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General Astronomy >> General Observing and Astronomy

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taylornate
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Reged: 01/04/13

Re: Meteorite hits Russia, people injured new [Re: GlennLeDrew]
      #5682181 - 02/15/13 07:06 PM

Quote:

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...




What is "true space motion" and what would be the relevance of it? Any measurement of velocity needs a reference frame, and in this situation I think ours would be the most relevant one.


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GlennLeDrew
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Re: Meteorite hits Russia, people injured new [Re: taylornate]
      #5682203 - 02/15/13 07:24 PM

Orbits are calculated with respect to the Sun, or more properly, I suppose, the barycenter of the Solar system, which is still inside the Sun. Two related bodies must therefore have quite similar orbital parameters, even if over time they have drifted some distance apart.

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GlennLeDrew
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Re: Meteorite hits Russia, people injured new [Re: GlennLeDrew]
      #5682208 - 02/15/13 07:27 PM

It just occurred to me... What might have resulted if an airliner were at altitude and more or less below the point of the airburst?

And could it be possible for some such situation in the past to have been the cause of a mysterious disappearance of an aircraft?..


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StarStuff1
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Re: Meteorite hits Russia, people injured new [Re: GlennLeDrew]
      #5682304 - 02/15/13 08:38 PM

Once while exiting a comutter jet I asked the pilot if he ever saw and/or thought about the possibilities of meteors hitting the aircraft. He said H*** yes, he had seen several go below his aircraft before they "popped".

Duhhh!


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Achernar
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Re: Meteorite hits Russia, people injured new [Re: GlennLeDrew]
      #5682379 - 02/15/13 09:21 PM

It would have been torn apart in mid air, and that of course would be the end for everyone aboard if it was close to the epicenter. But more likely, I would expect for every plane destroyed in this way, a larger number would be damaged or passengers and crew would see something. An interesting idea, since these blasts do occur over remote areas of ocean, and unpopulated areas, it might explain the disappearance of a few aircraft. But the only way it could be put to the test would be exhaustive studies of cases of aircraft gone missing and data collected by the military to see if any occurred at the right place and time frame. If an explosion occurred in an area where a lost aircraft was supposed to be, it should at least be circumstantial evidence to support it. Eye witness testimony and ground based RADAR would prove falling meteoroids could be a threat to aircraft.

Taras


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careysub
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Re: Meteorite hits Russia, people injured new [Re: StarStuff1]
      #5682434 - 02/15/13 09:54 PM

Quote:

Once while exiting a comutter jet I asked the pilot if he ever saw and/or thought about the possibilities of meteors hitting the aircraft. He said H*** yes, he had seen several go below his aircraft before they "popped".

Duhhh!




When the AirFrance airliner went down over the Atlantic quite mysteriously a few years ago one theory that was seriously considered was that it was hit by a meteor.

Calculations indicated that since the beginning of air travel there was a roughly 50% chance of a meteor strike on an aircraft occurring.


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taylornate
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Reged: 01/04/13

Re: Meteorite hits Russia, people injured new [Re: GlennLeDrew]
      #5682540 - 02/15/13 11:03 PM

Quote:

Orbits are calculated with respect to the Sun, or more properly, I suppose, the barycenter of the Solar system, which is still inside the Sun. Two related bodies must therefore have quite similar orbital parameters, even if over time they have drifted some distance apart.




If you are thinking in terms of energy related to the collision, wouldn't the Earth be the most sensible reference frame? Unless I misinterpreted what you were replying to.


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careysub
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Re: Meteorite hits Russia, people injured new [Re: GlennLeDrew]
      #5682581 - 02/15/13 11:22 PM

Quote:

It just occurred to me... What might have resulted if an airliner were at altitude and more or less below the point of the airburst?

And could it be possible for some such situation in the past to have been the cause of a mysterious disappearance of an aircraft?..




Yes indeed it could down an airliner.

This is a scenario that has actually been considered as a serious candidate in at least two airliner crashes (Air France Flight 447 and TWA Flight 800).

One risk estimate was that there is a 50% chance of such an event downing an airliner through the cumulative history of commercial aviation to date.


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chrisg
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Re: Meteorite hits Russia, people injured new [Re: careysub]
      #5682704 - 02/16/13 01:15 AM

Wondering if its possible that any of the explosions heard were echos from sound waves bouncing off the top of the atmosphere. Could that happen?

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Happy Birthday JayinUT
I'm not Sleepy
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Re: Meteorite hits Russia, people injured new [Re: chrisg]
      #5682744 - 02/16/13 01:57 AM

NASA based on new data from a variety of sites has increased the mass from 7000 to 10,000 tons and from 49 feet long to 55 feet long. Paul Chodas of NASA said in the latest release that this is a 100 year event.

Quote:

"We would expect an event of this magnitude to occur once every 100 years on average," said Paul Chodas of NASA's Near-Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, Calif. "When you have a fireball of this size we would expect a large number of meteorites to reach the surface and in this case there were probably some large ones."






See this link at NASA.

In terms of energy NASA is reporting on their site that this object exploded with:

Quote:

nearly 500 kilotons of energy released




I believe but someone can please correct me that that equals about.5 megatons? Not sure but I think that is right. Anyway, what an interesting day. I actually made a record of the day to remember it. Should be one for the history books.

Edit: If you want to see what a 500 kiloton nuclear blast would do you can go to this link which is to NukeMap, type in your city if it isn't there and set the yield to 500 and see the impact, it is huge! Talk about appreciating the energy expended in that impact with the atmosphere, wow!

Edit: I put in 5000 instead of 500 which is the correct amount. 500 is still a massive amount of energy. I corrected the amount.

Edited by JayinUT (02/16/13 06:05 AM)


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Dave Mitsky
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Re: Meteorite hits Russia, people injured new [Re: JayinUT]
      #5682830 - 02/16/13 05:00 AM

500 kilotons equals 0.5 megaton.

Dave Mitsky


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dan777
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Re: Meteorite hits Russia, people injured new [Re: JayinUT]
      #5682982 - 02/16/13 09:00 AM

Quote:

... what an interesting day. I actually made a record of the day to remember it. Should be one for the history books.



Indeed, this event and the transit of Venus within less than 12 months of each other and then the total solar eclipse passing across the US in 2017.


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Special Ed
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Re: Meteorite hits Russia, people injured new [Re: dan777]
      #5683064 - 02/16/13 09:39 AM

S&T published this thoughtful and informative article on their website. The first video, which is a compilation, is pretty stunning.

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JIMZ7
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Re: Meteorite hits Russia, people injured new [Re: Special Ed]
      #5683082 - 02/16/13 09:50 AM

Just incredible videos! This morning a video from San Francisco showed a bright meteorite burning up in the night sky. What will the heavens bring next.

Jim


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careysub
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Re: Meteorite hits Russia, people injured new [Re: chrisg]
      #5683181 - 02/16/13 10:43 AM

Quote:

Wondering if its possible that any of the explosions heard were echos from sound waves bouncing off the top of the atmosphere. Could that happen?




Yes, definitely and in fact almost certainly. Large atmospheric nuclear explosions (and the current ~200 kt estimate of the Chelayinbk blast classifies it as large) often had shock wave "echo" zones in bands hundreds of kilometers from the explosion, far outside the normal limit of effects.

It is more like refraction than reflection though, sound waves being bent in natural wave-guide.


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Happy Birthday JayinUT
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Re: Meteorite hits Russia, people injured new [Re: careysub]
      #5683286 - 02/16/13 11:26 AM

Just curious where your getting 200 kilotons when NASA is reporting 500 kilotons. Do you have a link?

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Achernar
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Re: Meteorite hits Russia, people injured new [Re: JayinUT]
      #5683390 - 02/16/13 12:19 PM

Yes, .5 megatons is equal to 500,000 tons of TNT. That is a little more than the destructive power of just one of the eight nuclear warheads aboard a Trident D-5 missile carried by a our Trident submarines. That's enough to level a major city. In other words, a blast of this magnitude near the ground will destroy every building for several miles in every direction unless they are specially constructed military facilities. Even if the actual blast was closer to 200,000 tons of TNT, that still would have been the equivalent of a Tomahawk cruise missile carrying a nuclear warhead against a city. Russia was most fortunate this object exploded at a high altitude and not directly over Chelyabinsk. Fourty people are now in the hospital with serious injuries, and most of the 1,200 injured were cut by flying glass.

Taras


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Starhunter249
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Reged: 06/07/10

Re: Meteorite hits Russia, people injured new [Re: Achernar]
      #5683448 - 02/16/13 12:43 PM

I was doing the math on how high this object was when it exploded. I calculated the altitude to be approx 20.4 miles above the earth. This is based on a video taken 300km away. The angle approx 5 degrees from the horizon. A sextant used at the location the video was shot would provide a more accurate measurement of angle above horizon. I could be way off on the angle; the angle could be larger which would increase its altitude at final explosion. I also took the curvature of the earth into account at 300km distance which is approx. 4 miles of additional height at horizon. I did not account for the elevation of the city of Chelyabinsk and the city of where the video was taken 300km away which could impact the calculation by a few miles.

What is also interesting is the time from the final flash and the shock wave heard. I have read various accounts from a minute to 3 minutes. Temperature and altitude effect the speed of sound and we are assuming the shock wave is traveling near or at the speed of sound. Colder air temperatures decreases wave velocity. Temperature at ground level was 4 degrees that morning and only gets colder as you ascend altitude until you reach the tropopause. The tropopause is a layer that separates the troposphere and the stratosphere. This is where the air is the coldest in the atmosphere. Above the tropopause is the stratosphere, the air temperature gets warmer as altitude increases, opposite of the troposphere. The air temperature at 20 miles above sea level is about -40 F. Speed of sound is about 0.19 miles per second. At ground level it was 4 degrees above zero which is about 0.20 miles per second. I donít know what the tropopause temperature is but you can assume its approx -70 F which is 0.184 miles per second. That would slow it down slightly compared to the -40 F at 100000 feet. We can ignore it. Assuming the shock wave is traveling at the speed of sound it would take as long as 107 seconds and as quick as 102 seconds. The true time is in between. As the wave is traveling thru warmer air, itís speeding up. Air density does have a small slight factor on wave speed by it can be neglected for the purpose of estimates. If the meteor exploded at 10 miles as some experts of suggested, the interval would be half the time I estimated. Eye witness said it occurred several minutes later. If we can get an accurate time between flash and boom. We can get a better idea of the altitude of detonation.

Estimates of the energy released are about 300 kilotons. This is massive amount of energy, 30 times greater than the bomb dropped on Hiroshima. The troposphere which is about 11 miles at mid latitude absorbed much of the impact of the shock waves traveling first thru the stratosphere. If the explosion occurred inside the troposphere, this thing would be devastating to the city below. The Tunguska event, scientists estimate it detonated 3 to 6 miles above the earth and release 10 to 15 megatons of energy devastating 830 square miles of forest (from Wikipedia). Although the event on 2/15/2013 was much smaller in energy compared to Tunguska, the city below would have been severely damaged (not flattened like Tunguska)if the object exploded at 30,000 feet (5 miles) at 300 kilotons. At 10 to 12 miles above surface at 300 kilotons should result in more damage than blown windows and doors. I am not an expert in high altitude explosives but I believe this impact was higher in the atmosphere than preliminary estimates.


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hm insulators
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Re: Meteorite hits Russia, people injured new [Re: Achernar]
      #5683452 - 02/16/13 12:46 PM

I went out to my mother's house yesterday while all this was going on and one of the things that we discussed is that in our frantic, high-tech go-go-go world, we forget that we truly are connected to space. We discussed how so many of the ancient peoples of the world understood that we are part of a vast universe, from the ancient Babylonians, Egyptians and Greeks, the Native Americans (particularly the Mayans), and especially the Pacific Islanders, who were utterly superb navigators, using the stars to steer by and settle such places as Tahiti, Samoa and Hawaii.

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Happy Birthday JayinUT
I'm not Sleepy
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Re: Meteorite hits Russia, people injured new [Re: hm insulators]
      #5683493 - 02/16/13 01:05 PM

Peter Brown of the University of Western Ontario, Canada is giving an estimate of 300 kilotons but stating that can easily double as more data comes in. NASA continues to report it as a 500 kiloton event for now.

One thing I hope everyone remembers is that the NY Times is reporting that of those hospitalized 200 are children. May our thoughts go out to them and their families at this time.


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