Origin of Cosmic Rays Revealed 225
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."
We've traced the cosmic rays! (Score:4, Funny)
You can't change the title ! (Score:2)
Re:We've traced the cosmic rays! (Score:5, Funny)
It also cleans my laundry with the power of oxygen.
Re:DO NOT PANICE (Score:4, Funny)
Re:DO NOT PANICE (Score:2, Funny)
Eep. (Score:5, Funny)
Re:Eep. (Score:5, Funny)
http://www.npl.washington.edu/AV/altvw13.html [washington.edu]
Re:Eep. (Score:5, Funny)
Re: (Score:2)
Re:Eep. (Score:2)
Because we have a model that says "If neutrinos have the following list of properties, then we should see the following things occuring in our experiments." Then we go look in the experiments, and we see "those things" occuring. Thus, we can say with high confidence, "Since neutrinos appear to have those properties after all, we predict with high confidence that thus-and-such a number are passing through you every second."
Re: (Score:2)
Re:Eep. (Score:4, Informative)
Well, you go into your neutrino detector lab, and you measure the number of neutrino interactions that you see in a certain amount of time. When you combine the known properties of the detector with the know properties of neutrinos (from other experiments that don't directly measure rates) with the rate of observed interactions, you can calculate the number of neutrinos that must have gone through the experiment without interacting in order to produce the number that DID interact. Turns out that that number is mind-bogglingly large.
Re:Eep. (Score:5, Funny)
Re:Eep. (Score:2, Funny)
Maybe for you guys in the US, but what about the rest of us? We'll be doomed I tell you. DOOOMED!
Let me guess (Score:4, Funny)
Not through these precious bodily fluids (Score:4, Funny)
Not with my handy-dandy tinfoil hat.
Re:Not through these precious bodily fluids (Score:5, Funny)
Unfortunately, I've had to have a scrith-reinforced prosthetic spine installed, and I have to stand on a floor plate made of Xeelee construction material... Exotic matter comes with its own set of health hazards.
Re:Not through these precious bodily fluids (Score:2)
CoralCache Link... (Score:5, Informative)
Enjoy.
cosmic rays (Score:3, Funny)
You mean it's like intergalactic spam?
Kill it with laws! (Score:2, Funny)
WHAT??! We need to BAN THEM, like NOW!
Re:Kill it with laws! (Score:2)
Here are some beautiful visualizations... (Score:5, Informative)
a nice description of the telescopes (Score:4, Informative)
Re:Here are some beautiful visualizations... (Score:2, Funny)
Uh, no... (Score:5, Informative)
I think you are confusing them with neutrinos, but even then you are wrong... billions of those pass through us every second.
Uh, YES (Score:5, Informative)
They are called muons [wikipedia.org]. There is a lot more than a thounsand per day! And they can do A LOT of damage. Oh, and muons are produced from cosmic ray interractions in the upper atmosphere.
Neutrino detectors are unbelievably cool. (Score:5, Interesting)
Re:Neutrino detectors are unbelievably cool. (Score:3)
Literally, in this case [wisc.edu]. Very, very cool indeed.
Re:Neutrino detectors are unbelievably cool. (Score:2)
Re:Uh, YES (Score:5, Informative)
Re:Uh, no... (Score:2, Informative)
IIRC, when an energetic cosmic ray collides with the atmosphere, it creates a cascade of thousands of other high-energy particles that can reach us.
When I was a kid, I saw a large gizmo on exhibit (maybe a spark chamber?) that showed each cosmic ray-generated particle going through it as a neon flash. It was getting hit every couple of seconds.
Re:Uh, no... (Score:5, Interesting)
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.
Re:Uh, no... (Score:2, Interesting)
Re:Uh, no... (Score:3, Insightful)
Are you trolling? Free neutrons have a half-life of about 10 minutes [gsu.edu]
Re:Uh, no... (Score:3, Funny)
Damn it!. And here I thought I was being trasformed onto the Thing [ffplaza.com], when in fact I just need to pick up some tinactin.
Thanks a lot. Though I was curious as to why the transformation was starting between my toes.
Cosmic dose. (Score:4, Interesting)
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 [ncrponline.org], for more information. Murray's "Nuclear Energy" has a pie chart of all sources and might be in your local library. This [inel.gov] 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.
Re:Cosmic dose. (Score:3, Informative)
That's during a severe solar flare, which is a relatively uncommon event. Otherwise, we would have a lot of dead astronauts and cosmonauts.
See http://www.asi.org/adb/m/03/11/solar-flares.html [asi.org].
Long suspected, finally proven. (Score:5, Informative)
In a way, it makes sense that they'd be partly responsible for the blue in our atmosphere -- the rest comes from the Sun bombarding the layers of gases up there. Sometimes science is just a way of jerryrigging loose facts together to create a plausible test or explanation for strange phenonema.
Re:Long suspected, finally proven. (Score:2)
Re:Long suspected, finally proven. (Score:2, Informative)
Not quite. The blue wavelengths are scattered, and that's why the sky is blue; that much is true. The reason the sun looks red at sunset is because its light has had the blue wavelengths scattered out before it reaches you.
Re:Long suspected, finally proven. (Score:2)
*A* source, not *the* source (Score:5, Insightful)
What is more interresting than a source of cosmic rays is the source of the gamma bursts. Some background is here [wikipedia.org].
Re:*A* source, not *the* source (Score:3, Funny)
well, you get the point. And when you eventually get to the narc who had the last 8%, you're the one that gets in trouble.
The Terrible Secret of Space (Score:3, Funny)
Pak chooie unf.
Re:The Terrible Secret of Space (Score:2)
I can use Google [jonathonrobinson.com]
Powerful (Score:4, Interesting)
I have a question that's barely related. (Score:3, Interesting)
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?
Re:I have a question that's barely related. (Score:2)
A Bugg
Re:I have a question that's barely related. (Score:2, Informative)
The missing mass is not really missing anymore. We know how much of it there is, where it is, and what it is not (!), just not what it is. It comes in two forms: dark energy and dark matter. Dark matter is clumpy, non-baryonic, non-interacting (at least with normal matter, except via gravity) stuff. Without it, galaxies, galaxy clusters, and larger structures probably would not have formed. Dark energy is stranger stuff. It may or may not be related to the cosmological constant or to t
Re:I have a question that's barely related. (Score:3, Informative)
We can (relatively) easily measure gamma rays with a few MeV in energy. Once you get beyond a few MeV, single photons will interact with Cosmic Microwave Background photons and via pair production create pairs of particles like e+,e
Re:I have a question that's barely related. (Score:5, Informative)
Einstein really said E = sqrt(p^2*c^2+m^2*c^4), where E = Energy, p = momentum, c = speed of light, m = rest mass. For things that are not moving this reduces to the more familiar E = mc^2.
Einstein also said, via general relativity, that gravitational fields are controlled by something known as the stress-energy tensor. In essense, it says that gravitational forces result from all energy, momentum and pressure in the universe (though mostly energy unless very high velocities are involved).
EM radiation has energy E = hv, where h is Planck's constant and v is the frequency of light. It has no rest mass (m = 0), but from above we see E = pc = hv => p = hv/c, so it has momentum. Since it has energy it creates a gravitational field, and this field would be equivalent to a particle with the same rest mass energy. [Caveat: Because momentum also contributes to the stress-energy tensor, the fields are not actually identical but the momentum correction is typically small.]
So in short a beam of gamma rays does create a gravitational field (though a very very small one for typically numbers of gamma rays).
Re:I have a question that's barely related. (Score:2)
No, a beam of gamma rays will have a small effect on gravity. Since energy and mass are equivalent, gravitationally, replacing a object with it's mass equivalent in energy shouldn't make a difference.
However, your beam of gamma rays will be equivalent to so little mass that it probably won't be measurable.
Re:I have a question that's barely related. (Score:3, Informative)
1MJ photon (Score:2)
I've read (somewhere) that the highest energy *photon* ever observed was ~1MJ. That is on the order of 10^24eV! Not sure of the error on this though.
As for highest energy cosmic rays, well, they seem to get to 10^20eV [auger.org]. But there is a cutoff limit for cosmic rays since they interact with microwave background (see that same page).
Angular diameter (Score:4, Informative)
an expanding shell of debris which, seen from the Earth, is twice the diameter of the Moon [unattributed quote from the original article]
So its diameter is a function of viewing position. Sounds like angular diameter [wikipedia.org]. That's still huge, though not as huge as M31 in Andromeda [wikipedia.org].
Re:Angular diameter (Score:2)
"Things look smaller the farther away they are".
It still doesn't explain (Score:3, Funny)
Re:It still doesn't explain (Score:5, Funny)
They didn't. Cosmic rays just activated the x-factor in the fantastic four, which would have stayed dormant otherwise, because they weren't mutants.
"Normal" mutants get their x-factor activated naturally, during the teen years.
(OMG, I can't believe I knew that)
Cosmic rays and computers (Score:5, Interesting)
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
Cosmic Ray and DNA... (Score:5, Interesting)
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.
Re:Cosmic Ray and DNA... (Score:2)
Error correcting enzymes exist in all organisms because everything which is "warm" will have DNA errors that need to be corrected. Bacteria and other organisms that "like" to mutate
Re:Cosmic rays and computers (Score:4, Funny)
Re:Cosmic rays and computers (Score:2)
Close but no cigar (Score:4, Informative)
Close but no cigar.
The rapid passage of a charged particle deposits enough energy on nearby charged particles to jog them out of place - creating a sudden conductive sea of electron-hole pairs. These charge carriers are then swept away by the local field, becoming a burst of current.
This affects memory and logic devices in two ways:
1) It can suddenly leak away the charge stored in the capacitance of a dynamic RAM.
2) It can momentarily turn "on" a transistor that should be off (even turning it more "on" than it normally would be, so its conduction swamps that of its turned-on partner in a totem-pole stage.)
Leaking the stored charge in a RAM flips the bit - in a particular direction. Turning on a transistor that should be off may flip a bit in a flop. latch, or static RAM, or momentarily cause the wrong level on a logic line.
Nothing to do with changed capacitance (although the sudden appearance of an extra conductive region does represent an increased capacatance on some nearby conductors).
Cosmic rays (fast charged nuclear fragments) can do this. Another problem was alpha particles from heavy elements in the ceramic integrated circuit packages once used for memory and mil-spec ICs (which is why they disappeared). A third was alpha particles from the decay of radon gas. (Turns out some locations in Silicon Valley have a lot of radon.)
And -- they can vote, too! (Score:2)
Le rayon cosmique qui a touché la mémoire d'une des urnes électroniques de Schaerbeek, ce rayon cosmique permettra de sensibiliser des députés encore acquis au vote électronique.
The official review reduced this to exactly 4,096 extra votes and was therefore able to conclud
Re:Cosmic rays and computers (Score:4, Informative)
Here is a summary of IBM's 15 year experiments with cosmic rays:
IBM's research on cosmic rays [ibm.com]
I quote from this:
The cosmic ray intensity is greatest at high terrestrial altitudes, and approaches zero under extensive shielding. IBM has conducted extensive field testing3 of components at high altitudes (10,000 ft), at moderate altitudes (5000 ft), at sea level, and under shielding of 50 ft of concrete. All elevated-altitude tests showed cosmic-ray-induced fails in electronic components. In all tests, the observed fail rate scaled directly with the cosmic ray intensity, over a total observed change of more than 1000× .
There is also another related article at IBM.
IBM's research on cosmic ray densities at different places on earth [ibm.com]
Osho
Re: (Score:2)
Found some more info (Score:4, Interesting)
http://www.pparc.ac.uk/frontiers/archive/update.a
It includes a picture of the telescope array as well as a small image of the gamma ray map.
Re:Found some more info (Score:2, Informative)
It chopped the end off my link.
I'll try again:
Here.
(The "Here" text above is DEFINATELY enclosed with correct HTML, and contains the full URL)
Hmmmmmmm, now thats interesting.
Slashcode is screwing the link up.
I will just paste it exact in plain text - it is balking on the "&style=update" parameter of the URL.
Here it is in plaintext:
http://www.pparc.ac.uk/frontiers/arch i ve/update.as p?id=15U3&style=update
and incase all that fails, this is a working link to the archived issue, the HESS l
Oh, all right then, I'll do it. (Score:2, Funny)
[In Eyeore intonation, with a heavy heart]:
"I, for one, welcome our new supernoverlords."
There. Somebody had to.
If you want to see cosmic rays for yourself... (Score:5, Informative)
Why I love science writers (Score:4, Informative)
((1000 light-years)*(size of moon))/(moon orbital height)
across,
((9.5 × 10^18 meters) * (3,476,000m))/ (384,403,000 m)
That's about 86 light years in diameter. Its average velocity is left as an exercise to the homebound.
Oops! (Score:4, Informative)
Re:Why I love science writers (Score:3, Interesting)
BUT, it's not that simple. Redshift is really due to an integral of pointwise expansion wherever the photon happens to be. Since space is not expanding at a constant rate, we need to know how
Re:Why I love science writers (Score:2, Informative)
Objects 1000 ly away are inside of, or darned close to, our own galaxy. The distance to such objects is not measured by redshift, because a) they're moving in roughly the same direction we are, astronomically speaking, and b) redshift is used when measuring distrances in the millions or billions of light years; it'd be darned hard to measure the redshift of an object just 1000 ly away, even if it did have a redshift value that
Not unexpected (Score:5, Informative)
So supernovae were a prime suspect source back then.
We had three (not four) 2 metre (not 12 metre) telescopes with about 30 'pixels' each (compared to a few thousand for HESS.) (I actually worked on another part of the experiment, which used particle detectors to detect higher energy showers.)
A significant problem is to distinguish between showers created by gamma rays and ones created by charged particles (mostly protons.) The charged particle showers are 'uninteresting', because the direction they come from is uncorrelated to their source - they move on curved paths due to galactic magnetic fields. Unfortunately, they are about 99% of the cosmic rays. We were not able to distinguish, so we had a large 'signal to noise' problem.
There was a single telescope similar to these ones in the mid 80s (the Whipple Telescope, I think) which claimed to be able to distinguish by details of shower structure. (We didn't have the resolution, nor perhaps the light gathering power, to make use of this.) I presume HESS has built on this work.
Note that this result does not necessarily tell us about the very highest energy cosmic rays. There is a change in the slope of the spectrum at (from memory) about 10^15 electron volts, so it is likely that different processess are involved on either side of this boundary. I think there were also theoretical reasons to think that supernovae could not accelerate particles to such high energies.
As I recall, the models for acceleration generally required shock waves in a gas with magnetic fields. Particles could repeatedly bounce across the shock, getting accelerated each time. (Think of a ball bouncing between two walls that are moving towards each other.)
Article author is confused (Score:2, Informative)
- Gamma rays are not cosmic rays
- Gamma rays do not cause Cherenchov radiation
Primary cosmics rays are subatomic particles with extremely high energy. The most energetic ones have an energy comparable to the energy of a tennis serve.Tennis serve (Score:2)
Re:Article author is confused (Score:2)
Please translate that to something I can understand - like elbow bends with a full pint of beer. What kind of unit is a "tennis serve"?
google couldn't handle "1 tennis serve in elbow bends", but it could do "1 mile per gallon in furlongs per pint", yeilding a happy constant I hadn't thought of before: "1 mile per gallon = 1 furlongs per US pint"
Re:Article author is confused (Score:2)
Re:Article author is confused (Score:4, Informative)
Via pair production, gamma rays produce the same kinds of secondary particle showers that the far more common primary cosmic rays do. However, because of momentum conservation, the particle shower is much more tightly focused and produces a distinctive Cherenchov cone that allows gamma rays particle showers to be easily distinguished from cosmic ray showers.
As noted in the article, the fact that gamma are currently being produced in the supernova remnant strongly argues that cosmic rays are also being accelerated there. The physics for this was proposed long ago, but no one has been able to directly measure it.
Cosmic Ray Experiences/Background (Score:5, Interesting)
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 (Score:5, Interesting)
Misleading header (Score:4, Interesting)
misleading (Score:5, Informative)
The group's publications page is here [dur.ac.uk] (click on observations section), but they don't seem to have a preprint of this paper. Nature will let you read the abstract of the paper [nature.com] for free.
The research seems to be just a more direct confirmation of something that was already thought to be understood, but had never really been verified.
It's clobberin' time! (Score:4, Insightful)
I'm surprised noone else caught the Fantastic Four reference in the "from the...department" line of the summary - it was the first thing I thought of when I saw the phrase "cosmic rays"!
Origin of cosmic rays revealed... (Score:2, Funny)
Origin = Location, not Origin = why/how (Score:3, Insightful)
There's a lot of energy being beamed about, and well, you'd think that it would stop eventually, but it keeps on coming.
Compared to X-Rays (Score:2)
Gamma rays are the most penetrating form of radiation we know, around a billion times more energetic than the X-rays produced by a hospital X-ray machine.
We know that too much X-ray exposure is not considered good. Why does something a billion times more energetic that passes through our bodies everyday does not have any adverse health effect? Aging anyone??
Re:Compared to X-Rays (Score:3, Informative)
1) The charged particle component of cosmic rays is sheilded by the Earth's magnetic field
2) The uncharged (neutron) component of cosmic rays does not interact with matter very much - it is very penetrating simpley because it passes through most matter without colliding with anything.
3) Gamma rays, like neutrons, tend to pass though quite a bit of matter without actually interacting with it.
Or more simply, we are transparent
Re:Compared to X-Rays (Score:2, Interesting)
Call me Reed. Reed Richards. (Score:2, Funny)
Blender 4D? the Cosmic Ray tracer. (Score:2)
Obligatory SG-1 quote... (Score:2, Funny)
H.E.S.S. and cosmic rays (Score:5, Informative)
A Supernova remnant (SNR) is a very rapidly expanding bubble of hot gas, created by the explosion of a massive star. It is thought that the shock wave caused by these expanding bubbles in our galaxy accelerate surrounding hydrogen gas to very high energies, which then become the cosmic ray protons which we see at the earth today. Protons form the bulk of the cosmic ray flux between MeV and EeV energies, and at least up PeV energies they seem to be formed in our Galaxy, probably by SNRs.
The SNRs are really light years across, the ones we see are generally in the local quadrant of our galaxy, thus are really not far away in the cosmic scale of things. Happily not close enough to fry us though! Cosmic redshift does not occur within our galaxy, by the way.
We detect gamma rays at very high energies by looking at their interactions with the upper atmosphere. The gamma rays themselves do not generally penetrate to the ground, we measure the Cherenkov light emitted by the shower of charged paticles which stem from the gamma ray interaction.
One reason gamma rays are interesting is that they , like other photons, travel directly to us from their source, so we can use them to make pictures of what the source looks like. We believe in this case that the gamma rays are produced in the supernova remnant by interactions of the accelerated protons, and thus are a tracer which proves the existence of the comsic rays at the SNR, and thus that SNRs generate cosmic rays.
The particles which pass through us every day are mostly muons, which are by-products of the interaction of cosmic ray protons with the atmosphere.
More information can be found at:
http://www.mpi-hd.mpg.de/hfm/HESS/HESS.html [mpi-hd.mpg.de]
Shell of debris approaching (Score:2, Interesting)
The article doesn't state how distant that supernova is/was, only that it happened 1,000 years ago. Does that mean the supernova explosion was observable from Earth 1,000 years ago (saying nothing about its distance), or that the explosion actually happened 1,000 years ago (putting it at a distance of 1,000 lightyears)?
In either case, if the shell of debris has now travelled half a degree of angular separation from the original point of explosion (uniformly in all directions), I suppose that debris will ev
Re:Shell of debris approaching (Score:3, Informative)
What we see now is 1000 years after it exploded, so we just call it 1000 years old for simplicity.
The shell should be too old and dispersed
Re:Shell of debris approaching (Score:2, Interesting)
Would it be possible to determine its age (and thus its distance) by observing the expansion of the shell over a period of say, a few decades, and extrapolate from that? Maybe the observation method doesn't allow for sufficiently accurate measurements of the positions of the outermost gamma ray sources, or there are natural fluctuations in their appearance rendering the calculations meaningless?
I recall reading about visible-light observation of what was first thought to be debris from another supernova ex
Re:Shell of debris approaching (Score:3, Informative)
The second point refers to SN 1987a, which was observed to explode 17 years ago (hence the name).