Black Holes May Gain Mass From the Expansion of the Universe Itself (scitechdaily.com) 38
nickwinlund77 shares a report from SciTechDaily: Since the first observation of merging black holes by the Laser Interferometer Gravitational-Wave Observatory (LIGO) in 2015, astronomers have been repeatedly surprised by their large masses. Though they emit no light, black hole mergers are observed through their emission of gravitational waves -- ripples in the fabric of spacetime that were predicted by Einstein's theory of general relativity. Physicists originally expected that black holes would have masses less than about 40 times that of the Sun, because merging black holes arise from massive stars, which can't hold themselves together if they get too big. The LIGO and Virgo observatories, however, have found many black holes with masses greater than that of 50 suns, with some as massive as 100 suns. Numerous formation scenarios have been proposed to produce such large black holes, but no single scenario has been able to explain the diversity of black hole mergers observed so far, and there is no agreement on which combination of formation scenarios is physically viable. This new study, published in the Astrophysical Journal Letters, is the first to show that both large and small black hole masses can result from a single pathway, wherein the black holes gain mass from the expansion of the universe itself.
Astronomers typically model black holes inside a universe that cannot expand. "It's an assumption that simplifies Einstein's equations because a universe that doesn't grow has much less to keep track of," said Kevin Croker, a professor at the UH Mnoa Department of Physics and Astronomy. "There is a trade-off though: predictions may only be reasonable for a limited amount of time." Because the individual events detectable by LIGO-Virgo only last a few seconds, when analyzing any single event, this simplification is sensible. But these same mergers are potentially billions of years in the making. During the time between the formation of a pair of black holes and their eventual merger, the universe grows profoundly. If the more subtle aspects of Einstein's theory are carefully considered, then a startling possibility emerges: the masses of black holes could grow in lockstep with the universe, a phenomenon that Croker and his team call cosmological coupling. The most well-known example of cosmologically-coupled material is light itself, which loses energy as the universe grows. "We thought to consider the opposite effect," said research co-author and UH Manoa Physics and Astronomy Professor Duncan Farrah. "What would LIGO -- Virgo observe if black holes were cosmologically coupled and gained energy without needing to consume other stars or gas?"
Astronomers typically model black holes inside a universe that cannot expand. "It's an assumption that simplifies Einstein's equations because a universe that doesn't grow has much less to keep track of," said Kevin Croker, a professor at the UH Mnoa Department of Physics and Astronomy. "There is a trade-off though: predictions may only be reasonable for a limited amount of time." Because the individual events detectable by LIGO-Virgo only last a few seconds, when analyzing any single event, this simplification is sensible. But these same mergers are potentially billions of years in the making. During the time between the formation of a pair of black holes and their eventual merger, the universe grows profoundly. If the more subtle aspects of Einstein's theory are carefully considered, then a startling possibility emerges: the masses of black holes could grow in lockstep with the universe, a phenomenon that Croker and his team call cosmological coupling. The most well-known example of cosmologically-coupled material is light itself, which loses energy as the universe grows. "We thought to consider the opposite effect," said research co-author and UH Manoa Physics and Astronomy Professor Duncan Farrah. "What would LIGO -- Virgo observe if black holes were cosmologically coupled and gained energy without needing to consume other stars or gas?"
Lot's of conjecture (Score:4, Interesting)
I used to feel bad because I didn't understand all of astro-physics, but now I understand that there is a lot of conjecture involved. A lot of impressive science has been done, but we're still working on it.
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Only the biggest are detected first (Score:2)
These are all seriously distant past detections right? Back when things were still settling down from the Big Bang. The cluster densities back then must have been such that the night sky would've been a hell of a lot brighter.
Colossal stars would've been the norm. Lasting only a few thousand years maybe. With every single one of them forming a Black Hole ... or being gobbled up by a Black Hole even earlier.
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Its actually contrary to understanding, but the old (now) physics guards fell in love with collapsing stars in the 70's and act as if considering other methods of black hole formation as cheating on their love.
The same is true in other fields, where the old guard basically needs to die before the progress of understanding can continue, such as with ancient egypt and so forth.
Re:Only the biggest are detected first (Score:4, Informative)
These are all seriously distant past detections right? Back when things were still settling down from the Big Bang.
No. The largest black hole collision detected [indiatoday.in] happened about 7 billion years ago. That is about half the current age of the Universe and plenty of time for the reverberations from the Big Bang to have settled down.
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And how even is the spread?
The title is the main point. Only the biggest collisions are being picked up. Of course they're going to give a biased data set. Just like with the size of exoplanets detected so far.
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Also, that large collection of early really big ones ain't just gonna vanish once formed. Obviously, a decent number of them got dressed up as the galaxies we see today.
But many more maybe are just causing mayhem over and over again.
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"These are all seriously distant past detections right? Back when things were still settling down from the Big Bang. The cluster densities back then must have been such that the night sky would've been a hell of a lot brighter."
If we detect a black hole event today, all of the adjacent information that we detect comes from the same time as the black hole event. This would include information about "cluster densities" in the area of the black hole event. At least, that's my understanding of how we view the
Mass == Energy (Score:2, Interesting)
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Thank goodness we have smarter people than them, right here on Slashdot!
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Thank goodness we have smarter people than them, right here on Slashdot!
Well, it's "special" relativity which is for special people. Compare with "general" relativity which any thicko from the general public could fully understand. Here on Slashdot we're so clever that we don't even look at that and go straight on to the special version which gives us full insight uncorrupted by any "general" knowledge.
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special version which gives us full insight uncorrupted by any "general" knowledge.
Yep, we’re special because we can’t see the gravity of the situation
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Ayup - Black Holes must be very special since even Special Relativity cannot explain them. Both Einstein and Hawking must have been suffering from early onset dementia.
Einstein and Hawking both were perfectly capable of explaining Black Holes. You are thinking of singularities.
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A singularity is merely the result of taking the equations to their logical extreme... In one sense, we don't know for sure they exist... their very existance in human belief is BECAUSE of the Einstein equations, not despite them.
Re:Mass == Energy (Score:4, Interesting)
Vacuum energy. Empty space isn't entirely empty due to quantum fluctuations.
Hawking radiation results from virtual particle pairs near the horizon where one particle gets sucked in and the other is finally free of the sibling. This is the cause of black hole evaporation because the process reduces the mass and rotational energy of the black hole. No I don't get how it reduces the mass either. The Hawking radiation might be the thermal radiation from a black hole but the precise relationship is not yet known.
The mechanism alluded to in the article describes a coupling between the expansion energy and Einstein's equations. This isn't proof, it is merely a model that says there is a pathway in our physics theories that allow this to occur.
Re: Mass == Energy (Score:2)
Related to Hawking radiation, I read somewhere that it is possible that most black holes are currently gaining energy (and therefore mass) because the Hawking radiation emitted is smaller than radiation absorbed from background radiation (currently 2.7 kelvin).
Only black holes smaller than around one Earth mass are 'hot' enough to emit more than they absorb, and therefore shrink.
As the Universe cools, it is conjectured that more black holes will enter this state.
That's my understanding anyway
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Re: Mass == Energy (Score:2)
In soviet Russia you suck the black hole?
It's OK (Score:4, Funny)
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Your usage of the term "edge" in this post makes me think one of us two fundamentally misunderstands how universe and its expansion works. Based on anecdotal evidence, it is most likely it's me.
Re:Hawking Radiation = Black Hole Evaporation (Score:5, Interesting)
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It's not expanding, it's asymptotically contracting because the equation is actually (E)^2 = (mc^2)^2. The Big Bang was merely the creation of the event horizon that we exist within. On the outside of the event horizon both time and space asymptotically approach zero, and on the inside of the event horizon both time and space asymptotically approach infinity. It's all about relative perspective.
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This sounds a bit like blackhole cosmology.
https://en.wikipedia.org/wiki/... [wikipedia.org]
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It's not expanding
Uh oh, Better call Saul [nsf.gov] and tell him his Nobel Prize is garbage.
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Seems to me strange to hear information opposite of what we've been told regarding [Stephen] Hawking Radiation. Expansion of the universe would likely happen at the edges instead of throughout the entire universe since that would mean that the universe is not expanding but bloating instead and new particles with mass would have to come into existence throughout all matter, like a cancer growing on the inside.
Competing effects. Hawking radiation slowly bleeds mass energy out of black holes over time, yes. It works best for tiny ones, works very slowly on big ones.
This article says the expansion of space could add mass, and do it faster than Hawking radiation leaks it. The energy is coming from vacuum energy, which is reasonably well understood in QM. Dark Energy could be a source too, it grows as space stretches, but no one understands it at the moment. Note that the expansion of the universe doesn't happen
I blame the universe (Score:2)
A lot of things will be increasing in mass (Score:1)
poof (Score:3)
You know that bit from Douglas Adams about the universe being replaced with a more complicated version every time we figure it out? Yeah, that just happened.
Dark matter? (Score:2)
Since black holes don't emit light, this matter is really, really dark!