How often are black holes born?

[Airbrush]

Today is "How the Universe Works" on The Science Channel for the next 8 hours. Anyone else follow the series?

 

Today I am watching an episode called "Megaflares" and I believe I caught an error. They said that every day we see about one gamma ray burst, or about 350 per year. They said that every gamma ray burst is the birth of a black hole. Do some gamma ray bursts mean the birth of a neutron star? I heard someone say that about one black hole is born every day in the observable universe. But that must be wrong, there must be many more born each day because for every gamma ray burst WE CAN SEE means many more are happening that are NOT POINTED DIRECTLY AT US.

 

So about how many black holes are born each day in the observable universe? In our galaxy?

Edited March 7, 2017 by Airbrush

[swansont]

Are GRBs directional?

[DrP]

I was going to ask the same as SwansonT. With a neutron star they are flung out from the poles (IIRC) and the signal pulsates due to the spinning... I think it might be Omni directional for BHs - but I do not known a lot about them, so would be interested to know. I would 'guess' that it would be in all directions for the BH.... but that is my uneducated guess.

Edited March 7, 2017 by DrP

[Airbrush]

Yes, the only gamma ray bursts we can see across the universe are pointed directly at us. So for every one pointed directly at us there must be billions or trillions going off that are pointed away from us.

Edited March 7, 2017 by Airbrush

[DrP]

Do BHs have poles then or something? What causes the radiation burst to just go in a single direction?

[Airbrush]

In 2 directions are polar jets from the collapsing star. I think it is the rotation of the giant star that is going supernova.

 

"...The intense radiation of most observed GRBs is believed to be released during a supernova or hypernova as a rapidly rotating, high-mass star collapses to form a neutron star, quark star, or black hole."

 

That answers one of my questions. GRBs also can mean a new neutron star or quark star.

 

https://en.wikipedia.org/wiki/Gamma-ray_burst

[swansont]

Yes, the only gamma ray bursts we can see across the universe are pointed directly at us. So for every one pointed directly at us there must be billions or trillions going off that are pointed away from us.

 

That's a bit extreme. That implies jets that are exceedingly narrow — a tiny fraction of a degree.

 

 

http://chandra.si.edu/photo/2016/grb/

 

Specifically, the researchers found that the jet is beamed into an angle of only about five degrees based on the X-ray observations, plus optical observations with the Gemini Observatory and the DCT and radio observations with the National Science Foundation's Karl G. Jansky Very Large Array. This is roughly equivalent to a circle with the diameter of your three middle fingers held at arms length. This means that astronomers are detecting only about 0.4% of this type of GRB when it goes off, since in most cases the jet will not be pointed directly at us.

 

So more like 1 in 200. For this type of GRB.

[MigL]

Have to agree with Swansont and DrP...

 

Gravitational collapse is completely symmetrical ( see the 'no hair' theory as it relates to BHs ) so any and all radiation due to collapse is completely symmetrical or omnidirectional. This happens very quickly so omnidirectional bursts are short-lived.

 

Once the BH has formed any further infalling material follows a spiral trajectory. and this energetic angular acceleration of the EXTERNAL infalling material causes the polar radiation jets. These polar 'bursts' last as long as there is infalling material and the very large BHs at the center of young galaxies which display such jets are quasars.

[Delta1212]

 

That's a bit extreme. That implies jets that are exceedingly narrow a tiny fraction of a degree.

 

 

http://chandra.si.edu/photo/2016/grb/

 

 

So more like 1 in 200. For this type of GRB.

Wouldn't it be 1 in 250?

[swansont]

Wouldn't it be 1 in 250?

 

 

Yeah. I was still a tad closer with my rounding to 1 significant digit than the smaller of the other estimates.

[Airbrush]

Thanks for the info about how wide the GRB beam is that hits us. It's not such a narrow focused beam I imagined. So that means that in the observable universe about 250 black holes or neutron stars are born per day? We don't know how many of those 250 objects are black holes?

[DrP]

Does the BH spin and pulse like the Neutron star? I have not heard about that.. the neutron star spins at quite a high frequency for its size/mass and is detected as a regular and constant 'tick tick tick tick tick tick tick tick.......' that is so regular that it looks like it has been sent as a signal. I wasn't aware of black holes doing this. I thought we detected them by looking at their influence on other stars... i.e. we see other stars effected by a huge mass, work out where that mass should be, look for it and see nothing so assume a BH.

 

I might just sit out of this conversation from now on unless I have further questions.... I am only repeating what I have heard from watching documentaries and picked up here and there and do not really know anything other than what I have heard about it - I know that there are many others here that are very knowledgeable about such things as it is their field of study. I'll read up on quasars after reading MigL's post.

[Airbrush]

​"A pulsar is a highly magnetized, rotating neutron star or white dwarf, that emits a beam of electromagnetic radiation. This radiation can be observed only when the beam of emission is pointing toward Earth (much the way a lighthouse can be seen only when the light is pointed in the direction of an observer), and is responsible for the pulsed appearance of emission."

 

https://en.wikipedia.org/wiki/Pulsar

 

Do rotating black holes also emit a beam?

 

My guess is the way to tell the difference between the gamma ray burst that signals the birth of a black hole, or a neutron star, is LARGER GRB's are from newly formed black holes.

Edited March 8, 2017 by Airbrush