Black Hole Explanation for Dark Matter

[noxid]

Could the observed missing mass of the universe/galaxies be a result of unobserved black holes or other dense but faint objects

[imatfaal]

Could the observed missing mass of the universe/galaxies be a result of unobserved black holes or other dense but faint objects

 

Unlikely - firstly there would need to be a huge number (numerically more than the stars) and secondly black holes (despite the name) are not very dim.

 

A black hole by itself - completely isolated - would be completely black but they never are by themselves. Their huge density means that the the gravitational forces and gradients are very very large in the vicinity, this means that matter falling into them accelerates to very high speeds, and in order to conserve angular momentum the infalling matter spins in a disc and creates jets outwards along the axes. These accretion discs are very hot (due to stuff bumping into each other) and they glow with ultraviolet and x-ray light, the jets can sometimes create the highest energy gamma radiation making some black holes the brightest things around.

[Janus]

Another reason against this idea is, that for that many black holes to exist now, then nucleosynthesis during earlier ages in the universe would have resulted in a different relative distribution of elements in the universe. In other words, by measuring the relative abundances of elements in visible universe, we can set an limit as to how many black holes it can have.

[noxid]

Another reason against this idea is, that for that many black holes to exist now, then nucleosynthesis during earlier ages in the universe would have resulted in a different relative distribution of elements in the universe. In other words, by measuring the relative abundances of elements in visible universe, we can set an limit as to how many black holes it can have.

can you explain this a little more

[Mordred]

Every element has a unique spectral signature. This allows us to measure those elements as well as their distribution.

 

BB nucleosynthesis based on particle physics models and the thermodynamics of said elements allows us to approximate the available material for star formation. This in turn provides a means to estimate the number of Black holes. Every particle can be estimated by the above.

 

Baryonic matter (visible matter and standard model of particles) with measurements only accounts for roughly 3% of the mass of the universe.

 

If the missing mass were in the form of Black holes we wouldnt have any baryonic matter left outside of black holes.

In point of detail although the BH itself isn't visible. Its influences upon the thermodynamics of the interstellar and intergalactic material is detectable. see Imaatsfal post.

 

Rather than rely on My and Janus say so... here is an article that details the energy budget.

 

 

http://arxiv.org/pdf/astro-ph/0406095v2.pdf "The Cosmic energy inventory"

 

these two articles give a good coverage of nucleosynthesis.

 

http://arxiv.org/pdf/hep-th/0503203.pdf "Particle Physics and Inflationary Cosmology" by Andrei Linde

http://www.wiese.itp.unibe.ch/lectures/universe.pdf:"Particle Physics of the Early universe" by Uwe-Jens Wiese Thermodynamics, Big bang Nucleosynthesis

Edited August 8, 2016 by Mordred