Astronomers Detected a 'Ghost Particle' and Tracked It To Its Source (space.com) 47
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.
About Time (Score:5, Funny)
I'm just glad IceCube is doing something useful with the rest of his life.
Re: About Time (Score:1)
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IceCube knows which joint blazars at
IceCube 'scopes to point interphasers at
Neutrino made no force, still snapped 'em
IceCube nails the source, distilled fat datum
word
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Fuck tha positron! Detectin straight from the underground
How did they find the source? (Score:2)
I am wondering how they managed to find the source.
Does the detector give them a vector of direction? After that how many calculations are needed? I would think you would have to figure in Earth's rotation, Earth's orbit, the sun's orbit, and the galaxy's path. Presumably the neutrino was traveling somewhat below C so there must be an adjustment there. All that to get a direction to look. Am I off base on this or is it not that complex?
All I can say is Astronomers must have fiendish concentrati
Re:How did they find the source? (Score:5, Informative)
Re:How did they find the source? (Score:4, Informative)
I've just quickly looked at the Science article. Here [cloudfront.net] 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.
Re:How did they find the source? (Score:4, Insightful)
Yes, they can track the neutrino through the detector, and that gives them a direction. In this case the single detection had a 90% error box of 1.6 degrees x 0.8 degrees. Gamma ray instruments looking in this direction detected increased activity of the blazar, with a combined significance of 3 sigmas. Adding the previous neutrino detections from this apparent source allows even more accurate source determination.
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Re:How did they find the source? (Score:5, Informative)
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 [cloudfront.net].
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.
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But how can they observe a direction unless the same neutrino interacts with more than one detector? Is that the chance encounter they are waiting for?
And once the neutrino interacts with the first detector, isn't it changed (I would think destroyed)?
The neutrinos do not interact with the detectors. Instead they react with the hydrogen in the water to produce charged leptons (electrons, muons, or taus depending on the neutrino type) which then produce Cherenkov radiation as they move through the ice and the detectors see that. Since momentum is conserved, the leptons move in approximately the same direction as the neutrino was.
https://pippagoldenberg.wordpr... [wordpress.com]
Neutrinos are electrically neutral leptons, and interact very rarely with matter. When they d
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However, incredibly high energy neutrinos like this are not the ones you want to use because, even with a really distant source, the
See daughter particles, not neutrinos (Score:4, Interesting)
Yes, they can track the neutrino through the detector, and that gives them a direction.
Not quite - we cannot see neutrinos directly. What we see are the particles they produce when they interact in the ice. At these energies, the boost of the particles created is so large that it basically has the same direction as the original neutrino. However, if the neutrino produces an electron or a tau (unless it is really high energy) this produces a cascade of particles which we see as a point source that has little to no pointing. Only when the neutrino produces a muon do we get a long track that we can point back to the source.
Re:How did they find the source? (Score:5, Informative)
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.
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However, since you were performing these calculations in 1989, I'm still kinda wondering why it took them so long to do this. Are these calculat
Track Pointing (Score:4, Informative)
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.
Sorry if this is a dumb question, but... (Score:2)
How could they possible track where the neutrino came from given their incredibly sporadic observability for measurement, a spinning earth, a spinning solar system, a spinning arm of the milky way - and 4 billion light years distance?
The article says they notified astronomers of a patch of sky that was a candidate for the source - how could this be correct if our galaxy is spinning?
Again, apologies if this is a dumb question, but thank to Einstein I think everything's relative - especially the orientation o
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how fast does the earth spin for an object going essentially lightspeed? Not at all, essentially. A distant galaxy subtends an incredibly minute portion of the sky, irrelevant its spin, all components of a photon or neutrinos velocity will sum up to lightspeed in one direction.
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You seem to be forgetting that the neutrino has been traveling to us for, apparently, 4 billion years. The speed at which galaxies move over 4 billion years is significant - not to mention the rotation of our galaxy relative to the orientation of the speculated galaxy is huge.
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BTW, it takes a little over 200 million years to completely rotate around the center of our galaxy (i.e. a 'cosmic year')