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I Why is the time of formation of this Black Hole in question?

  1. Dec 7, 2017 #1
    I have to 'question' the logic asked in the 'title question' asked in this artical: https://newatlas.com/most-distant-s...ail&utm_term=0_65b67362bd-2151ebbb0d-91583997

    It seems to me that the "star stuff" (To quote Carl Sagan) at the outer edges of the universe is the oldest! Then WHY would anyone especially a Theoretical Astronomical Physicist think it odd that a black hole would be able to form in the oldest portion of the universe? The other thing that puzzles me is the emphasis placed on the time that this black hole formed could even be figured/assumed, let alone assigning it's forming to 'the dawn of the universe'. Remember, I am NOT questioning that the the "star stuff" at the edge of the universe is representative of the 'the dawn of the universe'; but, seeing as it IS the "star stuff" formed at the 'the dawn of the universe' it IS the oldest; and therefore, has had even more time to coalesce into black holes than the rest of the black holes, which (to me) obviously formed later!

    (I am adding to this question here), I know what the article says about redshift, but the movement of many things in the universe have yet to be understood, and whatever caused the redshift of this particular black hole may have been an oddity of the young universe that just hasn't been observed before, and may have left no other evidence that it existed. OR, something perhaps as an unimaginable consequence of the expanding universe snapping a tendril of it's underlying matrix carrying this item along with it further and faster than it would have traveled without that incident. Just a thought.
    Last edited: Dec 7, 2017
  2. jcsd
  3. Dec 7, 2017 #2


    Staff: Mentor

    Try reading about the observable universe and see if that answers your question:


    My understanding is that stars that far out were created "shortly" after the big bang and so are first generation stars. Since we understand black holes as being made by the collapse of a supermassive star then it stands to reason you have to have supermassive stars first. The scientists are confused about the timing. It may indicate that cosmological theory has to be reconsidered, and adapted to explain this new observation properly. Its the scientific method in action.
  4. Dec 7, 2017 #3

    It is possible that the birth of a star was completely skipped, that the mass was so great that it just turned directly into a black hole?
  5. Dec 7, 2017 #4


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    A black hole created by that means is what is known as a primordial black hole. There is no clear evidence that any primordial black holes exist or ever did exist, and there is likewise no agreement over the process that would be involved in creating one in that manner.

    This is the only means by which black holes below the critical stellar mass needed to create a black hole could be formed, so observation of even a single black hole with a mass below this threshold would prove that there are some primordial black holes, but none have been observed so far.

    There is no difference between a primordial black hole of equal to or more than the critical stellar mass, and an ordinary black hole formed by the collapse of a star and subsequently absorbing other matter, at any given point in time (one of the important conclusions of general relativity is that only a handful of parameters fully describe all black holes which are otherwise identical to each other from the perspective of someone outside the event horizon).

    So, the only way that the two could be distinguished is by subtle means such as the timing issue noted by the investigators in the link in the original post. In other words, it must be a primordial black hole if it existed before stars of the right size had time to form and collapse to form a black hole of the observed size which then grew to the observed size through mergers with other matter, or if there are too many black holes, too early for all of them to have been created by stellar collapse.

    Processes like Big Bang Nucleosynthesis rule out lots of windows of time where we know that primordial black holes can't be created because theory without primordial black holes fits the data and can't be tweaked. They also have to form very early on after the Big Bang because later on, matter and energy aren't sufficiently dense and the distribution of matter and energy in the universe is too homogeneous, to form a black hole.

    This is a time period that is hard to model because the energy scale immediately after the Big Bang was much higher than anything that can be reproduced in a particle accelerator, so any model involves guesswork about the nature of very high energy physics (possibly beyond the Standard Model). For example, we don't fully understand why the Big Bang was an expansion, rather than a collapse into a huge black hole. In addition, modeling this involves a wickedly complex factual circumstance where everything in the universe in crammed together at a stage where everything has lots of other stuff near it to interact with and there are hundreds of different possible cosmological inflation scenarios can't be distinguished with current data of which one has t be chosen for purposes of a model.
  6. Dec 8, 2017 #5


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    Just so you're clear, there IS NO "outer edge of the universe"
  7. Dec 8, 2017 #6
    A primordial black hole would have been formed within seconds after the Big Bang. We are talking about a black hole that has been formed hundreds of million years later. That is not a primordial black hole, even if it results from a direct collapse.
  8. Dec 8, 2017 #7


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    There is no mechanism by which a black hole could come into being hundreds of millions of years later.
  9. Dec 8, 2017 #8

    stefan r

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    If I read that correctly then it is wrong.

    The material in the Milky Way came out of the Big Bang about 13.8 billion years ago. All objects in the Milky Way are younger than 13.8 billion years old. If a particle of light traveled 13.1 billion years to get here then it was emitted by something less than 700 million years old.

    If we make an observation then there must be a mechanism that created the data. Article published in Nature:
  10. Dec 8, 2017 #9
  11. Dec 9, 2017 #10
    I wonder whether the red shift observed and used to calculate distance might be in part due to the emitted photons coming from close to the event horizon, and it is not entirely a cosmological red shift. Can someone explain a method that might be used to distinguish a red shift from near an event horizon and cosmological red shift?
  12. Dec 9, 2017 #11
    Can you support that with a suitable reference?
  13. Dec 9, 2017 #12
    The acceleration due to gravity at the horizon would only be about 2 x 10^4 meters/second^2, so not much of a gravitational red shift.
  14. Dec 9, 2017 #13
    Hi websterling:

    Your response confuses me.

    First: Why is acceleration relevant?

    Second: How did you calculate this acceleration?

    Third: If the wavelength of a photon is observed from very far from the event horizon of a black hole (BH), when the photon was emitted from a source which was at a distance very close to the BH's event horizon, then the red shift will have caused the wavelength of the observed photon to be very much larger than for a photon that was emitted by an ordinary star at the same distance as the BH is from the observer. If the red shift is used to calculate the velocity of the distance of the emitting object, and if Hubble's equation's used with this velocity to calculate distance from the object at the time it was emitted, then this distance will be very much farther away then the true distance. From this over large distance, the brightness of the object will be correspondingly over estimated. I do not know the method used to calculate the mass of such an object, but it seems plausible that this would also be correspondingly over-estimated.

  15. Dec 9, 2017 #14

    stefan r

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    The object in the quasar is extremely bright. We are detecting ionized hydrogen surrounding the object. The Lyα spectral line from hydrogen which is far from the black hole will have its line at the highest frequency. If we could see the hydrogen emissions from deeper in the hole the photons would be red-shifted more. You should still see the sharp cutoff in the spectrum. Figure 1 looks fairly sharp to me.

    In the sun we see stuff outside the photosphere.
  16. Dec 9, 2017 #15
    Hi @stefan r:

    Thank you for your post. It is clear to me (1) that your technical understanding of the Banados et al paper is far better than mine, and (2) that you find the conclusions about the mass and age of the black hole likely to be valid with a high degree of confidence. Consequently, I feel I must also accept these conclusions, although I also confess my level of confidence is not as high as yours since I really don't understand the technical discussion.

    Does the paper include a clear to you explanation of the reason for high degree of confidence that the 7.5 red-shift is entirely cosmological, and not tainted by photons coming from a source near the event horizon? I gather that the researchers concluded what you say in the quote from your post above, in particular "which is far from the black hole". What I would like to understand, if that is possible, is what information from their observations make them have a high degree of confidence that the above quote is valid. Can you cite for m e that particular pages in the paper that discuss this point?

  17. Dec 10, 2017 #16
    Hi @stefan r:

    I have just been reading
    These articles give a good explanation about the questions I asked you about the mass and distance determination.
    Reverberation mapping is an astrophysical technique for measuring the structure of the broad emission-line region (BLR) around a supermassive black hole at the center of an active galaxy, and thus estimating the hole's mass. It is considered a "primary" mass estimation technique, i.e., the mass is measured directly from the motion that its gravitational force induces in the nearby gas.​
    I also gather that the gas being analyzed is astronomically known to be far enough form the event horizon so that the black hole influence on the red shift is negligible.

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