Monday, March 6, 2023

3903 - BLACK HOLES - are more active than thought?

 

-   3903  -  BLACK  HOLES  -  are more active than thought?    Black holes at galactic centers blast out 10 times more light than previously thought. Blackholes in the hearts of galaxies are usually shrouded in dust.   Black holes residing at the center of galaxies produce way more energy than scientists previously thought.


             ------------  3903  -   BLACK  HOLES  -  are more active than thought?

                 -    Black holes residing at the center of galaxies are active galactic nuclei that devour huge amounts of matter, releasing massive amounts of energy in the form of electromagnetic radiation in the process.

-

-     Scientists have known that these black-hole-powered active galactic centers produce more radiation than all the stars combined that inhabit the galaxies that surround them. Now astronomers have found that the amount of this radiation, or light, that these central black holes exude, could be about ten times larger than previously estimated.

-

-    The researchers reached this conclusion by calculating how much of the ultraviolet light coming from these black holes gets absorbed by the dust that surrounds them. It was a known fact that this dust reduces the amount of radiation from the active galactic nuclei that astronomers can detect.

-

-   A team from the University of California Santa Cruz managed to answer this question by analyzing in detail the dimming effect of the dust surrounding one of the brightest known active galactic black holes, one found inside the galaxy known as NGC 5548 located some 245 million light-years away from Earth.

-

-    When there are intervening small particles along our line of sight, this makes things behind them look dimmer.   We see this at sunset on any clear day when the sun looks fainter and it does not burn your eyes. 

-

-   The dimming of the evening sun and the reddening of the solar disk both have the same cause. The same effect applies to the distant galactic centers, which appear redder than they actually are. In the case of the sun, however, astronomers can easily compare the dimmed light with the actual wavelength composition of the sun's radiation and its intensity.

-

-     To do the same for distant galaxies is much more complicated, as estimates of the intensity of the various wavelength components of undimmed radiation from distant active galactic nuclei are mostly based on theoretical predictions.

-

-    In the new study, they used seven different indicators to estimate the amount of dust that obscures the center of NGC 5548, and found them all to be in good agreement. The dimming they found was considerable when looking out at NGC 5548, over ten times more significant than what astronomers experience due to the dust in our own galaxy, the Milky Way..

-

-    What happens at the center of a black hole?   All of the possibilities are very weird.  It could be that deep inside a black hole, matter doesn't get squished down to an infinitely tiny point. Instead, there could be a smallest possible configuration of matter, the tiniest possible pocket of volume.

-

-    This is called a “Planck starZ”, and it's a theoretical possibility envisioned by loop quantum gravity, which is itself a highly hypothetical proposal for creating a quantum version of gravity.

-

-    In the world of loop quantum gravity, space and time are quantized, the universe around us is composed of tiny discrete chunks, but at such an incredibly tiny scale that our movements appear smooth and continuous.

-

-    This theoretical chunkiness of space-time provides two benefits. One, it takes the dream of quantum mechanics to its ultimate conclusion, explaining gravity in a natural way. And two, it makes it impossible for singularities to form inside black holes.

-

-    As matter squishes down under the immense gravitational weight of a collapsing star, it meets resistance. The discreteness of space-time prevents matter from reaching anything smaller than the Planck length (around 1.68 times 10^-35 meters).

-

-   All the material that has ever fallen into the black hole gets compressed into a ball not much bigger than this. Perfectly microscopic, but definitely not infinitely tiny.

-

-   This resistance to continued compression eventually forces the material to un-collapse ( explode), making black holes only temporary objects. But because of the extreme time dilation effects around black holes, from our perspective in the outside universe it takes billions, even trillions, of years before they go boom.

-

-    Another attempt to eradicate the singularity, one that doesn't rely on untested theories of quantum gravity, is known as the “gravastar”.  The difference between a black hole and a gravastar is that, instead of a singularity, the gravastar is filled with dark energy.

-

-   Dark energy is a substance that permeates space-time, causing it to expand outward. It sounds like sci-fi, but it's real: dark energy is currently in operation in the larger cosmos, causing our entire universe to accelerate in its expansion.

-

-   As matter falls onto a gravastar, it isn't able to actually penetrate the event horizon (due to all that dark energy on the inside) and therefore just hangs out on the surface. But outside that surface, gravastars look and act like normal black holes.    A black hole's event horizon is its point of no return the boundary beyond which nothing, not even light, can escape.

-

-    However, recent observations of merging black holes with gravitational wave detectors have potentially ruled out the existence of gravastars, because merging gravastars will give a different signal than merging black holes, and outfits like LIGO (the Laser Interferometer Gravitational-Wave Observatory) and Virgo are getting more and more examples by the day.

-    Planck stars and gravastars may have awesome names, but the reality of their existence is in doubt. So maybe there's a more mundane explanation for singularities, one that's based on a more nuanced and realistic view of black holes in our universe.

-

-    The idea of a single point of infinite density comes from our conception of stationary, non-rotating, uncharged, rather boring black holes. Real black holes are much more interesting characters, especially when they spin.

-

-    The spin of a rotating black hole stretches the singularity into a ring. And according to the math of Einstein's theory of general relativity, once you pass through the ring singularity, you enter a wormhole and pop out through a white hole (the polar opposite of a black hole, where nothing can enter and matter rushes out at the speed of light) into an entirely new and exciting patch of the universe.

-

-    One challenge: the interiors of rotating black holes are catastrophically unstable.   The problem with rotating black holes is that, well, they rotate. The singularity, stretched into a ring, is rotating at such a fantastic pace that it has incredible centrifugal force. And in general relativity, strong enough centrifugal forces act like “antigravity”, they push, not pull.

-

-    This creates a boundary inside the black hole, called the “inner horizon”. Outside this region, radiation is falling inward toward the singularity, compelled by the extreme gravitational pull. But radiation is pushed by the antigravity near the ring singularity, and the turning point is the inner horizon.

-

-    If you were to encounter the inner horizon, you would face a wall of infinitely energetic radiation, the entire past history of the universe, blasted into your face in less than a blink of an eye.

-

-    The formation of an inner horizon sows the seeds for the destruction of the black hole. But rotating black holes certainly exist in our universe, so that tells us that our math is wrong and something funky is going on.

-

What's really happening inside a black hole? We don't know.  The origin of dark energy has been perplexing scientists for decades.  When astronomers discovered that the universe is expanding at an accelerating rate, they theorized that some force must be pushing things farther apart and overcoming gravity, which should be slowing things down. That force was suggested to be dark energy, but no one has ever figured out from where it comes.

-

-    Black holes acquire mass in two ways: accretion of gas and mergers with other black holes. But in studying nine billion years of black hole evolution in dormant giant elliptical galaxies, the researchers discovered that the older black holes are much larger than they should be based on those two methods of growth.

-

-     That means there must be another way these black holes are acquiring mass. Researchers suggest the answer is dark energy in the form of vacuum energy, a kind of energy included in spacetime itself that pushes the universe further apart, accelerating the expansion.

-

-    If the theory holds, then this is going to revolutionize the whole of cosmology, because at last we've got a solution for the origin of dark energy that's been perplexing cosmologists and theoretical physicists for more than 20 years

-

-   The idea that black holes are a source of dark energy isn't new. In fact, it's part of Einstein's theory of general relativity. But this is the first time astronomers have obtained observational evidence to support the theory.

-

-    There's evidence the typical black hole solutions don't work for you on a long, long timescale, and we have the first proposed astrophysical source for dark energy.

-

                   March 5, 2023      BLACK  HOLES  -  are more active than thought?       3903                                                                                                                        

----------------------------------------------------------------------------------------

-----  Comments appreciated and Pass it on to whomever is interested. ---

---   Some reviews are at:  --------------     http://jdetrick.blogspot.com ----- 

--  email feedback, corrections, request for copies or Index of all reviews

---  to:  ------    jamesdetrick@comcast.net  ------  “Jim Detrick”  -----------

--------------------- ---  Monday, March 6, 2023  ---------------------------

 

 

 

 

         

 

-

 

 

 

 

           

 

 

No comments:

Post a Comment