APOD: The Great Russian Meteor of 2013 (2013 Feb 18)

[neufer]

It’s interesting that we call our protective shell (from the sun’s harmful radiation and other ejected material) “the Earth’s Magnetic Field” Gives one the impression that it could repel or attract a metallic object. We all know that it is a gravitational effect that allows the more massive meteor/meteorite to contact the Earth so it’s somewhat confusing we refer to our protective field as such.

The Earth's magnetic field is only about 0.5% as strong as a typical bar magnet, and falls off with distance. Only a few percent of meteoroids are iron, and even those spend so little time in the Earth's magnetic field that there is insignificant impact on their trajectories. Of course, both DA14 and the Russian meteor body were stony, with little iron content, and therefore even less affected.

I just submitted my first query to whatif@xkcd.com :

The solar wind is a tenuous "superconducting" gas that is easily repelled by the Earth’s magnetic field.

Would it be possible to produce a large enough superconducting metalized Mylar ("Echo") balloon
such that the magnetic repulsion from the Earth would balance out the gravitational attraction
in a low earth stationary equatorial orbit?

[Chris Peterson]

Thanks Chris, you've answered many of my suppositions. But why would all of the objectsorbiting from the formation of the Moon be gone in a few million years? Aren't the annual meteor showers due to passage through debris strewn regions?

All naturally occurring orbital systems with more than two bodies are ultimately unstable, including the entire Solar System. Within the Solar System are regions of greater or less stability. The planets exist in highly (but not perfectly) stable orbital positions. The asteroids in the belt have distributed themselves into relatively stable zones, and unstable zones have been cleared out. All small bodies with orbits that pass anywhere near the orbits of planets are in relatively unstable orbits, since they will be repeatedly perturbed, with the result that they will either be deflected into the Sun, or ejected from the Solar System completely. So we can generally assume that bodies found orbiting in the inner system are recent additions, perturbed (usually by Jupiter) from some other location, generally the asteroid belt. And after a few million years or less, they will be perturbed into radically different orbits.

[Chris Peterson]

Chris, you're incorrectly ascribing bogus statistical rules to scottjsw (and I). You say that the odds that "you will be outside, wearing a swimsuit, and eating a sandwich when a huge fireball passes over" is small, and it is. The earth is like a particular person, not all the people on earth. The same for the car crash analogy.

I don't think so. It is the time of the event that is like a particular person. The odds of any coincidence happening at a specific time is very small, yet every coincidence will happen at a specific time.

Extremely unlikely astronomical coincidences happen every day, including ones much, much more unlikely than a couple of relatively large objects passing so close in space and time. There are billions of possible unlikely events, and billions of years for them to occur. We simply notice certain ones and not others. It's a kind of selection bias.

The odds of a 50 meter (or larger) asteroid coming as close (or closer) to the earth as 2012 DA14 did is not known - I've heard it's once in one hundred years on average. Scientists say it is a "record close approach for a known object of this size."

But this is a misleading way of expressing things. What about a similar object that passes a little farther away? It would still be reported as a rare event. It's like the big deal made a few years back when Mars was particularly close. Closer than it will be for 100 years! Sounds impressive, but it's barely closer than a dozen other apparitions.

The Russian meteor was "the largest object known to have entered the Earth's atmosphere since the 1908 Tunguska event."

I think that's arguable. I have good reason to believe that larger infrasound events have been recorded. But regardless, it doesn't matter. Even if a coincident event like this only happens every 10,000 years, it's happened a half million times in the history of the Solar System. Things that happen with that frequency can be observed every day.

[MargaritaMc]

So the two meteors are only related by being in the same solar system with us. Which is about the same as my relationship to President Obama.

What a coincidence! WHAT is the is the probability of Geckzilla and Barack Obama being alive, on the same planet, at the very same time, in the total life span of the Universe?

I am currently doing some remedial maths, and the study of probability has just been introduced. At a very basic level, I hasten to add, so I am not competent to contribute to this debate. But it has taught me enough to show me that what I sense intuitively about the probability of an occurrence is not necessarily correct.

It occurs to me that an Introduction to Probability would be a useful tool for Forum members (as are Robert Nemiroff's lectures on Introductory Astronomy and on Physics).

I don't know what the formal forum rules would be about putting up something in the Resources section, but if it were permissible, is there anyone able - and willing! - to tackle this?
(Chris...?)

Margarita

[rstevenson]

It occurs to me that an Introduction to Probability would be a useful tool for Forum members (as are Robert Nemiroff's lectures on Introductory Astronomy and on Physics).

I've often thought that people should be introduced to probability and statistics way back in grade school. But there would be one unintended consequence of a society which understands statistics: lottery sales would take a nose dive.

Rob

[neufer]

So the two meteors are only related by being in the same solar system with us.

Which is about the same as my relationship to President Obama.

What a coincidence! WHAT is the is the probability of Geckzilla and Barack Obama being alive,
on the same planet, at the very same time, in the total life span of the Universe?

Geckzilla & Barack Obama are in a relationship? (Who knew?)

'How often have I said to you that when you have eliminated the impossible,
whatever remains, however improbable, must be the truth?' - Sherlock Holmes, The Sign of Four

[Sam]

I remember this podcast as addressing many of these probability issues: http://www.radiolab.org/2009/jun/15/.
Sam

[bystander]

Russian Fireball Largest Ever Detected by CTBTO’s Infrasound Sensors
CTBTO | 2013 Feb 18


17 infrasound stations in the CTBTO's network detected the infrasonic waves
from the meteor that broke up over Russia's Ural mountains on 15 Feb. 2013.
The furthest station to record the sub-audible sound was 15,000 km away in
Antarctica. (Credit: CTBTO)

[MargaritaMc]

I remember this podcast as addressing many of these probability issues: http://www.radiolab.org/2009/jun/15/.
Sam

That is very interesting podcast and very relevant to this current discussion. Thank you, Sam, for posting it.

M.

[neufer]

I remember this podcast as addressing many of these probability issues:
http://www.radiolab.org/2009/jun/15/.

That is very interesting podcast and very relevant to this current discussion. Thank you, Sam, for posting it.

Click to play embedded YouTube video.

I would be a little more suspicious of any PODcasts on this subject if I were you, Margarita. And you best stay awake

<<In deep space, a race of gelatinous creatures abandon their dying world. Pushed through the universe by solar wind, they make their way to Earth and land in San Francisco. Some fall on plant leaves, assimilating them and forming small pods with pink flowers. Elizabeth Driscoll, an employee at the San Francisco health department, is one of several people who bring flowers home. The next morning, Elizabeth's partner, Geoffrey Howel, suddenly becomes distant, and she senses that something is wrong. Her colleague, health inspector Matthew Bennell (Donald Sutherland), suggests that she see his friend, psychiatrist Dr. David Kibner (Leonard Nimoy).>>

Your friendly APOD blogger,
Art Neuendorffer

[MargaritaMc]

Neufer wroteI would be a little more suspicious of any PODcasts on this subject if I were you, Margarita. And you best stay awake

Toooooo late...

I've been pod-snatched...

[Beyond]

Hold on... aren't we all APODers already

[neufer]

Hold on... aren't we all APODers already

There's nothing to be afraid of, Beyond. They were right. It's painless. It's good. Come. Sleep.

[Beyond]

Hold on... aren't we all APODers already

There's nothing to be afraid of, Beyond. They were right. It's painless. It's good. Come. Sleep.

ha-ha, are you kidding When i fall asleep, they're of me

[neufer]

Memorable quotes for Invasion of the Body Snatchers (1956)

Wilma Lentz: There's no emotion. None. Just the pretense of it. The words, the gesture, the tone of voice, everything else is the same, but not the feeling.

Dr. Miles J. Bennell: In my practice, I've seen how people have allowed their humanity to drain away. Only it happened slowly instead of all at once. They didn't seem to mind... All of us - a little bit - we harden our hearts, grow callous. Only when we have to fight to stay human do we realize how precious it is to us, how dear.

[retrogalax]

Hello,

Can we say that the meteor "exploded" (because of temperature or pressure) ? Is this that created the sound wave ? The white smoke is water ? From where comes the (stunning) flash of light ? Did you see at 1.10 there is a plume.
Is it rock vaporisation ? Hopefully it went top of our heads.

[Chris Peterson]

Can we say that the meteor "exploded" (because of temperature or pressure) ? Is this that created the sound wave ? The white smoke is water ? From where comes the (stunning) flash of light ? Did you see at 1.10 there is a plume.
Is it rock vaporisation ? Hopefully it went top of our heads.

"Explosion" is a reasonable term, frequently applied when meteors violently break apart.

A body larger than a few millimeters moving through the atmosphere at a hypersonic speed experiences very large forces on the leading surface created by compressing air in front of it (this is called ram pressure). If those forces create stresses that exceed the material strength of the body, it will break into two or more pieces. The rapid compression of air in front of the body creates heat, which burns or melts away the outer surface, a process called ablation. This is a very efficient way of removing heat, and the body itself undergoes very little change in temperature from whatever it had in space. When that body breaks up, a lot of new surface area is exposed, which immediately begins ablating. This is the primary source of heat and light we experience when a meteor explodes. It also creates the primary shock wave, recorded by instruments and detected audibly if the event is large enough or occurs close enough to the ground. The primary body may generate a conventional supersonic shock wave (sonic boom) on the ground if it survives low enough in the atmosphere (below about 50 km). The individual, typically short-lived bodies produced by an explosion can also generate sonic booms (again, only below about 50 km), resulting in a sound often compared to artillery fire, and quite recognizable in some of the Russian videos immediately after the primary explosion.

The trail itself is primarily dust particles (smoke) from the ablating meteoroid. These trails are usually not pure white. The very white appearance of the smoke trail in the case of the Russian meteor may be indicative of its material properties, but has also been suggested to result from some sort of water condensation, similar to a contrail. The details of the trail structure and color remain under investigation.

[bystander]

Click to view full size image

What’s the Difference Between a Comet, Asteroid and Meteor?
Universe Today | Nancy Atkinson | 2013 Feb 20

‘Name That Space Rock’ — Credit and copyright: Tim Lillis.
— describes the difference between all those flying rocks from space.

[Beyond]

Pictures from a professional photographer who just happened to have set up his camera pointing where the Russian meteor exploded in the sky.
http://www.dailymail.co.uk/news/article ... rough.html

[epitalon]

Hello all,

I would like to know something, please:
what are the conditions on velocity, relative to earth, if any, for an asteroid to enter earth atmosphere after half a U-turn around earth.
I mean: could an asteroid have a parabole or an elongated elipse trajectory, relative to earth, and enter earth atmosphere at its perigee ?

I have in mind that the russian meteor could be on a trajectory similar to 2012 DA 14, approach earth from the south of ecliptic plane and still enter earth atmosphere on a line parallel to the ecliptic plane.

Where I could be wrong ?
Why scientists are so certain about that the russian meteor came from another direction than 2012 DA 14....

Thanks in advance

[Chris Peterson]

I would like to know something, please:
what are the conditions on velocity, relative to earth, if any, for an asteroid to enter earth atmosphere after half a U-turn around earth.
I mean: could an asteroid have a parabole or an elongated elipse trajectory, relative to earth, and enter earth atmosphere at its perigee ?

This is only possible if the body is in orbit around the Earth in the first place. Otherwise it doesn't have a perigee at all. A body in a solar orbit can't be captured by the Earth except by aerobraking- losing energy after dipping into the atmosphere. Such a meteor can, potentially, touch the atmosphere on one side of the Earth and again on the other, or even go all the way around. It will, however, still have the same inclination it had while in solar orbit.

I have in mind that the russian meteor could be on a trajectory similar to 2012 DA 14, approach earth from the south of ecliptic plane and still enter earth atmosphere on a line parallel to the ecliptic plane.

Not possible. The Russian meteoroid was in solar orbit (a well established orbit, based on the many video observations of the event). That orbit was very different from DA14's orbit. DA14 is in an orbit similar to Earth's. The meteoroid that created the Russian meteor was in an orbit that extended to the asteroid belt, and was on a completely different inclination. There are no plausible mechanisms that could have shifted a piece of DA14 into that different orbit in the hours before the meteor.

Why scientists are so certain about that the russian meteor came from another direction than 2012 DA 14....

Because orbital dynamics is a completely understood science, and both of these bodies were very well observed.

[epitalon]

This is only possible if the body is in orbit around the Earth in the first place. Otherwise it doesn't have a perigee at all. A body in a solar orbit can't be captured by the Earth except by aerobraking- losing energy after dipping into the atmosphere. Such a meteor can, potentially, touch the atmosphere on one side of the Earth and again on the other, or even go all the way around. It will, however, still have the same inclination it had while in solar orbit.

Thanks Chris for your kind response.
I understand know that I must not consider only the speed of the small body relative to earth but its total kinetic energy (relative to the sun). Am I right ?

So, if a small body with the same orbit as 2012DA 14 (11 degree of inciination relative to the ecliptic), if slowed down then caught by earth gravitational field, would end up turning around earth in the same plane (with same 11 degree of inciination relative to the ecliptic) ?
I understand that it would not turn around for long, because of the air drag...

[Chris Peterson]

Thanks Chris for your kind response.
I understand know that I must not consider only the speed of the small body relative to earth but its total kinetic energy (relative to the sun). Am I right ?

Like many interesting physics problems, it is possible to construct orbital dynamics questions from the perspective of total energy (not just kinetic energy). I think that your intuition here, seeing how energy must be involved in a change of orbital parameters, is solid.

So, if a small body with the same orbit as 2012DA 14 (11 degree of inciination relative to the ecliptic), if slowed down then caught by earth gravitational field, would end up turning around earth in the same plane (with same 11 degree of inciination relative to the ecliptic) ?

Correct. Actually, there's more involved than just the inclination- all of the orbital parameters for the Russian meteoroid were very different from that of DA14. But inclination is probably the easiest to visualize. It requires a lot of energy to change orbital inclination. In fact, the energy that would be necessary to make a sudden change from DA14's inclination to that of the Russian meteoroid would have probably fragmented a body the size and composition of the latter. The change could have occurred over a long period, of course, but in that scenario the two pieces would have drifted very far apart, and their original relationship could no longer explain the coincidence of their near simultaneous arrival at Earth.

I understand that it would not turn around for long, because of the air drag...

It could just be an Earth-grazer, and either remain is solar orbit, or come back to the Earth at some time in the future. But if it touched the atmosphere twice, I think we can safely conclude that the second time will be its end.