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New simulations show how supermassive black holes form
Researchers from Japan add a new wrinkle to a popular theory and set the stage for the formation of monstrous black holes.
- A new theory takes the direct-collapse theory explaining the creation of supermassive black holes around which galaxies turn ones step further.
- The advance is made possible by a super-powerful computer, ATERUI II.
- The new theory is the first that accounts for the likely assortment of heavy elements in early-universe gas clouds.
It seems that pretty much every galaxy we see is spinning around a supermassive black hole. When we say "supermassive," we mean BIG: Each is about 100,000 to tens of billions times the mass of our Sun. Serving as the loci around which our galaxies twirl, they're clearly important to maintaining the universal structures we see. It would be nice to know how they form. We have a pretty good idea how normally-huge-but-not-massive black holes form, but as for the supermassive larger versions, not so much. It's a supermassive missing piece of the universe puzzle.
Now, in research published in Monthly Notices of the Astronomical Society, astrophysicists at Tohoku University in Japan reveal that they may have solved the riddle, supported by new computer simulations that show how supermassive black holes come to be.
The direct collapse theories
Glowing gas and dark dust within the Large Magellanic Cloud
Image source: ESA/Hubble and NASA
The favored theory about the birth of supermassive black holes up to now has been the "direct-collapse" theory. The theory proposes a solution to a cosmic riddle: Supermassive black holes seem to have been born a mere 690 million years after the Big Bang, not nearly long enough for the standard normal black hole genesis scenario to have played out, and on such a large scale. There are two versions of the direct-collapse theory.
One version proposes that if enough gas comes together in a supermassive gravitationally bound cloud, it can eventually collapse into a black hole, which, thanks the cosmic background-radiation-free nature of the very early universe, could then quickly pull in enough matter to go supermassive in a relatively short period of time.
According to astrophysicist Shantanu Basu of Western University in London, Ontario, this would only have been possible in the first 800 million years or so of the universe. "The black holes are formed over a duration of only about 150 million years and grow rapidly during this time," Basu told Live Science in the summer of 2019. "The ones that form in the early part of the 150-million-year time window can increase their mass by a factor of 10 thousand." Basu was lead author of research published last summer in Astrophysical Journal Letters that presented computer models showing this version of direct-collapse is possible.
Another version of the theory suggests that the giant gas cloud collapses into a supermassive star first, which then collapses into a black hole, which then — presumably again thanks to the state of the early universe — sucks up enough matter to go supermassive quickly.
There's a problem with either direct-collapse theory, however, beyond its relatively narrow time window. Previous models show it working only with pristine gas clouds comprised of hydrogen and helium. Other, heavier elements — carbon and oxygen, for example — break the models, causing the giant gas cloud to break up into smaller gas clouds that eventually form separate stars, end of story. No supermassive black hole, and not even a supermassive star for the second flavor of the direct-collapse theory.
A new model
Image source: NAOJ
Japan's National Astronomical Observatory has a supercomputer named "ATERUI II" that was commissioned in 2018. The Tohoku University research team, led by postdoctoral fellow Sunmyon Chon, used ATERUI II to run high-resolution, 3D, long-term simulations to verify a new version of the direct-collapse idea that makes sense even with gas clouds containing heavy elements.
Chon and his team propose that, yes, supermassive gas clouds with heavy elements do break up into smaller gas clouds that wind up forming smaller stars. However, they assert that's not the end of the story.
The scientists say that post-explosion, there remains a tremendous inward pull toward the center of the ex-cloud that drags in all those smaller stars, eventually causing them to grow into a single supermassive star, 10,000 times larger than the Sun. This is a star big enough to produce the supermassive black holes we see when it finally collapses in on itself.
"This is the first time that we have shown the formation of such a large black hole precursor in clouds enriched in heavy-elements," says Chon, adding, "We believe that the giant star thus formed will continue to grow and evolve into a giant black hole."
Modeling the behavior of an expanded number of elements within the cloud while faithfully carrying forward those models through the violent breakup of the cloud and its aftermath requires such high computational overhead that only a computer as advanced as ATERUI II could pull off.
Being able to develop a theory that takes into account, for the first time, the likely complexity of early-universe gas clouds makes the Tohoku University idea the most complete, plausible explanation of the universe's mysterious supermassive black holes. Kazuyuki Omukai, also of Tohoku University says, "Our new model is able to explain the origin of more black holes than the previous studies, and this result leads to a unified understanding of the origin of supermassive black holes."
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Astronomers find these five chapters to be a handy way of conceiving the universe's incredibly long lifespan.
- We're in the middle, or thereabouts, of the universe's Stelliferous era.
- If you think there's a lot going on out there now, the first era's drama makes things these days look pretty calm.
- Scientists attempt to understand the past and present by bringing together the last couple of centuries' major schools of thought.
The 5 eras of the universe<p>There are many ways to consider and discuss the past, present, and future of the universe, but one in particular has caught the fancy of many astronomers. First published in 1999 in their book <a href="https://amzn.to/2wFQLiL" target="_blank"><em>The Five Ages of the Universe: Inside the Physics of Eternity</em></a>, <a href="https://en.wikipedia.org/wiki/Fred_Adams" target="_blank">Fred Adams</a> and <a href="https://en.wikipedia.org/wiki/Gregory_P._Laughlin" target="_blank">Gregory Laughlin</a> divided the universe's life story into five eras:</p><ul><li>Primordial era</li><li>Stellferous era</li><li>Degenerate era</li><li>Black Hole Era</li><li>Dark era</li></ul><p>The book was last updated according to current scientific understandings in 2013.</p><p>It's worth noting that not everyone is a subscriber to the book's structure. Popular astrophysics writer <a href="https://www.forbes.com/sites/ethansiegel/#30921c93683e" target="_blank">Ethan C. Siegel</a>, for example, published an article on <a href="https://www.forbes.com/sites/startswithabang/2019/07/26/we-have-already-entered-the-sixth-and-final-era-of-our-universe/#7072d52d4e5d" target="_blank"><em>Medium</em></a> last June called "We Have Already Entered The Sixth And Final Era Of Our Universe." Nonetheless, many astronomers find the quintet a useful way of discuss such an extraordinarily vast amount of time.</p>
The Primordial era<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMjkwMTEyMi9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYyNjEzMjY1OX0.PRpvAoa99qwsDNprDme9tBWDim6mS7Mjx6IwF60fSN8/img.jpg?width=980" id="db4eb" class="rm-shortcode" data-rm-shortcode-id="0e568b0cc12ed624bb8d7e5ff45882bd" data-rm-shortcode-name="rebelmouse-image" data-width="1440" data-height="1049" />
Image source: Sagittarius Production/Shutterstock<p> This is where the universe begins, though what came before it and where it came from are certainly still up for discussion. It begins at the Big Bang about 13.8 billion years ago. </p><p> For the first little, and we mean <em>very</em> little, bit of time, spacetime and the laws of physics are thought not yet to have existed. That weird, unknowable interval is the <a href="https://www.universeadventure.org/eras/era1-plankepoch.htm" target="_blank">Planck Epoch</a> that lasted for 10<sup>-44</sup> seconds, or 10 million of a trillion of a trillion of a trillionth of a second. Much of what we currently believe about the Planck Epoch eras is theoretical, based largely on a hybrid of general-relativity and quantum theories called quantum gravity. And it's all subject to revision. </p><p> That having been said, within a second after the Big Bang finished Big Banging, inflation began, a sudden ballooning of the universe into 100 trillion trillion times its original size. </p><p> Within minutes, the plasma began cooling, and subatomic particles began to form and stick together. In the 20 minutes after the Big Bang, atoms started forming in the super-hot, fusion-fired universe. Cooling proceeded apace, leaving us with a universe containing mostly 75% hydrogen and 25% helium, similar to that we see in the Sun today. Electrons gobbled up photons, leaving the universe opaque. </p><p> About 380,000 years after the Big Bang, the universe had cooled enough that the first stable atoms capable of surviving began forming. With electrons thus occupied in atoms, photons were released as the background glow that astronomers detect today as cosmic background radiation. </p><p> Inflation is believed to have happened due to the remarkable overall consistency astronomers measure in cosmic background radiation. Astronomer <a href="https://www.youtube.com/watch?v=IGCVTSQw7WU" target="_blank">Phil Plait</a> suggests that inflation was like pulling on a bedsheet, suddenly pulling the universe's energy smooth. The smaller irregularities that survived eventually enlarged, pooling in denser areas of energy that served as seeds for star formation—their gravity pulled in dark matter and matter that eventually coalesced into the first stars. </p>
The Stelliferous era<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMjkwMTEzNy9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYxMjA0OTcwMn0.GVCCFbBSsPdA1kciHivFfWlegOfKfXUfEtFKEF3otQg/img.jpg?width=980" id="bc650" class="rm-shortcode" data-rm-shortcode-id="c8f86bf160ecdea6b330f818447393cd" data-rm-shortcode-name="rebelmouse-image" data-width="481" data-height="720" />
Image source: Casey Horner/unsplash<p>The era we know, the age of stars, in which most matter existing in the universe takes the form of stars and galaxies during this active period. </p><p>A star is formed when a gas pocket becomes denser and denser until it, and matter nearby, collapse in on itself, producing enough heat to trigger nuclear fusion in its core, the source of most of the universe's energy now. The first stars were immense, eventually exploding as supernovas, forming many more, smaller stars. These coalesced, thanks to gravity, into galaxies.</p><p>One axiom of the Stelliferous era is that the bigger the star, the more quickly it burns through its energy, and then dies, typically in just a couple of million years. Smaller stars that consume energy more slowly stay active longer. In any event, stars — and galaxies — are coming and going all the time in this era, burning out and colliding.</p><p>Scientists predict that our Milky Way galaxy, for example, will crash into and combine with the neighboring Andromeda galaxy in about 4 billion years to form a new one astronomers are calling the Milkomeda galaxy.</p><p>Our solar system may actually survive that merger, amazingly, but don't get too complacent. About a billion years later, the Sun will start running out of hydrogen and begin enlarging into its red giant phase, eventually subsuming Earth and its companions, before shrining down to a white dwarf star.</p>
The Degenerate era<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMjkwMTE1MS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYxNTk3NDQyN30.gy4__ALBQrdbdm-byW5gQoaGNvFTuxP5KLYxEMBImNc/img.jpg?width=980" id="77f72" class="rm-shortcode" data-rm-shortcode-id="08bb56ea9fde2cee02d63ed472d79ca3" data-rm-shortcode-name="rebelmouse-image" data-width="1440" data-height="810" />
Image source: Diego Barucco/Shutterstock/Big Think<p>Next up is the Degenerate era, which will begin about 1 quintillion years after the Big Bang, and last until 1 duodecillion after it. This is the period during which the remains of stars we see today will dominate the universe. Were we to look up — we'll assuredly be outta here long before then — we'd see a much darker sky with just a handful of dim pinpoints of light remaining: <a href="https://earthsky.org/space/evaporating-giant-exoplanet-white-dwarf-star" target="_blank">white dwarfs</a>, <a href="https://earthsky.org/space/new-observations-where-stars-end-and-brown-dwarfs-begin" target="_blank">brown dwarfs</a>, and <a href="https://earthsky.org/astronomy-essentials/definition-what-is-a-neutron-star" target="_blank">neutron stars</a>. These"degenerate stars" are much cooler and less light-emitting than what we see up there now. Occasionally, star corpses will pair off into orbital death spirals that result in a brief flash of energy as they collide, and their combined mass may become low-wattage stars that will last for a little while in cosmic-timescale terms. But mostly the skies will be be bereft of light in the visible spectrum.</p><p>During this era, small brown dwarfs will wind up holding most of the available hydrogen, and black holes will grow and grow and grow, fed on stellar remains. With so little hydrogen around for the formation of new stars, the universe will grow duller and duller, colder and colder.</p><p>And then the protons, having been around since the beginning of the universe will start dying off, dissolving matter, leaving behind a universe of subatomic particles, unclaimed radiation…and black holes.</p>
The Black Hole era<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMjkwMTE2MS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYzMjE0OTQ2MX0.ifwOQJgU0uItiSRg9z8IxFD9jmfXlfrw6Jc1y-22FuQ/img.jpg?width=980" id="103ea" class="rm-shortcode" data-rm-shortcode-id="f0e6a71dacf95ee780dd7a1eadde288d" data-rm-shortcode-name="rebelmouse-image" data-width="1400" data-height="787" />
Image source: Vadim Sadovski/Shutterstock/Big Think<p> For a considerable length of time, black holes will dominate the universe, pulling in what mass and energy still remain. </p><p> Eventually, though, black holes evaporate, albeit super-slowly, leaking small bits of their contents as they do. Plait estimates that a small black hole 50 times the mass of the sun would take about 10<sup>68</sup> years to dissipate. A massive one? A 1 followed by 92 zeros. </p><p> When a black hole finally drips to its last drop, a small pop of light occurs letting out some of the only remaining energy in the universe. At that point, at 10<sup>92</sup>, the universe will be pretty much history, containing only low-energy, very weak subatomic particles and photons. </p>
The Dark Era<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMjkwMTE5NC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY0Mzg5OTEyMH0.AwiPRGJlGIcQjjSoRLi6V3g5klRYtxQJIpHFgZdZkuo/img.jpg?width=980" id="60c77" class="rm-shortcode" data-rm-shortcode-id="7a857fb7f0d85cf4a248dbb3350a6e1c" data-rm-shortcode-name="rebelmouse-image" data-width="1440" data-height="810" />
Image source: Big Think<p>We can sum this up pretty easily. Lights out. Forever.</p>
Dr. Katie Mack explains what dark energy is and two ways it could one day destroy the universe.
- The universe is expanding faster and faster. Whether this acceleration will end in a Big Rip or will reverse and contract into a Big Crunch is not yet understood, and neither is the invisible force causing that expansion: dark energy.
- Physicist Dr. Katie Mack explains the difference between dark matter, dark energy, and phantom dark energy, and shares what scientists think the mysterious force is, its effect on space, and how, billions of years from now, it could cause peak cosmic destruction.
- The Big Rip seems more probable than a Big Crunch at this point in time, but scientists still have much to learn before they can determine the ultimate fate of the universe. "If we figure out what [dark energy is] doing, if we figure out what it's made of, how it's going to change in the future, then we will have a much better idea for how the universe will end," says Mack.
A unique exoplanet without clouds or haze was found by astrophysicists from Harvard and Smithsonian.
- Astronomers from Harvard and Smithsonian find a very rare "hot Jupiter" exoplanet without clouds or haze.
- Such planets were formed differently from others and offer unique research opportunities.
- Only one other such exoplanet was found previously.
Munazza Alam – a graduate student at the Center for Astrophysics | Harvard & Smithsonian.
Credit: Jackie Faherty