Posted on 02/16/2013 11:40:13 AM PST by Ernest_at_the_Beach
A Russian policeman works near an ice hole, said by the Interior Ministry department for Chelyabinsk region to be the point of impact of a meteor seen earlier in the Urals region, at lake Chebarkul some 80 kilometers (50 miles) west of Chelyabinsk February 15, 2013 (Reuters / Chelyabinsk region Interior Ministry)
Russian scientists investigating the meteorite explosion in the Urals explained the nature of the event that caused havoc in the region. NASA said the shockwave force was equal to a 500-kiloton explosion – 30 times the Hiroshima blast.
The object was identified as a solitary 10-ton bolide by the Russian Academy of Sciences (RAN). Bolides, or bright fireballs, are large meteors that explode in the lower atmosphere, and unlike meteorite showers they can be dangerous, scientists explained.
The Chelyabinsk fireball entered the atmosphere moving at a speed of about 20 km/s. The object, which was several meters in diameter, then burst into pieces at a height of 30-50 km above the ground, RAN reported.
Three consecutive explosions shattered the meteorite further. Large fragments moving at a high speed caused a powerful flash and a strong shockwave, with most of its energy released at a height of 5 to 15 km above the earth, with the atmosphere absorbing most of that energy.
NASA has increased its estimate of the energy released during the blast to nearly 500 kilotons of TNT. The calculations were based on the data from infrasound stations across the globe, some being over 6,500 kilometers away from Chelyabinsk. In comparison, the US atom bomb 'Little Boy' destroyed Hiroshima in 1945 with only 16 kilotons.
The impact and the sound of the blast reached the ground minutes after the explosion, causing havoc and panic in Chelyabinsk. While most of the object burned down during the fall, the remaining parts showered over the region, possibly adding to the damage and injuries.
The actual power of the blast is still being discussed, with some scientists estimating it as low as 0.1 kilotons and others saying it could be nearly 500 kilotons, depending on the height the explosion was registered. Conflicting reports also centered on the trajectory of the falling body.
The combustion products won’t stay in the atmosphere for long, and will soon come down with precipitation, Russian scientists said. The meteorite is believed to have caused no significant pollution, but the elements it emitted could only be identified after studying its fragments, they added. So far, RAN and Emergency services have denied the possibility of radioactive pollution.
MET-7 view (Copyright 2013 © EUMETSAT)
Russian space agency Roscosmos earlier admitted they did not track the meteorite that fell near Chelyabinsk, although several other flybys were detected by Roshydromet overnight. “Our ground facilities and, as I understand, those abroad too did not monitor this celestial body,” the agency spokesman said.
Astronomers around the globe didn’t notice the object coming either, and rushed in search of its traces on satellite images after the news spread.
“Objects like that are nearly impossible to see until a day or two before impact,” Timothy Spahr of the Minor Planet Center in Cambridge, Massachusetts told Nature Magazine.
Although the meteor was relatively small to detect, some argued its blast was comparable with the power of a nuclear bomb.
According to Canadian astronomer Margaret Campbell-Brown, the blast could be even more powerful than North Korea’s recent nuclear test. Citing the data from two infrasound stations near the impact site, she estimated the object to be 15 meters in diameter with a mass of around 40 tons.
“That would make it the biggest object recorded to hit the Earth since Tunguska,” Campbell-Brown told Nature Magazine.
Most scientists both in Russia and abroad do not believe the Chelyabinsk bolide had anything to do with the asteroid 2012 DA14, which is expected to fly by just hours later.
Weather sattelite Meteosat 10 has taken an image of the meteriote shortly after entering the atmosphere (Copyright 2013 © EUMETSAT)
Weather sattelite Meteosat 10 has taken an image of the meteriote shortly after entering the atmosphere (Copyright 2013 © EUMETSAT)
Geez, I don't think so! Why would there be? The angle of the shock wave to the flight path just gets steeper as the Mach number increases. I believe at high Mach numbers, there are qualitatively new effects, but this is due to intensification of the shock front.
The double boom from the Space Shuttle was due to two separate shock waves orginating from the nose and the tail, I think.
Some are more memorable:
Now that's a REAL problem. Climate Change indeed.
I think he’s right about harmonics but not sure if those are audible.
Smaller fireballs are extremely common events, which often wouldn’t make any more than the local media previously.
It’s the “attention effect” once again.
But the Cuba fireball detonation is reported to have shaken windows, which is definitely not an everyday thing.
There’s going to be a documentary on this at 8PM Eastern tonight on the Science Channel (my cable’s guide hasn’t updated to show this yet.)
the shuttle is what i based it on but never though of the tail creating it's own sonic boom... guess yer right
What the heck was THAT?
That is what the Russian girl was saying on her cell phone,...see #21!
Why do they keep calling it a meteorite?
It is only a meteorite after it hits the ground.
Before that it is a meteor.
“These results come with ABSOLUTELY NO WARRANTY”
Their results are consistent with NASA’s 15/300kt/20 degree/20000m/sec scenario, except the over pressure, which was demonstrably greater, about 5X greater.
I don’t think the calculator is including the sonic boom from the passage, just the explosion.
However, an article in Nature states the blast damage was from the explosion, not the sonic boom:
http://www.nature.com/news/russian-meteor-largest-in-a-century-1.12438
On further thought, I suspect that the overpressure was much higher than the calculator because the (simple) calculator may simply have the air blast effects be spherical, when in reality they were focused along the path.
The paper explaining the calculator is quite technical and can be found here:
http://impact.ese.ic.ac.uk/ImpactEffects/effects.pdf
great satellite pics of meteor
The term “meteor” is a piece of arcana referring to any atmospheric phenomenon, such as a cloud, or lightning. Meteors as we know them were not understood, and the association of found meteorites with the percieved “meteor” was controversial. So the term was analogous to “UFO”, in referring to an unknown phenomenon in general terms.
“Meteor” as a general term fell out of use and is now reserved for the particular phenomenon that we understand very well, for the most part. However its is still phenomenological, referring to the observed appearance, and not any cause or object associated with it.
Hence, we have “meteoroid” for a rock in space, and “meteorite” for whatever makes it to the ground, but what is it when it is seen producing the “meteor” that we see? A nice question, but a purely rhetorical one.
A meteoroid is a modestly-sized rock (up to boulder size) anywhere in the solar system, and the visual appearance upon entering the atmosphere is called a meteor.
I concede this is not particularly important information and I am just keeping the thread alive
The calculator notes, also state that the minimum velocity at impact is 11 km/sec (I’m buying it), but that the maximum velocity for a solar system object is 72 km/sec. Classically, the maximum velocity on impact with the earth for a solar system body is 44 km/sec = sqrt( 2*(mu_sun/R_earth_orbit + mu_earth/R_top_of_atmosphere))
The maximum orbital energy for an object to be graviationally bound to another body is 0. More than that and it has escape velocity. When the energy is 0, the velocity is:
v = sqrt( 2*mu/R)
For earth mu = 398600.4418 km^3/sec^2, R ~ 6491 km from center, = 11 km/sec
For the sun mu = 132712440018 km^3/sec^2 , R ~ 150,000,000 km from center, = 42.07 km/sec
The energy adds, regardless of path, so the resultant velocity is root of the sum of the squares, or about 44 km/sec
Spherical dissipation goes as 1/R^3, line source as 1/R^2, so you may be on to something.
Check your spelling.
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