Chandra View of Tycho's Remnant

[Fraser]

SUMMARY: In 1572, Danish astronomer Tycho Brahe observed and studied an exploding star that would later be named after him. NASA's Chandra X-Ray Observatory shows that the Tycho's Supernova remnant is an expanding bubble of debris which is inside a larger bubble of high-energy electrons. Astronomers think that remnants like this could be a source of cosmic rays; high-energy nuclei found throughout the galaxy which constantly bombard the Earth.

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[cran]

Just look at it! The structure, the turbulence, it's beautiful!

[The supersonic expansion (about six million miles per hour) of the stellar debris has created two X-ray emitting shock waves - one moving outward into the interstellar gas, and another moving back into the debris. These shock waves produce sudden, large changes in pressure and temperature, like an extreme version of sonic booms produced by the supersonic motion of airplanes.] -from the article.

Does my heart good to read that ... quite chuffed, really

[iantresman]

When I first saw this, I thought it was a picture of a cellular organism. Now I can see why Irving Langmuir named plasma after blood plasma (See Origin of the Term "Plasma" for Ionized Gases).

And there are some many other plasma characteristics, such the filamentary blue shell of extremely high energy electrons, the source of x-rays, and the acceleration of stellar debris.

It is no surprise that "standard theory" gets the outward-moving shock waves wrong when the article refers to "interstellar gas". Everything screams plasma!

Regards,
Ian Tresman

[Greg]

What strikes me about this picture is how many pockets of gas and dust there is and how stirred up it looks. It is not hard to imagine how such an event can generate lots of new stars in the resulting nebula.

[Jerry]

http://www.spaceref.com/news/viewpr.html?pid=17874

Four centuries later, the Chandra results on Tycho's remnant show that some modern ideas of the aftermath of supernova explosions may have to be revised. The report by Hughes and colleagues demonstrates that the shock wave produced by the explosive disruption of the star behaves in a way that cannot be explained by the standard theory.

Chandra result for Tycho's remnant significantly changes astronomers' view of the evolution of supernova remnants. A large component of cosmic ray nuclei alters the dynamics of the shock wave, and may require changing the way that astronomers estimate the explosive energy of a supernova from the properties of its remnant.

This is what Middleditch and others, studying gamma ray energies, concluded more than a year ago.

This has major implications for the interpretation of supernova types, removing some (assumed) constraints while imposing others.

Like the local anisotropies found in the WMAP power function, this observation unwinds one of the primary assumptions in the 'precision cosmology' model advanced by the alphas less than three years ago: There are known, quantifiable differences between Supernova Ia and other supernova types, that allow the use of the light curves from Ia to validate Hubble flow.

We are almost back to square one...maybe even further.

[publiusr]

Is Tycho a spherical explosion or are we seeing one lobe pointed at us?

[iantresman]

This finding is important for understanding the origin of cosmic rays...

Peratt suggests in Physics of the Plasma Universe (1992, p.170) that:

"Cosmic rays are extraordinarily isotropic on earth, having a degree of anisotropy of about 0.1 for low energy particles, then decreasing to ±5E-4 for particles approaching energies of 10^20 eV. At one time, it was generally believed that cosmic rays were born in the shock waves produced by supernovae. However, it is now realized that the degree of anisotropy that would be produced by such shocks is far larger than that observed.

"Colgate (1990) points outs that because of the high anisotropy of any shock wave acceleration together with the complete lack of any laboratory evidence that shock-wave/charge particle acceleration actually exists, that field-aligned electric fields are the most plausible mechanism for producing cosmic rays.

Regards,
Ian Tresman

[VanderL]

This is what Middleditch and others, studying gamma ray energies, concluded more than a year ago.

This has major implications for the interpretation of supernova types, removing some (assumed) constraints while imposing others.

Like the local anisotropies found in the WMAP power function, this observation unwinds one of the primary assumptions in the 'precision cosmology' model advanced by the alphas less than three years ago: There are known, quantifiable differences between Supernova Ia and other supernova types, that allow the use of the light curves from Ia to validate Hubble flow.

We are almost back to square one...maybe even further.

Would you mind being a bit more specific? How does this cosmic ray business relate to SN 1a and the Hubble flow? Thanks.

Cheers.

[VanderL]

Peratt suggests in Physics of the Plasma Universe (1992, p.170) that:

"Cosmic rays are extraordinarily isotropic on earth, having a degree of anisotropy of about 0.1 for low energy particles, then decreasing to ±5E-4 for particles approaching energies of 10^20 eV. At one time, it was generally believed that cosmic rays were born in the shock waves produced by supernovae. However, it is now realized that the degree of anisotropy that would be produced by such shocks is far larger than that observed.

"Colgate (1990) points outs that because of the high anisotropy of any shock wave acceleration together with the complete lack of any laboratory evidence that shock-wave/charge particle acceleration actually exists, that field-aligned electric fields are the most plausible mechanism for producing cosmic rays.

Regards,
Ian Tresman

Hi Ian,

Even if electric fields accelerate charged particles to cosmic ray energies, how would this explain the isotropy? Point sources in the Milky way should be anisotropic, no? Imo, the measured isotropy means the sources are either very far away, or the source is the closest "shell" we know of; the heliospheric boundary.

Cheers.

[iantresman]

Even if electric fields accelerate charged particles to cosmic ray energies, how would this explain the isotropy? Point sources in the Milky way should be anisotropic, no? Imo, the measured isotropy means the sources are either very far away, or the source is the closest "shell" we know of; the heliospheric boundary.

I'll have to get a copy of Colgate's paper. Until then, a slide presentation Cosmic-rays and Particle Cosmic-rays and Particle Acceleration (PDF, Part II, Part III, Summary page (HTML)) may provide an explanationa (p.40-41). The authors say:

• "An anisotropic distribution of relativistic particles generate resonant Alfvén waves at a rate which is proportional to the anisotropy and the relative streaming speed
• "The self-generated waves will then scatter the particles, maintaining isotropy and reducing the streaming speed to ~ cA"

Regards,
Ian Tresman

[Greg]

My understanding was that the magnetic fields of superdense objects directed high energy particles along their polar axis towards us. I do not know to what extent electric fields impact on this primary process for generating cosmic rays, if any. I am not sure how you would determine that any cosmic rays detected on Earth would be emanating from this Ia remenant.
Since we are dealing with a Ia remenant, recall that it is the peak brightess that is the "standard candle" that we use to determine distances to galaxies. I am not sure what bearing the comments posted by Jerry Jensen has on this.

As usual, I would like to see a link or reference to an article that describes the mechanism by which electric fields effect a supernova remenant and direct cosmic ray flow and some testable evidence in that article to back up their assertions.

[iantresman]

I'll have to get a copy of Colgate's paper.

Stirling Colgate tells me that I should be referring to his paper: "The Isotropy of Ultra High Energy Cosmic Rays and Multiple Supernova I Galactic Source," [Abstract] Proceedings of 18th International Cosmic Ray Conference, Bangalore, India, August 22-September 3, 1983, OG6-4 p238.

He's also referred me to a later paper, online at: Cosmic Ray Acceleration by E-Parallel Reconnection of Force-Free Fields (2004), Stirling A. Colgate, Hui Li.

And the following article: Acceleration mechanisms 2: force-free reconnection (2004) [Abstract] Stirling A. Colgate, Hui Li.

Regards,
Ian Tresman

[Greg]

Ok. I was hoping the discussion would get more interesting. I am a little skeptical of Fermi stochastic acceleration as a means of particle acceleration. I can see the logic behind first order acceleration associated with shock fronts. I have more trouble buying into second order Fermi acceleration. My chief concern would be that interior of such a (SN Ia) nebula would be so chaotic as to provide no net acceletation to any given particle. But I imagine that in any given population some of them would beat the odds and accelerate.
I do not think the magnitude of acceleration would be that great for the same reason above. I was indeed thinking along the lines of UHE particles as described in the Colgate/Hui abstract. Either way I think it is going to be darn near impossible to get the data to prove or disprove this theory either way, unless maybe we were on course to fly through such a nebula in the span of a few million years. So far even the evidence for shock wave Fermi acceleration is lacking, much less for second order or "turbulence" Fermi acceleration. The quest to detect turbulence Fermi acceleration associated with solar flares has fallen flat the last I heard, punching holes in some of the plasma universe theories. Below is a link to an article that reflects some of my thinking on this topic.

http://www.journals.uchicago.edu/ApJ...92/975692.html

[iantresman]

Ok. I was hoping the discussion would get more interesting. I am a little skeptical of Fermi stochastic acceleration as a means of particle acceleration. I can see the logic behind first order acceleration associated with shock fronts. I have more trouble buying into second order Fermi acceleration.

Only electric fields will accelerate charged particles?

Regards,
Ian Tresman

[Greg]

I am not sure what your question is referring to exactly. The first thing I think if you were to ask me about how particles are accelerated is a black hole, quasar, or neutron star. The means by which particles are accelerated has more to do with magnetic field interactions with particles around these superdense rotating objects. I have heard and read (some) about first order Fermi acceleration associated with shock fronts and found it plausible. There seems to be some evidence of similar mechanisms at work regarding solar flares. Regarding second order Fermi acceleration or "turbulence acceleration," I am not as convinced. Generally I picture the environments (solar flares, Ia nebluae) purported to accelerate particles as hopelessly chaotic and incapable of providing much of a net boost. The picture of the Tycho Brahe remenant I think visually demonstrates the chaos inherent in that nebula.

I realize that there is some recent papers that I haven't kept up on (largely from Japan) on this, but so far what little I have read about it I have not found that convincing. The big problem with attributing this mechanism to SN IA remenants as a source of cosmic "rays" is a lack of evidence. This not necessarily a fault of the theory, but the fact that we can't put a probe in one and find out if the mechanisms described by the theory are correct or not.

[iantresman]

I am not sure what your question is referring to exactly. The first thing I think if you were to ask me about how particles are accelerated is a black hole, quasar, or neutron star.

Why use a sledge-hammer to crack a nut, you don't create x-rays mechanically in the lab. Terrestrial lightning will accelerate particles electrically to produce x-rays and even cosmic rays! So why not elsewhere in the universe? Plasma is over 99.9% of the universe by volume, our Solar System is over 98% plasma by mass. And plasmas will generate electric fields.

Regards,
Ian Tresman

[Greg]

I guess we are talking about different species of cosmic rays. Basically what I was trying to get at was that the higher energy cosmic rays are thought to emanate from distant sources in the fashion outlined above. I have my doubts about them being generated from turbulence in a SN IA nebula as I don't think that particles can be sufficiently accelerated to such high energies by that process.
Low energy cosmic rays emitted from the sun (SEPs)and slightly higher energy anomalous rays (ACRs) (which is now thought to originate from kupier belt dust interacting with the solar wind and magnetic fields) are asssociated with plasma and related energy fields. The link below describes cosmic ray definitions in better detail.
http://helios.gsfc.nasa.gov/supernova.html

This link below is to an article describing a putative source for ACRs.

http://www.space.com/scienceastronom...ns_021105.html