Kerr Watch

Number of days writer Richard Kerr has failed to inform his Science readers of the confirmation of nanodiamonds at the YDB: 3 years, 11 months, and 6 days

Recent Comments

CT Post Calendar

November 2014
M T W T F S S
« Sep    
 12
3456789
10111213141516
17181920212223
24252627282930

The Cosmic Tusk Newsletter

Loading...Loading...


Bolide Shockwave Injures 1000+ in Russia: Black Swan — or I Told You So?

 

 

 

 

The Bos!

Slow feed but great vids

Plugged!: Younger Dryas Impact Event

Feb Fireball Season

San Fran

Cuba and video

Japan

Miami

Brazil 2012

Iowa 1875 and here

1913

Fireball Hush-Up?

NASA Urges Vigilance for Weird Fireballs

NASA 2012 Press Release “The Fireballs of February”

Year of the Snake?

Black Swan

As readers know, the Tusk is generally uninterested in current events related to our subject. We stick to the past unless we simply cannot ignore the present. But, in the end, we study the past so that we may be more prepared for what happened this morning in Russia.

This humble blog has some of the most informed and open-minded readers in fields related to this event of any source on the internet. I hope our regular commentors and others will develop an informative thread of observations.

 

190 comments to Bolide Shockwave Injures 1000+ in Russia: Black Swan — or I Told You So?

  • Hermann Burchard

    From some of the pictures, this was a grazing impact, the trail begins and ends in the upper atmosphere.

    This French newspaper report has a few additional infos. Newly updated, it reports 950 injured persons.

    http://www.lefigaro.fr/international/2013/02/15/01003-20130215ARTFIG00312-de-nombreux-blesses-apres-la-pluie-de-meteorites-en-russie.php

    On one of the videos explosions are heard.

  • Steve Garcia

    I don’t think I will be saying anything important that others here don’t already know or think:

    Why anyone’s first real reaction would be that the two are not connected flummoxes me. They were on parallel orbits only a day apart. It is not like it is a population of objects like the Taurids. What are the chances that two objects on the same path, separated only by time and a very slight side-to-side would be crossing Earth’s orbit within a day?

    My own 1st reaction is: Are there more?

    This was such a wonderful, basically benign, warning shot across the bow. It is great that no one was killed. But 950 injured – wow. 3000 buildings actually damaged – wow.

    2nd thought: A bit deeper into the atmosphere and it might nearly have been another Tunguska, more or less (probably less). Hermann notes that it grazed and mostly kept on going.

    3rd thought: No one had a CLUE this was coming.

    4th thought: Jonny and others here may be able to estimate its size and compare it to Tunguska.

    5th thought: Yeah, 3000 buildings damaged (Le Figaro) as easily as 3. The explosion shock wave doesn’t discriminate.

    6th thought: If it had impacted, what damage?

    7th thought: That hole in the ice was about the same size as the impact in Peru a couple of years ago. (Yes, water/ice vs ground…) And that was only one of many fragments.

    8th thought: Half the pieces went essentially down, half up. The pieces that went up may be strewn downfield a long way. It should be a great time for meteor hunters north of there. Damage on a much smaller scale is possible there, too.

    9th thought: WOW! The blast was terrific! MUCH greater than sonic booms I’ve heard, which also broke windows in the 1950s. I wondered if it was the sonic boom or the shock wave of the blast. One link on Le Figaro (no text) attributed the damage to the sonic boom. Yes? No?

    10th thought: The one video shows plywood getting blown inward. From that the force there could be estimated pretty closely.

    11th thought: The brightness – it to some degree substantiates reports in 1908 of Tunguska lighting up the sky all the way to western Europe.

    12th thought: Is this pairing of the two objects an anomaly? Or will we find out that this is the norm? How many other companions of this one flew by (or will fly by) without being even seen?

    13th thought? Not intending to be alarmist, but are more pieces coming? We never saw this one coming, and often where there is smoke, there is fire. How many other pieces are accompanying this asteroid 2012 DA14? Legitimate questions – and ones we can’t do a darned thing about.

    ‘Nuff for now. I will let others throw in more scientific thoughts…

  • Hermann Burchard

    Steve,
    6th thought: If it had impacted, what damage?

    One of the links leads to this thought (& more, but silly):

    GoldMorg Com writes ; very very very very coincidental, Chelyabinsk, where huge radioactive stockpiles are. A direct full hit would have caused a nuclear disaster for Eurasia that is thousand times worse than Chernobyl.

  • Jonny

    They are not on parallel orbits Steve, very much opposite in that one could describe them as anti-parallel. The russian meteorite is seen moving left to right in front of the rising sun, and thus must be travelling north to south. 2012 DA14 is moving south to north. This is as about as dynamically unrelated as you can get. This is cosmic coincidence, nothing more.

    The Russian meteorite is thought to be about 10 tonnes in mass. That puts it in the 2-5 meter class of object. Travelling at 15 km/sec it would have had an energy of around 270 tonnes of TNT. A big explosion certainly, but if had made it through to ground (and being the size it is its unlikely), it would have caused local destruction and serious loss of life if it was in an urbanised area. The thing to bear in mind is that we can expect an event of this size to occur approximately once per year somewhere in the world.

  • Steve Garcia

    Thanks on that, Jonny. I had evidently misread that.

    Once per year? Since I can’t recall any quite like this, the question would be where have they been exploding (besides over oceans)? This one is by far the largest one I’ve heard of in my time.

    If they are that common, then no big deal, right? What’s 270 tonnes of TNT (35 Hiroshimas) among friends, after all?

    The big thing to take away, then, is that we are at their mercy. We don’t see them coming, so we are ducks in a shooting gallery – if they happen to come our way. The operative term there is “happen to”. We have no control, no detection, no plan, no preparation. Just sit and wait for the lightning to strike. And hope it “happens to” happen in someone else’s back yard. Thanks, David Morrison, et al.

    This being the first time (that we know of) that we’ve had the possible ability to protect ourselves from such things, the biggest problem is coming to realize that it has happened before and will happen again. Without adequate funding, neither our realization can happen, nor any plan will ever happen.

    I know, that makes me sound like an alarmist. But, this isn’t like global warming where the Kyoto Protocols would only have reduced the 2100 global temperature by ~0.12°C, so wrong or right, it didn’t make a hill of beans difference. With NEOs and comets, if we screw it up we get to wear rabbit skins and shiver in rock overhangs for a millennium.or ten. That is, those few who survive the impact and the real environmental disaster that follows.

  • Jonny

    From here http://www.nature.com/news/russian-meteor-largest-in-a-century-1.12438 the size was about 15 meters and about 7000 tonnes as measured from infrasound stations(I was going by a precious BBC news report). This sounds more probably given its effects than a sub 5 meter object. If travelling at 15 km/sec this gives it an energy of 188 Kilotonnes of TNT, which is about 12-13 hiroshima bombs. This is the lower end of the energy estimate of the 13 August 1930 airburst over the neighbourhood of the River Curuça in the Brazilian Amazon (estimated to be between 0.2 and 2 MegaTonnes). Of course the nature article seems to ignore the 1930 and the 1935 airburst over British Guiana the later of which has an uncertain energy but is likely bigger than the Russian meteor in size due to it levelling an elongated area of forest 32 kilometers across.

  • Jonny

    Steve,

    Hirohsima was about 15 Kilotonnes (but, not 7 Tonnes). Given the energy estimate measured from the infrasound stations I would be more inclined to go with the second post of mine. You might be interested to see these videos here http://say26.com/meteorite-in-russia-all-videos-in-one-place, particularly the office based videos, where it looks like the overpressure from the sonic boom blows those close to teh window away from it.

    Jonny

  • Jonny

    Approximate path of the Russian meteor in comparison to 2012 DA14 from the Daily Telegraph http://s.telegraph.co.uk/graphics/html/Years/2013/February/images/Meteor5.png

  • Hermann Burchard

    Jonny,

    A big explosion certainly, but if had made it through to ground (and being the size it is its unlikely), it would have caused local destruction . . .

    This rock would not have reached the grround as it was grazing the upper atmosphere, as Steve noted, . . . it grazed and mostly kept on going. “”. . It kept going,” meaning a remnant left the atmosphere and the body did not completely burn up.

    The brilliant light indicates explosions from heating the outer layers upon contact with dense air, and probably caused repeated ablation or spalling of outer layers without complete destruction. This should be considered when estimating the size.

    The delay of the sound of the blasts of three minutes translates into an altitude of 60 km (speed of sound may not have been standard). It should be possible to measure the trail from photos and confirm entry into and departure from air density levels sufficient to cause incandescent heating.

  • Steve Garcia

    Jonny -

    I can’t believe I did math in my head that mad. Yep, 270/20 is not 35. I am embarrassed. I was using 20 as Hiroshima as what was reported. It’s what is listed in Wiki, among others. So it was about 9 Hiroshimas. But I sure did the math wrong. Can I blame it on cobwebs? I guess not…

    It is O/T a bit, but for U.S. A-Bombs tests from 1945 to 1963, 270 kt would be more powerful than any fission-only bomb tested, and is more powerful than a handful of H-Bomb tests. Other tests in this range were relatively small fission-fusion bombs. Generally, anything at or above about 100 kt was fusion of some sort. (They were tests, after all, and the aim was toward various designs of fusion bombs.)

    The Nature article said it was about 15 meters across, about 50 feet – about half the width of the Tunguska object’s estimated size. Given 2 of these in 105 years, what does that do to the astronomers’ estimated rates?

  • Jonny

    Hermann,

    I dont think this was an object that skipped in and out of our atmosphere. Given that there are reports of at least two fragments hitting the ground. Also from Spaceweather.com quoting Bill Cooke, head of NASA’s Meteoroid Environment Office.

    “The asteroid was about 15 meters in diameter and weighed approximately 7000 metric tons. It struck Earth’s atmosphere at 40,000 mph (18 km/s) and broke apart about 12 to 15 miles (20 to 25 km) above Earth’s surface. The energy of the resulting explosion was in the vicinity of 300 kilotons of TNT.”

    Penetrating that deep into the atmosphere usually means that the object wont be leaving it again, usually it sheds too much energy to its surroundings.

  • Jonny

    Steve,

    The average frequency of events for this energy size is typically about 1 every 60-100 years (according to conventional impact assessment). Tunguska class is considered to be 1 every thousand years (give or take), though Duncan Steel and others suggest the more sobering figure of 1 in 300 years for Tunguska like impacts.

    Alas though, it may not likely change astronomers estimated frequency rates, since those rates are based upon size distributions of near earth objects, and with most statistics, a single event will not upset those statistics, particularly since the interval from the last biggish event (either 1930 or 1935) is of the order of timescale one would expect for objects of this size.

  • Hermann Burchard

    Johnny,
    thank you very much for your reply! Am working on a deadline job for a paper to be submitted, so am awake at this time.

    Ok, you can easily check this out by looking at the videos that George has linked to this blog above, under Slow feed but great vids. The entire trail took about ten (10) seconds and has an explosive widening in the central part in the densest part altitude ~60 km of the atmospher, as confirmed on numerous videos including one from about 730 (?) km away with the trail just above the horizon. The formula for the horizon is d=113*sqrt(h), with d=distance and h=altitude both in km.

    The succession of about five or six explosions after the initial main one can be heard on several of the videos and can only be due to spalling of overheated layers of a potentially large rock (larger than NASA estimate) as layer after layer breaks off until the rock leaves the atmosphere still in one, but a little smaller, piece!

    Gotta look at the vidies!

  • Trent Telenko

    FWIW, There are now new videos this morning from San Francisco of a new (smaller) meteor event

  • Jonny

    Hi Hermann,

    While the entry into atmosphere was shallow it was not shallow enough to pass back out, and it does seem as if it penetrated into the lower atmosphere before disintegrating. The shallow entry would have given the bolide a better chance of survival and reaching these lower altitudes by virtue of decelerating the body significantly before it reached the denser lower atmosphere (this is the reason why it is thought the Tunguska object was able to survive to its detonation altitude). The final and brightest “flare” we see on the videos (a nice animated gif is here http://i.imgur.com/SnVvLv8.gif is followed by rapidly cooling fragments. This marks the destruction of the bolide, and I would hazard a guess that this is the source of the shock wave that injured so many people through debris, and not a sonic boom.

    Also see this new release of data from infrasound stations (http://www.nasa.gov/mission_pages/asteroids/news/asteroid20130215.html) which has revised the estimate of its size and energy.

    “The estimated size of the object, prior to entering Earth’s atmosphere, has been revised upward from 49 feet (15 meters) to 55 feet (17 meters), and its estimated mass has increased from 7,000 to 10,000 tons. Also, the estimate for energy released during the event has increased by 30 kilotons to nearly 500 kilotons of energy released. These new estimates were generated using new data that had been collected by five additional infrasound stations located around the world – the first recording of the event being in Alaska, over 6,500 kilometers away from Chelyabinsk. The infrasound data indicates that the event, from atmospheric entry to the meteor’s airborne disintegration took 32.5 seconds. The calculations using the infrasound data were performed by Peter Brown at the University of Western Ontario, Canada”

    Note there is no statement telling us that it skipped back out. We would expect some sort of infrasound “tail” in the Energy-time domain indicating that after the main detonation, a remnant leaving the atmosphere. If this were the case, I would fully expect an announcement to the effect that this was skipping asteroid. This was a true impact event, in that all of the energy of the bolide was dumped into our atmosphere (through ablation and disintegration) having penetrated down to about 20-25 kilometers.

  • George Howard

    Thanks, Trent.

  • Hermann Burchard

    Jonny,
    this video from George’s post shows the whole trail, no sign not a smidgeon of entering lower atmosphere.

    http://www.youtube.com/v/iCawTYPtehk?hl=en_US&version=3

    The fact that the trail is visible from Orenburg, 770 km from Chelyabink (same post) proves it was at the 60 km altitude for the ten seconds the trail appeared in the skies of Russia.

    Sadly, NASA doesn’t comment on the need to revise the 25 km altitude, nor on the five or six minor explosions after the main blast, enough to explain debris picked up by police.

    Why the irrelevant remark there is no statement telling us that it skipped back out
    when you could viddy the viddies yourself?

  • The dash cam video I looked at clearly showed a fairly abrupt terminal parabolic arc with burnout of the pieces. It didn’t skip.

  • Hermann Burchard

    TLE,

    no sign of such an arc on the dash cam video posted in my comment preceding:

    http://www.youtube.com/v/iCawTYPtehk?hl=en_US&version=3

    What you think is burnout of the pieces, in reality is the tail end of the trail where the rock is leaving our sad and lonely planet’s happy atmosphere, as you can tell when you compare the entry segment with the tail.

  • Jonny

    Permit me to ask you a few questions Hermann.

    1) What did you use to calibrate your distances and angular scale from the videos to arrive at your conclusion?

    2) how did you take into consideration the projection effect to allow for the fact that the meteor may have had some forward or away from you component of velocity even though it could look from the videos that it was simply moving perpendicular to you? Hence the flaring point could be substantially closer or further from the camera than you think

    3) Did you take into consideration any slope in the terrain which could make the horizon appear lower than it is?

    4) you have stated a formula for calculating the the height, namely d = 113 sqrt(h) where d is the distance, and h is the height. can you explain how you got this, and what the co-efficient of 113 represents, since it looks to me that this equation is not dimensionally balanced given that you have dimensions of length on the one side, and dimensions of length to the power of a half on the other. The only way this would balance is if the 113 had dimensions of length to the power of half. If we reduce this to dimensions we get L = k L^(1/2), implying that k should have a dimensionality of L^(1/2) for the equation to balance. If this is not the case then you formula is not physically correct.

    As for the so called irrelevant remark, it is not irrelevant. Asteroids that skip in and out of the atmosphere are interesting, and if this were the case, then it is likely that in the “press releases” and updates, some mention would be made of it. The general consensus amongst academia is that it deposited teh bulk of its energy at teh 20 to 25 kilometer mark, meaning it did not escape back out again.

  • That’s just about the best video of a distant capture of the entire event and it has already been turned into a .gif. However that is a very distant shot of it, but even so you can see it is following a convex trajectory. The known observed skipper spent a lot more time in the atmosphere and traveled much longer through the sky before departing. Even the Thomas Jefferson skipper behaved quite a bit differently. If you look here you can see the very end of the luminous event at 4:40 to 4:47. It didn’t skip. That’s the end of my discussion at least of the meteor skipping phenomenon. Platinum iridium ratios I might talk about. Also, if anyone wishes to discuss deep space and lunar space architectures that facilitate asteroid derotation and capture I could talk about that as well. But it didn’t skip.

  • Hermann Burchard

    Jonny,

    are you not simply trying to ignore that events in Chelyabinsk at altitude 25 km cannot possibly be above the horizon when viewed from 770 km in Orenburg?

    You are asking me for a tutorial on
    what the co-efficient of 113 represents?

    Sorry that I did not include the proof of the horizon formula, thinking you would do it yourself, as presumably you are in command of basic high school math, up to Pythagoras’s Theorem?

    Here, the value of the co-efficient c is valid for an ideal spherical Earth of exact circumference 40,000 km:

    c = 112.838…
    = 200/sqrt(pi)

    Even more precisely, the co-efficient c in the horizon formula depends on h very slightly for moderate size h, and the exact formula is

    c = [200/sqrt(pi)] * sqrt(1+pi*h/40,000).

    You are right, about dimensions I was being sloppy. For the sake of discussion, let us set
    1 km = 1.
    Then the circumference of Earth is just 40,000.

    TLE,
    the path in that video looks much more curved in the tail than the one from George’s list. But if you consider possible trouble with the optics of viewing through the windahield in your case at its very edge vs in the center of the windshield done from a great distance in the one that I have posted, you will appreciate that I cannot give much credence to the one your evidence.

    End of Discussion?

    Oh baby baby, the world is so much more deep and complicated than you can possibly imagine!

  • Trent Telenko

    Havana reported a fireball.

    See —

    http://www.havanatimes.org/?p=87801

    Cuba Town Also Rocked by Celestial Body
    February 15, 2013 | | Print Print | 14 65 590

    HAVANA TIMES — Homes in the central Cuban town of Rodas, Cienfuegos shook on Wednesday evening after an explosion overhead, reported ANSA news service.

    Witnesses reported the fall of a celestial phenomenon that ended with a huge explosion with a very bright light in the sky that shook their homes, said ANSA citing the Cuban morning TV news program as its source.

    Experts are scouring the area in search of any remains that fell to Earth. No reports of injuries or damage to property has come in.

    Meanwhile in Russia on Friday, a piece of a meteorite caused extensive material damage and nearly a thousand injures were reported in the Ural region of the country. See report. (http://www.havanatimes.org/?p=87761)

  • This from Alan Boyle’s Cosmic Log

    Estimates raised for nuclear-sized asteroid blast that hit Russia

    I note that he makes no mention of the thing skipping back out of the atmosphere.

  • Hermann Burchard

    Dennis,
    the 770 km from Chelyabinsk to Orenburg mentioned in the Russian blog posted on Tusk is the long route, by Google maps, best roads.

    A shorter round is only 715 km, very curvy.

    Hence, I took the trouble to use spherical geometry & determined the distance of the two cities is 558.74 km as the crow flies. For this horizon distance my formula requires an altitude of only 24.45 km, in agreement with NASA.

    Hence my crude estimate of reported 3 minutes for blast sound wave = 60 km to source was vastly incorrect, Jonny.

    The edge of windshield argument remains valid, as the center windshield shows almost no terminal curvature, I still believe it skipped, maybe NASA guys can look into it.

  • Jonny

    Hermann,

    My apologies, i did not realize that you were using the “distance to the horizon” formula in that original post, and was confused by the horizon formula, and hence was in a completely different mind set than yourself, hence the questions. Thanks for explaining, its clearer now what you were doing.

  • Hermann Burchard

    Jonny,
    thanks for your kind sentiment.

    Of course Tuskers all know, you are one of George’s best/ favorite commentors, for your expert contributions.

  • George Howard

    What an enjoyable dialogue, thanks folks.

  • Trent Telenko

    Another FYI, Feb 15, 2009 there was a fireball over Texas and fragments were later found near the city of West, Texas.

    See:

    Houston Chronicle

    http://www.chron.com/disp/story.mpl/ap/tx/6270243.html

    A reporter from Austin Texas captured the meteor on his video:

    ttp://www.news8austin.com/content/top_stories/default.asp?ArID=232127

    Meteorite hunter suspects meteor landed near Waco:

    http://www.news8austin.com/content/top_stories/default.asp?ArID=232127

    Meteorite hunters descend upon West, Texas:

    http://www.wacotrib.com/blogs/content/shared-gen/blogs/communities/breakingnews/entries/2009/02/18/meteorite_hunters_searching_ne.html

    http://www.wacotrib.com/news/content/multimedia/players/brightcove.html?bcpid=1475275870&bclid=1493222307&bctid=13607945001

  • Hello for all

    Last year on fev/2012 a news about a possible earthquake in Pernambuco call my attencion, yes they do exist in my home state, even in small intesidade and frequency. But the story that was published I think something else about it! Earthquake in Brazil? It can be! But this story was poorly told!

    What do You think about it? It is worth checking the phenomenon in Flores. See below. Unfortunately the news is not echoed and faded into oblivion.

    http://www.florespe.net/c.php?id=2945&d=Abalo-sismico-de-media-proporcao-atinge-comunidade-rural-no-municipio-de-Flores%20&cat=Paginas

    ” Last Tuesday (21/feb/2012) at about 10.40 am, the ground shook in the town of Saco dos Caldeirões, rural region of Flores in Pernambuco, distant 385 km from Recife.

    According to reports from farmers, Paulo Henrique and his brother Gerard, a flame of fire that looked like a rocket ascended with great speed occupying the space of the sky. The brothers Paul and Gerald worked on their property when they were surprised by a great shot that hit the ground heavily.

    At that moment they ran toward their residences for shelter, leaving behind farming tools they used in replanting. All this caused panic in the community, who never witnessed such an event.

    Our onsite team found a small crater caused natural phenomenon, forming a hole about one meter wide and half a meter deep.

    The farmer Anália, mother of Paul and Geraldo says that at the time of the blast was about 800 meters from the site, and who worked with her husband, and he heard a roar that shook the ground.

    “All I saw was a list of fire that went up to heaven, leaving behind a lot of smoke, it seemed fires of St. John, this happened in broad day,” said lady Analia.

    This is just a curiosity! will the meteors are falling increasingly in populated areas?

    regards
    pierson

  • chicken little

    wow all those mega tons ;P

    and it didn’t kill off all OR any animals.

    it didn’t even create a black mat with 4 or 5 inches of ash at least

    then it didn’t deposit 4 feet at least of sterile sand in the process of washing all those dead animals into the newly formed Atlantic void .

    it didn’t deposit thorium or any other minerals on the earth either .

    it didn’t move any islands that we got here on nor create new continents in that process .

    it didn’t drop the sea level by someplace in the 1500 to 2000 ft .

    mostly It also didn’t stop the world from turning for 24 hours or move it some degrees.

    it isn’t in anyway going to alter any kind of Radioactive isotopes or effect IN ANYWAY THE current AGREED UPON dating systems .

    THAT LITTLE FLAMING SPIT BALL WILL NOT GIVE ANYONE THE ANSWERS THAT CHANGED THE FACE OF OUR WORLD !

  • Trent Telenko

    Chicken Little needs to go and read this link, as it is more his speed than the Tusk –

    http://www.bibliotecapleyades.net/ciencia/esp_ciencia_tunguska13.htm

  • To CL: It sure showed 1000+ Russians how painful flying glass can be. Also interesting are the reports that the blast was 3 minutes after (!) the flash. It’s important to understand that any blast induced shock wave loses energy with time as it propagates. This means the shock imparted energy that reached the ground was far less energy than was released in the fireball. This agrees with the intense luminosity, duration and very white color of the prolonged ” flash”, all pointing to substantial energy release. How high up is the question.
    The relatively shallow angle approach of the Russian incident gives a slower heating rate (still astronomical energy) compared to steep angle cosmic visitor, which may distribute the delivered energy over longer time and over a longer distance, all of which may have given mercy to the Russian victims.
    Weird things can also happen with atmospherics in terms of dispersion or focusing of shock wave energy, making hot spots and protected regions at the surface
    TimH

  • Dr. B -

    My interpretation of the NASA speak is that the trajectory was grazing (shallow angle high altitude) and that the bolide disintegrated or fragmented upon “fireballing” (if that word is OK to use)….

    500 ktons – that will wake the neighbors even in the roughest hood

    Brighter than the sun. Good lessons here. Don’t look at it. and stay clear of glass windows or shock wave sensitive structure for several minutes after the flash. Naturally I trust our government so we won’t likely have another one of these for another 100 yrs or so. Unless one hits sooner.

    TimH

  • Steve Garcia

    Hermann and all -

    Word imprecision:

    The phrase “ .. . so it was grazing through the atmosphere” is almost ridiculously imprecise. It has two words that each could have two meanings.

    The term “through” along with “grazing” appear to mean that it grazed and then eventually exited the atmosphere.

    “Grazing” could mean that the path was a non-ground-impact quasi-tangential path.

    And “through” could mean that it exited, but it can also mean that it was simply moving along IN the atmosphere, like, “The airplane was flying through the sky,” in which of course the airplane never left the atmosphere.

    Does anyone have any idea if the term “grazing” has a technical definition? It might.

    As to the word “through” I believe the writer/speaker was just being careless, in which case who knows WHAT he meant?

  • Hermann Burchard

    Steve,
    thanks for your comment: The fact you noted, that NASA’s

    phrase . . . is almost ridiculously imprecise

    had not escaped my attention!

    To my “completely unbiased” POV, the fact merely was proof certain that NASA got the term “grazing” from CosmicTusk, my comment:


    February 15, 2013 at 10:12 am

    From some of the pictures, this was a grazing impact, the trail begins and ends in the upper atmosphere.

    They were embarrassed to rely on the Tusk and hid their feelings under vague, “ridiculously imprecise” language, d’accord?

  • Jonny

    Grazing does have a precise terminology in some branches of physics. In Grazing angle X-ray diffraction for example, it means that the incident x-ray beam is nearly parallel plane defined by the surface the sample under scrutiny. In other words, it describes the angle of incidence as being low with respect to a specific plane.

    In impact terminology, grazing impacts also have a degree of precision of language, and refer to low angles of incidence with respect to the plane of the ground (compared to oblique impacts, which are high angled impacts, where the angle of incidence is closer to the normal of the plane of the ground).

    So for the term “so it was a grazing impact through the atmosphere” in impact lexicography means that the angle of incidence of the impactor as it moved through the atmosphere was very low with respect to the plane of the ground. While this does not forbid an object skipping out of the atmosphere (since a high altitude object travelling at a fast enough speed at low incidence angle will do so), it is not implicit that this should be the case, since the exact angle of incidence is important as well as the objects velocity and cross section, the latter two of which effects its aerodynamic drag (since drag scales with area and with the square of its velocity). The quicker it slows down the quicker its angle of incidence increases, as its horizontal component of velocity is retarded.

  • Steve Garcia

    Questions…

    1. The updated 500 kt blast would put this event squarely in the middle range of H-bombs tested by the USA in the 1940s through 1963.

    That makes Chelyabinsk lucky it was no lower. (Though had it been on a lower trajectory, the burst would have happened earlier in its path…)

    * * * *

    2. Speaking of which, does anyone care to comment on what damage would have been done if the path were a ground impact path? Everyone at NASA seems to make sure such questions aren’t addressed, and none of the science writers seems to want to ask them.

    3. The Figaro article shows a path map coming from somewhere around the Bering Strait. This is supported by the mention of the first infrasound detection being in Alaska.
    (See http://tiny.cc/iezrsw) But Jonny corrected me on the path vs the flyby asteroid, saying one was gong N-S and one was going S-N.

    For me that brings up the question of its direction. What have they determined it to be?

    4. Curiosity: What plane does this put the orbit relative to the ecliptic? Was it high inclination?

  • Has anyone considered the posibility that the lower end of the contrails simply mark the point along the Russian meteor’s path where the fragments had slowed enough to go into ‘dark flight’, and not a point of departure as it skipped back out of the atmosphere?

  • Steve Garcia

    Actually, Dennis, that seems to be what I hear Jonny saying. But I may be wrong on that. My own first impression was that they /it had skipped back out to space, but for now I am accepting the dark flight explanation which (I think) Jonny says happened.

    Change points:

    Okay, NASA saw asteroid 2012 DA14 coming, but they missed the Chelyabinsk meteor, which was only 2/3 smaller.

    Am I the only one who wonders if a Tunguska object – reckoned at 1/3 less than 2012 DA14 – could have also been missed by NASA?

    And if a second Tunguska had blown up that high over Chelyabinsk, what would have been the damage?

    And one more:

    Tunguska did not blow down trees with its sonic boom. Why is everyone attributing the damage in Chelyabinsk to the sonic boom and not the big airburst?

    And even one more:

    Tunguska is always reckoned as one big blast, and the blast pattern seems to support that. The Chelyabinsk meteor had one big one and about 3 or 4 smaller ones. Tunguska has been reckoned to have been a comet (because nothing was found), and other reasons, too. But comets are supposed to be so much more friable than meteors or asteroids – so should Tunguska be given another look? If the Feb 15th meteor had at least 4 air bursts, why would Tunguska not have had multiple bursts, too? Secondary ones might have been too weak to show up in the on-the-ground evidence (perhaps).

    And finally:

    Any number of pieces of the Feb 15th meteor have been found downfield. Why would not Tunguska have such pieces downfield also? Ones that might be found even now?

    And is it not now in the realm of possibility that Tunguska was a “grazing” meteor?

  • Jonny

    Steve,

    The original North to south was based on an estimate of direction travel seen in videos, since it appeared to move from left to right across the region of sky where the sun was rising. Since then a more accurate determination of its trajectory does seem to have it coming North East to the south west. This was probably done through triangulation of infra-sound data, and/or from triangulation of eyewitnesses and locations of the video footage. This still means that the DA14 and the meteor are unrelated, and indeed looking at the two orbits of the objects they do indeed seem to unrelated.

    I have not been able to find “official” figures for the meteor’s pre impact orbital elements, but some figures I have seen place its inclination at about 4 degrees to the ecliptic, with a semimajor axis of about 1.66 AU, eccentricity about 0.52 and aphelion of 2.5 au, making this an asteroidal belt object. These were admitted to be preliminary based upon the videos and weather satellite images, so they may have changed with more accurate determined data.

    I didnt saying anything about dark flight but rather the point of complete disruption so i cannot claim recognition for that, but dark flight would be consistent with the contrail. When a meteor enters dark flight it no longer ablates, meaning it is not “dusting” the atmosphere, meaning that it is no longer seeding the air with small dust particles which act as nucleation centres for water droplet condensation. So the end of the contrail would likely indicate the point at which any surviving fragments enter dark flight.

    The tunguska object is determined to be between 45 and 100 meters in size, depending upon its composition (smaller for asteroidal material, larger for more comet like material). Therefore the Tunguska object would be comparable to DA14 for the lower estimate of size, not 1/3 its size. Explosive energy falls off with the square of distance (i.e. it is a 1/r^2 relation), so if a Tunguska class object detonated above Chelyabisnk, at the height of the recent meteor (about 25 kilomters), the ground energy would have been about 10% that of the ground energy of the Tunguska event. This is back of the envelope stuff though, and of course there are always other factors such as blast wave focusing etc to consider.

    The continued of attribution of the damage being caused by teh sonic boom may be a throw back to the old 10 tonne mass estimate. Other than this I cannot say why this should be. The tunguska object did though effect trees by its passage. Alexey Zolotov was able to find traces of the ballistic shockwave in the levelled trees around the epicentre of the tunguska site.

    With regards tunguska, eyewitness accounts do report secondary explosions before the main impact, however the problem with this is that the timing is a little off, as the reports tend to indicate that the explosions were heard first, then the object seen, before the object explodes, and then the big explosion occurred. For an object travelling far faster than the speed of sound this should not be the case. For example K. A. Kokorin of Kezhma told the interviewer that he heard sounds like cannon fire, and when he went outside to look seen the object in the sky. He reported the sounds continued until it disappeared behind the trees at which point it stopped. this could of course be strong electrophonic phenomena from the plasma sheath of the bolide. Also see this which seems to imply there was explosions heard BEFORE the impact

    “…At that time I was ploughing my land at Narodima (6 km to the west of Kezhma). When I sat down to have my breakfast beside my plough, I heard sudden bangs, as if from gun-fire. My horse fell on its knees. From the north side above the forest a flame shot up. I thought the enemy was firing, since at that time there was talk of war. Then I saw that the fir forest had been bent over by the wind and I thought of a hurricane. I seized hold of my plough with both hands, so that it would not be carried off. The wind was so strong that it carried off some of the soil from the surface of the ground, and then the hurricane drove a wall of water up the Angara. I saw it all quite clearly, because my land was on a hillside”

    “Letter to A. V. Voznesenskii, 25 July 1908:

    On the 17th of June, at approximately 7:15 in the morning, the workers building a bell tower saw a fiery block, flying, it seems, from the southeast to the northwest. At first, two bangs resounded (not unlike gunfire), then an extremely strong bang accompanied by shaking. More bangs were heard. They noticed a shaking of the earth. One girl (the priest’s maid-servant) fell off a bench. The populace became frightened. They saw that fiery sphere in Karapchanskii, and heard the bangs. The day was clear, and for that reason the thunder put the public in a state of bewilderment. In Nizhne-Ilimsk two Tunguses recounted that the meteor had, in falling, formed a lake which boiled for two full days. The Tunguses were prepared to show people that lake, but no one believed their story.”

    Which brings us to the idea of fragments being found of the Tunguska object. Lake Cheko is a conical lake downrange from the tunguska airburst site, and some believe could be a crater caused by a large fragment from the impactor hitting teh earth, which would tie in with the above “tunguses” statement that a lake was made by the event.

    By all accounts, the Tunguska object is thought to have been a low angled impact (of course it does depend upon the exact definition of grazing!). V.A. Bronshten has estimated that the initial angle of incidence would be no more than about 15 degrees with the final angle of impact being as much as 40 degrees at the end of its trajectory. Experiments have shown that impact would have had to be at 30 degrees. Its shallow trajectory would have ensured that a large fragment (even if made of low density material) could survive to lower altitudes, since low inclinations mean there is more time to slow the object before it reaches higher density of air.

  • Lets also remember that these incomprehensibly ancient objects may not be of uniform composition at all, having complex and convoluted histories of formation in various regions of space over a huge range of epochs. A good example may be a rocky core which then collects a far greater amount of ice over hundreds of millions or even billions of years, during which time other chunks of rock may also become embedded.

    Now our ancient object arrives at Earth going tens of times the speed of sound in our atmosphere. It’s astronomical kinetic energy is converted to heat through frictional heating. Quickly. The steeper the approach angle the greater the rate of heating. The ablation (burn) rate is as non-uniform as the density distribution within the object, likely with no two objects the same, like snow flakes. Cosmic snowflakes. The high temp (hotter than surface of the Sun) and resultant rapid pressurization suddenly applied to our long sleeping visitor wakes it up in the form of explosive fragmentation. So what does that leave us with?

    Chaos.

    Irregular ablation rate and irregular shock wave. The shock wave (same as sonic boom) is an over-pressure discontinuity which travels faster than the speed of sound by a factor dependent on the degree of over-pressure. An over-pressure (shock strength) of just 1 or 2 psi can cause fatal internal injury. That isn’t much since atmospheric pressure is nearly 15 psi and a nuke can generate over-pressure of a few to several ATMOSPHERES, which will cover long distance before disappating to non-lethal levels.

    During propagation, a shock wave may be slightly or highly focused or reflected (extreme cases) by normal/natural atmospheric gradients and surface morphology. All of these factors make any exact prediction or even reconstruction after an event a very complex task, since it depends on so many variables including irregularities in the object itself which are lost in the destructive process.

    Blah blah blah….

  • Steve Garcia

    Jonny -

    Great responses to my questions. Much appreciated. And its much appreciated that you have all of this information in your head (or know where to find it).

    For Tunguska size, I had 150 feet in my head, 3 times as wide as this meteor. 45 meters comes to about 145 feet, so I must have had that smaller size stuck in my head. I don’t confuse width with mass, but width is convenient. Mass increases as a factor of r^3.

    In reading the accounts of bangs (none of which I had run across before) it occurs to me that people up field of the burst point could certainly have heard the sonic boom before the burst, then have time to go outside or whatever. Also, from memory as a kid, I do seem to recall multiple booms from single aircraft, but I am probably wrong on that. I am glad to hear there were multiple bangs heard at Tunguska. It seems to render the two events more similar to each other.

    However, I do still wonder if this will change minds about Tunguska being a comet vs meteor. Tunguska was deeper into the atmosphere, suggesting its friability was more toward the meteor end than comet. As you say, larger objects will be able to get lower before bursting, so some combination of size and cohesion ties the two together. And while that lake had a nice round hole in its ice, no impact crater on the ground will ever exist from this event. Again, similarities.

    While I’d like that there exist downfield craters from fragments of Tunguska, the area around the burst is so littered with bogs that finding and identifying one of them as from a fragment seems worse then needle-and-haystack stuff. And it was the dead of summer, so all those bogs were likely to have thawed by then. That latter is not necessarily true, though. I know of one lake in southern Maine that doesn’t thaw till the 1st of June; in Siberia the end of June may or may not have a full thaw yet. That one guy was still plowing, after all, at the end of June, so for that locale it was early in the planting season.

    Thomas mentioned reflection of the shock wave off ground topology. Good point in one way – perhaps those multiple sonic booms I heard as a kid were echoes off of buildings (I lived quite close to downtown St Louis then).

    T.H. pointed to one of my points about the non-uniformity of aggregated bodies. He is thinking the same way, that non-uniform bodies will heat up irregularly, which would lead to pieces breaking off in some irregular sequence – and that no two objects would be the same. Yep.

    I think that in time T.H.’s “snowflake” realization will be recognized, and those who try to predict what future objects will do based on past ones will continually be proven in error. It is just too early in the observation period to have seen all the classes of possibilities. Astronomers even now are very often caught unawares by what objects do. It’s not yet a good science for making successful predictions on such things as bursts. Actual ground impacts, perhaps, but air bursts seem to be able to do all sorts of things.

  • Hermann Burchard

    Since it seems to matter, an authoritative site (JPL?) had Chelyabinsk (Ch.)meteoroid come from “East by South” which I think means ESE. This agrees with the Orenburg video. That city is to the SSW by 559 km or 347 miles. The meteor is low over the horizon and descends toward the left (W), skims the horizon, then the bright flash of the explosion from below the horizon, difficult to reconcile with a NE approach. — Steve, yes, “sonic boom” must be replaced by “airburst, explosive blast shock” or whatever, an initial one 42 km E of Ch., & four or five smaller ones of them from successive ablations or spalling. — The size is still uncertain and may be larger than now stated if it the trail end’s dimming means it left the atmosphere, so that Ch. was spared the Tunguska type downward momentum torch (Boslough).

  • The reason you remember a double sonic boom off supersonic aircraft is that one is attached to the leading edge of the vehicle and one to the trailing edge. Both are equally powerful. They are physically close together, so you hear the ba-boom sound at passage. The high speed aerodynamics guys use Schlieren photography to see the attached shockwaves. An example is at the link:

    http://www.nasa.gov/centers/dryden/news/FactSheets/FS-033-DFRC.html

    When things are exploding or you get a stream of supersonic objects, the sounds get more complex. For example, on a military gunnery range, it is possible to get 3 noises when you hear an aircraft like an A-10 strafe a controlled target. The first noise is the shockwave of the bullets in flight; second is the bullet stream coming out of the gun; final are the impacts on the other side of the target.

    With a supersonic object exploding overhead, you should get several sounds (shock waves) including but not limited to the shock waves attached to the supersonic body itself, the noise of the structural failure of the body itself, and reflected sound waves off nearby structures / clouds / other shockwaves. It should be complex and noisy for a while. Cheers -

  • Hermann Burchard

    agimarc:
    excellent expert explaining! Would you listen to this YouTube video with Chelyabinsk meteor noises,
    and give your interpretation, please:

    http://www.youtube.com/watch?v=vXpTxCH6HIE

    There seem to be 5 or so ba-booms after initial main at 40 km S of city (Wikipedia) which helps explain a 3 minute delay after the flash.

    View from Orenburg:
    http://www.youtube.com/watch?v=1EWD5mRkyow

    Bright flash still above horizon, trail end as well upon repeated viewing explained by site being 40 km South of city center.

    BTW, “South of East” approach by Wikipedia, and stands for 101.25 degrees off N, what one might call EESE, ESE being 112.5 degrees off N.

  • One problem I have with the idea of the thing skipping back out of the atmosphere is the assumption that it had the structural itegrity to do so after surviving a 500 kiloton detonation. Nah…

  • Hermann Burchard

    Dennis,
    good point! But if you examine trail end, thinning and dimming at the end, almost constant speed, well after main debris cloud is emplaced, what else can one conclude?

    http://www.youtube.com/watch?v=iCawTYPtehk&feature=player_embedded

    The fairly tame debris cloud too suggests a body staying intact, perhaps because much larger than school bus size?

Leave a Reply

  

  

  

You can use these HTML tags

<a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>