# Percentage of stars that become black holes

1. Feb 10, 2013

### revo74

What percentage of stars become black holes? I tried to find this information through Google searching and the only thing I could find was a statement that said less that 1 in 1,000 stars in our Milky Way galaxy have enough mAss to become a black hole.

2. Feb 10, 2013

### Mordred

I don't know what the percentage would be but if the value you googled is accurate and the universe is homogeneous and isotropic. Then 1 in 1000 stars would be 0.1%

3. Feb 10, 2013

### Chronos

An interesting question that is not easily answered. Classically, a black hole is one possible outcome of a core collapse event. It takes an estimated 3 solar masses of remanant material to exceed neutron degeneracy pressure and allowing for a black hole to form. Unfortunately, there is nothing tidy about a core collapse supernova. They tend to shed large amounts of mass before going boom and the explosion itself is assymetrical, expelling appreciable amounts of the remaining mass. So, the minimum mass for a black hole precursor star is highly uncertain. We know that about 8 solar masses is the minimum required for a core collapse event. To the best of our knowledge, a neutron star results when the precursor star is less than about 20 solar masses. It gets rather muddy after that. In theory a star much more massive should collapse directly into a black hole. Observation, however, does not affirm theory as stars in excess of 20 solar masses are known to have left neutron star remnants. Now, back to the OP, stars exceeding 20 solar masses are extraordinarily rare. According to Wiki, fewer than 100 such stars are known to exist.

4. Feb 10, 2013

### revo74

How many stars do we know the solar masses of?

In your opinion how many 1 in how many stars becomes black holes? Give me your best estimate if you don't know.

5. Feb 10, 2013

### Chronos

We can only measure the masses of stars that belong to multiple star systems - which is about half of all stars in our galaxy. My best guess is the odds of any given star forming a black hole at the end of its life is less than 1 in a billion.

6. Feb 14, 2013

### Damo ET

If you were to pick a star at random, the chance would be extremely low. As Chronos has guestimated, "one in a billion" matches the number of large mass stars that we are aware of at present. But looking at it a different way, we know which stars to look at to see a future Black hole, as a high % of the massive stars will go down this path.
The thing to take into consideration would be that you must take into account the life span of different stars. If we just look at the number of potential BH stars that we see now, the number of existing BH we would expect would be far less than actually populate the Milky Way at present. As the life span of the massive stars is only a fraction of that of a typical star, many many thousands of generations of massive stars have come and gone which have produced Black Holes in the time that our own sun has been going through its sequence.

Damo

7. Feb 14, 2013

### Chronos

Let's not forget that core collapse is not the only possible evolutionary route for a black hole. A merger event involving sufficiently massive objects is also plausible and strongly suspected to be responsible for certain types of supernovae.

8. Feb 15, 2013

### Naty1

Have to pick a time frame and a cosmological model. Some cyclic models have mostly
black holes at the end of one universe and the birth of the next.

Here is one paper in which multiple big bangs may occur and may show signs of prior supermassive black holes..

http://phys.org/news/2010-11-scienti...verse-big.html [Broken]

Concentric circles in WMAP data may provide evidence of violent
pre-Big-Bang activity By V. G. Gurzadyan, and R. Penrose

"A merger event involving sufficiently massive objects..." yes...

within, say galactic sized bodies, seems likely as stars die out and gas coalesces...isn't that how the supermassive black holes at many galactic centers got started?? Meantime accelerated expansion is spreading distant galaxies away from one another.....

Last edited by a moderator: May 6, 2017
9. Feb 15, 2013

### Chronos

The physics behind supermassive black holes is a mystery. It is difficult to explain how it appears black holes with billions of solar masses could have originated so early in the history of the universe. It appears we have pooched some part of the physics involved.

10. Feb 18, 2013

### Damo ET

Myself, not being an Astrophysicist of any level (more a commoner with a curiosity), can't help but think that with what has been modeled with what we think we know is a fairly stable base to assume some of the missing physics. Dark matter and dark energy surely must have had effects which we aren't able to simulate properly until we know more about the nature of what they are.
Given how critical and balanced all the forces need to be to even model a simulated universe, I would imagine that even anomalies in the expansion rate just after the big bang would cause some pretty funky results. Now whether these anomalies where caused by the BB or even existed pre BB, I have no idea.
Feel free to shoot this idea down as its purely speculation on my part, but I wonder if a SMBH reaches a critical mass as in a cyclic universe and goes "Big Bang". As we are unable to see inside the event horizon to know what is going on, I wonder if some of the other BHs 'it' had 'consumed' had not yet merged with the singularity at the SMBH center when it exploded, and were ejected without being destroyed along with all the other matter within it. This may give the current view of galaxies a more plausible beginning.

Damo

11. Feb 18, 2013

### Mordred

Like you I am not a scientist. I have looked at numerous BH multiverse models and they fail to answer a few questions for me.

1) blackholes are not known to explode. They gradually lose mass via Hawking radiation. So by the time a Blackhole loses enough mass to no longer remain a blackhole. It would not have enough mass to account for everything we see.
2) blackholes do not feed at a constant rate. Yet every model Ive seen describing BH universes mathematics rely upon Homogeneous and isotropic. A blackholes inconsistent feeding rates. Would not be Homogeneous. As matter/radiation enters the inside of an event horizon and spews into the supposed universe. The energy density would be greater you get to the source. So it would not be isotropic. In other words denser toward the wormhole. Due to its inconsistent feeding rates we should see fluctations in the CMB as well as a swirl pattern caused by torsion.
3) The early large structure formation required dark matter as the initial gravity source. Without dark matter large structures would have formed later. None of tje alternate models. MOND or the BH model
account for that.

Just my take

edit I forgot to add spacetime is expanding evenly throughout all non gravitationally bound regions. The only model where this makes sense is via dark energy as quantum vacuum fluctuations. If a BH were supplying that energy the expansion would not be evenly distributed.

Last edited: Feb 18, 2013