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View Full Version : The Jury Is In: Exploding Stars Really do Pelt us With Cosmic Rays



Fraser
2009-Jun-25, 06:20 PM
Mmm, pretty … and a tad menacing, at least in its explosive past. This is RCW 86, part of a stellar remnant whose explosion was recorded in 185 AD. By studying the remnant in detail, a team of astronomers has been able to*nail down the source of cosmic rays that bombard Earth.(...)Read the rest of [...]

More... (http://www.universetoday.com/2009/06/25/the-jury-is-in-exploding-stars-really-do-pelt-us-with-cosmic-rays/)

Jeff Root
2009-Jun-25, 07:36 PM
I don't see a link in Anne's article to anything more in depth. There appears
to be no mechanism suggested for the creation of cosmic rays. The article
says the researchers measured the speed of the shock wave, and found it
to be moving at between 1 and 3 percent the speed of light. That's an
astonishing speed. I presume that the speed of the shock wave is the
speed of the fastest particles in the expanding supernova remnant, at the
very outer edge. If the shock wave were moving faster than the particles,
it would have vanished long ago at the outer edge of the SNR.

The speed of cosmic ray particles is a considerably greater percentage of
light speed. How is energy transferred from the bulk of hot gas into a few
particles to turn them into cosmic rays?



The temperature of the gas turned out to be 30 million degrees Celsius.
This is quite hot compared to everyday standards, but much lower than
expected, given the measured shock wave’s velocity. This should have
heated the gas up to at least half a billion degrees.
Whatever the temperature at the time the supernova occurred 1,824
years ago (ignoring the light travel time), why hasn't it cooled down
to less than room temperature by now? I would expect the SNR to
have a temperature only a few degrees higher than the background.
Why is it still so hot? Why are the researchers surprised at the SNR's
low temperature, rather than at its high temperature?

-- Jeff, in Minneapolis

trinitree88
2009-Jun-26, 03:42 PM
I don't see a link in Anne's article to anything more in depth. There appears
to be no mechanism suggested for the creation of cosmic rays. The article
says the researchers measured the speed of the shock wave, and found it
to be moving at between 1 and 3 percent the speed of light. That's an
astonishing speed. I presume that the speed of the shock wave is the
speed of the fastest particles in the expanding supernova remnant, at the
very outer edge. If the shock wave were moving faster than the particles,
it would have vanished long ago at the outer edge of the SNR.

The speed of cosmic ray particles is a considerably greater percentage of
light speed. How is energy transferred from the bulk of hot gas into a few
particles to turn them into cosmic rays?


Whatever the temperature at the time the supernova occurred 1,824
years ago (ignoring the light travel time), why hasn't it cooled down
to less than room temperature by now? I would expect the SNR to
have a temperature only a few degrees higher than the background.
Why is it still so hot? Why are the researchers surprised at the SNR's
low temperature, rather than at its high temperature?

-- Jeff, in Minneapolis

Jeff. Initial supernova shocks can be a lot higher than 1-3% c....more like 10 % c. I believe the post 1987a article by Alex Filipenko had it at 25,000 km/sec + or - 5,000 km/sec. That's cooking.
Remember that the speed of the wind blowing across your sailboat has little to do with the speed of the molecules. Say the wind is blowing 30 m/sec....about 60 mph...the speed of sound is related to the molecular mean velocity, which is ~ 331 m/sec at 0 C. The Maxwellian distribution of velocities allows for some to go much faster than that, too. This little high speed "tail" in Maxwell's distribution is what gave Teller et al the brainstorm to try a fusion bomb. You don't need all of the deuterium/tritium traveling at the right speed, just enough of them in the tail to facilitate fusion before the whole thing vaporizes. see: http://en.wikipedia.org/wiki/Maxwell-Boltzmann_distribution

So, with regards to the shock wave, the fastest members will escape first, through the interaction zone, and we see them in advance of the shock itself...kind of like wild animals smelling underground gases from microfissures, and leaving their burrows in advance of earthquakes as the ground distorts in a Young's Modulus shear....the cosmic rays are forerunners of impending shock fronts. pete see;http://en.wikipedia.org/wiki/Young's_modulus