Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!

 


Forgot your password?
Close
typodupeerror
×
Space Science

Scientists May Have Detected Neutrinos From Another Galaxy 151

Posted by timothy from the taste-nearly-identical dept.
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."
This discussion has been archived. No new comments can be posted.

Scientists May Have Detected Neutrinos From Another Galaxy More

Scientists May Have Detected Neutrinos From Another Galaxy

Comments Filter:

  • in joules. please (Score:1)

    by Anonymous Coward

    What will it be in joules, 1 peta electronVolt?
    Could I boil a kettle on this neutrino (potentially)?

    • Re:in joules. please (Score:5, Informative)

      by click2005 ( 921437 ) * on Thursday April 25, 2013 @02:13PM (#43548715)

      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

      • Re:in joules. please (Score:5, Funny)

        by P-niiice ( 1703362 ) on Thursday April 25, 2013 @02:22PM (#43548805)
        are you not familiar with the upside the head measurement of force? measured in FredSanfords

      • But can we harness that power to make magic?

      • Re:in joules. please (Score:4, Informative)

        by Rene S. Hollan ( 1943 ) on Thursday April 25, 2013 @02:46PM (#43549051)

        160 uJ, give or take.

      • Re: (Score:1)

        by trum4n ( 982031 )
        But what is that in m/s?

        • Re: (Score:2)

          by ceoyoyo ( 59147 )

          Lots. You'd have to know the neutrino mass to calculate it precisely.

          • Re: (Score:1)

            by trum4n ( 982031 )
            Lots as in near light speed?

            • Re:in joules. please (Score:4, Informative)

              by ceoyoyo ( 59147 ) on Thursday April 25, 2013 @04:21PM (#43550081)

              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.

          • Actually, rounding to the nearest 10^-20 m/s, it would be 299,792,458 m/s.

            We don't know what the mass of a neutrino is, but we do know they're light ( 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.

            • 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.

              • We don't know what the mass of a neutrino is, but we do know they're light (m
                Not quite - IceCube looks for muon neutrinos and these have a mass limit of 0.19 MeV/c^2 [lbl.gov]. The lowest mass constraint is actually 2 eV/c^2 for electron anti-neutrinos from tritium decay spectrum measurements.

                • Re:in joules. please (Score:4, Informative)

                  by femtobyte ( 710429 ) on Thursday April 25, 2013 @04:29PM (#43550149)

                  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 [princeton.edu]:

                  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.

              • We don't know what the mass of a neutrino is, but we do know they're light

                I thought that was photons.

      • Interesting. So if one of these neutrinos hits me, will I feel it? I understand due to electroweak unification (of these very high energy neutrinos) it will cause interaction with our body.

        • The neutrino is going to go straight through you with a 99.99999% probability. But if it does stop inside your body and deliver its energy, it should give of one hell of a whack. Wonder if you would be able to feel that?
          • 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 "loca

          • Not your "everyday" Neutrino (Score:5, Informative)

            by Roger W Moore ( 538166 ) on Thursday April 25, 2013 @04:30PM (#43550167) Journal

            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.

            • Putting some rough numbers on this:
              At lower energies, neutrino cross sections [cupp.oulu.fi] scale roughly proportional to energy with sigma/E ~ 10^-38 cm^2 / GeV. At high energy [fnal.gov], the cross section at 10^15 eV is around 10^-33 cm^2. Thus, compared to an ~1MeV neutrino with a cross section on the order of 10^-41 cm^2, the PeV neutrino has ~10^8 greater cross section. You are about 10^-7 the thickness of the earth. Thus, you are roughly 10x more likely to be hit by a PeV neutrino passing through than the earth is to be hit

      • It’s very roughly equivalent to the energy of a raindrop hitting you on the head

        Does that mean that hitting people repeatedly with PeV neutrinos is a form of torture, too? Damn, the current administration won't be amused.

    • Re: (Score:2)

      by hpa ( 7948 )
      1 PeV is approximately 160 microjoule.

  • IceCube? (Score:5, Funny)

    by excelsior_gr ( 969383 ) on Thursday April 25, 2013 @02:21PM (#43548791)

    WORD! That's a fly name for an experiment dawg!

  • Seriously, I'm getting very annoyed when particles or chunks of meteorites are somehow identified as coming from some specific place... WTF?

    A Neutrino is a Neutrino. It has no identifying characteristic. The nature of a single variable, the charge, may describe the sort of event the particle originated from, but hardly any specificity of the actual event or where that event took place. At least a chunk of space rock might be comprised of minerals that are similar to those from a neighboring planet (though t

    • Re: (Score:1)

      by Jicehix ( 778864 )

      anything happening inside the event horizon of a black hole doesn't really matter...

      Are you saying matter doesn't matter ?

    • Re: (Score:1)

      by Anonymous Coward

      So many words for all of them to be so wrong.

    • Re: (Score:1)

      by Anonymous Coward

      A Neutrino is a Neutrino. It has no identifying characteristic.

      Way to be oblivious there. If they are detecting a passing neutrino, then the particle has a velocity, right? So, a finite mass moving at a finite velocity has an energy, which is different than that of the same particle moving at a different speed (independent of direction). And if the energy of two identical particles can be different, then you can identify a difference between them. Which is kinda the whole point of TFA, and the IceCube experiment itself. The scientists try to understand all the dat

    • Its the nrg. The point of origin can be norrowed down by eliminating sources that don't have that amount of nrg. Simple.

    • Re:ID Tags on the particles? (Score:5, Interesting)

      by tnk1 ( 899206 ) on Thursday April 25, 2013 @02:56PM (#43549171)

      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.

    • Re:ID Tags on the particles? (Score:5, Insightful)

      by Giant Electronic Bra ( 1229876 ) on Thursday April 25, 2013 @03:09PM (#43549269)

      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.

    • 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".

  • Finally, (Score:3)

    by medv4380 ( 1604309 ) on Thursday April 25, 2013 @02:37PM (#43548955)
    but doesn't it correlate to any possible event yet, or are we just guessing about were it came from?

    • Re:Finally, (Score:4, Informative)

      by PhxBlue ( 562201 ) on Thursday April 25, 2013 @02:52PM (#43549109) Homepage Journal
      If it's a supernova event, hopefully we'll spot it in the next day or two.

  • these neutrino's (Score:3)

    by zlives ( 2009072 ) on Thursday April 25, 2013 @02:51PM (#43549101)

    These neutrino's were not the neutrinos they were looking for

  • it must have been a good day.

  • Please explain : aren't neutrinos, ah...'neutral'? (Score:3, Interesting)

    by Altesse ( 698587 ) on Thursday April 25, 2013 @03:01PM (#43549213) Homepage
    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 ?
    • 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.

    • Re: (Score:3, Informative)

      by Anonymous Coward

      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).

    • Because neutrinos don't interact much, there are very few ways for them to release their kinetic energy, even when there is a lot of it. Neutral refers to the fact that neutrinos don't interact electromagnetically. They also don't interact via the strong force, and gravitational interaction of anything on this scale is negligible (although neutrinos are believed to have very small but nonzero masses). That leaves only weak nuclear interactions, which happened to occur twice in this detector.

    • Re: (Score:1)

      by Anonymous Coward

      The bigger question is how did a chargeless neutrino particle get accelerated to that energy. Most current theories like 2nd order Fermi acceleration act on charged particles bouncing among moving plasma shock waves. Imagine a ping pong ball bouncing between between two walls in a cubic room that are approaching each other. There's no limit to how fast the ball can go because upon each bounce it gains a bit more speed from the wall and it doesn't matter that the ball speed is greatly higher than the wall

  • So why would a neutrino from a gamma ray burst in a galaxy far far away have more energy than one from a gamma ray burst within our own galaxy? And then there's the probability of being in the path of one in our own galaxy vs outside....

  • Could dark matter be super low-energy neutrinos? (Score:5, Interesting)

    by Thagg ( 9904 ) <thadbeier@gmail.com> on Thursday April 25, 2013 @03:35PM (#43549539) Journal

    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?

  • From the galaxy called, Neutrinos With Attitude!

  • Since when we do know for sure that neutrionos exists?

    • Re:Neutrinos??? (Score:4, Interesting)

      by marcosdumay ( 620877 ) <(marcosdumay) (at) (gmail.com)> on Thursday April 25, 2013 @04:16PM (#43550031) Homepage Journal

      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.

      • And 5 - No, there were so many attempts to "catch" the elusive neutrino, with zero results.
        Sorry pal, you are apparently too old and are taking the wet dreams for reality.

    • Since when we do know for sure that neutrionos exists?

      Since 1987 when they measured it [wikipedia.org]?

      These two [wikipedia.org] guys [wikipedia.org] share a Nobel for it.

      Seriously, we've known they have mass for 25 years now. And you're asking how we know we know they even exist?

  • A guy with a name like "Dar waiter" called (Score:3)

    by Tablizer ( 95088 ) on Thursday April 25, 2013 @03:54PM (#43549781) Journal

    The scary part is when those galaxies insist we return them.

  • Intergalactic Neutrino Detector (Score:3)

    by H0p313ss ( 811249 ) on Thursday April 25, 2013 @04:01PM (#43549875)

    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.

  • At best we can only detect vector and derived energy, but we don't know where they came from or if they actually came from dark matter space in an area we don't traditionally think of as an origin point.

  • Say WHAT? There isn't even consensus that these cosmic neutrinos are either neutrinos or cosmic, much less where they come from. Extra-galactic is reasonable, but I would put it more in the 20-30% range, not 99%.

    From the ABSTRACT of the actual paper [arxiv.org]:

    Though the two events could be a first indication of an astrophysical neutrino flux, the moderate significance and the uncertainties on the expected atmospheric background from neutrinos produced in the decay of charmed mesons do not allow for a firm conclusion

Slashdot Top Deals

Ocean: A body of water occupying about two-thirds of a world made for man -- who has no gills. -- Ambrose Bierce

Close