James Webb Telescope Detects Earliest Known Black Hole (npr.org) 7
The Hubble Space Telescope's discovery of GN-z11 in 2016 marked it as the most distant galaxy known at that time, notable for its unexpected luminosity despite its ancient formation just 400 million years after the Big Bang. Now, in a paper published in Nature, astrophysicist Roberto Maiolino proposes that this brightness could be due to a supermassive black hole, challenging current understanding of early black hole formation and growth. NPR reports: This wasn't just any black hole. First -- assuming that the black hole started out small -- it could be devouring matter at a ferocious rate. And it would have needed to do so to reach its massive size. "This black hole is essentially eating the [equivalent of] an entire Sun every five years," says Maiolino. "It's actually much higher than we thought could be feasible for these black holes." Hence the word "vigorous" in the paper's title. Second, the black hole is 1.6 million times the mass of our Sun, and it was in place just 400 million years after the dawn of the universe. "It is essentially not possible to grow such a massive black hole so fast so early in the universe," Maiolino says. "Essentially, there is not enough time according to classical theories. So one has to invoke alternative scenarios."
Here's scenario one -- rather than starting out small, perhaps supermassive black holes in the early universe were simply born big due to the collapse of vast clouds of primordial gas. Scenario two is that maybe early stars collapsed to form a sea of smaller black holes, which could have then merged or swallowed matter way faster than we thought, causing the resulting black hole to grow quickly. Or perhaps it's some combination of both. In addition, it's possible that this black hole is harming the growth of the galaxy GN-z11. That's because black holes radiate energy as they feed. At such a high rate of feasting, this energy could sweep away the gas of the host galaxy. And since stars are made from gas, it could quench star formation, slowly strangling the galaxy. Not to mention that without gas, the black hole wouldn't have anything to feed on and it too would die.
Here's scenario one -- rather than starting out small, perhaps supermassive black holes in the early universe were simply born big due to the collapse of vast clouds of primordial gas. Scenario two is that maybe early stars collapsed to form a sea of smaller black holes, which could have then merged or swallowed matter way faster than we thought, causing the resulting black hole to grow quickly. Or perhaps it's some combination of both. In addition, it's possible that this black hole is harming the growth of the galaxy GN-z11. That's because black holes radiate energy as they feed. At such a high rate of feasting, this energy could sweep away the gas of the host galaxy. And since stars are made from gas, it could quench star formation, slowly strangling the galaxy. Not to mention that without gas, the black hole wouldn't have anything to feed on and it too would die.
... die? (Score:2)
Do black holes need to continue 'feasting', as the summary calls it, in order to maintain themselves? If it stops getting extra material, won't it just sit there until the end of the universe, forever stuck at its size and density since nothing can escape it?
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They do lose energy over time in the form of Hawking Radiation. That's when virtual particle pairs randomly come into existence at the edge of the event horizon. One flies away, but the other falls in. It's incredibly slow, but eventually all black holes will evaporate this way. When their mass gets below black hole level, they explode.
That's my layman's understanding!
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I swim in these waters and your lay understanding is spot on. Here's support from ChatGPT:
Yes, according to current scientific understanding, black holes can undergo a process called Hawking radiation, proposed by physicist Stephen Hawking. This process involves the gradual loss of mass and energy from a black hole over an extremely long period. Eventually, if a black hole continues to radiate energy, it will lose mass and shrink until it theoretically reaches a point known as "black hole evaporation." At this point, the black hole would no longer exist. It's important to note that this process takes an incredibly long time, especially for stellar-mass black holes, making it practically unobservable on human timescales.
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The "evaporation timescale" for a solar-mass black hole is, IIRC, on the order of 10^100 years. A mere 10^10 times longer than the longest-lived of just-barely fusing red dwarves.
Yeah, qualifies as "slow", but credibly slow.
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Re:unproven hypotheses. (Score:4, Interesting)
The other, on the formation rate of stars and black holes in galaxies is open to a lot of questioning too. Specifically, the inferences of the brightness of the galaxies (from which their distance is deduced, beyond the minimum distances given by cosmology and spectroscopy) are heavily dependent on the assumption (granted as such by cosmologists) that these galaxies formed with a mixture of star sizes similar to those forming in the Milky Way at present (the "Initial Mass Function"). That assumption is under serious re-consideration, in part because of the discovery of (seemingly) really ancient galaxies like this, and moderate changes to the inferred IMF of distant galaxies make serious changes to the inferred distances and ages.
There are a lot of eggs up in the air in cosmology - due to observations like this.
Which makes me more interested in reading about them, not less.