Slashdot Mirror
Scientists May Have Detected Neutrinos From Another Galaxy
The Bad Astronomer writes "A experiment called IceCube — consisting of sensitive light detectors buried deep in the Antarctic ice — has detected two ultra-high-energy neutrinos, each with over a peta-electronVolt of energy (a quadrillion times the energy of a visible light photon), the highest energy neutrinos ever seen. The two events, nicknamed Bert and Ernie, have a 99% chance of originating outside our galaxy, likely created either by a supermassive black hole or an exploding gamma-ray burst."
FTA:
Out of the countless detections it’s seen, two of them—nicknamed, seriously, Bert and Ernie—were phenomenally, unbelievably energetic: Each had an energy over one thousand trillion times the energy of a visible light photon. That’s huge, far larger energies than even the Large Hadron Collider can create. It’s very roughly equivalent to the energy of a raindrop hitting you on the head which may not sound like much, but remember we’re taking about a single subatomic particle with that much energy
I am a free slashdotter. I will not be modded, blogged, DRM'd, patented, podcasted or RFID'd. My life is my own.
It was obviously the explosion created from the enormous energy from a supergate in the galaxy Atlantis lives in.
That would be our galaxy. It moved here in the final episode (San Francisco I think).
I am a free slashdotter. I will not be modded, blogged, DRM'd, patented, podcasted or RFID'd. My life is my own.
WORD! That's a fly name for an experiment dawg!
are you not familiar with the upside the head measurement of force? measured in FredSanfords
you big dummy.
but doesn't it correlate to any possible event yet, or are we just guessing about were it came from?
In my country a person like you would be called an ant-fucker. Because ant-fuckery is the only way to describe this level of pedantry. Don't get me wrong, it's not meant as a grave insult. Polite people use the term in casual conversation and nobody is offended.
So if I flip a coin and cover it up, and ask you "What are the chances it is heads?" you would answer back "it's either 100% or 0%"? What kind of pedantic choice of interpretation is that?
160 uJ, give or take.
In Liberty, Rene
Not without, at least, dinner and drinks. (tits would be a big help too)
Solving Unix problems since 1989...
Its the nrg. The point of origin can be norrowed down by eliminating sources that don't have that amount of nrg. Simple.
Python: 'And then suddenly you have a language which says "we're all stuck with whatever the whiniest coder wants".'
These neutrino's were not the neutrinos they were looking for
I believe it is Sithic philosophy that states you are either absolutely for or absolutely against something.
So I would not argue with Troyusrex, unless you want to get force choked.
Neutrinos, as matter, have plenty of characteristics that could be used to identify them. And saying that it comes from a specific place is not really that difficult since things coming in from space don't take U-turns or pit stops. They come at us in a straight line only perturbed by gravity or other objects that we can observe and compensate for. So if a particle has a certain energy level and direction that does not match anything inside the galaxy, you can do a pretty reasonable job of figuring out where it came from.
As for black holes, yes, nothing is coming out of a black hole's singularity, but the black hole does affect matter outside its event horizon and it is expected that certain black holes will cause matter to be accelerated in such a way that it attains highly energetic characteristics. This is what they mean, or they mean that the neutrino was created in the initial supernova/hypernova that generated the black hole to begin with. Probably the former, as most large black holes are probably generated by accretion over time, and not sudden stellar compression.
Troyusrex: I'm familiar with this use of probability, so allow me to clarify:
There's no need for quantum anything. Probability is simply how one quantifies uncertainty. Here's an example: suppose I flip a coin and you do not see it. I might see it come up heads, and so I would assign a 100% probability that it came up heads. You would assign a probability of 50% to each possible outcome. Who's right? We both are: we're both describing our personal states of awareness about what happened, and they are different.
In this case, the scientists who conducted the experiment are 99% sure that they originated outside our galaxy, presumably because they were able to reject most in-galaxy source explanations. But they cannot be 100% sure.
If you want to learn more, read about Bayesian probability theory.
I have moderation points but unfortunately there is not a +1 Pedant mod.
Please explain for the layman that I am, how can these neutrinos be so energetic ? I thought neutrinos were very elusive particles that don't interact much with matter, and that's why they're so difficult to detect. With that much energy, these neutrinos should interact with matter and do heavy 'damage', à la cosmic particles, no ?
While the angular resolution of IceCube is not GREAT it DOES detect the direction from which the particles it detects came. This happens because, as others pointed out, the neutrino has a momentum. When it slams into a nucleus in the dectector the resulting collision debris carries away that momentum, thus the velocities of those particles, which are easily determined allows an estimate of the velocity of the original neutrino and thus its point of origin in the sky.
Of course the distance it came from is not readily determined, but if there's nothing terribly energetic nearby, then presumably you're looking at something from further away, and when we're talking about PeV neutrinos it has to be VERY energetic, not something we'd likely miss if it was nearby. Remember, we detected 2 neutrinos, that means there were literally trillions more (well, far more than that probably) that simply passed on through the detector with the same energies.
"Malo periculosam, libertatem quam quietam servitutem." -- Jefferson
Not only is he young, he doesn't know how to use the Internet to find out about this "obscure" Fred Sanford.
I can't explain completely, but I can say the energy level has most to do with the momentum of the particle. The faster a particle goes, the more energetic it is. It's a very simplistic explanation, and only one facet of what energizes a particle, but should work for laymen such as us. As for the interaction: if I remember right, neutrinos are very small. They tend to fly between the atoms, which at that scale are very far apart.
The comment modding system exists precisely so you can register your admiration without the rest of us having to hear about your nostriladamus incident.
"Only a Sith deals in absolutes."
Therefore, Obi Wan is a Sith.
/* No Comment */
One of the properties that IceCube takes advantage of is that at higher energies, neutrinos are much more likely to interact with matter and produce particles that it can detect. There's actually a specific energy close to the observed energy of these particles for an electron anti-neutrino where there is a spike in the probability to interact with electrons (6.3 PeV, the Glashow resonance).
Or a -1 Pedant mod
Back when it was thought that neutrinos were massless, it was impossible to believe that there were huge masses of neutrinos surrounding galaxies, as they would have to travel at the speed of light. But now that we know that neutrinos have mass, maybe they could travel a lot more slowly, slow enough to be captured by a galaxy.
Think about it; there are a huge amount of neutrinos created every microsecond in every star in every galaxy, and they hardly interact with anything. They've been accumulating since the big bang.
What happened to the early photons? Those created as the universe first became transparent initially were very high energy indeed, but as the universe has expanded they've lost energy, to the point that they correspond to a temperature of just 3 degrees kelvin. What happens to neutrinos of a similar vintage?
I love Mondays. On a Monday, anything is possible.
The surrounding ice around the detector array acts as a scintillator which generates a minute track of light as the particle passes thru the area. That immediately gives directionality, and energy in eV is computed by summing the light response from the entire detector array during that "event".
Chance. I do not think that word means what you think it means.
D'oh, formatting ate my math symbols. Above should read:
We don't know what the mass of a neutrino is, but we do know they're light (m < 1 eV / c^2). Thus, a neutrino with total energy E = 10^15 eV has a Lorentz factor of gamma = E/m*c^2 > 10^15. Thus beta = v/c = sqrt(1-1/gamma^2) > 1-0.5*10^-30: the neutrino is moving at a velocity within 1 part in 10^30 of the speed of light.
The scary part is when those galaxies insist we return them.
Table-ized A.I.
I'm 40 and live in the UK so I watched Sanford and Son when it was called Steptoe and Son.
From now on in all job interviews I shall state my hobby as "Intergalactic Neutrino Detector" and refuse to work for anyone who doesn't giggle or laugh.
XML is a known as a key material required to create SMD: Software of Mass Destruction
Same thing happened to the neutrinos as happened to the photons. They cooled down. Currently, the neutrino background is ~1.7K, I believe (they're a bit cooler than photons as photons decoupled from matter much later in the early universe than neutrinos did). Neutrinos are, on cosmological scales, treated mostly the same way photons are (they behave in a similar fashion). In any case, the current energy in neutrinos is about ~60% of that in photons, and photons are about 4 orders of magnitude below the energy in dark matter.
We can also predict how the universe would evolve if neutrinos made up the bulk of dark matter. Since it didn't evolve that way, dark matter has to be something else.
"None can love freedom heartily, but good men; the rest love not freedom, but license." --John Milton
If the neutrino does interact inside your body, it's highly unlikely that much of the energy will stay there. The neutrino would transfer some chunk of its 10^15 eV of energy to another particle, such as a proton, in your body. A 10^15 eV proton will also shoot right through you --- smashing up nuclei and creating a big cascading shower of ionizing radiation (the signal this scientific experiment is looking for in the antarctic ice), most of which will escape your body. The "impact" will thus not be a "localized" nudge that you'd feel (like a raindrop), but distributed as radiation damage (not much above background levels, so pretty much harmless) to a large volume of flesh.
Note that this is different than an aunt-fucker, which is sort of like a cross-eyed mother fucker.
Well, ok. Welcome to the XXI century, I have some news for you:
1 - We didn't spray nuclear bombs through the Earth at the 60's. You didn't have to hide in that shelter.
2 - You must have noticed that technology evolved a bit. Unfortunately, space exploration and nuclear fusion didn't move as fast as expected.
3 - We know that neutrinos exist, that they have mass, and that they come in 3 different flavours (and oscilate between them).
4 - But, no, they are not responsible for the dark mass. We still don't know WTF is that.
Rethinking email
Yup. If you want a number, 3 x 10^8 m/s (i.e. the speed of light in a vacuum) works pretty well. A neutrino with that much energy must be going at 99.many-nines % of the speed of light. The actual number of nines depends on the mass.
Even regular solar neutrinos go at essentially the speed of light, as far as the m/s scale goes, and they have energies that are far lower.
We've got poor direct limits on muon neutrino mass from muon neutrino experiments; however, there are other sources of much stronger constraints on neutrino masses. See the "summed mass" limits a few pages down in your reference.
From a Borexino neutrino experiment page at Princeton:
The current limits from cosmological considerations are less than about 0.5 eV (one millionth of the electron mass!) for the sum of the masses of all three neutrino types. The known values of the mass-squared differences imply that the heaviest neutrino type cannot be less massive than about 0.05 eV.
The neutrino is going to go straight through you with a 99.99999% probability.
Actually that is probably not quite true. For the vast majority of neutrinos you encounter on a daily basis (from radioactive decay, relic Big Bang neutrinos, solar etc.) you are completely correct. Indeed for these, as the article states, they will pass through the earth without blinking.
However PeV neutrinos are NOT your everyday neutrino. These guys have such an incredible energy (over 100 times the proton energy in the LHC) that the earth is actually opaque to them. In fact if you look at the IceCube analysis they look for down going neutrino i.e. ones coming in from above despite the problems with the back grounds from cosmic rays. This is because they cannot look for neutrinos which have passed through the earth because, at these energies, there will be none!
The reason for this is that neutrinos interact with matter through W and Z bosons. These have a mass ~80 to 90 times the mass of a proton. The reason that normally neutrinos do not interact is that there is insufficient energy to make a "real" W or Z in the interaction and this heavily suppresses the chance of it happening (due to quantum mechanics it can till occur though). Above a PeV the energy becomes high enough that this energy suppression effect gets a lot smaller and so the chance of interacting becomes a lot higher - eventually becoming slightly stronger than electromagnetism at really high energy when real W's and Z's can be created.
So the upshot of this is that a really high energy neutrino might actually have a reasonable chance of interacting in your body and the article is completely wrong when it describes the earth as basically transparent to these neutrinos...although it is an understandable mistake given that it is transparent to most neutrinos.
Peta-burro-hectares by centon.
Fascism: An authoritarian and nationalistic right-wing system of government and social organization. See also: NAZI's
Nope.
Or at least, they could still only account for a small fraction of observed dark-matter.
http://www.astro.princeton.edu/~dns/MAP/Bahcall/node6.html
Slashdot gets worse every day... Pipedot: News for nerds, without the corporate slant
Mark your preferred definition of probability
[ ] Bayesianism
[ ] Frequentism
[x] Ridiculous frequentism
No, your wife being an aunt doesn't make you an aunt fucker. You would also need to fuck your wife.
Ah yes, please excuse me for not fitting in all the details of my result above. I'm really more an experimentalist than a theorist, so I didn't feel up to calculating the conversion from first principles. But I did have a bit of spare beam time on the schedule. Finding appropriate nano-horses was a bit tricky. My first attempt started with a pony (just a small horse to first order), but its energy output didn't scale very linearly when I chopped it into pieces. I finally ended up using fetal sea-horses for the comparison, though the first couple batches didn't fare well during pumpdown, and left a bit of a mess on the scintillator calorimeters. Anyway, I don't want to bore you with all the sticky details, which I've got to get back to scrubbing off the inside of our vacuum chamber.
When a neutrino impacts a particle in the detector, it creates a cascade of new particles. Since the momentum of the neutrino is conserved in the cascade of particles that can be more easily detected, the direction that the neutrino came from can be determined.
If you want a vision of the future, imagine a youtube comments section scrolling - forever.