Re: Large meteor, possible meteorite near Chelyabinsk, Russi
Posted: Sat Feb 16, 2013 4:16 pm
by Chris Peterson
neufer wrote:It heated the air to ionization; the rapid expansion of which would have created quite a bit of sound.
Certainly, the air was ionized. I simply point out that it is clearer and simpler to recognize that the source of the light was the release of thermal energy as air was compressed in front of the meteoroid. And while there was sound created (that is, pressure waves in the air), that sound did not reach the ground.
Perhaps the visible smoke trail started at a height of 32 miles.
The meteor would have been visible much higher than 32 miles. I think the graphic was referring to the height when it exploded.
There clearly had to be a strong sonic boom:
No, there did not. Sonic booms are not heard on the ground with objects traveling higher than about 30 miles. If this object exploded at around that height, it's likely that no sonic boom ever made it to the ground, or that any sonic boom just capable of doing so was completely overwhelmed by the shock wave from the terminal disruption.
Re: Large meteor, possible meteorite near Chelyabinsk, Russi
Posted: Sat Feb 16, 2013 5:08 pm
by Doum
Chris Peterson wrote:
Doum wrote:10 to 20 km altitude explosion did that level of damage. How many time stronger would the chockwave be if the explosion happen at 4 or 5 km altitude ( Denser atmosphere)?
It's complicated. The body broke up when it did because the ram pressure forces on it exceeded its material strength. It could not have descended much deeper. If it were made of something stronger (like iron) it could get closer to the ground, but it would also be shedding more energy as it went, making it a smaller, slower body when it finally did explode. So had this exact object penetrated deeper, it would not necessarily have produced more damage. Of course, if it survived low enough, the products of the explosion might hit the ground carrying something of their original velocity, which could be very damaging. That's what happened in the case of the Sikhote-Alin event in 1947- thousands of individual pieces of iron embedded themselves in trees and created dozens of small craters. Over a city, that could be devastating. But the Sikhote-Alin parent body was probably ten times more massive than this one.
I understand now. Thanks for clarifying it.
Re: Large meteor, possible meteorite near Chelyabinsk, Russi
Posted: Sat Feb 16, 2013 5:14 pm
by buck020
BMAONE23 wrote:How much distruction would this asteroid cause if it struck Antarctica? Heat melting Ice and Snow, fracturing Ice Shelves, and causing a large influx of fresh water into the southern oceans. Anyone care to estimate the size of the tsunami's
You guys are what Snake Oil salesmen are all about...
!
Re: Large meteor, possible meteorite near Chelyabinsk, Russi
Posted: Sat Feb 16, 2013 5:48 pm
by SsDd
Just a couple of .gifs from around the internet.
I think it is mandatory in russia to have a dashboard camera on your car, which explains all these videos (I digress)
Click to play embedded YouTube video.
Re: Large meteor, possible meteorite near Chelyabinsk, Russi
Posted: Sat Feb 16, 2013 6:55 pm
by neufer
Chris Peterson wrote:
neufer wrote:
[The meteor] heated the air to ionization; the rapid expansion of which would have created quite a bit of sound.
Certainly, the air was ionized. I simply point out that it is clearer and simpler to recognize that the source of the light was the release of thermal energy as air was compressed in front of the meteoroid. And while there was sound created (that is, pressure waves in the air), that sound did not reach the ground.
We disagree about where/when most of the air was ionized.
I'm assuming that it happened during the brightest phase (at approximately the maximal disintegration/breakup of the externally heated bolide) at an altitude of ~10 kilometers above the Earth's surface.
The sudden increase in bolide surface area near the top of the troposphere produced maximal light and maximal sonic boom.
(Noise from "an explosion" is caused by the sudden release of internal gas.)
Chris Peterson wrote:
neufer wrote:
Perhaps the visible smoke trail started at a height of 32 miles.
The meteor would have been visible much higher than 32 miles. I think the graphic was referring to the height when it exploded.
There clearly had to be a strong sonic boom:
No, there did not. Sonic booms are not heard on the ground with objects traveling higher than about 30 miles. If this object exploded at around that height, it's likely that no sonic boom ever made it to the ground, or that any sonic boom just capable of doing so was completely overwhelmed by the shock wave from the terminal disruption.
Russian Dash-Cams
Posted: Sat Feb 16, 2013 7:06 pm
by neufer
SsDd wrote:
I think it is mandatory in russia to have a dashboard camera on your car, which explains all these videos (I digress)
King Henry V Act 3, Scene 7
ORLEANS: Foolish curs, that run winking into the mouth of a
Russian bear and have their heads crushed like
rotten apples! You may as well say, that's a
valiant flea that dare eat his breakfast on the lip of a lion.
MACBETH: Approach thou like the rugged Russian bear,
The arm'd rhinoceros, or the Hyrcan tiger;
Take any shape but that, and my firm nerves
Shall never tremble: or be alive again,
And dare me to the desert with thy sword;
If trembling I inhabit then, protest me
The baby of a girl. Hence, horrible shadow!
Unreal mockery, hence!
Why So Many Crazy Russian Car Crashes Are Caught On Camera
by Alex Davies, Business Insider, Dec. 12, 2012
<<Videos of car accidents filmed from dashboard cameras have become such a popular genre on YouTube, it seems every driver must be filming his every move. Why is that?
In a post on Animal, Russian ex-pat and journalist Marina Galperina offers a few reasons, which boil down to dangerous driving conditions and the unreliability of Russian traffic police.
Driving in Russia is hazardous: Last year, 200,000 traffic accidents killed 28,000 people. (More than 32,000 died in car accidents in the United States in 2011, a much lower figure per capita.) Addressing those high levels in 2009, President Dmitry Medvedev blamed the "undisciplined, criminally careless behavior of our drivers," along with poor road conditions. Drivers certainly play a role, but Medvedev did not mention Russia's traffic police, which, Galperina writes, "is known throughout their land for brutality, corruption, extortion and making an income on bribes." That is not hyperbole. Russia ranks 133rd among the world's nations in corruption (where number one is the least corrupt), according to Transparency International. Much of that corruption is on the part of the traffic police, an institution that, along with kindergartens and higher education, was ranked by Russians as the country's most corrupt. In a recent poll, 32 percent of Russians surveyed called traffic police the most corrupt institution. So going to the police with a legitimate complaint is far from sure to produce a good result.
In addition to authorities they deem untrustworthy, Russian drivers must contend with the possibility of being attacked by another driver. [Dash-Cam] videos compile fights between drivers that feature crowbars, slapping, punching, and worse.
Then there are pedestrians who get themselves hit by cars on purpose, for a payoff.
Overall, in a country where traffic conditions are horrible, insurance scams and roadside fights are always a possibility, and the police are widely viewed as corrupt, video evidence of one's innocence can be a very valuable thing.>>
Re: Large meteor, possible meteorite near Chelyabinsk, Russi
Posted: Sat Feb 16, 2013 7:20 pm
by dship14
Can you imagine what would have happened had this happened 12/21/12? People would have been panic-stricken thinking the Mayan prophecy was starting--grocery store shelves would have been stripped bare and, most likely, the National Guard called out to maintain order. Those scenarios are scary ... humans are such foolish animals.
Re: Large meteor, possible meteorite near Chelyabinsk, Russi
Posted: Sat Feb 16, 2013 7:22 pm
by Chris Peterson
neufer wrote:We disagree about where/when most of the air was ionized.
I'm assuming that it happened during the brightest phase (at approximately the maximal disintegration/breakup of the externally heated bolide) at an altitude of ~10 kilometers above the Earth's surface.
Where do we disagree? I certainly agree with everything you say here (except possibly for the value of 10 km for the final altitude- a value that is poorly known and probably higher, given the more accurate estimates now available for the interval between the terminal explosion and the arrival of the shock wave; 30-50 km is probably more likely).
The sudden increase in surface area near the top of the troposphere produced maximal light and maximal sonic boom.
As I said, there was plenty of acoustic energy released even while the meteor was very high. It is not clear at this point if the terminal explosion even occurred in the troposphere. If the values of 150 seconds between the terminal explosion and the arrival of the shock wave are accurate, detonation occurred in the stratosphere. Sonic booms are unable to propagate to the ground with enough energy to be audible from above about 30 miles. Of course, if a significant part of the pre-explosion path was below that height, sonic booms on the ground are likely. But I haven't heard reports of anything that sounds like your typical sonic boom (following behind a supersonic object, where the shock cone intersects the ground). All of the videos with sound, and all of the reports I've seen, indicate only the sound of the shock front from the terminal explosion, no preceding sonic booms.
Noise from an explosion is caused by the sudden release of internal gas.
Not in the case of a meteor. The terminal explosion occurs because the stresses on the body exceed its material strength, causing it to shatter. This results in a near instantaneous large increase in the surface area of hypersonic bodies, a huge release of thermal energy, and consequent shock wave through the atmosphere. We perceive some of the frequency components of that shock wave as noise. Of course, the individual bodies produced by the explosion each create their own sonic booms, as well- although very briefly since these bodies rapidly become subsonic. I believe that we can hear those secondary sonic booms mixed in with the sound of the primary explosion.
Re: Large meteor, possible meteorite near Chelyabinsk, Russi
<<Divers have finished examining the bottom of Lake Chebarkul in the Chelyabinsk region, where pieces of a meteoroid presumably fell on Friday, but have found nothing, the Emergency Situations Ministry's department for the Chelyabinsk region told Interfax. "The examination has been completed, and no pieces have been found," it said.
Emergency Situations Ministry spokesperson Irina Rossius told journalists later on Saturday that the divers found no traces of the meteorite in the lake. "Emergency Situations Ministry divers finished examining the water area and found no traces of the meteorite," Rossius said.
A number of media outlets reported earlier that some of the meteoroid's fragments had fallen into Lake Chebarkul. It was reported earlier that a team of six divers planned to examine the lake for four hours. The meteoroid that fell over the Chelyabinsk region on Friday had disintegrated in the atmosphere into several dozens of relatively large fragments.>>
Re: Large meteor, possible meteorite near Chelyabinsk, Russi
Posted: Sat Feb 16, 2013 8:28 pm
by MargaritaMc
Owlice kindly wrote
Margarita, from Wikipedia:
...and gave lots of information that I should have looked up for myself! Thank you, very much, Owlice.
Margarita
Re: Large meteor, possible meteorite near Chelyabinsk, Russi
Posted: Sat Feb 16, 2013 8:48 pm
by MargaritaMc
Sky and Telescope NEWS BLOG by Robert Naeye
For those who follow the asteroid impact threat, the 300- to 500-kiloton meteor blast over Russia on February 15th was just a matter of time. It shone brighter than the Sun, and when the shock wave swept across cities and towns more than a minute later, it blew out countless windows and injured at least 1,100 people, mostly by flying glass; see many more Russian videos and photos. At least one large meteorite fragment accompanied by small black pieces landed in a lake near Chebarkul, a town in the Chelyabinsk region.
As astronomers are keenly aware, Earth sits in a cosmic shooting gallery. Every day, grains, pebbles, and chunks left over from the formation of the solar system streak into the upper atmosphere. Most vaporize very high, causing no harm and giving us beautiful shooting stars.
But occasionally, perhaps every few decades to few centuries, our planet gets smacked by an object big enough to cause substantial damage. That's what happened February 15, 2013, at 9:20 a.m. local time in the Ural Mountains of west-central Russia (3:20 Universal Time).
According to analysis by meteor expert Peter Brown (University of Western Ontario), the incoming meteoroid carried about 300 kilotons of kinetic energy (about 20 Hiroshimas), entered Earth’s atmosphere at 20 kilometers per second (typical for near-Earth asteroids), was about 15 meters (50 feet) across, and weighed about 7,000 tons. It entered the atmosphere at a grazing angle of less than 20° and burst at a height of 15 or 20 kilometers (10 or 12 miles). An early track-back analysis has put the outer end of its former orbit in the asteroid belt.
(UPDATE: Later in the day NASA released its own estimates: a 10,000-ton object and 500 kilotons of energy.)
This makes it the largest object to hit Earth since the Tunguska event in 1908, beating the Sikhote-Alin meteor in 1947 (also in Russia)..
Re: Large meteor, possible meteorite near Chelyabinsk, Russi
Posted: Sat Feb 16, 2013 10:04 pm
by DinoD
Curious: After the initial report of the Chelyabinsk Event it was quickly followed by curiously adamant (almost panicked) denunciations that the meteor over Russia had "any relationship" to 2012 DA14 that was passing through Earth's ring plane several hours later. I may be under a mistaken presupposition that astronomical bodies within a miniscule space of 3 days of each other are almost certainly "related" and definitely "associated" (i.e. concentrated meteor showers). These 2 by mere hours and late reports of another in the San Francisco Bay Area a few hours after the 2012 DA14 pass. Even a different trajectory hardly means they are not related given plenty of potential for an earlier breakup or collison in the DA14 orbit. I would expect anyevery NEO to have "relations" from either small breakups or "an in progress gathering". Big Media, of course, is a terrible source of credible news...as we even witnessed a few days before DA14 arrived that a CNN news anchor was wondering if the close passing of the asteroid was caused by 'Global Warming' (a particular marketing fever they seem to have). So my question for the gifted here is, "Why the instant denunciations by both the ESA & NASA before any observations, research and conclusions could even be gathered from the event itself?"
Re: Large meteor, possible meteorite near Chelyabinsk, Russi
Posted: Sat Feb 16, 2013 11:13 pm
by vdinets
Russia does, indeed, have a major problem with pseudoscience (and a much greater problem with government-enforced religion), but it is worth noting that in all those videos, people behind the cameras immediately call it a meteorite rather than a UFO or the chariot of St. Nicholas.
For those studying Russian, the meteorite videos are also a rich source of four-letter words to learn
Re: Large meteor, possible meteorite near Chelyabinsk, Russi
Posted: Sat Feb 16, 2013 11:13 pm
by mtbdudex
Has there been any db estimates on the SPL of the initial shock wave and the others that immediately followed due to the meteorite that exploded over Russia yesterday?
Must be huge to cause so much damage!
Re: Large meteor, possible meteorite near Chelyabinsk, Russi
Posted: Sun Feb 17, 2013 12:22 am
by Chris Peterson
DinoD wrote:Curious: After the initial report of the Chelyabinsk Event it was quickly followed by curiously adamant (almost panicked) denunciations that the meteor over Russia had "any relationship" to 2012 DA14 that was passing through Earth's ring plane several hours later. I may be under a mistaken presupposition that astronomical bodies within a miniscule space of 3 days of each other are almost certainly "related" and definitely "associated" (i.e. concentrated meteor showers). These 2 by mere hours and late reports of another in the San Francisco Bay Area a few hours after the 2012 DA14 pass. Even a different trajectory hardly means they are not related given plenty of potential for an earlier breakup or collison in the DA14 orbit. I would expect anyevery NEO to have "relations" from either small breakups or "an in progress gathering". Big Media, of course, is a terrible source of credible news...as we even witnessed a few days before DA14 arrived that a CNN news anchor was wondering if the close passing of the asteroid was caused by 'Global Warming' (a particular marketing fever they seem to have). So my question for the gifted here is, "Why the instant denunciations by both the ESA & NASA before any observations, research and conclusions could even be gathered from the event itself?"
In fact, the bodies having radically different orbits demonstrates beyond reasonable doubt that they are unrelated. Certainly, bodies like DA14 can be tidally disrupted into two or more separate pieces. But those pieces will have virtually identical orbits. There is simply no plausible mechanism that could produce pieces with different heliocentric (or geocentric) velocities, inclinations, semimajor axes, etc. just before passing Earth. There are opportunities for three-body interactions over the period of many orbits to shift pieces into very different orbits, but there is no reason that the pieces would happen come together again at the Earth, just hours apart (that would be hugely more unlikely than the simple coincidence of a 10 meter body burning up in the atmosphere close to the passage of an unrelated asteroid, which isn't really all that unlikely at all).
I don't know what the ESA said. The very first comment by NASA, however, was made after the initial orbital parameters of the Siberian meteor had been determined, and therefore it could be stated with certainty that the two events were unrelated. By that point, scientists in the meteor research community had already determined that there was no association, either.
I would hardly characterize the comments by NASA or by various scientists as "panicked". As you note, science stories in the popular press are frequently very poor. I think there was simply an interest in heading off misreporting as much as possible.
It was previously recognized that DA14 has a small potential to produce a meteor shower, and the radiant for that shower has been calculated. (I didn't record any meteors from it, if there were any.) The problem is, there is very little to suggest that asteroids produce showers, for the simple reason that they don't typically have debris trails the way comets do. I'm sure that people in California are analyzing the recent fireball, and will quickly determine from its radiant alone if it could possibly be related to DA14. By far the most likely scenario is that it was simply a sporadic meteor. Fireballs of this sort happen every day, so there's nothing surprising about it occurring when a large asteroid happened to be passing.
Re: Large meteor, possible meteorite near Chelyabinsk, Russi
Posted: Sun Feb 17, 2013 5:27 am
by vdinets
More news from Chelyabinsk (from lenta.ru, a Russian news website):
On a more serious note, it is interesting (although perhaps meaningless) that a very similar event took place in exactly the same region in 1941 (Katavsky bolide, see http://en.wikipedia.org/wiki/List_of_meteor_air_bursts).
The same Wiki page mentions that 1932 large meteor at Arroyomolinos de Leon, Spain, was part of δ-Arietids meteor shower.
Re: Large meteor, possible meteorite near Chelyabinsk, Russi
Posted: Sun Feb 17, 2013 6:21 am
by DinoD
Thank you CHRIS!
Re: Large meteor, possible meteorite near Chelyabinsk, Russi
Posted: Sun Feb 17, 2013 7:43 am
by saturno2
My solidarity to those injured by the explosion of the meteor fallen in
Chelyabinsk, Russia.
In the second video present by sheershoff, is that the meteor suffers a big
explosion, which is practically desintegrates.
The meteorites should be very small.
The material maybe had low density.
Re: Large meteor, possible meteorite near Chelyabinsk, Russi
Posted: Sun Feb 17, 2013 5:32 pm
by JohnD
Does anyone know how widely across the Chelyabinsk area was the presssure shock wave distributed?
In England, I live as just North of 54 degrees, while that city is at 55.
Would I have been affected if it had come in over us?
John
Re: Large meteor, possible meteorite near Chelyabinsk, Russi
Posted: Sun Feb 17, 2013 5:45 pm
by Chris Peterson
JohnD wrote:Does anyone know how widely across the Chelyabinsk area was the presssure shock wave distributed?
In England, I live as just North of 54 degrees, while that city is at 55.
Would I have been affected if it had come in over us?
Shock waves dissipate very rapidly. The terminal explosion occurred directly over the city, which is why there was so much damage. A few kilometers in either direction and the overpressure was too low to cause damage. It was probably audible within about a 50 km radius of the terminal explosion. Given a terminal explosion height of 27 km, and an entry angle of 15°, an area extending about 75 km backwards from the terminal explosion point might potentially have experienced a sonic boom from the meteoroid passing over.
All of this would have been similarly experienced at your location in England had the meteoroid been a few minutes further back along its orbit.
Re: Large meteor, possible meteorite near Chelyabinsk, Russi
Posted: Sun Feb 17, 2013 6:31 pm
by Chris Peterson
I've seen a couple of videos out of Russia showing people east of Chelyabinsk holding approximately centimeter sized objects that appear to be ordinary stony meteorites, probably chondrites, with fresh fusion crusts. These look genuine. With such small material, most may go unfound until the snow melts.
Re: Large meteor, possible meteorite near Chelyabinsk, Russi
Posted: Mon Feb 18, 2013 10:11 am
by saturno2
According to the NASA, meteor of Chelyabinsk, release energy of about
500 kilotons , about 30 times the Hiroshima bomb.
I think that the " Bolide of Chelyabinsk" can be considered a super-bomb.
1 kiloton has the destructive power of 1,000 tons of TNT.
500 kilotons = 500,000 tons of TNT " Super-bomb"
Re: Large meteor, possible meteorite near Chelyabinsk, Russi
Posted: Mon Feb 18, 2013 11:58 am
by MargaritaMc
As this is now being discussed on two threads, I am cross-posting this link to a post in today's Apod discussion.
where there is a query about the possibility that the meteoroid did not actually impact the surface.
I'd certainly be interested to have this commented on.
M
Re: Large meteor, possible meteorite near Chelyabinsk, Russi
Posted: Mon Feb 18, 2013 1:52 pm
by zorts
NASA experts will hold a teleconference for news media at 4 p.m. EST today to discuss a meteor that streaked through the skies over Russia's Urals region this morning.
Is there a transcript of recording of this conference available? I can't find one on the NASA web site.
