What Happens to Black Holes, Pulsars, Quasars, and White Dwarfs at the Ends of their Life Cycles?

Question: What happens to black holes, pulsars, quasars, and white dwarfs at the end of their life cycles? — Monte

Answer: The life cycle endpoints for these objects are all very different.  Black Holes are not currently known to die out.  Black holes have been theorized to emit Hawking Radiation, but this is a very slow process that, to my knowledge, will not result in an end to the existence of the Black Hole.  Pulsars and White Dwarfs become compact objects which slowly cool over many millions of years.  Quasars result from jets of matter which emanate from massive black holes located at the centers of some galaxies.  As is the case with Black Holes, the process by which Quasars evolve and potentially die is not known.

Jeff Mangum

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What Methods Have Scientists Used to Confirm the LIGO Discovery of Gravity Waves?

Question: Information says that the gravitational waves, recently detected by LIGO, correspond (according to Einstein theory equations) to the effect of two black holes merging (with the masses of both black holes being estimated).
So the fact of two celestial mass black holes merge – is it established scientific astronomical (cosmological) fact or just a best possible implied assumption (indirect conclusion, based on inference from the General Relativity mathematical model)?  — Alex

Answer: My answer echos closely the answer to your question given on Physics Stack Exchange, which noted that the gravitational wave detection results from the LIGO interferometer conform to standard scientific practices regarding any reasonable burden of proof. LIGO detected the merger of two black holes with its two detectors, both of which produced a gravity wave signal that corresponds very closely to that which one would predict from a theoretical prediction of what the signal from two merging black holes would look like.   The LIGO collaboration has held their discovery to a very high standard of proof, giving a great deal of confidence in the veracity of their results.

Jeff Mangum

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What if the Big Bang Started as a Gigantic Supernova and Associated Black Hole?

Question: A cosmological “what if ”
Here’s my question:

suppose for the sake of argument, the big bang happened somewhat differently, that it was like a huge mega supernova, and created super-duper massive black hole. A universal black hole. THE black hole of the entire known universe!

slowing down all the stuff that blew away from it.
the stuff coalesced into galaxies which are all still expanding away from each other.

such a scenario would have all the galaxies at different heights in a huge potential well. now…if our galaxy were further up such a potential well, all the light from all the galaxies further down would be red shifted.

also photons emitted from those galaxies would not only come ‘straight’ up the potential well but also would spiral up the potential well.

If our galaxy were near the ‘top’, light from one galaxy would reach us from many directions, all such photons would be red-shifted, and would have taken different lengths of time to reach us because of the many different spiral geodisics they could have taken. In other words, many of the galaxies we see could in fact be the SAME galaxy seen from a different direction in the sky and at vastly different times in its evolution as well as from its different orientations.

pretty much all the galaxies would appear to be receeding from ours (whether they are or not)

furthermore, between our galaxy and the more red-shifted ones further down the well,  the space-time would become more and more stretched the further away from our galaxy you’d go.
And therefore it would appear that the expansion of the universe was therefore ‘speeding up’.

Thus explaining the embarassing ‘dark’ energy issue.

In other words, all the distant galaxies might not be ‘spread out’ over the night sky as they appear to be, but instead be all more or less in the same ‘direction’ (downwards), in one and the same huge potential well of “THE” black hole of the entire Universe, that would make a galactic supermassive black hole look like an electron neutrino!

There would be no ‘center’ because any such center would be in all directions, it would therefore be ‘spread out’ as the surface of a sphere.

So maybe therefore, our view of the universe has been ‘inside out’ as it were.

This view seems consistent with general relativity.

How would we know? observationally, how could we tell the difference?
(it sure would explain the ‘dark’ energy /cosmic acceleration issue, plus it’s a lot less absurd)

— Tom


Answer: I think that your scenario has one basic flaw in that if the giant supernova which led to the “central” black hole did exist, we would observe a “source” or center for the overall expansion of the universe.  In fact, what we see are all galaxies (excluding local gravitational interactions between galaxies located near each other) moving away from each other rather than moving away from a common point.  You might want to take a look at some of the questions and answers that have been posted to the cosmology section of this blog for further information.


Jeff Mangum

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What is a Black Hole Made of?

Question: I googled this question while looking for an answer to something even more vague:  what is a black hole made of?   If the 3 observable properties or a black hole are supposed to be mass, charge, and angular momentum, then what “inside” the black hole can still provide those properties if all matter in a black hole has supposedly been destroyed?   The only thing I’ve been able to imagine is that a black hole does not actually destroy any matter that falls into it … it just prevents us from observing it.    Otherwise the implication is that mass, charge, and angular momentum can exist independently of matter.  — Rob

Answer: As you already know, black holes are places where extreme gravitational attraction draws everything, even light, to a single point in space.  The problem with understanding exactly what happens to the stuff that pulled into a black hole is that physicists really don’t have a complete understanding of how gravity works under the extreme conditions found in a black hole.  Called “quantum gravity”, an understanding of how gravity works in a black hole requires physicists to figure out what happens to gravity at atomic-scale levels.  The physical properties of a black hole, which as you have said are mass, charge, and angular momentum, are measurable and are properties that derive from the event horizon of the black hole.  Inside the event horizon, which is where quantum gravity effects start to come into play, are poorly understood.  In the end, your suggestion that matter is not “destroyed” when it enters a black hole but just becomes unobservable to us, is plausible.  Physicists cannot be definitive on this issue, though, as we just don’t have a good understanding of how gravity works at the center of a black hole.

Jeff Mangum

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What Happens When Two Black Holes Exert Their Gravitational Forces on Each Other?

Question: Hi there, I had a question more open to speculation than hard fact but here goes. What happens (or could potentially happen) if two black holes exerted their gravitational forces upon one another? Would the larger simply absorb the smaller? Or would the force of the two black holes work like similar ends of a magnet?  — Daniel

Answer: I believe that the end result of such a mutual attraction would be the merger of the two black holes into one larger black hole.

Jeff Mangum

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What Happens to Matter Which Falls Into a Black Hole?

Question: So i was reading an article on black holes and i came across hawking saying matter which falls into black holes get destroyed,and it is a paradox as matter can neither be destroyed or created but transformed.  So a doubt was nagging me…. If matter cant be destroyed then how will a star which explodes or dies be converted into something like a black hole which is no kind of matter unless it is a transformed form of the star’s mass and energy.  And isn’t it possible that a matter which falls into black hole be converted to this same form of energy (in form of gravitational pull) instead of being destroyed or pulled into another galaxy?

Answer: The outcome of matter which falls into a black hole is largely a matter of speculation.  You can read a nice summary of what happens to matter as it approaches then enters a black hole at the Astronomy Cafe article on this subject. The major problem with any theory which postulates the properties of matter which falls into a black hole is that there are few observable quantities to guide such theories.

Jeff Mangum

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Can Event Horizons be Created at Lagrange Points in a Multiple Neutron Star System?

Question: I have been interested in astronomy since I was a child. My question arose while I was studying the effects of Lagrangian points between multiple bodies.

Imagine a scenario of a binary (or multiple) neutron stars system. Provided the neutron stars are all very close to their critical mass and are running in a very compacted orbits around each other. Is it possible that the gravitational interaction between the neutron stars, similar to the principle of Lagrangian points, creates a spot of event horizon in the system?

I am deeply intrigued in this question, as I imagine the event horizon would be mobile and deforms corresponding to the motion of neutron stars. Also, with no singularity in the system, the event horizon would probably behave differently compare to those around a black hole.  — Peterson

Answer: As you likely already know, Langrange Points are positions where the gravitational pull of two massive objects, such as the Earth and the Sun, precisely equals the centripetal force required for a small object to move with them.  This is quite different than an event horizon, which is a boundary in space-time beyond which information cannot be transmitted.  In other words, objects which are within an event horizon cannot be detected from an observer outside the event horizon.  Event horizons are associated with very massive objects, such as black holes, which create gravitational fields that are so strong that they halt the travel of light propagating from the black hole.  Neutron stars are not massive enough to produce event horizons.  Also, Langrange Points do not naturally have the physical properties to create a massive object that can lead to an event horizon.

Jeff Mangum

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Do Black Holes Create Dark Energy?

Question: Hi, my name is Kemp and I just finished watching a program from the Discovery Channel entitled “Understanding the Universe”. The program triggered an odd question, do blackholes create dark energy and/or dark matter relative to their size?  — Kemp

Answer: No.  The only connection between black holes and dark energy is the “darkness” of their names.  Black holes are sources of intense gravity from which even light cannot escape.  Dark energy is the theoretical entity that accounts for the majority of the energy content of the universe and is responsible for the overall acceleration of the expansion of the universe.

Jeff Mangum

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Black Holes and Gravitational Redshifting of Emission

Question: What do black holes look like on radio telescope images? Specifically how does a visible light image of a black hole compare to a radio telescope image of the same black hole?

I’m curious whether gravitational time dilation and redshifting causes visible light to change into radio frequency EM energy, and therefore not be visible. What happens to visible light when it is redshifted too much? Can it turn back into visible light when it leaves the gravity field? Is there a frequency at which there is a required energy to quantize the photons back into visible light?  — Ray


Answer:  Let me first answer your first question about what black holes look like when measured with a radio telescope.  In fact, there are no direct measurements that we can make that tell us what a black hole looks like.  Black holes are always measured through indirect means, such as measuring objects in their gravity field that tell us about the black hole’s existence.  For example, at radio wavelengths we can measure emission from the water molecule that traces the gas in the disk around a black hole.  By measuring the velocity of this water emission we can infer the mass of the black hole.

As for your second question about gravitational time dilation and redshifting, the expansion of the universe does shift emission at shorter wavelengths down to longer wavelengths, such as radio waves.  The redshifting of EM waves does not wrap around back to shorter wavelengths, though.  The shifting to longer wavelengths monotonically approaches infinite wavelength.

Jeff Mangum

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How Do Black Holes Form?

Question: How do black holes form?  — Harsh

Answer: I think that my colleagues at NASA have produced a very nice explanation of what black holes are and how they form.  In a nutshell, when a massive object has not way to support itself against gravity, it collapses in upon itself.  If that object is massive enough, then its gravitational pull can arrest even the propagation of light, making it appear “black” to us.

Jeff Mangum

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