Advanced life should have peaked billions of years ago, according to an article (2023)

Do humans lack entertainment? Are SETI, the Drake Equation, and the Fermi Paradox just a product of our ignorance about advanced life in the universe? How do we know if we are wrong?

A new study focuses on black holes and their powerful impact on Earthstar formationThis suggests that we, as advanced life forms, may be relics of a bygone era in the universe.

Universe Today readers are familiar with SETI, the Drake equation, and the Fermi paradox. All three are different ways humans deal with their situation. All of this ties into one big question: are we alone? We ask these questions as if humans are waking up on this planet and looking around and wondering where everyone else is. What happened.

We live in the age of exoplanet discoveries, and astronomers are busy searching for potentially habitable planets—that is, planets with liquid surface water. It's a simple definition of habitability, but it's useful for cataloging the thousands of exoplanets we've discovered and the millions more waiting to be discovered. Because, a priori tell us, a single planet is the key to finding life.

But what about habitability, especially a wide-angle view of other advanced life forms? Is combing individual planets a way to find other life? Or are some galaxies more likely to develop life of their own, which could take billions of years to develop? Do black holes in galaxies affect the possibility of advanced life?

David Garofalo is an associate professor of physics at Kennesaw State University in Georgia. Garofalo studies the physics of black holes and in a new paper explains how black holes affect the existence of advanced life.

The paper is "Advanced life culminating in black holes billions of years ago." It can be found atarXivServer for preprints, upcoming magazine publicationsGalaxyGarofalo is the sole author and the article has not been peer reviewed.

Garofalo explains how feedback from black holes can promote or prevent star formation. Its presence depends on the environment and whether the SMBH is in a poor or rich environment.

"The link between black holes and star formation allows us to link black holes to places and times when extraterrestrial intelligence (ETI) is most likely to emerge," Garofalo wrote.

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The Drake Equation tries to shape how we think about other intelligent civilizations. This is a probability equation that attempts to calculate the number of intelligent, communicating civilizations that exist in the galaxy. Garofalo's efforts extend beyond the galaxy and into space. But the universe is vast and ancient. Where to start?

Garofalo started with black holes, feedback, and star formation.

"Our understanding of the processes that determine where and when star formation peaks in the universe has matured enough that we can begin to explore the question of intelligence more broadly in space and time." Garofalo writes. , but the effect is different.

Garofalo has extensively studied black holes, and this paper draws heavily on his research and the work of others in the same field. Garofalo believes that advanced life peaked billions of years ago, all due to the direct link between mergers, black holes, star formation, and the formation of planets around those stars. It starts with the possible merger of the black hole.active galactic nucleus(AGN,) This is an expression for asuper massive body(SMBH) at the center of a galaxy that has accumulated enough matter to shine brightly. Some AGN emit jets that depend on the nature of the matter accumulating in the black hole. Matter is the gas in a galaxy, and different galaxies have different gaseous environments.

Feedback from the black hole plays an important role in Garofalo's work. Different black holes trigger different types of feedback, and some trigger higher rates of star formation. Jets are the main way a black hole interacts with its surrounding medium, extracting matter from itself.accretion diskto your environment.

Sometimes all this feedback drives star formation. But sometimes it injects too much energy into its galaxy or cluster of galaxies, which can stifle star formation. It makes the gas too hot, and for it to collapse and form a star, the gas has to be cold. A key part of Garofalo's work is determining when feedback from the black hole promotes star formation and when it suppresses it.

Sometimes due to mergers, a black hole's accretion disk spins in the opposite direction of the black hole itself, affecting feedback and jets. "Counterrotation is associated with several general relativistic effects that maximize the power and collimation of the jet," Garofalo wrote. "This jet passes through the cold gas and pushes it into a state of higher density, which triggers star formation."

But that counter-spinning accretion disk can slow down and stop the black hole's rotation. Finally he reversed and accelerated again. When a black hole has zero spin, it stops producing jets, and so does its feedback to galaxies or clusters of galaxies. The zero spin state also tilts the accretion disk. At that point, "the incoming gas forms a disk that maintains the angular momentum of the volume of gas in the larger galaxy's reservoir," Garofalo explains. The duration of the spin-zero state depends on whether the galaxy is gas-poor or gas-rich. It persisted for about eight million years in a gas-poor environment.

But in denser environments, where gas is more abundant, things change. "In contrast, in denser environments, black holes tend to be more massive, with more powerful jets and larger back effects," Garofalo explains. This is due to a change in the way gas collects on the disk. A different type of flow is needed than in the sparse environment.

The different fluxes mean that black holes in dense environments take two orders of magnitude longer to spin. result? "Thus, on average, the most fertile environments produce powerful collimated jets that promote star formation on time scales about two orders of magnitude longer than the most isolated environments," Garofalo writes. Eventually the spin reaches zero, the jet stops. Crucially, the jets will only reemerge in denser environments.

That's a lot of information for us non-astrophysicists, but Garofalo clarified a key part for us, and it boils down to sparse or dense environments. "The key difference is that in the isolated environment there was only positive AGN feedback, while in the richer environment there was both positive and negative feedback." That means they target the galaxy's gas more directly, heating it up and suppressing star formation.

In this case, the result is fewer stars. Fewer stars means fewer planets, which means fewer opportunities for higher life. But this effect goes beyond the speed at which stars and planets form. When a galaxy's gas heats up, it emits a halo of X-rays that permeates the galaxy and affects the chemical composition of the planets, preventing them from becoming habitable.

This is bad news for advanced life in galaxies and galaxy clusters with denser gas. While there was more gas, the material from which stars form, the gas superheated and stifled star formation.

But what about rare gas galaxies and star clusters?

"In contrast, in more isolated environments, stars evolve towards the main sequence without being perturbed by active feedback from galactic nuclei," concludes Garofalo. This is also critical because we are not just talking about the emergence of life, life could have appeared on Earth in a few hundred million years. We are talking about advanced life like ours, which took 4.5 billion years to appear on Earth. Main sequence stars are the longest-lived and most stable stars. Compared to other stars, the possibility of advanced life around main sequence stars is much higher.

Taking all these factors into account, Garofalo reformulated Drake's equations to include feedback from black holes. "He tells us where in the universe we are most likely to find advanced life. The answer lies in isolated wild environments," he explained.

But the place where advanced life can appear is only a part. Garofalo wondered when that would be most likely. It all goes back to the original black hole merger, which produced a counter-growing black hole. "Counter-rotating accretionary black holes are the products of mergers, with the merger function peaking at redshift 2," he wrote. About 11 billion years ago, when the universe was 2.8 billion years old, the redshift was 2.

"Therefore, this is a redshift that corresponds to the time when the largest number of isolated field galaxies undergo mergers leading to the inflow of cold gas into the nuclei of the newly formed galaxies and counter-rotating deposition around them." newly formed black holes," he concludes. Garofalo.

This is the era of active galactic nuclei and their jets. They initiated the creation of stars and planets. Earth formed 4.5 billion years ago, and our advanced life forms capable of interstellar communication are only just emerging. So, using our reference point, that's around 4.5 billion years after the correct time.black holeAdvanced life can appear in real galaxies. Garofalo rounded it up to 5 billion years. "So we assume a reference value of 5 billion years, which brings us to 7.8 billion years after the Big Bang, or 6 billion years ago."

At this point, astute readers may have questions about metallicity. The lower abundance of metals 6 billion years ago, will that affect the types of planets that form and whether advanced life can arise on them?

unnecessary.

Garofalo points out that the galaxies most likely to have critical AGN are isolated elliptical galaxies. But these aren't dead old red elliptical galaxies. What Garofalo says is different. Instead, "these isolated elliptical galaxies are not expected to contain low metallicity because they are powered by AGN that is fused with abundant cold gas, which may come from disk galaxies," he explained. old red and dead ovalGalaxyThey are also known to be populated by older stars and dominated by M-type dwarfs, or red dwarfs, whose habitable zone "is closer to the star and subject to stellar flares and tidally locked rotation, which is not conducive to the development of life". ' Garofalo wrote. But a subset ofelliptical galaxyWhat you are talking about is not dominated by red dwarfs.

So we have it. If Garofalo is right, then we need to rethink SETI. "Given the time and place identified for ETI in this paper, we expect that SETI searches will require signs of a Kardashev Type III civilization," he wrote in his conclusion. A Kardashev Type III civilization is one that captures all the energy emitted by its galaxy.

According to Garofalo's writings, humans are truly retarded. "To the extent that one day we could be talking about a peak in the emergence of technologically advanced life in the universe, our simplified investigation of the origin of life in the context of AGN feedback suggests that time has passed," he said. . Resume. "So we on Earth are late."

We may be late, but we are not necessarily alone. Other partygoers may have recently arrived. We are here so others can be here too.

This is an open question when it comes to communication with another advanced civilization. But look at us. Advanced life is just emerging. Perhaps one day, the two civilizations will come into contact.

To do this, we need to know where to direct our efforts in this vast universe. If this work holds up, it could help advance the search for extraterrestrial intelligence by showing us where to look.

And where it shouldn't be.