Hawking radiation accounting for dark matter?

Question

We don't know what form matter takes when it is ejected from a black hole via Hawking Radiation, but what if its dark matter?

I don't really like these "What if" questions with no evidence but it was mentioned on a post on Space.com and it got me thinking... Super Massive Black Hole at the center of nearly every galaxy... nearly every galaxy requires dark matter to allow its farther stars to orbit the center with the same angular velocity as inner stars... hmmm?

I guess there would be hole in this theory if there was a smaller galaxy with no Super Massive Black Hole but a large amount of dark matter. So, does anyone know of a galaxy without a SMBH but has been observed to have proportionally just as large amount of dark matter as a large galaxy?

Answer 1

Black Holes only exist in people's heads.  They are not with us here on earth.  Develop a new real source of propulsion for cars and become the world's hero.  Stop the use of plastics which are choking our oceans and fish.  

Answer 2

When black holes evaporate, they most probably *do* eject dark matter. But the amount of Hawking radiation in the universe is laughably minuscule. It does not account for the dark matter problem.

SMBH's are difficult to detect unless there is infalling matter. So there are lots of galaxies where thy have not been detected yet, but that doesn't mean that they are not there. Whether there exist galaxies without central black holes is unknown.

SMBH's themsselves are woefully insufficient to provide the gravity observed in galaxy rotation curves, so their equally massive radiation products would be exactly as insufficient.

Answer 3

Originally, dark matter was needed to get the rotation rates of galaxies to agree with reality.  You measure the rotation rate of a galaxy, and add up all the mass of the stars, gas, dust, black holes, and such.  You find you've gotten maybe 25% of what you need to make the galaxy turn at the rate you've observed.

So, no.  Black holes are not dark matter.  There are hundreds of other things that aren't dark matter either.

Now that we've directly detected dark matter, it's not nearly so mysterious.

And now that we have orbiting xray telescopes, black holes aren't so hard to detect.