Chris Peterson wrote: ↑Thu Feb 24, 2022 3:42 pm
johnnydeep wrote: ↑Wed Feb 23, 2022 1:22 pm
Still seems hard to believe that the energy released can beat fusion. I wonder what percent of the infalling matter's mass gets converted to energy in the accretion disk. Or is that not happening at all and all the energy ultimately coming from the change in gravitational potential energy? (Hmm, I seem to remember being confused about this in prior posts about things falling onto neutron stars...)
What does that mean, "beat fusion"? If all the matter in the accretion disc underwent fusion, it would be vastly more energetic. As it is, something like a third of the mass in the disc is eventually converted to energy, which is a huge amount of energy. In a star, you have only the tiniest amount of material that is undergoing fusion. When hydrogen fuses to helium, the energy conversion is very efficient. But it is also very rare. If all the material in a star fused simultaneously, you would also have an intensity greater than a galaxy. In fact, that's pretty much what happens in a supernova.
Fusion is basically a process by which:
- 56 protons of mass 56.4075 Daltons are transformed into one
iron-56 nuclei of mass 55.935 Daltons for an efficiency of ~ 1%
This does not come close to efficiency of a quasar 
https://en.wikipedia.org/wiki/Foe_(unit) wrote:
<<A foe is a unit of energy equal to 10
44 joules or 10
51 ergs, used to express the large amount of energy released by a supernova. This unit of measure is convenient because a supernova typically releases about one foe of
observable energy in a very short period (which can be measured in seconds).
[Note: a core collapse supernova can release ~100 foe of neutrinos.] In comparison, if the Sun had its current luminosity throughout its entire lifetime, it would release ≈ 1.2 foe. One solar mass has a rest mass energy of 1787 foe.>>
https://en.wikipedia.org/wiki/Quasar wrote:
<<Since quasars exhibit all the properties common to other active galaxies such as Seyfert galaxies, the emission from quasars can be readily compared to those of smaller active galaxies powered by smaller supermassive black holes. To create a luminosity of 10
40 watts (the typical brightness of a quasar), a supermassive black hole would have to consume the material equivalent of 10 solar masses per year.
The brightest known quasars devour 1000 solar masses of material every year. The largest known is estimated to consume matter equivalent to 10 Earths per second. Quasar luminosities can vary considerably over time, depending on their surroundings.
Radiation from quasars is partially "nonthermal" (i.e., not due to black-body radiation), and approximately 10% are observed to also have jets and lobes like those of radio galaxies that also carry significant (but poorly understood) amounts of energy in the form of particles moving at relativistic speeds. Quasars can be detected over the entire observable electromagnetic spectrum, including radio, infrared, visible light, ultraviolet, X-ray and even gamma rays. Most quasars are brightest in their rest-frame ultraviolet wavelength of 121.6 nm Lyman-alpha emission line of hydrogen, but due to the tremendous redshifts of these sources, that peak luminosity has been observed as far to the red as 900.0 nm, in the near infrared. A minority of quasars show strong radio emission, which is generated by jets of matter moving close to the speed of light. When viewed downward, these appear as blazars.>>
[quote="Chris Peterson" post_id=320889 time=1645717357 user_id=117706]
[quote=johnnydeep post_id=320850 time=1645622554 user_id=132061]
Still seems hard to believe that the energy released can beat fusion. I wonder what percent of the infalling matter's mass gets converted to energy in the accretion disk. Or is that not happening at all and all the energy ultimately coming from the change in gravitational potential energy? (Hmm, I seem to remember being confused about this in prior posts about things falling onto neutron stars...)[/quote]
What does that mean, "beat fusion"? If all the matter in the accretion disc underwent fusion, it would be vastly more energetic. As it is, something like a third of the mass in the disc is eventually converted to energy, which is a huge amount of energy. In a star, you have only the tiniest amount of material that is undergoing fusion. When hydrogen fuses to helium, the energy conversion is very efficient. But it is also very rare. If all the material in a star fused simultaneously, you would also have an intensity greater than a galaxy. In fact, that's pretty much what happens in a supernova.[/quote]
Fusion is basically a process by which:
[list]56 protons of mass 56.4075 Daltons are transformed into one
iron-56 nuclei of mass 55.935 Daltons for an efficiency of ~ 1%[/list]
[b][u][color=#0000FF]This does not come close to efficiency of a quasar[/color][/u][/b] :!:
[quote=https://en.wikipedia.org/wiki/Foe_(unit)]
<<A foe is a unit of energy equal to 10[sup]44[/sup] joules or 10[sup]51[/sup] ergs, used to express the large amount of energy released by a supernova. This unit of measure is convenient because a supernova typically releases about one foe of [b][u]observable[/u][/b] energy in a very short period (which can be measured in seconds). [b][Note: a core collapse supernova can release ~100 foe of neutrinos.][/b] In comparison, if the Sun had its current luminosity throughout its entire lifetime, it would release ≈ 1.2 foe. One solar mass has a rest mass energy of 1787 foe.>>[/quote]
[quote=https://en.wikipedia.org/wiki/Quasar]
<<Since quasars exhibit all the properties common to other active galaxies such as Seyfert galaxies, the emission from quasars can be readily compared to those of smaller active galaxies powered by smaller supermassive black holes. To create a luminosity of 10[sup]40[/sup] watts (the typical brightness of a quasar), a supermassive black hole would have to consume the material equivalent of 10 solar masses per year. [b][u][color=#0000FF]The brightest known quasars devour 1000 solar masses of material every year.[/color][/u][/b] The largest known is estimated to consume matter equivalent to 10 Earths per second. Quasar luminosities can vary considerably over time, depending on their surroundings.
Radiation from quasars is partially "nonthermal" (i.e., not due to black-body radiation), and approximately 10% are observed to also have jets and lobes like those of radio galaxies that also carry significant (but poorly understood) amounts of energy in the form of particles moving at relativistic speeds. Quasars can be detected over the entire observable electromagnetic spectrum, including radio, infrared, visible light, ultraviolet, X-ray and even gamma rays. Most quasars are brightest in their rest-frame ultraviolet wavelength of 121.6 nm Lyman-alpha emission line of hydrogen, but due to the tremendous redshifts of these sources, that peak luminosity has been observed as far to the red as 900.0 nm, in the near infrared. A minority of quasars show strong radio emission, which is generated by jets of matter moving close to the speed of light. When viewed downward, these appear as blazars.>>[/quote]