How Did Black Holes Grow So Quickly? The Jets

Within nearly every galaxy is a supermassive black hole. The beast at the heart of our galaxy contains the mass of millions of suns, while some of the largest supermassive black holes can be more than a billion solar masses. For years, it was thought that these black holes grew in mass over time, only reaching their current size after a billion years or more. But observations from the Webb telescope show that even the youngest galaxies contain massive black holes. So how could supermassive black holes grow so large so quickly? The key to the answer could be the powerful jets black holes can produce.

Although it seems counterintuitive, it is difficult for a black hole to consume matter and grow. The gravitational pull of a black hole is immensely strong, but the surrounding matter is much more likely to be trapped in orbit around the gravitational well than to fall directly in. To enter a black hole, material needs to slow down enough to fall inward. When a black hole has a jet of material speeding away from its polar region, this high-velocity plasma can pull rotational motion from the surrounding material, thus allowing it to fall into the black hole. For this reason, black holes with powerful jets also undergo the most powerful growth.

We can see many fast-growing black holes in the distant Universe as quasars, or active galactic nuclei. We know, then, that in the middle age of the cosmos, many supermassive black holes were gaining mass rapidly. One idea is that the youngest supermassive black holes also had active jets, which would allow them to gain a million solar masses or more quite quickly. But proving this is difficult.

The problem is that it’s extremely difficult to observe jets from the earliest period of the cosmos. Light from that distant time is so redshifted that their once brilliant beacon has become dim radio light. Before this recent study, the most distant jet we observed had a redshift of z = 6.1, meaning it traveled for nearly 12.8 billion years to reach us. In this new study, the team discovered a blazar with a redshift of z = 7.0, meaning it comes from a time when the Universe was just 750 million years old.

A blazar occurs when the jet of a supermassive black hole is lined up to be pointed directly at us. Since we’re looking directly into the beam, we see the jet at its most powerful. Blazars normally allow us to calculate the true intensity of a jet, but in this case, the redshift is so strong that our conclusions must be a bit more subtle.

How distant jets could be Doppler magnified. Credit: Bañados, et al

One possibility is that the jet of this particular supermassive black hole really is pointed directly our way. Based on this, the black hole is growing so quickly that it would easily gain more than a million solar masses within the first billion years of time. But it would be extremely rare for a black hole jet to point directly at us from that distance. So statistically, that would mean there are many more early black holes that are just as active and growing just as quickly. They just aren’t aligned for us to observe.

Another possibility is that the blazar isn’t quite aligned in our direction, but the cosmic expansion of space and time has focused its energy toward us over 12.9 billion years. In other words, the blazar may appear more energetic than it actually is, thanks to relativistic cosmology. But if that is the case, then the jet of this black hole is less energetic but still powerful. And statistically, that would mean most early black holes are equally powerful.

So this latest work tells us that either there was a fraction of early black holes that grew to beasts incredibly fast, or that most black holes grew quickly, beginning at a time even earlier than we can observe. In either case, it is clear that early black holes created jets, and these jets allowed the first supermassive black holes to appear early in cosmic time.

Reference: Bañados, Eduardo, et al. “A blazar in the epoch of reionization.” Nature Astronomy (2024): 1-9.

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Quantum Correlations Could Solve the Black Hole Information Paradox

The black hole information paradox has puzzled physicists for decades. New research shows how quantum connections in spacetime itself may resolve the paradox, and in the process leave behind a subtle signature in gravitational waves.

For a long time we thought black holes, as mysterious as they were, didn’t cause any trouble. Information can’t be created or destroyed, but when objects fall below the event horizons, the information they carry with them is forever locked from view. Crucially, it’s not destroyed, just hidden.

But then Stephen Hawking discovered that black holes aren’t entirely black. They emit a small amount of radiation and eventually evaporate, disappearing from the cosmic scene entirely. But that radiation doesn’t carry any information with it, which created the famous paradox: when the black hole dies, where does all its information go?

One solution to this paradox is known as non-violent nonlocality. This takes advantage of a broader version of quantum entanglement, the “spooky action at a distance” that can tie together particles. But in the broader picture, aspects of spacetime itself become entangled with each other. This means that whatever happens inside the black hole is tied to the structure of spacetime outside of it.

Usually spacetime is only altered during violent processes, like black hole mergers or stellar explosions. But this effect is much quieter, just a subtle fingerprint on the spacetime surrounding an event horizon.

If this hypothesis is true, the spacetime around black holes carries tiny little perturbations that aren’t entirely random; instead, the variations would be correlated with the information inside the black hole. Then when the black hole disappears, the information is preserved outside of it, resolving the paradox.

In a recent paper appearing in the journal preprint server arXiv, but not yet peer-reviewed, a pair of researchers at Caltech investigated this intriguing hypothesis to explore how we might be able to test it.

The researchers found that these signatures in spacetime also leave an imprint in the gravitational waves when black holes merge. These imprints are incredibly tiny, so small that we are not yet able to detect them with existing gravitational wave experiments. But they do have a very unique structure that stands on top of the usual wave pattern, making them potentially observable.

The next generation of gravitational wave detectors, which aim to come online in the next decade, might have enough sensitivity to tease out this signal. If they see it, it would be tremendous, as it would finally point to a clear solution of the troubling paradox, and open up a new understanding of both the structure of spacetime and the nature of quantum nonlocality.

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M87 Releases a Rare and Powerful Outburts of Gamma-ray Radiation

In April 2019, the Event Horizon Telescope (EHT) collaboration made history when it released the first-ever image of a black hole. The image captured the glow of the accretion disk surrounding the supermassive black hole (SMBH) at the center of the M87 galaxy, located 54 million light-years away. Because of its appearance, the disk that encircles this SMBH beyond its event horizon (composed of gas, dust, and photons) was likened to a “ring of fire.” Since then, the EHT has been actively imaging several other SMBH, including Sagittarius A* at the center of the Milky Way!

In addition, the EHT has revealed additional details about M87, like the first-ever image of a photon ring and a picture that combines the SMBH and its relativistic jet emanating from its center. Most recently, the EHT released the results of its latest observation campaign. These observations revealed a spectacular flare emerging from M87’s powerful relativistic jet. This flare released a tremendous amount of energy in multiple wavelengths, including the first high-energy gamma-ray outburst observed in over a decade.

The EHT is an international collaboration of researchers from thirteen universities and institutes worldwide that combines data from over 25 ground-based and space-based telescopes. The research, which was recently published in the journal Astronomy & Astrophysics, was conducted by the Event Horizon Telescope Collaboration, the Event Horizon Telescope- Multi-wavelength science working group, the Fermi Large Area Telescope Collaboration, the H.E.S.S. Collaboration, the MAGIC Collaboration, the VERITAS Collaboration, and the EAVN Collaboration.

The observatories and telescopes that participated in the 2018 multiband campaign to detect the high-energy gamma-ray flare from the M87* black hole. Credits: EHT Collaboration/Fermi-LAT Collaboration/H.E.S.S. Collaboration/MAGIC Collaboration/VERITAS Collaboration/EAVN Collaboration

The study presents the data from the second EHT observational campaign conducted in April 2018 that obtained nearly simultaneous spectra of the galaxy with the broadest wavelength coverage ever collected. Giacomo Principe, the paper coordinator, is a researcher at the University of Trieste associated with the Instituto Nazionale di Astrofisica (INAF) and the Institute Nazionale di Fisica Nucleare (INFN). As he explained in a recent EHT press release:

“We were lucky to detect a gamma-ray flare from M87 during this EHT multi-wavelength campaign. This marks the first gamma-ray flaring event observed in this source in over a decade, allowing us to precisely constrain the size of the region responsible for the observed gamma-ray emission. Observations—both recent ones with a more sensitive EHT array and those planned for the coming years—will provide invaluable insights and an extraordinary opportunity to study the physics surrounding M87’s supermassive black hole. These efforts promise to shed light on the disk-jet connection and uncover the origins and mechanisms behind the gamma-ray photon emission.”

The second EHT and multi-wavelength campaign leveraged data from more than two dozen high-profile observational facilities, including NASA’s Fermi Gamma-ray Space Telescope-Large Area Telescope (Fermi-LAT), the Hubble Space Telescope (HST), Nuclear Spectroscopic Telescope Array (NuSTAR), the Chandra X-ray Observatory, and the Neil Gehrels Swift Observatory. This was combined with data from the world’s three largest Imaging Atmospheric Cherenkov Telescope arrays – the High Energy Stereoscopic System (H.E.S.S.), the Major Atmospheric Gamma-Ray Imaging Cherenkov (MAGIC), and the Very Energetic Radiation Imaging Telescope Array System (VERITAS).

During the campaign, the Fermi space telescope gathered data indicating an increase in high-energy gamma rays using its LAT instrument. Chandra and NuSTAR followed by collecting high-quality data in the X-ray band, while the Very Long Baseline Array (VLBA) and the East Asia VLBI Network (EAVN) obtained data in radio frequencies. The flare these observations revealed lasted approximately three days and occupied a region roughly three light-days in size, about 170 times the distance between the Sun and the Earth (~170 AU).

Light curve of the gamma-ray flare (bottom) and collection of quasi-simulated images of the M87 jet (top) at various scales obtained in radio and X-ray during the 2018 campaign. Credits: EHT Collaboration/Fermi-LAT Collaboration/H.E.S.S. Collaboration/MAGIC Collaboration/VERITAS Collaboration/EAVN Collaboration

The flare itself was well above the energies typically detected around black holes and showed a significant variation in the position angle of the asymmetry of the black hole’s ‘event horizon’ and its position. As Daryl Haggard, a professor at McGill University and the co-coordinator of the EHT multi-wavelength working group, explained, this suggests a physical relation between these structures on very different scales:

“In the first image obtained during the 2018 observational campaign, we saw that the emission along the ring was not homogeneous, instead it showed asymmetries (i.e., brighter areas). Subsequent observations conducted in 2018 and related to this paper confirmed that finding, highlighting that the asymmetry’s position angle had changed.”

“How and where particles are accelerated in supermassive black hole jets is a long-standing mystery,” added University of Amsterdam professor Sera Markoff, another EHT multi-wavelength working group co-coordinator. “For the first time, we can combine direct imaging of the near event horizon regions during gamma-ray flares caused by particle acceleration events and thus test theories about the flare origins.”

This discovery could create opportunities for future research and lead to breakthroughs in our understanding of the Universe.

Further Reading: EHT, Astronomy & Astrophysics

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Astronomers Find a Black Hole Tipped Over on its Side

Almost every large galaxy has a supermassive black hole churning away at its core. In most cases, these black holes spin in concert with their galaxy, like the central hub of a cosmic wagon wheel. But on December 18, 2024, NASA researchers announced they had discovered a galaxy whose black hole appears to have been turned on its side, spinning out of alignment with its host galaxy.

The galaxy, NGC 5084, was discovered centuries ago by German astronomer William Herschel, but it took new techniques, recently developed at NASA’s Ames Research Center, to reveal the unusual properties of the black hole.

The new method is called SAUNAS (Selective Amplification of Ultra Noisy Astronomical Signal). It enables astronomers to tease out low-brightness X-ray emissions that were previously drowned out by other radiation sources.

When the team put their new technique to the test by combing through old archival data from the Chandra X-ray observatory – a space telescope that acts as the X-ray counterpart to Hubble’s visible-light observations – they found their first clue that something unusual was going on in NGC 5084.

Four large X-ray plumes, made visible by the new technique, appeared in the data. These streams of plasma extend out from the centre of the galaxy, two in line with the galactic plane, and two extending above and below.

While plumes of hot, charged gas are not unusual above or below the plane of large galaxies, it is unusual to find four of them, rather than just one or two, and even more unusual to find them in line with the galactic plane.

NGC 5084, as seen by in visible light. Adam Block/Mount Lemmon SkyCenter/University of Arizona.

To make sure that they weren’t just seeing some error or artifact in the Chandra data, they started looking more closely at other images of the galaxy, including both the Hubble space telescope and the Atacama Large Millimeter Array (ALMA).

These observations revealed a dusty inner disk spinning in the centre of the galaxy at a 90-degree angle to the rest of NGC 5084.

The team also looked at the galaxy in radio wavelengths using the NRAO’s Expanded Very Large Array. All together, these observations painted a picture of a very strange galactic core.

“It was like seeing a crime scene with multiple types of light,” said Ames research scientist Alejandro Serrano Borlaff, lead author of the paper published this week in The Astrophysical Journal. “Putting all the pictures together revealed that NGC 5084 has changed a lot in its recent past.”

Borlaff’s coauthor and astrophysicist at Ames, Pamela Marcum, added that “detecting two pairs of X-ray plumes in one galaxy is exceptional. The combination of their unusual, cross-shaped structure and the ‘tipped-over,’ dusty disk gives us unique insights into this galaxy’s history.”

The plumes of plasma suggest that the galaxy has been disturbed in some way during its lifetime. It might be explained, for example, by a collision with another galaxy, which caused the black hole to tip on its side.

With this discovery, SAUNAS has demonstrated that it can bring new life to old data, uncovering new surprises in familiar galaxies. This surprise twist on a galaxy we’ve known about since 1785 offers tantalizing hope that there might be other weird and wonderful discoveries to come, even in places we thought we’d seen everything.

Learn more:

“NASA Finds ‘Sideways’ Black Hole Using Legacy Data, New Techniques.” NASA.

Alejandro S. Borlaff et al. “SAUNAS. II. Discovery of Cross-shaped X-Ray Emission and a Rotating Circumnuclear Disk in the Supermassive S0 Galaxy NGC 5084.” The Astrophysical Journal.

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Where’s the Most Promising Place to Find Martian Life?

New research suggests that our best hopes for finding existing life on Mars isn’t on the surface, but buried deep within the crust.

Several years ago NASA’s Curiosity rover measured traces of methane in the Martian atmosphere at levels several times the background. But a few months later, the methane disappeared, only for it to reappear again later in the year. This discovery opened up the intriguing possibility of life still clinging to existence on Mars, as that could explain the seasonal variability in the presence of methane.

But while Mars was once home to liquid water oceans and an abundant atmosphere, it’s now a desolate wasteland. What kind of life could possibly call the red planet home? Most life on Earth wouldn’t survive long in those conditions, but there is a subgroup of Earthly life that might possibly find Mars a good place to live.

These are the methanogens, a type of single-celled organism that consume hydrogen for energy and excrete methane as a waste product. Methanogens can be found in all sorts of otherwise-inhospitable places on Earth, and something like them might be responsible for the seasonal variations in methane levels on Mars.

In a recent paper submitted for publication in the journal AstroBiology, a team of scientists scoured the Earth for potential analogs to Martian environments, searching for methanogens thriving in conditions similar to what might be found on Mars.

The researchers found three potential Mars-like conditions on Earth where methanogens make a home. The first is deep in the crust, sometimes to a depth of several kilometers, where tiny cracks in rocks allow for liquid water to seep in. The second is lakes buried under the Antarctic polar ice cap, which maintain their liquid state thanks to the immense pressures of the ice above them. And the last is super-saline, oxygen-deprived basins in the deep ocean.

All three of these environments have analogs on Mars. Like the Earth, Mars likely retains some liquid water buried in its crust. And its polar caps might have liquid water lakes buried underneath them. Lastly, there has been tantalizing – and heavily disputed – evidence of briny water appearing on crater walls.

In the new paper, the researchers mapped out the temperature ranges, salinity levels, and pH values across sites scattered around the Earth. They then measured the abundance of molecular hydrogen in those sites, and determined where methanogens were thriving the most.

For the last step, the researchers combed through the available data about Mars itself, finding where conditions best matched the most favorable sites on Earth. They found that the most likely location for possible life was in Acidalia Planitia, a vast plain in the northern hemisphere.

Or rather, underneath it. Several kilometers below the plain, the temperatures are warm enough to support liquid water. That water might have just the right pH and salinity levels, along with enough dissolved molecular hydrogen, to support a population of methanogen-like creatures.

Now we just have to figure out how to get there.

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Can Entangled Particles Communicate Faster than Light?

Entanglement is perhaps one of the most confusing aspects of quantum mechanics. On its surface, entanglement allows particles to communicate over vast distances instantly, apparently violating the speed of light. But while entangled particles are connected, they don’t necessarily share information between them.

In quantum mechanics, a particle isn’t really a particle. Instead of being a hard, solid, precise point, a particle is really a cloud of fuzzy probabilities, with those probabilities describing where we might find the particle when we go to actually look for it. But until we actually perform a measurement, we can’t exactly know everything we’d like to know about the particle.

These fuzzy probabilities are known as quantum states. In certain circumstances, we can connect two particles in a quantum way, so that a single mathematical equation describes both sets of probabilities simultaneously. When this happens, we say that the particles are entangled.

When particles share a quantum state, then measuring the properties of one can grant us automatic knowledge of the state of the other. For example, let’s look at the case of quantum spin, a property of subatomic particles. For particles like electrons, the spin can be in one of two states, either up or down. Once we entangle two electrons, their spins are correlated. We can prepare the entanglement in a certain way so that the spins are always opposite of each other.

If we measure the first particle, we might randomly find the spin pointing up. What does this tell us about the second particle? Since we carefully arranged our entangled quantum state, we now know with 100% absolute certainty that the second particle must be pointing down. Its quantum state was entangled with the first particle, and as soon as one revelation is made, both revelations are made.

But what if the second particle was on the other side of the room? Or across the galaxy? According to quantum theory, as soon as one “choice” is made, the partner particle instantly “knows” what spin to be. It appears that communication can be achieved faster than light.

The resolution to this apparent paradox comes from scrutinizing what is happening when – and more importantly, who knows what when.

Let’s say I’m the one making the measurement of particle A, while you are the one responsible for particle B. Once I make my measurement, I know for sure what spin your particle should have. But you don’t! You only get to know once you make your own measurement, or after I tell you. But in either case nothing is transmitted faster than light. Either you make your own local measurement, or you wait for my signal.

While the two particles are connected, nobody gets to know anything in advance. I know what your particle is doing, but I only get to inform you at speed slower than light – or you just figure it out for yourself.

So while the process of entanglement happens instantaneously, the revelation of it does not. We have to use good old-fashioned no-faster-than-light communication methods to piece together the correlations that quantum entanglement demand.

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IceCube Just Spent 10 Years Searching for Dark Matter

Neutrinos are tricky little blighters that are hard to observe. The IceCube Neutrino Observatory in Antarctica was built to detect neutrinos from space. It is one of the most sensitive instruments built with the hope it might help uncover evidence for dark matter. Any dark matter trapped inside Earth, would release neutrinos that IceCube could detect. To date, and with 10 years of searching, it seems no excess neutrinos coming from Earth have been found!

Neutrinos are subatomic particles which are light and carry no electrical charge. Certain events, such as supernovae and solar events generate vast quantities of neutrinos. By now, the universe will be teeming with neutrinos with trillions of them passing through every person every second. The challenge though is that neutrinos rarely interact with matter so observing and detecting them is difficult. Like other sub-atomic particles, there are different types of neutrino; electron neutrinos, muon neutrinos and tau neutrinos, with each associated with a corresponding lepton (an elementary particle with half integer spin.) Studying neutrinos of all types is key to helping understand fundamental physical processes across the cosmos. 

Chinese researchers are working on a new neutrino observatory called TRIDENT. They built an underwater simulator to develop their plan. Image Credit: TRIDENT

The IceCube Neutrino Observatory began capturing data in 2005 but it wasn’t until 2011 that it began full operations. It consists of over 5,000 football-sized detectors arranged within a cubic kilometre of ice deep underground. Arranged in this fashion, the detectors are designed to capture the faint flashes of Cherenkov radiation released when neutrinos interact with the ice. The location near the South Pole was chosen because the ice acts as a natural barrier against background radiation from Earth. 

A view of the IceCube Lab with a starry night sky showing the Milky Way and green auroras. Photo By: Yuya Makino, IceCube/NSF

Using data from the IceCube Observatory, a team of researchers led by R. Abbasi from the Loyola University Chicago have been probing the nature of dark matter. This strange and invisible component of the universe is thought to make up 27% of the mass-energy content of the universe. Unfortunately, dark matter doesn’t emit, absorb or reflect light making it undetectable by conventional means. One train of thought is that dark matter is made up of Weakly Interacting Massive Particles (WIMPs.) They can be captured by objects like the Sun leading to their annihilation and transition into neutrinos. It’s these, that the team have been hunting for. 

The paper published by the team articulates their search for muon neutrinos from the centre of the Earth within the 10 years of data captured by IceCube. The team searched chiefly for WIMPs within the mass range of 10GeV to 10TeV but due to the complexity and position of the source (the centre of the Earth,) the team relied upon running Monte Carlo simulations. The name is taken from casino’s in Monaco and involves running many random simulations. This technique is used where exact calculations are unable to compute the answer and so the simulations are based on the concept that randomness can be used to solve problems.

After running many simulations of this sort, the team found no excess neutrino flux over the background levels from Earth. They conclude however that whilst no evidence has been found yet, that an upgrade to the IceCube Observatory may yield more promising results as they can probe lower neutrino mass events and hopefully one day, solve the mystery of the nature of dark matter. 

Source : Search for dark matter from the centre of the Earth with ten years of IceCube data

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