My question is prompted by suspicion of three current ideas in astrophysics:

  1. GR predicts a singularity at the center of a BH without regard to QM.
  2. quasar hyper-luminosity is caused by an acretion disk outside of a SMBH's EH.
  3. the Quasar Age or Quasar Epoch has ended.

So, assume under the conditions of a unified theory of GR and QM, that there is some dynamic process occurring within a SMBH's EH that generates a hyper-luminous ball of energy. Call it a Quasar Ball, or QB. Normally, this super bright QB is shielded from a local observer's view by the EH. But, what if the observer is 10 billion light years away, and the SMBH is receding from the observer at a significant fraction, say 90%, of the speed of light? Herein lies the circumstances for my question in the title.

Could the QB on the inside of the EH of the distant SMBH now be visible under certain relativistic conditions? Most of the matter and energy of the SMBH is still compactified into a tiny central volume, but not into a singularity. So, when the central volume of the SMBH (the QB) recedes from the observer at 90% of the speed of light, does the spherical EH instantly follow right along? Or, is there a time lag for gravity to propagate across the Schwarzschild radius of the SMBH in order to form a new EH boundary. If indeed there is a time lag involved on the EH keeping up with SMBH central volume movement, then does this provide an opportunity for a distant observer to peer inside the EH? What might the distant observer see? Possibly a hyper-luminous ball of energy which we all know as a quasar? No singularity, nor acretion disk, nor Quasar Age needed.

  • 3
    $\begingroup$ The "quasar epoch" hasn't ended. The nearest quasar is about 600 million light years from Earth. Quasars are rare, but 600 million years ago is "now" in terms of epochs of the universe. There are quasars existing right now, but none closer than 600 million light years. $\endgroup$
    – James K
    Sep 15, 2021 at 5:38
  • 6
    $\begingroup$ Light can't escape the EH. See astronomy.stackexchange.com/questions/29163/… & the Physics.SE links I posted on astronomy.stackexchange.com/q/46713/16685 Even if we had a theory that unites GR & QM it wouldn't permit trajectories away from the centre of a BH (even as observed inside the EH) because such trajectories require travel backwards in time. $\endgroup$
    – PM 2Ring
    Sep 15, 2021 at 6:44
  • $\begingroup$ In this scenario, light would be so redshifted as to be impossible to detect. The ratio of the change of wavelength to the actual wavelength would be greater than one, and thus redshifted into extinction, so even if there was something to see, we wouldn’t be able to see it. $\endgroup$
    – Justin T
    Sep 15, 2021 at 7:05

2 Answers 2


the Quasar Age or Quasar Epoch has ended.

As pointed out by James K., the Quasar epoch has not ended. Today quasars are rarer then some Gyr ago, but they are still here. The closest one is about 600 million light years away and it is receding at about 12500 km/s, which is 4% of the speed of light. This fact alone proves that quasars are not a consequence of a black hole moving at relativistic speed.

Or, is there a time lag for gravity to propagate across the Schwarzschild radius of the SMBH in order to form a new EH boundary.

The event horizon is a well defined hypersurface that encloses the black hole. The fact that a given point of spacetime is inside or outside the event horizon doesn't depend on the observer. So no, there is no lag. What's inside the black hole stays inside the black hole, no matter how fast the black hole is going.


What we call a quasar is really the ultra-heated accretion disk outside of a supermassive black hole. A quasar is more of a state of an accretion disk than a distinct object in itself. The accretion disk almost certainly extends inside the event horizon of the black hole where it releases even higher amounts of radiation, but all that radiation is bend towards the center of the black hole and can not leave it.

  • 3
    $\begingroup$ "The accretion disk almost certainly extends inside the event horizon of the black hole" -- not quite. The inner edge of the accretion disk is defined by the innermost stable circular orbit (ISCO). At radii < ISCO, GR predicts unstable orbits, so the material spirals in towards the BH without orbiting. $\endgroup$
    – Jim421616
    Sep 21, 2021 at 22:26

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