actually, if the calculated energy release is correct and the zinc factory was directly under the main part of the explosion, the overpressure would be about 1.37 kPa, making the actual observed damage to the building more plausible, albeit still rather excessive for the calculated overpressure.

Your Inputs:
Distance from Impact: 43.00 km ( = 26.70 miles )
Projectile diameter: 19.00 meters ( = 62.30 feet )
Projectile Density: 6000 kg/m3 (rocky-iron)
Impact Velocity: 30.00 km per second ( = 18.60 miles per second )

Energy:
Energy before atmospheric entry: 9.70 x 10^15 Joules = 2.32 MegaTons TNT
The average interval between impacts of this size somewhere on Earth is 210.0 years

Major Global Changes:
The Earth is not strongly disturbed by the impact and loses negligible mass.
The impact does not make a noticeable change in the tilt of Earth's axis (< 5 hundreths of a degree).
The impact does not shift the Earth's orbit noticeably.

Atmospheric Entry:
The projectile begins to breakup at an altitude of 37000 meters = 121000 ft
The projectile bursts into a cloud of fragments at an altitude of 18000 meters = 59100 ft
The residual velocity of the projectile fragments after the burst is 19.5 km/s = 12.1 miles/s
The energy of the airburst is 5.58 x 10^15 Joules = 1.33 MegaTons.
Large fragments strike the surface and may create a crater strewn field. A more careful treatment of atmospheric entry is required to accurately estimate the size-frequency distribution of meteoroid fragments and predict the number and size of craters formed.

Air Blast:
The air blast will arrive approximately 2.35 minutes after impact.
Peak Overpressure: 950 Pa = 0.0095 bars = 0.135 psi
Max wind velocity: 2.23 m/s = 4.99 mph
Sound Intensity: 60 dB (Loud as heavy traffic)

[Bill Harris]

It will be interesting to see what the "yield" of this bolide calculates out to be. I don't know how much of an exact correlation between the the yield of an atomic device and this asteroid will be. A bomb is designed to stay smallish and compact as the fission/fusion reaction is taking place and then the fireball can expand at it's own rate. An asteroid is either a rubble pile of coalesced fragments or a highly fractured rock. On atmospheric entry the surface is very hot and ablative while the interior is still deep-space cold, It holds together until the aerodynamic stresses cause it to rupture into many fragments. At that point the surface:volume ratio goes very high and who knows what the dynamics of that is.

At any rate, this was a nice surprise. In the media I've heard the size of the passing asteroid mistakenly listed as "half the size of a football" (not of a football field) and my first thought was "Ha, how ironic, this meteorite was probably half-football sized", but from what I read here, it was somewhat bigger.

We should be able to collect many fragments that made it to ground-- the snow ought to help spotting the impact sites.

--Bill