Origin of Cosmic Rays Revealed

neutron_p writes "An international team of astronomers has produced the first ever image of an astronomical object using high energy gamma rays, helping to solve a 100 year old mystery - an origin of cosmic rays. The astronomers studied the remnant of a supernova that exploded some 1,000 years ago, leaving behind an expanding shell of debris which, seen from the Earth, is twice the diameter of the Moon. Cosmic rays are extremely energetic particles that continually bombard the Earth, thousands of them passing through our bodies every day."

Comments

Powerful

[vlad_grigorescu]

These things are very powerful. The Russians have been conducting experiments on the sea floor for years and lots of them are energetic enough to go through. It's been assumed for a while that supernovas are the source of cosmic rays but it has been hard to pinpoint their origin, since cosmic rays can be deflected by magnetic fields.

Re:Uh, no...

[meringuoid]

The curious thing about these muons is this. Muons have a very, very short half-life; they decay extremely rapidly. Even moving near lightspeed, they should decay significantly between (say) a mountaintop lab and a sea-level lab, because of the travel time on the way down, but they don't.

It's almost as if time was slowed down for these high-velocity particles... and indeed this is the case. It's a classic demonstration of relativity in action.

I have a question that's barely related.

[Anonymous Coward]

What's the highest frequency EM raidation that can be detected/measured with the technology we have today?

Could there be massive amounts of EM radiation flying around the universe that is simple undetectable? Could this not be the "missing mass" that is conjectured in discusions of universal inflation and what not?

Anyone know?

Neutrino detectors are unbelievably cool.

[turnstyle]

Now that we've veered off onto neutrinos, let me point out how unbelievably cool neutrino detectors are. Start your journey via Google Images.

Cosmic rays and computers

[osho_gg]

Cosmic rays are of some real practical significance in the world of computers. Cosmic rays are attributed as a reason (among others) for why sometimes we see unexplained behavior in Computers - mainly memory (RAM) where suddenly 0 bits become 1 and 1 bits become 0. These heavily charged extremely small particles have the property that they change the capacitance of parts of semiconductors when passed through them. This could change certain bits 0 and 1 (which are all stored as capacitance inside RAM and other places in computers) into 1 and 0.

This has, along with semi-conductor material and process defects etc., led to the whole field of Error Correcting Codes in computers - where such kind of errors can be prevented by things such as parity bits and what not. This works on the presumption that the probability of such bitswaps occurring on two bits is very small compared to just 1 bit. So, high-reliability computing servers etc. always tend to use memories with good ECC.

I have heard anecdotal evidence that IBM did some thourough testing of how such a behavior of bit-flipping due to cosmic rays changes at different elevation. When the elevation was high (7000 feet or so) - it occurred far more often then at the sea level. They did such tests below the surface of the earth and as they went deeper into the earth - such cosmic rays bit-flipping effect decreased but still remained. Only, after they went something like 40 feet or so below the surface of the earth - such behavior completley went away.

So, next time you wonder why you are paying more for ECC-RAM - think of cosmic rays (and material defect and what not ...)

Osho

Found some more info

[LiquidCoooled]

Went looking around for more information, and came up with this:

http://www.pparc.ac.uk/frontiers/archive/update.as p?id=15U3&

It includes a picture of the telescope array as well as a small image of the gamma ray map.

Cosmic Ray and DNA...

[ImaLamer]

Much like your own DNA.

We all think that mutations happen daily, but that is far from the case. In fact genetic mutation is very rare because we have error correcting enzymes which travel back and forth on DNA strands correcting them as they change. Typically the DNA "code" is changed as subatomic particles rip through your body, just as you've explained with RAM.

Yes, our DNA mutates. It doesn't stay that way however. Statistically there are more errors in a 300 page book then in a mile long DNA sequence. Actually there are about 0 errors in DNA because of this self-correcting mechanism.

* Source: Shadows of Forgotten Ancestors by Ann Druyan and Carl Sagan.

Cosmic Ray Experiences/Background

[Michael Snoswell]

A long time ago (early 80s) I worked in a lab that used scintillation counters to measure biological activity (Background: you'd put a radioactively labelled (eg with tritium or C14)reagent in with the other cocktail for a test you're conducting in a little test tube. After say 5 mins you'd stop the reaction (say with perchloric acid), syphon off the top layer and put it into scintillation liquid (not sure what it was, but largely based on toluene) and put the vials into the scintillation counter which would have hundreds of little tubes in a conveyor belt and one by one drop the tubes deep inside the lead shielding to measure flashes of light as the isotopes decayed, hence telling you v accurately how much of the original substance under test had bound to the labelled reagent).

Anyway, every few days the counter would go completely stupid, and every few weeks copletely bananas (a technical term). It turned out the major machine crashes coincided with all scintillation counters in the building going crazy at the same time. We had over a dozen of these machines (all different brands) and they had about 6inches of lead around the detectors, so that was quite some energetic particles we were getting. The all the manufacturers' reps said there was little we could do to fix this, unless we wanted to be underground.

Talking to a friend at the local uni cosmic ray observatory (500+ scintillation counters spread over about a square kilometer), he said the more energetic showers were smaller in radius as the particles have less time to spread out from the initiating collision of a cosmic particle with the upper atmosphere. Usually they spread out to 50 to a few hundred metres across, with a massive cascade of all sorts of particle by the time it reaches ground level.

Interestingly, the initial byproducts of cosmic ray collisions have a v short life which means they should decay before reaching sea level. However as they travel close to the speed of light the depth of the atmosphere is foreshortened (Lorenzian contraction) to only a few hundred metres deep - a simple proof of relativity in action (or likewise, time is going slower for the cosmic particles).

It has been said that cosmic rays are the largest contributor to genetic mutations, beyond background radiation levels due to radioactive isotopes occuring naturally in the ground. Similarly, work place studies show airline hostesses/stewards have the far largest dosage of radiation of any occupation as they spend so much time above the bulk of the atmosphere. (Pilots spend less time in the air due to safety/fatigue regulations).

I also recall reading that it's extremely difficult to work out where cosmic rays originate as they are usually charged particles that follow curved paths through space due to the small but significant magnetic fields of stars and the galaxy itself. Due to timing of shows hitting detectors we can easily measure the angle a particle was going when it hit the atmosphere, but the particle took a very convoluted path prior to that, so finding a close source (100ly) is significant.

Muon Clarification

[vlad_grigorescu]

The cosmic rays that the article discusses are not muons, they are most often protons. The muons are what we encounter on Earth. The proton (also called the primary cosmic ray) comes in, hits our atmosphere, and a shower of subatomic particles is produced. The muon is the most powerful of these subatomic particles that is commonly produced. The fact that muons have a short half-life, and yet they can still reach us, has been cited as proof of relativity, and the idea that when you travel close to the speed of light (which these things do), time will slow down.

Misleading header

[forand]

This is NOT the first gamma-ray image. I work on Glast which is the second generation of gammay observation satelites. EGRET was the most recent satelite to provide gamma-ray skymaps. Googled

Cosmic dose.

[twitter]

Thousands of cosmic rays do not pass through our bodies every day... They are stopped by the atmosphere. Cosmic rays are actually fairly dangerous radiation.

Cosmic Radiation makes up about 8% of the 360 mREM annual average background dose someone in the US receives. See the National Council on Radiation Protection and Measurements NCRP 93, 1988, for more information. Murray's "Nuclear Energy" has a pie chart of all sources and might be in your local library. This looks good too.

If you have a Sodium Iodine detector set and a scope, you can see it. Most common energies seen are around 20 MeV. They are big pulses next to the puny normal ones but you will detect one every twenty seconds or so.

You are correct, however, to note that most of these particles are blocked by the atmosphere and that you do get dosed at higher elevations. A person at 80,000 ft. according to the lesson plan cited above, gets about 10 R/hr. Each hour that's five hundred times the dose you get per year on the surface, ouch. By comparison, plants have a cow if you get more than a few unplanned mR.