Neutrino flux at event horizon

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Discussion Overview

The discussion revolves around the mass accretion of a black hole at the center of our galaxy due to neutrino flux, exploring the implications of neutrino mass and flux rates over time. It includes calculations and considerations of the physical properties of neutrinos and black holes.

Discussion Character

  • Exploratory, Technical explanation, Mathematical reasoning

Main Points Raised

  • Corby inquires about the mass a black hole could accrete in a year based on an average neutrino mass of 2.0 eV and the neutrino flux passing through it.
  • Another participant suggests calculating the product of neutrino flux and the black hole's cross section, while noting that a neutrino mass of 2 eV exceeds cosmological limits and that stellar neutrinos primarily possess kinetic energy.
  • A subsequent post provides specific values for neutrino mass (0.2 eV), black hole radius (13 million kilometers), and area (2.12E+17 square centimeters), leading to a calculated total neutrino flux of 2.12E+28 per second, resulting in an estimated mass increase of 238 grams per year.
  • Another participant comments that the neutrino flux is reduced away from stars, but the energies are higher, asserting that even a significantly larger mass increase would be negligible in terms of the black hole's overall mass.

Areas of Agreement / Disagreement

Participants express differing views on the significance of the mass increase due to neutrino accretion, with some suggesting it is negligible while others provide calculations that indicate a measurable amount, though still small relative to the black hole's mass.

Contextual Notes

There are assumptions regarding the average neutrino mass and flux values, as well as the conditions under which these calculations are made, which may affect the outcomes. The discussion does not resolve these uncertainties.

Who May Find This Useful

Individuals interested in astrophysics, particularly those studying black holes and particle physics, may find this discussion relevant.

corbymite
Hi, Assuming an average Neutrino mass of 2.0 Electron volts how much mass will a black hole with an event horizon the size of the one at the center of our galaxy accrete in a year? I've seen estimates of how many Neutrinos pass through our bodies each second and it seems like the mas would really add up over the surface area of a black hole.

Cheers,
Corby
 
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What do you get if you take this neutrino flux and multiply it with the black hole cross section? Compare it to the mass of the black hole.

2 eV is above the limits from cosmology, by the way. Stellar neutrinos will have most of their energy as kinetic energy and the neutrino mass is irrelevant for them.
 
OK use .2 Electron volts, a radius of 13 million kilometers, and an area of 2.12E+17 square Centimeters. If the Neutrino flux is say 1E+11 per square Centimeter then the total Neutrino flux would be 2.12E+28 per second or 6.68E+35 per year. Looks like this only would increase the black holes mass by 238 grams! Of course my values could be way off?
 
The neutrino flux is smaller if you are not near a star, but the neutrino energies are higher. Anyway, the mass is completely negligible, even 20 orders of magnitude more wouldn't have a notable effect.
 

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