Paulibus said:
Where have all the neutrinos created so prolifically by stars over the last 13,8 billion years gone? ...
It's a good general area in which to keep asking questions. If you google "peebles inventory" and look at category 8 "stellar neutrinos" you see:
nuclear burning 10
−6.8
white dwarf formation 10
−7.7
core collapse 10
−5.5
That points to something really astounding. If you add up all the normal everyday neutrino flux from all the fusion in all the stars that have ever existed, it is only about ONE TENTH the amount of neutrinos that have been produced by the comparatively few brief SUPERNOVA events that have occurred.
I think you probably know that the majority of stars are less massive than the sun, which itself is not massive enough to go supernova. Only a tiny minority of stars ever end with a core collapse explosion. But each such event results in a huge burst of neutrinos. That burst is part of what blows off the outer layers of the star, which seems incredible because we think of neutrinos as able to pass through dense material with very low probability of collision. If they don't collide they can't exert any pressure. But in a SN explosion there are so many produced in the core that even with a very very low collision probability enough nus collide, on their way out, that they exert enough force on the outer layers to blow them off. I should fetch a source for that, it sounds so incredible.
Here's an excerpt from the Wikip. article
==quote
http://en.wikipedia.org/wiki/Supernova ==
If the core mass is more than about 15 solar masses then neutron degeneracy is insufficient to stop the collapse and a black hole forms directly with no supernova explosion.
In lower mass cores the collapse is stopped and the newly formed neutron core has an initial temperature of about 100 billion kelvin, 6000 times the temperature of the sun's core.[71] 'Thermal' neutrinos form as neutrino-antineutrino pairs of all flavors, and total several times the number of electron-capture neutrinos.[72]
About 1046 joules, approximately 10% of the star's rest mass, is converted into a ten-second burst of neutrinos which is the main output of the event.[70][73] The suddenly halted core collapse rebounds and produces a shock wave that stalls within milliseconds[74] in the outer core as energy is lost through the dissociation of heavy elements. A process that is not clearly understood is necessary to allow the outer layers of the core to reabsorb around 10
44 joules[75] (1 foe) from the neutrino pulse, producing the visible explosion,[76] although there are also other theories on how to power the explosion.[70]
==endquote==
Anyway, I think we should stay interested in neutrino astronomy/cosmology for a while. I have a hunch it will open the door to some new physics.
