James Webb telescope reveals 3 possible 'dark stars' — galaxy-sized objects powered by invisible dark matter

By Robert Lea published about 3 hours ago

Three early galaxies discovered by the James Webb Space Telescope could actually be titanic stars powered by a dark matter heart.

Three objects seen by the JWST in December 2022 and identified as galaxies may actually be huge stars powered by dark matter (Image credit: NASA/ ESA)

The James Webb Space Telescope (JWST) may have found evidence of a strange and elusive type of star that only existed in the very early universe, when invisible dark matter was one of the only available fuel sources.

New research suggests that three of the earliest objects identified as galaxies by the JWST aren't galaxies at all, but rather "dark stars" — immense, ultrabright hypothetical objects that are powered by dark matter rather than nuclear fusion. If the theory is correct, then this could finally help scientists better understand dark matter, the universe's most mysterious component.

Related: James Webb telescope discovers the 4 oldest galaxies in the universe

"These things are atomic matter that is powered by dark matter, and one supermassive dark star could be as bright as an entire galaxy containing normal fusion-powered stars," astrophysicist Katherine Freese, an astrophysicist at the University of Texas at Austin and lead author of a new study published July 11 in  the journal Proceedings of the National Academy of Sciences, told Live Science.

Explosive annihilation


A map of gas and dark matter in a merging galaxy, with blue and green light indicating a gravitationally massive heart of dark matter at the galaxy's center. (Image credit: NASA Goddard)

According to theory, dark stars are enormous in comparison to "ordinary" stars that exist in the universe today, like the sun. Dark stars are hypothesized to have widths hundreds of times greater than the sun's. These stars, composed mostly of hydrogen and some helium, existed in protogalaxies when the universe contained mostly those two elements; heavier elements hadn't yet been forged by nuclear fusion in stars. However, about one thousandth of a dark star’s mass would be made of a secret fuel source  —  dark matter.


Dark matter, which is all but invisible because it doesn't interact with light, makes up an estimated 85% of the matter in the universe. Theory suggests that when two dark matter particles collide, they may "annihilate" each other, turning their combined mass into a shower of energetic gamma-ray radiation.

"If dark matter is self-annihilating, then the annihilation products could get stuck inside this hydrogen cloud,” that makes up dark stars, Freese said. “And what that means is you're taking all of the energy that used to be in the mass of the dark matter and dumping it into this cloud," Feese said.

Freese added that while "everyday" stars depend on high temperatures, dark matter annihilation could occur at any temperature.

"Dark matter annihilation doesn't care about the temperature," Freese said. "So you have dark matter annihilation throughout the entire [width] of the dark star. And the surface temperature is relatively cool. Because of that, there's no ionizing photons or other stuff coming off preventing the accretion of more matter."

In contrast, when normal stars have acquired enough mass to start nuclear fusion, the radiation that they pump out pushes away the gas envelope that surrounds them, preventing them from accreting more matter and thus growing further.

This means that, while dark stars may start out with a mass about the same as the sun, the objects can accrete more and more matter, growing to be a million times as massive as the sun, and a billion times as bright, Freese added.
Dark star, or ancient galaxy?

Given their huge size, dark stars would appear as more spread-out objects rather than as point-like objects, like modern-day stars. This is how three ancient objects detected by the JWST — namedJADES-GS-z13–0, JADES-GS-z12–0, and JADES-GS-z11–0 — could have been misidentified as galaxies, according to the new research. These candidate dark stars date to between 320 million and to 420 million years after the Big Bang.

But, the dark matter annihilation process can't continue forever. Dark stars sit in the dark-matter-rich centers of protogalaxies, which merge together continuously to form proper galaxies, and eventually, this moves dark stars away from their dark matter fuel.

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"As dark stars get displaced from the dark-matter-rich center, the dark stars start collapsing," Freese explained. "This will trigger fusion in the smaller ones, creating ordinary fusion-powered stars [which are all created from collapsing clouds of gas]. The bigger ones will collapse immediately into black holes."

This means that dark stars don't exist in the universe today, Freese added. However, it’s difficult to pinpoint exactly when in the 13.8-billion-year history of the universe that dark stars would have ceased to be.

Confirming the existence of dark stars via these JWST observations would be huge, but Freese pointed out that she and the team aren't quite there yet. This confirmation would require either looking at these candidate dark stars for much longer to build a more complete picture of their light output, or waiting for magnified observations that better reveal the light emissions of these objects, which could allow scientists to identify whether the objects have pure hydrogen and helium compositions, as would be expected from dark stars.

"The dark star idea has been hanging in there for many years, and it would be extremely exciting to me to have this proven correct," Freese concluded.

Invisible supernovas called 'bosenovas' may be exploding all around us, new research suggests

Paul Sutter

LIVE SCIENCE
Tue, July 25, 2023

A wispy red bubble of matter on a dense background of stars. 

A Hubble image of a supernova.

All around the universe, invisible stars may be dying in high-energy explosions, and new research suggests how scientists could actually detect these unseen catastrophes.

In a paper published June 28 in the preprint database arXiv, a team of astrophysicists explored what would happen when boson stars — theoretical large objects made of invisible dark matter — reached the ends of their lives. The result, they wrote, is a massive explosion similar to a supernova, only invisible: a "bosenova."
The invisible universe

Dark matter is a mysterious substance that makes up more than 85% of the mass of almost every galaxy in the universe. While astronomers have found multiple lines of evidence pointing to its existence, all of those lines depend on dark matter's gravitational influence on normal matter. We have yet to detect the presence of dark matter in any other way, so the identity of the particle that's responsible for dark matter remains in question.


Related: Strange star system may hold first evidence of an ultra-rare 'dark matter star'

For years, the leading theory was that the dark matter particle was heavy — as heavy, if not heavier than, particles like protons and neutrons. But searches for the interactions between heavy dark matter and normal matter have come up empty. So now, theorists are turning to models in which dark matter is extremely light.

For perspective, the lightest known particle is the neutrino, which is about 500,000 times lighter than an electron. In the most extreme models, the lightweight dark matter can be billions of times lighter than a neutrino.

If dark matter has such a small mass, it will behave in unexpected ways. For example, instead of zipping around the cosmos like particles, it would slosh around like waves. These waves could also bunch together into tight clumps in a phenomenon dubbed "boson stars," because in these models, dark matter is a kind of particle known as a boson.

These boson stars would maintain equilibrium through the interaction of two competing forces. On one hand is gravity, with the mass of the dark matter always wanting to pull the star into a tighter clump. But the dark matter has energy, which resists the pull of gravity, forming a stable star that would be completely invisible.

As the boson star aged, it would slowly gain mass, either by accumulating new dark matter or by merging with other boson stars, according to the new research. Eventually, the star's mass would increase to a critical tipping point where the energy of the dark matter could no longer resist the pull of gravity — so the boson star would begin to collapse.

This collapse would happen relatively slowly, and at first, nothing catastrophic would happen. But as the dark matter crammed together, individual particles would start to bump into each other, annihilating each other and releasing energy. The energy from the collapse would get released in the form of high-energy, high-velocity particles jetting away from the boson star. However, because these particles would be so incredibly light, they would appear as a burst of dark matter waves emitted by the dying boson star.

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As an analogy, when normal stars die in supernovas, they release a tremendous number of photons, or particles of light. But because photons are massless, they appear as waves of electricity and magnetism — light.

By contrast, the hypothetical event described by the researchers, which they dubbed a "bosenova," would be completely invisible. Bosenovas might even be going off near our own solar system, and we would never know it.

The only way to detect a bosenova explosion would be through detectors designed to find ultralight dark matter. Many experiments around the globe are already searching for lightweight dark matter. A bosenova would appear to these detectors as a surge of dark matter coming from a specific direction in the sky, just like a traditional supernova appears as a surge of light. Now that the researchers have outlined what a bosenova signature would look like, they hope these experiments will find traces of those fleeting signals.

Measuring helium in distant galaxies may give physicists insight into why the universe exists

The Conversation
July 27, 2023

The Universe 

When theoretical physicists like myself say that we’re studying why the universe exists, we sound like philosophers. But new data collected by researchers using Japan’s Subaru telescope has revealed insights into that very question.

Japan’s Subaru telescope, located on Mauna Kea in Hawaii.

Panoramio/Wikimedia Commons, CC BY-ND

The Big Bangkick-started the universe as we know it 13.8 billion years ago. Many theories in particle physics suggest that for all the matter created at the universe’s conception, an equal amount of antimatter should have been created alongside it. Antimatter, like matter, has mass and takes up space. However, antimatter particles exhibit the opposite properties of their corresponding matter particles.

When pieces of matter and antimatter collide, they annihilate each other in a powerful explosion, leaving behind only energy. The puzzling thing about theories that predict the creation of an equal balance of matter and antimatter is that if they were true, the two would have totally annihilated each other, leaving the universe empty. So there must have been more matter than antimatter at the birth of the universe, because the universe isn’t empty – it’s full of stuff that’s made of matter like galaxies, stars and planets. A little bit of antimatter exists around us, but it is very rare.

As a physicist working on Subaru data, I’m interested in this so-called matter-antimatter asymmetry problem. In our recent study, my collaborators and I found that the telescope’s new measurement of the amount and type of helium in faraway galaxies may offer a solution to this long-standing mystery.
After the Big Bang

In the first milliseconds after the Big Bang, the universe was hot, dense and full of elementary particles like protons, neutrons and electrons swimming around in a plasma. Also present in this pool of particles were neutrinos, which are very tiny, weakly interacting particles, and antineutrinos, their antimatter counterparts.


The Big Bang created fundamental particles that make up other particles like protons and neutrons. Neutrinos are another type of fundamental particle. 

Alfred Pasieka/Science Photo Library via Getty Images


Physicists believe that just one second after the Big Bang, the nuclei of light elements like hydrogen and helium began to form. This process is known as Big Bang Nucleosynthesis. The nuclei formed were about 75% hydrogen nuclei and 24% helium nuclei, plus small amounts of heavier nuclei.

The physics community’s most widely accepted theory on the formation of these nuclei tells us that neutrinos and antineutrinos played a fundamental role in the creation of, in particular, helium nuclei.

Helium creation in the early universe happened in a two-step process. First, neutrons and protons converted from one to the other in a series of processes involving neutrinos and antineutrinos. As the universe cooled, these processes stopped and the ratio of protons to neutrons was set.

As theoretical physicists, we can create models to test how the ratio of protons to neutrons depends on the relative number of neutrinos and antineutrinos in the early universe. If more neutrinos were present, then our models show more protons and fewer neutrons would exist as a result.

As the universe cooled, hydrogen, helium and other elements formed from these protons and neutrons. Helium is made up of two protons and two neutrons, and hydrogen is just one proton and no neutrons. So the fewer the neutrons available in the early universe, the less helium would be produced.

Because the nuclei formed during Big Bang Nucleosynthesis can still be observed today, scientists can infer how many neutrinos and antineutrinos were present during the early universe. They do this by looking specifically at galaxies that are rich in light elements like hydrogen and helium.


In a series of high-energy particle collisions, elements like helium are formed in the early universe. Here, D stands for deuterium, an isotope of hydrogen with one proton and one neutron, and γ stands for photons, or light particles. In the series of chain reactions shown, protons and neutrons fuse to form deuterium, then these deuterium nuclei fuse to form helium nuclei. 

Anne-Katherine Burns

A clue in helium


Last year, the Subaru Collaboration – a group of Japanese scientists working on the Subaru telescope – released data on 10 galaxies far outside of our own that are almost exclusively made up of hydrogen and helium.

Using a technique that allows researchers to distinguish different elements from one another based on the wavelengths of light observed in the telescope, the Subaru scientists determined exactly how much helium exists in each of these 10 galaxies. Importantly, they found less helium than the previously accepted theory predicted.

With this new result, my collaborators and I worked backward to find the number of neutrinos and antineutrinos necessary to produce the helium abundance found in the data. Think back to your ninth grade math class when you were asked to solve for “X” in an equation. What my team did was essentially the more sophisticated version of that, where our “X” was the number of neutrinos or antineutrinos.

The previously accepted theory predicted that there should be the same number of neutrinos and antineutrinos in the early universe. However, when we tweaked this theory to give us a prediction that matched the new data set, we found that the number of neutrinos was greater than the number of antineutrinos.
What does it all mean?

This analysis of new helium-rich galaxy data has a far-reaching consequence – it can be used to explain the asymmetry between matter and antimatter. The Subaru data points us directly to a source for that imbalance: neutrinos. In this study, my collaborators and I proved that this new measurement of helium is consistent with there being more neutrinos then antineutrinos in the early universe. Through known and likely particle physics processes, the asymmetry in the neutrinos could propagate into an asymmetry in all matter.

The result of our study is a common type of result in the theoretical physics world. Basically, we discovered a viable way in which the matter-antimatter asymmetry could have been produced, but that doesn’t mean it definitely was produced in that way. The fact that the data fits with our theory is a hint that the theory we’ve proposed might be the correct one, but this fact alone doesn’t mean that it is.

So, are these tiny little neutrinos the key to answering the age old question, “Why does anything exist?” According to this new research, they just might be.

Anne-Katherine Burns, Ph.D. Candidate in Theoretical Particle Physics, University of California, Irvine


This article is republished from The Conversation under a Creative Commons license. Read the original article.

New analysis of SuperCDMS data sets tighter detection limits for dark matter

by Kimberly Hickok, SLAC National Accelerator Laboratory

A collision of clusters of galaxies, showing separation of dark matter (shaded blue) from 

normal matter (shaded pink).  Credit: NASA

For nearly a century, dark matter has continued to evade direct detection, pushing scientists to come up with even more creative methods of searching. Increasingly sensitive detection experiments are a major undertaking, however, which means scientists want to be sure they analyze data from these experiments in the most thorough and robust way possible.

With that in mind, the Super Cryogenic Dark Matter Search (SuperCDMS) collaboration has published a reanalysis of previously published experimental data. Their study, published recently in Physical Review D, describes the team's search for dark matter via two processes called Bremsstrahlung radiation and the Migdal effect.

In a first-of-its-kind analysis, the team also worked with geologists to consider how the Earth's atmosphere and inner composition interact with dark matter particles to cause their energy to dissipate. The analysis represents one of the tightest limits on dark matter detection yet and sets the stage for future dark matter searches.

"As we search for dark matter, we need to extend detection sensitivities," said Noah Kurinksy, a staff scientist at SLAC and corresponding author on the study. "Having better ways to model these processes and understand these sorts of measurements is very important for the dark matter community."

Invisible scattering

In an experiment like SuperCDMS, physicists look for signs that dark matter has collided with the atomic nuclei—the protons and neutrons—inside a material such as silicon and germanium.

Usually, the assumption is that when a dark matter particle whacks into a nucleus, the collision is elastic: Any energy the dark matter particle loses is transferred into the motion of the nucleus, so that both particles recoil. "Your typical billiard balls scattering example," Kurinsky explained.

In recent years, however, researchers have proposed that dark matter may be detected through inelastic collisions, in which the energy from the collision is transferred to something else that's possibly easier to detect, such as photons or electrons. This could lead to more sensitive detection capabilities for dark matter detection experiments.

Example of an energy spectrum from the maximum likelihood fit for a Migdal signal model 

for a WIMP with a mass of 0.5 GeV/c2 and a cross section of 3×10−37 cm2 (black dashed 

curve). The data (blue histogram) have been logarithmically binned and overlaid with the 

background models (colored solid curves). The thick black line is the sum of all the models,

 signal and background. Normalization of the surface background model components 

(TL, SG and GC) are described in Sec. 5b. The plot on the bottom shows the residual 

between data and the model with the 1σ statistical uncertainty indicated by the shaded 

region. 

Credit: Physical Review D (2023). DOI: 10.1103/PhysRevD.107.112013

Considering that the SuperCDMS experiment is already one of the most sensitive dark matter detectors of its kind, "we wanted to know what the probability was that we see this particular type of signal in SuperCDMS data," said Daniel Jardin, a co-author of the new study and a postdoctoral scholar at Northwestern University who helped lead the analysis.

The team focused on two potential avenues for inelastic collisions to occur: Bremsstrahlung radiation and the Migdal effect.

Bremsstrahlung is a well-known and previously observed phenomenon caused by the deceleration of a charged particle—the word is German for "braking radiation." In a dark matter detector, this could happen when a dark matter particle collides with a nucleus, which then transfers some of its energy to a photon instead of just recoiling. If detected, that photon would suggest some mysterious, fast-moving particle—perhaps dark matter—slammed into the nucleus and sent the photon flying.

Another possible mode for inelastic collisions is through the Migdal effect. Although it has yet to be experimentally demonstrated, the idea is that when a dark matter particle strikes a nucleus, that nucleus gets knocked out of the center of its electron cloud. After some very short amount of time, the electron cloud readjusts around the nucleus, ejecting electrons that researchers could detect. In recent years, scientists have calculated what such a signal would look like should it happen within dark matter detectors.

Reanalyzing the data taking inelastic processes into account didn't reveal evidence of dark matter, Jardin said, but "each of these analyses extended the experiment's existing limits to lower masses." A previous SuperCDMS data analysis ruled out dark matter particles with masses as low as that of the proton. Taking Bremsstrahlung into account, the experiment can now rule out dark matter particle masses down to about a fifth of the proton mass—and even lower masses when the hypothetical Migdal effect is considered.

When Earth gets in the way

But the researchers didn't stop there. "We wanted to innovate beyond taking these ideas and applying it to our data," said Jardin. "So, we added other things that no one else has been doing."

Jardin and his colleagues not only extended the lowest limits of detection for dark matter interactions, but also considered the upper limit. "Researchers in the field are now realizing that if dark matter interacts strongly enough, it could interact with the atmosphere and the Earth on its way to the detector, which is deep underground. In that interaction there's actually an upper limit where you'd be blocked by the Earth itself," Jardin said.

In particular, the more strongly dark matter interacts with other types of matter on its way to the detector, the more energy it loses. At some point, a dark matter particle could lose so much energy that by the time it reaches the detector it can no longer create a detectable signal.

To calculate the energy limit for dark matter particles reaching the SuperCDMS experiment, the researchers modeled how the densities of Earth's atmosphere and inner layers might affect a dark matter particle pummeling through our planet to the detector. The team worked with geologists who determined the exact composition of the soil and rock surrounding the detector in the Soudan Mine in Minnesota.

With this information, the team could set upper limits for dark matter interaction strength depending on where the particle would be coming from, whether that's directly above the detector or the other side of the Earth.

After analyzing the SuperCDMS data with the new models established by the Bremsstrahlung and Migdal effects and the new upper limits, the team was able to expand the range of particle masses the experiment was sensitive to but found no evidence of dark matter interactions. Nonetheless, the analysis represents one of the most sensitive search for ultralight dark matter and helped researchers gain more information from existing data.

"We put a lot into this experiment, so we want to get the most out of it that we can," Jardin said. "We really don't know the mass of dark matter, and we don't know how it interacts with matter. We're just reaching out into the darkness, as best we can."

More information: M. F. Albakry et al, Search for low-mass dark matter via bremsstrahlung radiation and the Migdal effect in SuperCDMS, Physical Review D (2023). DOI: 10.1103/PhysRevD.107.112013

Journal information: Physical Review D 

Provided by SLAC National Accelerator Laboratory PandaX sets new constraints on the search for light dark matter via ionization signals

 

Astronomers shed new light on formation of mysterious fast radio bursts

by Tony Allen, University of Nevada, Las Vegas

The Chinese Five-hundred-meter Aperture Spherical radio Telescope (FAST). 

Credit: Bojun Wang, Jinchen Jiang & Qisheng Cui

More than 15 years after the discovery of fast radio bursts (FRBs)—millisecond-long, deep-space cosmic explosions of electromagnetic radiation—astronomers worldwide have been combing the universe to uncover clues about how and why they form.

Nearly all FRBs identified have originated in deep space outside our Milky Way galaxy. That is until April 2020, when the first Galactic FRB, named FRB 20200428, was detected. This FRB was produced by a magnetar (SGR J1935+2154), a dense, city-sized neutron star with an incredibly powerful magnetic field.

This groundbreaking discovery led some to believe that FRBs identified at cosmological distances outside our galaxy may also be produced by magnetars. However, the smoking gun for such a scenario, a rotation period due to the spin of the magnetar, has so far escaped detection. New research into SGR J1935+2154 sheds light on this curious discrepancy.

In the July 28 issue of the journal Science Advances, an international team of scientists, including UNLV astrophysicist Bing Zhang, report on continued monitoring of SGR J1935+2154 following the April 2020 FRB, and the discovery of another cosmological phenomenon known as a radio pulsar phase five months later.

Unraveling a cosmological conundrum

To aid them in their quest for answers, astronomers rely in part on powerful radio telescopes like the massive Five-hundred-meter Aperture Spherical radio Telescope (FAST) in China to track FRBs and other deep-space activity. Using FAST, astronomers observed that FRB 20200428 and the later pulsar phase originated from different regions within the scope of the magnetar, which hints towards different origins.

"FAST detected 795 pulses in 16.5 hours over 13 days from the source," said Weiwei Zhu, lead author of the paper from National Astronomical Observatory of China (NAOC). "These pulses show different observational properties from the bursts observed from the source."

This dichotomy in emission modes from the region of a magnetosphere helps astronomers understand how—and where—FRBs and related phenomena occur within our galaxy and perhaps also those at further cosmological distances.

Radio pulses are cosmic electromagnetic explosions, similar to FRBs, but typically emit a brightness roughly 10 orders of magnitude less than an FRB. Pulses are typically observed not in magnetars but in other rotating neutron stars known as pulsars. According to Zhang, a corresponding author on the paper and director of the Nevada Center for Astrophysics, most magnetars do not emit radio pulses most of the time, probably due to their extremely strong magnetic fields. But, as was the case with SGR J1935+2154, some of them become temporary radio pulsars after some bursting activities.

Another trait that makes bursts and pulses different are their emission "phases", i.e. the time window where radio emission is emitted in each period of emission.

"Like pulses in radio pulsars, the magnetar pulses are emitted within a narrow phase window within the period," said Zhang. "This is the well-known 'lighthouse' effect, namely, the emission beam sweeps the line of sight once a period and only during a short interval in time in each period. One can then observe the pulsed radio emission."

Zhang said the April 2020 FRB, and several later, less energetic bursts were emitted in random phases not within the pulse window identified in the pulsar phase.

"This strongly suggests that pulses and bursts originate from different locations within the magnetar magnetosphere, suggesting possibly different emission mechanisms between pulses and bursts," he said.

Implications for cosmological FRBs

Such a detailed observation of a Galactic FRB source sheds light on the mysterious FRBs prevailing at cosmological distances.

Many sources of cosmological FRBs—those occurring outside our galaxy—have been observed to repeat. In some instances, FAST has detected thousands of repeated bursts from a few sources. Deep searches for seconds-level periodicity have been carried out using these bursts in the past and so far no period was discovered.

According to Zhang, this casts doubt on the popular idea that repeating FRBs are powered by magnetars in the past.

"Our discovery that bursts tend to be generated in random phases provides a natural interpretation to the non-detection of periodicity from repeating FRBs," he said. "For unknown reasons, bursts tend to be emitted in all directions from a magnetar, making it impossible to identify periods from FRB sources."

More information: Weiwei Zhu et al, A radio pulsar phase from SGR J1935+2154 provides clues to the magnetar FRB mechanism, Science Advances (2023). DOI: 10.1126/sciadv.adf6198

Journal information: Science Advances 

Provided by University of Nevada, Las Vegas FAST helps reveal the origin of fast radio bursts

Mysterious 'kick' just after the Big Bang may have created dark matter

DARK MATTER IS ETHER 2.0

One of the lingering mysteries of the universe is why anything exists at all.  EXESTENTIALISM

© Provided by Live Science An artist's concept of the Big Bang.

That's because, in the universe today, matter and its antimatter counterpart should form in equal amounts, and then these two oppositely charged types of matter would annihilate each other on contact. So all the matter in the universe should have disappeared as soon as it formed, canceling itself out on contact with its antimatter counterpart.

But that didn't happen. Now, new research hypothesizes that early in the universe, there was a mysterious "kick" that produced more matter than antimatter, leading to today's imbalance. And that imbalance may have also led to the creation of dark matter, the mysterious substance that tugs on everything else yet doesn't interact with light.

Coincidence or conspiracy?

We don't know what dark matter is, but it's definitely out there. It makes up about 80% of all the matter in the universe, far outweighing the stars, galaxies, dust and gas that we can see.

And while dark matter is certainly a heavyweight in our universe, it is, oddly, not that much of a dominating factor.Typically, in physics, when one process dominates an interaction, it really takes over. Unless other physics comes into play, rarely do two competing forces come out in balance. For example, when the forces of gravity and electromagnetism compete inside a giant star, eventually gravity always wins and the star collapses. So the fact that dark matter is 80% of the mass in the universe — and not 99.99999% — and regular matter is 20% as opposed to zero, strikes physicists as odd. An 80/20 split doesn't seem even when it comes to, say, sharing lotto winnings, but to an astronomer, the two amounts are practically the same.

Compounding the issue is that, as far as we know, the generation of regular matter and dark matter had absolutely nothing to do with each other. We have no clue how dark matter originated in the early universe, but whatever it was, it's currently outside the bounds of known physics.

And regular matter? That's a whole other kettle of particles. In the extremely early universe (when it was a second old), physicists suspect that regular matter was in perfect balance with antimatter (which is the same as normal matter but with an opposite electric charge). We suspect this even split because we see this kind of symmetry play out today in our particle colliders, which can replicate the extreme conditions of the early universe: If you have a high-energy reaction that generates regular matter, it has an equal chance of generating antimatter instead.

But at some point (we're not exactly sure when, but it most likely happened when the universe was less than a minute old), the balance between matter and antimatter shifted, and regular matter flooded the universe, relegating antimatter to obscurity.

So, on one hand, we have a massive symmetry-breaking event that led to regular matter winning over antimatter. On the other hand, we have a completely mysterious event that led to dark matter becoming the dominant — but not super dominant — form of matter in the universe.Perhaps these two processes are connected, and the birth of dark matter was related to the victory of matter over antimatter, the new study proposes.
Mining for goldstone

In the study, published online Dec. 29, 2020, in the preprint database arXiv and not yet peer-reviewed, researchers make this claim by relying on something called the baryon number symmetry. Baryons are all of the particles made of quarks (such as protons and neutrons). The symmetry simply states that the number of baryons entering an interaction must equal the number exiting it. (They're allowed to change identities, but the total number must be the same.) The same symmetry holds for reactions involving antiquarks.

This symmetry reigns in all of our experiments in the present-day universe, but it must have been violated in the early cosmos — that's how we ended up with more matter than antimatter.

And in physics, every time a symmetry of nature gets broken, a new kind of particle, known as a "Goldstone boson," pops up to enforce the breaking of the symmetry. (In the modern universe, for instance, the pion is a kind of Goldstone boson that appears when a symmetry of the strong nuclear force is broken.)

Maybe the dark matter is a kind of Goldstone boson, associated with the breaking of baryon number symmetry in the early cosmos, the study proposes.
Kicking the can

The researchers behind the idea call it "the kick." Baryon number symmetry is never broken in our experiments, but something exciting must have happened in the early universe. It was a violent but brief event, snuffing out almost all antimatter. And whatever exotic mix of conditions happened, the baryon number symmetry broke, allowing a new Goldstone boson to appear.

So, the thinking goes, during that singular event, the universe became flooded with dark matter particles. But then, whatever conditions that led to the symmetry breaking ended, and the universe returned to normalcy. By then, however, it was too late; the dark matter — and all the rest of the matter — remained.

So after that first epic minute of the universe's history, once symmetry returned to the universe, dark matter was relegated to the shadows, never to interact with normal matter again.

And the reason that there is (very roughly) the same amount of dark matter and regular matter is that they were related, the study claims. The new model doesn't predict the exact 80/20 split between dark and normal matter. But it does suggest the reason that dark matter and normal matter are in roughly equal balance is because they had their origins in the same event.

It's a very clean and intriguing idea, but it still doesn't explain exactly how that early symmetry breaking took place. But that's for another paper.

Originally published on Live Science.

Related: The 11 biggest unanswered questions about dark matter

Related: 7 strange facts about quarks

Astronomers weigh ancient galaxies' dark matter haloes for 1st time

Robert Lea

SPCE.COM 
Thu, September 14, 2023 

Scientists think that dark matter produces a bright and spherical halo of X-ray emission around the center of the Milky Way.

A team of astronomers has, for the first time, "weighed" dark matter haloes surrounding actively feeding supermassive black holes in the bright hearts of ancient galaxies.

These black hole-powered hearts, or quasars, are often brighter than the combined light of every star in the galaxies around them. These super luminous central regions are "fired up" when supermassive black holes, which can have masses billions of times that of the sun, start greedily feeding on surrounding matter.

And according to a new study, scientists suggest dark matter haloes around such active galaxies could help funnel matter toward the central black hole, acting as a cosmic delivery service helping feed the titans. This new work indicates that such a feeding mechanism was indeed at work around hundreds of ancient quasars and suggests the process is one that's been constant throughout the history of the universe.

Related: Dark matter 'clumps' found by tapping into Einstein's general relativity theory
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"We measured for the first time the typical mass for dark matter halos surrounding an active black hole in the universe about 13 billion years ago," Nobunari Kashikawa, team leader and professor at the University of Tokyo’s Department of Astronomy, said in a statement. "We find the dark matter halo mass of quasars is pretty constant at about 10 trillion times the mass of our sun. Such measurements have been made for more recent dark matter halo mass around quasars, and those measurements are strikingly similar to what we see for more ancient quasars.

"This is interesting because it suggests there is a characteristic dark matter halo mass which seems to activate a quasar, regardless of whether it happened billions of years ago or right now."

Not only is that unexpected, but because supermassive black holes at the hearts of galaxies strongly influence the formation of stars and the growth of galaxies in general, this could have a profound impact on scientists' understanding of how galaxies grew in the early universe and, thus, how the cosmos evolved.
Weighing up the dark matter content of ancient galaxies

The vertical axis shows the mass of dark matter halos surrounding quasars, galaxies with active cores. The horizontal axis shows the age of the universe with the present on the left.

The nature of dark matter is a pressing problem for science because, despite making up around 85% of all matter in our universe, it doesn’t interact with light and thus remains effectively invisible to us.

Astronomers can infer the presence of dark matter via its gravitational effects and the influence of this effect on standard everyday matter that comprises stars, cosmic dust and gas clouds, planets in galaxies as well as on light passing through those galaxies. This elusive gravitational effect ultimately led scientists to the realization that most galaxies must be wrapped in a dark matter halo of sorts. With only the gravity of visible matter within them, galaxies would not be able to hold together while rotating at great speeds.

But even as these dark matter inference techniques are refined, measuring the mass of this unseeable substance in haloes around nearby galaxies is tricky. And measuring dark matter around more distant, and thus early, galaxies has been proven more challenging because light coming from these galaxies is so faint.

Kashikawa wasn't about to let these challenges phase him, however. He and his team wanted to better understand how black holes grew in the early universe, and thanks to the brightness of hundreds of the largest and most powerful of these supermassive black holes fueling quasars, the researchers were able to measure the dark matter haloes around ancient galaxies for the first time.

Light emanating from these ancient quasars has taken up to 13 billion years to travel the cosmos and reach over telescopes. During the epic journey, this light has lost energy, and its wavelengths have been stretched, shifting them down past the red end of the visible light spectrum and transforming them into infrared light wavelengths — a process astronomers call "redshift."

In 2016, Kashikawa and the team started collecting infrared data from a range of astronomical surveys conducted by a variety of instruments, primarily the Subaru Telescope at the summit of Maunakea, Hawaii.

This allowed them to see how the light from these quasars had been altered by the gravitational influence of dark matter, which, like all matter with mass, warps the fabric of space and thus causes the path of light to curve — a process astronomers call gravitational lensing. Measuring the degree of warping and comparing this to the amount of warping that should arise as a result of the mass of everyday matter in the form of gas, dust and stars in these galaxies reveals the mass of hidden dark matter.

"Upgrades allowed Subaru to see farther than ever, but we can learn more by expanding observation projects internationally," Kashikawa added. "The U.S.-based Vera C. Rubin Observatory and even the space-based Euclid satellite, launched by the EU this year, will scan a larger area of the sky and find more DMH around quasars.

"We can build a more complete picture of the relationship between galaxies and supermassive black holes. That might help inform our theories about how black holes form and grow."

The team’s work was published Sept. 8 in The Astrophysical Journal.

Scientists reveal distribution of dark matter around galaxies 12 billion years ago–further back in time than ever before

Peer-Reviewed Publication

NAGOYA UNIVERSITY

 

IMAGE: THE RADIATION RESIDUE FROM THE BIG BANG, DISTORTED BY DARK MATTER 12 BILLION YEARS AGO. view more 

CREDIT: REIKO MATSUSHITA

A collaboration led by scientists at Nagoya University in Japan has investigated the nature of dark matter surrounding galaxies seen as they were 12 billion years ago, billions of years further back in time than ever before. Their findings, published in Physical Review Letters, offer the tantalizing possibility that the fundamental rules of cosmology may differ when examining the early history of our universe. 

Seeing something that happened such a long time ago is difficult. Because of the finite speed of light, we see distant galaxies not as they are today, but as they were billions of years ago. But even more challenging is observing dark matter, which does not emit light.  

Consider a distant source galaxy, even further away than the galaxy whose dark matter one wants to investigate. The gravitational pull of the foreground galaxy, including its dark matter, distorts the surrounding space and time, as predicted by Einstein’s theory of general relativity. As the light from the source galaxy travels through this distortion, it bends, changing the apparent shape of the galaxy. The greater the amount of dark matter, the greater the distortion. Thus, scientists can measure the amount of dark matter around the foreground galaxy (the “lens” galaxy) from the distortion.    

However, beyond a certain point scientists encounter a problem. The galaxies in the deepest reaches of the universe are incredibly faint. As a result, the further away from Earth we look, the less effective this technique becomes. The lensing distortion is subtle and difficult to detect in most cases, so many background galaxies are necessary to detect the signal.  

Most previous studies have remained stuck at the same limits. Unable to detect enough distant source galaxies to measure the distortion, they could only analyze dark matter from no more than 8-10 billion years ago. These limitations left open the question of the distribution of dark matter between this time and 13.7 billion years ago, around the beginning of our universe. 

To overcome these challenges and observe dark matter from the furthest reaches of the universe, a research team led by Hironao Miyatake from Nagoya University, in collaboration with the University of Tokyo, the National Astronomical Observatory of Japan, and Princeton University, used a different source of background light, the microwaves released from the Big Bang itself.  

First, using data from the observations of the Subaru Hyper Suprime-Cam Survey (HSC), the team identified 1.5 million lens galaxies using visible light, selected to be seen 12 billion years ago.  

Next, to overcome the lack of galaxy light even further away, they employed microwaves from the cosmic microwave background (CMB), the radiation residue from the Big Bang. Using microwaves observed by the European Space Agency’s Planck satellite, the team measured how the dark matter around the lens galaxies distorted the microwaves.   

“Look at dark matter around distant galaxies?” asked Professor Masami Ouchi of the University of Tokyo, who made many of the observations. “It was a crazy idea. No one realized we could do this. But after I gave a talk about a large distant galaxy sample, Hironao came to me and said it may be possible to look at dark matter around these galaxies with the CMB.”  

“Most researchers use source galaxies to measure dark matter distribution from the present to eight billion years ago”, added Assistant Professor Yuichi Harikane of the Institute for Cosmic Ray Research, University of Tokyo. “However, we could look further back into the past because we used the more distant CMB to measure dark matter. For the first time, we were measuring dark matter from almost the earliest moments of the universe.” 

After a preliminary analysis, the researchers soon realized that they had a large enough sample to detect the distribution of dark matter. Combining the large distant galaxy sample and the lensing distortions in CMB, they detected dark matter even further back in time, from 12 billion years ago. This is only 1.7 billion years after the beginning of the universe, and thus these galaxies are seen soon after they first formed. 

“I was happy that we opened a new window into that era,” Miyatake said. "12 billion years ago, things were very different. You see more galaxies that are in the process of formation than at the present; the first galaxy clusters are starting to form as well.” Galaxy clusters comprise 100-1000 galaxies bound by gravity with large amounts of dark matter. 

“This result gives a very consistent picture of galaxies and their evolution, as well as the dark matter in and around galaxies, and how this picture evolves with time,” said Neta Bahcall,  Eugene Higgins Professor of Astronomy, professor of astrophysical sciences, and director of undergraduate studies at Princeton University. 

One of the most exciting findings of the researchers was related to the clumpiness of dark matter. According to the standard theory of cosmology, the Lambda-CDM model, subtle fluctuations in the CMB form pools of densely packed matter by attracting surrounding matter through gravity. This creates inhomogeneous clumps that form stars and galaxies in these dense regions. The group’s findings suggest that their clumpiness measurement was lower than predicted by the Lambda-CDM model.  

Miyatake is enthusiastic about the possibilities. “Our finding is still uncertain”, he said. “But if it is true, it would suggest that the entire model is flawed as you go further back in time. This is exciting because if the result holds after the uncertainties are reduced, it could suggest an improvement of the model that may provide insight into the nature of dark matter itself.” 

“At this point, we will try to get better data to see if the Lambda-CDM model is actually able to explain the observations that we have in the universe,” said Andrés Plazas Malagón, associate research scholar at Princeton University. “And the consequence may be that we need to revisit the assumptions that went into this model.” 

“One of the strengths of looking at the universe using large-scale surveys, such as the ones used in this research, is that you can study everything that you see in the resulting images, from nearby asteroids in our solar system to the most distant galaxies from the early universe. You can use the same data to explore a lot of new questions,” said Michael Strauss, professor and chair of the Department of Astrophysical Sciences at Princeton University. 

This study used data available from existing telescopes, including Planck and Subaru. The group has only reviewed a third of the Subaru Hyper Suprime-Cam Survey data. The next step will be to analyze the entire data set, which should allow for a more precise measurement of the dark matter distribution. In the future, the team expects to use an advanced data set like the Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) to explore more of the earliest parts of space. “LSST will allow us to observe half the sky,” Harikane said. “I don’t see any reason we couldn’t see the dark matter distribution 13 billion years ago next.”  

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JOURNAL

Physical Review Letters

ARTICLE PUBLICATION DATE

1-Aug-2022

SCIENCE FICTION; DARK MATTER

Physicists Have Developed a Method for Predicting the Composition of Dark Matter

By  NEW YORK UNIVERSITY JULY 21, 2022

An artist’s rendition of big bang nucleosynthesis, the early universe period in which protons “p” and neutrons “n” combine to form light elements. The presence of dark matter “χ” changes how much of each element will form. Credit: Image courtesy of Cara Giovanetti/New York University

A new analysis offers an innovative means to predict ‘cosmological signatures’ for models of dark matter.

A method for predicting the composition of dark matter has been developed by a team of physicists. Dark matter is invisible matter detected only by its gravitational pull on ordinary matter and whose discovery has been long sought by scientists. 

The new work centers on predicting “cosmological signatures” for models of dark matter with a mass between that of the electron and the proton. Previous methods had predicted similar signatures for simpler models of dark matter. This research establishes new ways to find these signatures in more complex models, which experiments continue to search for, the paper’s authors note. The paper was published on July 6 in the journal Physical Review Letters.

“Experiments that search for dark matter are not the only way to learn more about this mysterious type of matter,” says Cara Giovanetti, a Ph.D. student in New York University’s Department of Physics and the lead author of the paper. 

“Precision measurements of different parameters of the universe—for example, the amount of helium in the universe, or the temperatures of different particles in the early universe—can also teach us a lot about dark matter,” adds Giovanetti, outlining the method described in the Physical Review Letters paper.

In the research, the physicists focused on big bang nucleosynthesis (BBN)—a process by which light forms of matter, such as helium, hydrogen, and lithium, are created. The presence of invisible dark matter affects how each of these elements will form. Also vital to these phenomena is the cosmic microwave background (CMB)—electromagnetic radiation, generated by combining electrons and protons, that remained after the universe’s formation. The work was conducted with Hongwan Liu, an NYU postdoctoral fellow, Joshua Ruderman, an associate professor in NYU’s Department of Physics, and Princeton physicist Mariangela Lisanti, Giovanetti, and her co-authors.

The team of scientists sought a means to spot the presence of a specific category of dark matter—that with a mass between that of the electron and the proton—by creating models that took into account both BBN and CMB.

“Such dark matter can modify the abundances of certain elements produced in the early universe and leave an imprint in the cosmic microwave background by modifying how quickly the universe expands,” Giovanetti explains. 

In their research, the team made predictions of cosmological signatures linked to the presence of certain forms of dark matter. These signatures are the result of dark matter changing the temperatures of different particles or altering how fast the universe expands. 

Their results showed that dark matter that is too light will lead to different amounts of light elements than what astrophysical observations see. 

“Lighter forms of dark matter might make the universe expand so fast that these elements don’t have a chance to form,” says Giovanetti, outlining one scenario.

“We learn from our analysis that some models of dark matter can’t have a mass that’s too small, otherwise the universe would look different from the one we observe,” she adds.

Reference: “Joint Cosmic Microwave Background and Big Bang Nucleosynthesis Constraints on Light Dark Sectors with Dark Radiation” by Cara Giovanetti, Mariangela Lisanti, Hongwan Liu and Joshua T. Ruderman, 6 July 2022, Physical Review Letters.
DOI: 10.1103/PhysRevLett.129.021302

The research was supported by grants from the National Science Foundation (DGE1839302, PHY-1915409, PHY-1554858, PHY-1607611) and the Department of Energy (DE-SC0007968).