
The New Era of Multimessenger Astronomy - okket
https://multimessenger.desy.de/
======
Tepix
This is a fascinating scientific discovery and i love the visualization on
their website!

13 observatories and 5 satellites contributed to the discovery.

If you are interested in the topic and understand German, check out Episode
RZ073 of Raumzeit Podcast, topic: IceCube Neutrino Observatory which covers
this (no affilication).

[https://raumzeit-podcast.de/2018/06/06/rz073-icecube/](https://raumzeit-
podcast.de/2018/06/06/rz073-icecube/)

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dandare
Can someone please explain?

> Neutrinos are the lightest and least interacting of all known particles.
> They easily fly through planets, stars and whole galaxies, completely
> unaffected. Because of this, neutrinos can reach us from extreme
> environments in the cosmos, inaccessible by other messengers.

Two slides later:

> It spies for flashes of light generated when a cosmic neutrino hits an atom
> of the ice, sparking a cascade of secondary particles that leave their trace
> in the detector.

So why do neutrinos interact with atoms of ice in detectors but pass through
planets and galaxies?

~~~
stephengillie
There are so many of them, that occasionally one must interact with other
matter. One in a billion billion billion, sure, but there are trillions of
trillions of trillions of neutrinos flying past over a period of time.

Neutrinos are normally created by beta decay[0]. So when they are detected,
are they going through "beta reabsorbtion"? Does the (anti-)neutrino hit an
electron, form a W boson, then collide with a proton to form a neutron? Or is
there another interaction that causes the light?

[0][https://en.wikipedia.org/wiki/Beta_decay](https://en.wikipedia.org/wiki/Beta_decay)

~~~
welterde
The primary channel is the inverse beta decay where an anti-neutrino interacts
with a proton to produce a neutron and a positron (via a W boson like you
said). It can also just scatter of an electron (via either the W or the Z
boson).

But the important point is that it's only via the weak interaction (meaning
only via the W^\pm and Z^0 bosons).

~~~
stephengillie
At first, it sounds like an anti-neutrino can "spontaneously" emit a positron
to form a W boson, instead of finding an electron.

On re-reading, it's like the neutrino "bumps" the positive charge out of the
proton. Like the neutrino interacting with a down quark will convert them into
an up quark and a positron.

Edit: _Inverse beta decay, commonly abbreviated to IBD, is a nuclear reaction
involving electron antineutrino scattering off a proton, creating a positron
and a neutron.

... The IBD reaction can only be initiated when the antineutrino possesses at
least 1.806 MeV of kinetic energy (called the threshold energy). This
threshold energy is due to a difference in mass between the products (
positron and neutrino ) and the reactants ( antineutrino and proton ) and also
slightly due to a relativistic mass effect on the antineutrino. Most of the
antineutrino energy is distributed to the positron due to its small mass
relative to the neutron. _

[https://en.wikipedia.org/wiki/Inverse_beta_decay](https://en.wikipedia.org/wiki/Inverse_beta_decay)

To state the obvious, since the Neutrino is massless, its energy can only come
from momentum. Hence the distribution of the 1.806 MeV from the Wiki article
above:

    
    
      P+ to N:  1.293 MeV
      Positron: 0.511 MeV
      total:    1.804 MeV (rounding error?)

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SiempreViernes
Man, this is really high production value website that Ice Cube has managed to
produce. Would love to have one about the real multi-messenger breakthrough of
GW170817!

Now we get one about a milestone for a particular experiment instead : /

