Read more here -> interactions.org/press-release/our-galaxy-seen-through-new-lens-neutrinos-detected-icecube
See also comparison picture of the Milky Way as depicted with visible light and with neutrinos
The posted image is a composite of both; the neutrino depiction of the galaxy is in blue
What is actually used to capture neutrino images? Isn’t their whole thing that they basically don’t interact with matter almost at all?
1 cubic kilometer of ice on the south pole
More accurately, the IceCube Neutrino Observatory is a series of strings of optical sensors embedded in the Antarctic ice. They detect Cherenkov light emitted by super-high energy neutrinos that pass through the ice.
There are many other neutrino detectors that are much smaller, but those are designed for detecting lower energy neutrinos from the sun or nuclear reactors. IceCube was designed for extragalactic neutrinos with much, much higher energies which required making it so large.
Even more accurately, the neutrinos themselves cannot create Cherenkov radiation, as they don’t have electric charge. But every once in a while a neutrino interacts with the matter in the ice, and thus creates secondary particles, some of which will (a) have charge and (b) move faster than the local speed of light in the ice, and this will create Cherenkov radiation.
The main reason it is so large is simply that it can detect more neutrinos than smaller ones, but the construction and distance between sensors and thus its sensitivity to certain neutrino energies is in a way also a function of its size.
Neutrinos can interact with matter via the weak force, which is so weak and short ranged that most neutrinos incident on matter just pass through it. However, you can imagine if a HUGE chunk of neutrinos falls on matter, at least a few are bound to interact, statistically speaking. These interactions are like collisions, and the collision may result in generation of new particles. If these new particles are energetic enough, they emit a special type of radiation, which can be detected through sensors. So, you’re not directly capturing neutrinos, but are making the inference that they are there, because you know a weak force interaction has taken place if your sensor goes off. And to make sure something like cosmic radiation doesn’t affect detection, this particular detector is isolated under a huge sheet of ice in Antarctica.
I recall reading something - maybe it was from xkcd? - about how close to a supernova you’d have to be for the neutrino radiation alone to deliver a lethal dose. I think the conclusion was about 1au away, probably well inside the radius of the star that was exploding.
Since i believe supernovae are one of the few significant sources of neutrinos, to have to be so close to the source that you would have long since died of other causes before you could absorb significant energy from neutrinos speaks to how little they actually interact with matter.
My favorite fact from that article (indeed xkcd) isn’t about neutrinos though, but this:
Which of the following would be brighter, in terms of the amount of energy delivered to your retina:
- A supernova, seen from as far away as the Sun is from the Earth, or
- The detonation of a hydrogen bomb pressed against your eyeball?
The answer is the supernova, by 9 orders of magnitude. So the supernova at the Sun’s distance is about a billion times brighter than a hydrogen bomb pressed against your eyeball.
Oh i had forgotten that! Thanks for reminding me!
So would that actually make a difference to the speed at which you’re incinerated?
The neutrinos? According to the article you’d probably be inside the star to be at the neutrino-lethal distance, so you’ll clearly be dead before it even goes supernova. :-)
If it were still lethal at a distance you could survive, my slightly informed guess is that it could matter, as AFAIK supernovas tend to release the neutrinos before most of the light.
However I have no idea for how long the main part of the neutrino flood last or how long it’ll take to kill you, could be anything from less than a second to minutes or hours, at which time you’d certainly be dead from the rest of the supernova.
Between this and NANOgrav, what an insane day for astronomy, cosmology, physics.
Two mind-blowing breakthroughs in one day.Here is an image of neutrinos emitted from the sun taken THROUGH the Earth!
