A bunch of pop science articles just popped up talking about new high-energy neutrino detection. See this article, published today, for example. The answer to this question says that the source of high-energy neutrinos is still an open question, however, these news articles seem to be saying that there was a breakthrough in understanding where they come from. A comprehensive summary of the results and their implications, plus a link to an arXiv post, would be superb.
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3$\begingroup$ You may find some interest in the Science article. $\endgroup$– Daniel UnderwoodCommented Jul 13, 2018 at 1:41
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High energy Neutrinos also sometimes referred to as astrophysical neutrinos have previously been observed, but a source has never been well localized. For reference on some useful past work, this article talks about the relevant detection mechanisms and implications as well as some of the predictions: https://arxiv.org/pdf/1801.01551.pdf.
The newest observations (outlined in this paper but not on arxiv right now: http://science.sciencemag.org/content/early/2018/07/11/science.aat2890) are showing strong evidence that the event detected by IceCube in September 2017 is localized to a certain Blazar, Blazar TXS 0506+056. Blazars are very compact quasars (quasi-stellar radio source) that are associated with supermassive black holes at the center of giant galaxies.
Blazars are amongst the most energetic phenomena in the universe and as such have been hypothesized to be a source of astrophysical neutrinos for a long time. Blazars are formed in the same way that all active galactic nuclei (AGNs) are formed at the center of a galaxy around a super massive black hole (SMBH). As gas, dust and occasionally stars spiral inwards towards the SMBH, a hot accretion disk is formed which releases a large amount of energy in the form of photons, electrons, positrons and other elementary particles.
Perpendicular to the plane of the disc, a pair of jets transport energetic plasma away from the AGN. The jet is formed due to large winds and turbulence as well as magnetic fields near the center of the AGN. This jet is where it is hypothesized that we see these astrophysical neutrinos. These jets move at very high velocities with much of the plasma reaching speeds of 95-99% the speed of light.
The new observations which combined multiple wavelengths and many observational devices, have successfully localized the detection to an area of $\sim 1\ \text{arcmin}^2$ and therefore successfully isolates the observation to within the area of influence of a single blazar.
The next questions that must be asked are how the source is creating these neutrinos, primarily whether it is from a relativistic jet and whether or not the jet is baryonic. Now that we know what to observe to find them, it will be easier to continue the search for more information about their origin.
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1$\begingroup$ A better description of a blazar would be useful, particularly the orientation. $\endgroup$– ProfRobCommented Jul 13, 2018 at 6:27
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$\begingroup$ I added some more info on blazars. Feel free to comment, submit and edit or start a new answer if you have more input on useful information I am missing. I am not an expert on this subject but I work with researchers who are in this field so I have a decent idea of the big picture but am probably missing some specifics. $\endgroup$ Commented Jul 13, 2018 at 7:14
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$\begingroup$ The whole point is that a blazar is an AGN where the jet is basically directed towards us. $\endgroup$– ProfRobCommented Jul 13, 2018 at 15:33