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Astronomers Detected a 'Ghost Particle' and Tracked It To Its Source (space.com)
An anonymous reader quotes a report from Space.com: Astronomers have traced a high-energy neutrino to its cosmic source for the first time ever, solving a century-old mystery in the process. Observations by the IceCube Neutrino Observatory at the South Pole and a host of other instruments allowed researchers to track one cosmic neutrino to a distant blazar, a huge elliptical galaxy with a fast-spinning supermassive black hole at its heart. And there's more. Cosmic neutrinos go hand in hand with cosmic rays, highly energetic charged particles that slam into our planet continuously. So, the new find pegs blazars as accelerators of at least some of the fastest-moving cosmic rays as well. Astronomers have wondered about this since cosmic rays were first discovered, way back in 1912. But they've been thwarted by the particles' charged nature, which dictates that cosmic rays get tugged this way and that by various objects as they zoom through space. Success finally came from using the straight-line journey of a fellow-traveler ghost particle.
On Sept. 22, 2017, [...] IceCube picked up another cosmic neutrino. It was extremely energetic, packing about 300 teraelectron volts -- nearly 50 times greater than the energy of the protons cycling through Earth's most powerful particle accelerator, the Large Hadron Collider. Within 1 minute of the detection, the facility sent out an automatic notification, alerting other astronomers to the find and relaying coordinates to the patch of sky that seemed to house the particle's source. The community responded: Nearly 20 telescopes on the ground and in space scoured that patch across the electromagnetic spectrum, from low-energy radio waves to high-energy gamma-rays. The combined observations traced the neutrino's origin to an already-known blazar called TXS 0506+056, which lies about 4 billion light-years from Earth. The IceCube team also went through its archival data and found more than a dozen other cosmic neutrinos that seemed to be coming from the same blazar. These additional particles were picked up by the detectors from late 2014 through early 2015. The findings are reported in two separate studies published in the journal Science.
On Sept. 22, 2017, [...] IceCube picked up another cosmic neutrino. It was extremely energetic, packing about 300 teraelectron volts -- nearly 50 times greater than the energy of the protons cycling through Earth's most powerful particle accelerator, the Large Hadron Collider. Within 1 minute of the detection, the facility sent out an automatic notification, alerting other astronomers to the find and relaying coordinates to the patch of sky that seemed to house the particle's source. The community responded: Nearly 20 telescopes on the ground and in space scoured that patch across the electromagnetic spectrum, from low-energy radio waves to high-energy gamma-rays. The combined observations traced the neutrino's origin to an already-known blazar called TXS 0506+056, which lies about 4 billion light-years from Earth. The IceCube team also went through its archival data and found more than a dozen other cosmic neutrinos that seemed to be coming from the same blazar. These additional particles were picked up by the detectors from late 2014 through early 2015. The findings are reported in two separate studies published in the journal Science.
There was a link to it in the story: https://www.space.com/41147-co...
I've just quickly looked at the Science article. Here is the plot you want. (I hope that doesn't need institutional access to view.)
The 90% confidence contour for arrival direction of the neutrino is roughly elliptical with length/width (major/minor axis) about 1.5 degrees and 1 degree - so you are right, the direction of the neutrino has quite large uncertainty.
The high energy gamma rays detected by the MAGIC telescopes (in response to the neutrino triggered alert) have 95% confidence ellipse about 0.1 degree diameter. A previously identified gamma ray source has 95% confidence ellipse about 0.03 degrees in diameter. All are consistent with the location of TXS 0506+056.
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The hard bit is 'given the timings and intensities of flashes I detected in my detector, what was the direction of the primary neutrino?' That gives a direction relative to the detector array, then all you need to know is the sidereal time and location on Earth of the detector to turn it into a direction on the sky, with some simple addition of angles. The uncertainty in neutrino direction is on the order of a degree (I've commented elsewhere on this) so effects much smaller than a degree can be ignored.
I did calculations quite similar to this for a cosmic ray experiment in my MSc thesis in 1988/89. I used likelihood calculations to determine direction and uncertainty in direction. I expect this experiment does the same.
Quattuor res in hoc mundo sanctae sunt: libri, liberi, libertas et liberalitas.
But when they issued the alert, other telescopes started looking at that 1.6 by 0.8 degrees. Some telescopes detected high energy gamma rays in the area, and those telescopes had much better accuracy. And there was a previously detected gamma ray source, located with even higher spacial accuracy, within that error ellipse. And the galaxy in turn was within this smallest error ellipse.
Here is the picture.
Even the smallest error ellipse probably contains a bunch of galaxies. I presume that just one of them looked 'weird' in some way, and so was assumed to have interesting activity at its core. I haven't taken the time to drill down that far into their identification process.
Quattuor res in hoc mundo sanctae sunt: libri, liberi, libertas et liberalitas.
I am wondering how they managed to find the source.
When this neutrino interacted with the ice it converted itself into a muon which is a heavy cousin of the electron that can travel a huge distance through the ice at these energies. So what we saw was a track of light that moved through the whole ~1km width of the detector that we could then point back to a region of the sky. So we do not detect the neutrino itself only what it produces after an interaction and, if it produces a muon, we have a good long track if there is enough energy.
The light from the track is because the muon has a charge and travels incredibly close to the speed of light in vacuum. However, the speed of light in ice is quite a bit less than the speed in vacuum and so the muon emits a shockwave cone of light called Cherenkov radiation just like a supersonic aircraft emits a conical sonic shockwave of sound called the sonic boom.