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General Astronomy >> General Observing and Astronomy

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Tom Polakis
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Re: Meteorite hits Russia, people injured new [Re: bunyon]
      #5681023 - 02/15/13 09:54 AM

Quote:

Tom, another explanation is that it got much lower (closer to observer) than most. Most meteors stay very high and, therefore, go through less atmosphere and are visible for shorter lengths of time.




Paul,

Yeah, that's probably all it is. Now I just thought about that classic video of the grazer over the Grand Tetons from the 70's, and it moved at an equally "slow" rate. It's probably moving at thousands of miles per hour, but far away.

Tom


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Dave Mitsky
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Re: Meteorite hits Russia, people injured new [Re: CharlesW]
      #5681486 - 02/15/13 01:23 PM

The number of people injured now stands at more than 1,000.

The airburst is estimated to have occurred at 10,000 meters and the mass of the bolide at 10 tons. I've seen speeds ranging from 33,000 to 67,000 miles per hour mentioned.

Apparently, three craters have been found.

Dave Mitsky


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Mark9473
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Re: Meteorite hits Russia, people injured new [Re: Astrojensen]
      #5681515 - 02/15/13 01:32 PM

Quote:

Another video which seems to support that the meteor just grazed the atmosphere and went out back in space again



Thomas, what you're seeing is the meteoroid decelerating to the point that it no longer ionizes the air it passes through.


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csrlice12
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Re: Meteorite hits Russia, people injured new [Re: Mark9473]
      #5681526 - 02/15/13 01:36 PM

Wasn't there an asteroid or something that was supposed to travel between the Earth and the Moon recently?? Could this be that or a part of it?

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BrooksObs
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Re: Meteorite hits Russia, people injured new [Re: csrlice12]
      #5681548 - 02/15/13 01:45 PM

Csrlice - There is currently the asteroid 2012DA14 about to approach very close to earth, however the approach direction is almost directly from the south celestial pole, with the "radiant" of any associated pieces blocked as seen from earth's northern hemisphere where the meteor itself was seen from. Thus, the Russian event is simply a coincidence.

BrooksObs

Edited by BrooksObs (02/15/13 01:57 PM)


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Mark9473
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Re: Meteorite hits Russia, people injured new [Re: csrlice12]
      #5681549 - 02/15/13 01:46 PM

No, this meteorite event in Russia is from a stone that traveled north-to-south; the asteroid 2012 DA14 (that you can now follow live at http://www.ustream.tv/nasajpl2 ) is going south-to-north.

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careysub
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Re: Meteorite hits Russia, people injured new [Re: Astrojensen]
      #5681620 - 02/15/13 02:13 PM

Quote:

http://rt.com/news/meteorite-crash-urals-chelyabinsk-283/

Some reports indicate that the incoming meteorite was intercepted by a quick-response (automatic?) surface to air missile. This needs verification.




This story seems to have disappeared. Probably people misinterpreting the bolide trail.

Quote:

In any way: It has happened. A meteorite airburst has hit a populated area. This will hopefully wake some people up. It seems it was extremely close to a regional disaster. If it had happened over Moscow, then imagine the chaos...




Not just any populated area!

One of Russia's two nuclear weapons production cities (Chelyabinsk, that is, the other being Sarov). This must have been quite exciting for the Russian military.


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GlennLeDrew
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Re: Meteorite hits Russia, people injured new [Re: careysub]
      #5681722 - 02/15/13 02:56 PM

Do not base space motion *only* from trajectories as observed from a moving and rotating platform. The two principal components which have to be 'subtracted', as it were, are the Earth's own 29.7km/s motion and the location of the observer on the round Earth at the time of the event. The derived true space motion can differ quite substantially from the apparent motion.

In any event, I suspect this and DA14 to be unrelated. But we'll very soon know...


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careysub
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Re: Meteorite hits Russia, people injured new [Re: BrooksObs]
      #5681726 - 02/15/13 03:00 PM

ADDENDUM: Recent images of the damage show that blast pressures in the range of 2 psi were encountered - building walls show buckling. This is well outside of the pressure range any sonic boom can generate. This was an explosion.


Quote:

There is nothing in the images posted so far on the Internet to suggest that the reported damage is from an "airburst" event.




On the contrary - images and damage reports appear EXACTLY like an airburst event!

Quote:

Actual structural damage, except to one zinc factory is not evident beyond broken windows. Rather, it looks like the damage was generated by a relatively low altitude, very strong, sonic boom.




And this is exactly what a relatively high altitude explosion will do.

Windows break in the blast pressure regime of 0.5-1 psi with negligible other structural damage. A 1 kiloton explosion above a mere 1000 meters from the ground will not produce blast pressure much above 1 psi anywhere. For a 10 kiloton explosion this height is about 2.2 km.


Quote:

Likewise, the meteor does not terminate in a sudden flash but rather continues onward after a sharp peak in brightness (a point at which the double smoke trail suggests it broke into two major fagments?) for some distance before slowly fading out.




A meteor is not a bomb. There is no reason to expect it completely vanish when it explodes. In fact if it did that would be extremely surprising.

The explosion (when the body fragments and dumps most of its energy into the atmosphere very fast) should leave remnant large fragments that continue the trajectory.

Here is an excellent view of the explosion and termination.

http://www.youtube.com/watch?v=90Omh7_I8vI

Note that the remaining travelling remnant is small fraction of the brightness of the pre-explosion bolide. Also note the grossly swollen trail in the explosion region, where all the explosion debris is deposited.

The brilliant sudden flash is an explosion almost by definition.

Quote:

Nor is there anything to imply the strike was a grazing event, since all the video so far shows an angle of descent in the track, not near earth paralleling flight.




This is a non-sequitur.

Regardless on angle of entry (BTW, I measure about 15 degrees for this in multiple videos, a shallow entry angle) all moderately large meteors experience explosive fragmentation when the hit sufficiently dense air (except for the 1 in 1000 that is metallic and thus physically very strong).

There is no requirement that they have a negligible entry angle.

Edited by careysub (02/15/13 09:45 PM)


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Intensity2x
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Loc: Northern NJ
Re: Meteorite hits Russia, people injured new [Re: careysub]
      #5681747 - 02/15/13 03:10 PM

Preliminary data from NASA JPL:
Quote:

Preliminary information indicates that a fireball in Chelyabinsk, Russia, is not related to asteroid 2012 DA14, which is flying by Earth safely today.

The Russian fireball is the largest reported since 1908, when a fireball hit Tunguska, Siberia. The fireball entered the atmosphere at about 40,000 mph (18 kilometers per second). The impact time was 7:20:26 p.m. PST, or 10:20:26 p.m. EST on Feb. 14 (3:20:26 UTC on Feb. 15), and the energy released by the impact was in the hundreds of kilotons.

Based on the duration of the event, it was a very shallow entry. It was larger than the fireball over Indonesia on Oct. 8, 2009. Measurements are still coming in, and a more precise measure of the energy may be available later. The size of the object before hitting the atmosphere was about 49 feet (15 meters) and had a mass of about 7,000 tons.

The fireball, which was about one-third the diameter of asteroid 2012 DA14, was brighter than the sun. Its trail was visible for about 30 seconds, so it was a grazing impact through the atmosphere.

It is important to note that this estimate is preliminary, and may be revised as more data is obtained.





Energy release of "several hundreds of kilotons", thats a big boom.

Source: http://www.jpl.nasa.gov/news/news.php?release=2013-061


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Astrojensen
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Re: Meteorite hits Russia, people injured new [Re: Mark9473]
      #5681810 - 02/15/13 03:41 PM

Quote:

Thomas, what you're seeing is the meteoroid decelerating to the point that it no longer ionizes the air it passes through.




I realized this later. Now they also report multiple impact sites, so it seems safe to say it didn't escape back into space.


Clear skies!
Thomas, Denmark


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MawkHawk
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Re: Meteorite hits Russia, people injured new [Re: Astrojensen]
      #5681836 - 02/15/13 03:54 PM

Pretty gosh darn amazing, is all I can say... Spectacular.

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JayinUT
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Re: Meteorite hits Russia, people injured new [Re: MawkHawk]
      #5681864 - 02/15/13 04:09 PM

Biggest impact since Tunguska is a rather large event. Imagine if it had come down in a major urban center. On another avenue wish I could go meteorite hunting in Russia right now. I'd love to have a small fragment as seen in this Russian web site that shows a 30 foot impact hole on a reservoir with small fragments around the hole. The Russian link is in Russian which I translated in Google Chrome on my laptop. Nice that they put a ruler next to the fragments. One third of the size of the asteroid that flew by and we missed this one. I say we still need to fund finding this things as they fly in the inner solar system. We may not have an extinction level event but having one like this hit an urban area would not be good if you lived there or had family there.

Russian Link

Edit: On a side note this is probably the second largest impact since Tunguska if the NASA numbers hold. The third event is the Sikhote-Alin Meteorite that hit in eastern Siberia in 1947 in the then Soviet Union. That was a daytime event and like this one, the explosion was brighter than the Sun. Here is some info:

Link 1

Link 2

Edited by JayinUT (02/15/13 04:26 PM)


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Dave Mitsky
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Re: Meteorite hits Russia, people injured new [Re: JayinUT]
      #5681887 - 02/15/13 04:20 PM

There's more on the hole in the ice plus a video of the bolide from a weather satellite at http://www.slate.com/blogs/bad_astronomy/2013/02/15/russian_meteorite_fragmen...

Dave Mitsky


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WarmWeatherGuy
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Re: Meteorite hits Russia, people injured new [Re: JayinUT]
      #5681902 - 02/15/13 04:31 PM

I noticed on one of the videos that people are still confused about the shock waves. They are not created when an object goes through Mach 1. They are created while an object travels faster than Mach 1. The shock wave travels through the air at the same speed as the object. When the shock wave passes you then you will hear the sonic boom. If the object is traveling at Mach 1 the angle of the shock wave is 90 (perpendicular to the direction of travel). If a plane flies horizontally at Mach 1 you will hear the boom when it is overhead. As the Mach number increases the angle of the shock wave decreases. At Mach 2 the angle becomes 30 (60 from the perpendicular) and you will hear the boom after the plane has passed.

The angle of the shock wave is the arcsine of 1/M where M is the Mach number. So for Mach 1 the angle is 90, Mach 2 it is 30, Mach 3 it is 19.5.

This misconception was advertised on the news when a reporter heard the sonic boom from the space shuttle as it was coming in to land. The reporter claimed he heard the boom because the shuttle had just broken through the sound barrier. In reality he heard the boom because the shuttle flew by while traveling faster than Mach 1.


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northernontario
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Re: Meteorite hits Russia, people injured new [Re: Dave Mitsky]
      #5681914 - 02/15/13 04:36 PM

Wow.

Just like that.

jake


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careysub
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Re: Meteorite hits Russia, people injured new [Re: JayinUT]
      #5681967 - 02/15/13 04:59 PM

Quote:

Biggest impact since Tunguska is a rather large event. Imagine if it had come down in a major urban center. ...




As it is it came down over what was a closed military city devoted to the production of thermonuclear weapons. The only difference today is that it is not "closed". This had lots of potential for dangerous misinterpretations.

Quote:


Edit: On a side note this is probably the second largest impact since Tunguska if the NASA numbers hold. The third event is the Sikhote-Alin Meteorite that hit in eastern Siberia in 1947 in the then Soviet Union.




NASA is currently saying this is a 7000 ton object, far larger than the estimated 100 tons for Sikhote-Alin; and the largest over land since Tunguska.

An event this size hits Earth about every 40 years according to known meteor flux data. But remember that 75% of all meteor explosions occur over the ocean or uninhabited Antarctica. One of this size should occur over an inhabited continent every 160 years or so.

Tunguska was a genuinely rare event - about one per millenia event anywhere on Earth, or one-per-3000 years over land in current estimates.

The U.S. "Defense Support Program" (a "Manhattan Project" like non-descriptive name) recorded multiple kiloton size atmospheric explosions every year (the data was declassified from around 2000 to 2009 when they began reclassifying meteor intercept data).

Edited by careysub (02/15/13 06:16 PM)


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Achernar
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Re: Meteorite hits Russia, people injured new [Re: careysub]
      #5682019 - 02/15/13 05:28 PM

Yep, which could lead to an all-out nuclear war starting by mistake. Such an event over a large city or a sensitive military facility could be mistaken for a sneak attack. Missiles today can leave a target with little or no warning before they strike, and many of them can carry a neutron, chemical or nuclear warhead. It's very fortunate that the whole city was not destroyed, because Russia has a history of being the victim of sneak attacks, and retaliating with a devastating counter-attack against it's enemies. They are justly suspicious people when it comes to certain matters. Who knows what they would have done if an incoming asteroid did level a large Russian city killing millions.
Let's hope Putin and the military got good information about what was going on, because I have seen photos of re-entry vehicles plunging towards their targets, and they look just like that fireball, smoke trail and everything. The only way to tell an impact from space apart from nuclear explosions would be the fact an asteroid impact does not generate gamma rays and free neutrons, but a nuclear bomb will. Even worse nations such as India, Pakistan and North Korea have nuclear weapons, but do not have the early warning and space surveilliance systems we do, and a similar event over one of those countries can become a global nightmare.

Taras


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John Wunderlin
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Re: Meteorite hits Russia, people injured *DELETED* new [Re: careysub]
      #5682069 - 02/15/13 05:55 PM

Post deleted by John Wunderlin

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John Wunderlin
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Re: Meteorite hits Russia, people injured *DELETED* new [Re: John Wunderlin]
      #5682083 - 02/15/13 06:03 PM

Ok ignore my last posts... My napkin calculations were off.

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