Bizarre 'garden sprinkler-like' jet is spotted shooting out of neutron star

A strange 'garden sprinkler-like' jet coming from a neutron star has been pictured for the first time.

The S-shaped structure is created as the jet changes direction due to the wobbling of the disc of hot gas around the star -- a process called precession, which has been observed with black holes but, until now, never with neutron stars.

This particular object sits in the binary system Circinus X-1 more than 30,000 light-years from Earth and formed from the core of a massive supergiant star that collapsed around the same time Stonehenge was built.

It is so dense that a teaspoon of its material weighs as much as Mount Everest.

Binary systems have two stars that are bound together by gravity. In the case of Circinus X-1, one of these is a neutron star.

Both neutron stars and black holes are cosmological monsters which form when the biggest stars in the Universe die and collapse under their own gravity.

However, the latter are considerably more massive and can only be detected through their gravitational effects, while the former can be observed directly despite their denseness.

They are some of the most extreme objects in the Universe and have interiors almost entirely made of neutrons.

The jet emanating from the neutron star was spotted by a team of astronomers at the University of Oxford, who used MeerKAT -- a radio telescope in South Africa -- to create the most detailed, high-resolution images of Circinus X-1.

The pictures, which were presented at this week's National Astronomy Meeting at the University of Hull, include the first-ever image of an S-shaped jet coming from a confirmed neutron star -- a breakthrough that could help unravel the extreme physics behind the astronomical phenomenon.

Lead researcher Fraser Cowie said there was another system known for its S-shaped jets, called SS433, but recent results suggest that object is likely a black hole.

"This image is the first time we have seen strong evidence for a precessing jet from a confirmed neutron star," he said.

"This evidence comes from both the symmetric S shape of the radio-emitting plasma in the jets and from the fast, wide shockwave, which can only be produced by a jet changing direction.

"This will give valuable information about the extreme physics behind the launching of the jet, a phenomenon which is still not well understood."

The neutron star's huge density creates a strong force of gravity that strips gas from the companion star, forming a disc of hot gas around it that spirals down towards its surface.

This process, called accretion, releases huge amounts of energy per second with more power than a million Suns. Some of this energy powers jets -- narrow beams of outflowing material from the binary system travelling close to the speed of light.

Recent upgrades to the MeerKAT telescope have resulted in excellent sensitivity and higher-resolution images. With these the team saw clear evidence of an S-shaped structure, similar in shape to water spraying from a garden sprinkler, in Circinus X-1's jet.

Not only that, but researchers also discovered moving termination shocks -- the first recorded from an X-ray binary. These are regions where the jet violently rams into the surrounding material, causing a shockwave.

Cowie's team measured the waves moving at roughly 10 per cent of the speed of light, confirming that they were caused by the fast-moving jet and not something slower such as a wind of material from the stars.

"The fact that these shockwaves span a wide angle agrees with our model," Cowie said. "So we have two strong pieces of evidence telling us the neutron star jet is precessing."

Measuring the velocity of the shockwaves will also help astronomers understand what the jet causing them is made from.

The shockwaves effectively act as particle accelerators in space -- producing high-energy cosmic rays -- and the maximum energy of particles that can be accelerated depends on their velocity.

"Circinus X-1 is one of the brightest objects in the X-ray sky and has been studied for over half a century," Cowie said. "But despite this, it remains one of the most enigmatic systems we know of.

"Several aspects of its behaviour are not well explained so it's very rewarding to help shed new light on this system, building on 50 years of work from others."

He added: "The next steps will be to continue to monitor the jets and see if they change over time in the way we expect.

"This will allow us to more precisely measure their properties and continue to learn more about this puzzling object."

Read more at Science Daily

Unprecedented gamma-ray burst explained by long-lived jet

Last year, Northwestern University researchers reported new observational evidence that long gamma-ray bursts (GRBs) can result from the merger of a neutron star with another compact object (either another neutron star or black hole) -- a finding that was previously believed to be impossible.

Now, another Northwestern team offers a potential explanation for what generated the unprecedented and incredibly luminous burst of light.

After developing the first numerical simulation that follows the jet evolution in a black hole-neutron star merger out to large distances, the astrophysicists discovered that the post-merger black hole can launch jets of material from the swallowed neutron star.

But the key ingredients are the mass of the violent whirlpool of gas (or accretion disk) surrounding the black hole and the strength of the disk's magnetic field. In massive disks, when the magnetic field is strong, the black hole launches a short-duration jet that is much brighter than anything ever seen in observations. When the massive disk has a weaker magnetic field, however, the black hole launches a jet with the same luminosity and long duration as the mysterious GRB (dubbed GRB211211A) spotted in 2021 and reported in 2022.

Not only does the new discovery help explain the origins of long GRBs, it also gives insight into the nature and physics of black holes, their magnetic fields and accretion disks.

The study will be published Thursday (Aug. 31) in the Astrophysical Journal.

"So far, no one else has developed any numerical works or simulations that consistently follow a jet from the compact-object merger to the formation of the jet and its large-scale evolution," said Northwestern's Ore Gottlieb, who co-led the work. "The motivation for our work was to do this for the first time. And what we found just so happened to match observations of GRB211211A."

"Neutron-star mergers are a captivating multi-messenger phenomena, which result in both gravitational and electromagnetic waves," said Northwestern's Danat Issa, who co-led the work with Gottlieb. "However, simulating these events poses a challenge due to the vast spatial and temporal scale separations involved as well as the diverse physics operating across these scales. For the first time, we have succeeded in comprehensively modeling the entire sequence of the neutron star merger process."

During the research, Gottlieb was a CIERA Fellow at Northwestern's Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA); now he is a Flatiron Research Fellow at the Flatiron Institute's Center for Computational Astrophysics. Issa is a graduate student in the Department of Physics and Astronomy at Northwestern's Weinberg College of Arts and Sciences and member of CIERA. Issa is advised by paper co-author Alexander Tchekhovskoy, an associate professor of physics and astronomy at Weinberg and member of CIERA.

Curious kilonova

When astronomers first spotted GRB211211A in December 2021, they initially assumed that the 50-second-long event was generated from the collapse of a massive star. But, as they examined the long GRB's late-time emission, called the afterglow, they uncovered evidence of a kilonova, a rare event that only occurs after the merger of a neutron star with another compact object.

The finding (published in Nature in December 2022) upended the long-established, long-accepted belief that only supernovae could generate long GRBs.

"GRB 211211A reignited interest in the origin of long-duration GRBs that are not associated with massive stars, but likely originating from compact binary mergers," Gottlieb said.

From pre-merger to long GRB

To further reveal what occurs during compact-merger events, Gottlieb, Issa and their collaborators sought to simulate the whole process -- from before the merger all the way through to the end of the GRB event, when the GRB-producing jets shut off. Because it is such an incredibly computationally expensive feat, the entire scenario had never been modeled before. Gottlieb and Issa overcame that challenge by dividing the scenario into two simulations.

First, the researchers ran a simulation of the pre-merger phase. Then, they took the output from the first simulation and plugged it into the post-merger simulation.

"Because the space-time used by the two simulations is different, this remap was not as straightforward as we had hoped, but Danat figured it out," Tchekhovskoy said.

"The daisy chaining of the two simulations allowed us to make the computation much less expensive," Gottlieb said. "The physics is very complicated in the pre-merger stage because there are two objects. It gets much simpler after the pre-merger because there is only one black hole."

In the simulation, the compact objects first merged to create a more massive black hole. The black hole's intense gravity pulled the now-destroyed neutron star's debris toward it. Before the debris fell into the black hole, some of the debris first swirled around the black hole as an accretion disk. In the configuration studied, the emerging disk was particularly massive with one-tenth the mass of our sun. Then, when the mass fell into the black hole from the disk, it powered the black hole to launch a jet that accelerated to near light speed.

Disk properties matter

A surprise emerged as the researchers adjusted the strength of the massive disk's magnetic field. Whereas a strong magnetic field resulted in a short, incredibly bright GRB, a weak magnetic field generated a jet that matched observations of long GRBs.

"The stronger the magnetic field, the shorter is its lifetime," Gottlieb said. "Weak magnetic fields produce weaker jets that the newly formed black hole can sustain for a longer time. A key ingredient here is the massive disk that can maintain, together with weak magnetic fields, a GRB consistent with observations and comparable to the luminosity and long duration of GRB211211A. Although we found this specific binary system to give rise to a long GRB, we also expect that other binary mergers that produce massive disks will lead to a similar outcome. It's simply a question of the post-merger disk mass."

Of course, "long" is relative in this scenario. GRBs are divided into two classes. GRBs with durations less than two seconds are considered short. If a GRB is two seconds or longer, then it's considered long. Even events this brief are still exceptionally difficult to model.

"A major portion of this disk material ultimately gets consumed by the black hole, with the whole process lasting mere seconds," Issa said. "Here lies the main challenge: It is very difficult to capture the evolution of these mergers, using simulations on supercomputers, over a span of several seconds."

Read more at Science Daily

Galaxy changes classification as jet changes direction

A team of international astronomers have discovered a galaxy that has changed classification due to unique activity within its core. The galaxy, named PBC J2333.9-2343, was previously classified as a radio galaxy, but the new research has revealed otherwise. The work is published in Monthly Notices of the Royal Astronomical Society.

PBC J2333.9-2343, located 656 844 372 light years away, has now been classified as a giant radio galaxy that is 4 million light years across and happens to have a blazar in its core; a blazar is an active galactic nucleus (AGN) with a relativistic jet (a jet travelling close to the speed of light) directed towards an observer. Blazars are very high energy objects and are considered to be one of the most powerful phenomena in the Universe. The research has revealed that in PBC J2333.9-2343, the jet changed its direction drastically by an angle of up to 90 degrees, going from being in the plane of the sky, perpendicular to our line of sight, to pointing directly towards us.

A blazar jet is made of elemental charged particles like electrons or protons that move at velocities close to the speed of light. These move in circles around a strong magnetic field, causing the emission of radiation across the entire electromagnetic spectrum. In PBC J2333.9-2343, the jet is thought to originate from or close to the supermassive black hole in its centre.

With the jet pointing in our direction, the emission is strongly enhanced and can easily exceed that coming from the rest of the galaxy. This in turn drives high-intensity flares stronger than those coming from other radio galaxies, thus changing its categorisation.

The orientation of the jets to us determines how a galaxy is classified. When two jets point towards the plane of the sky, they are classified as a radio galaxy, but if one of the jets points towards us, then the AGN of the galaxy is known as a blazar. With jets in the plane of the sky and one directed at us, PBC J2333.9-2343 has been reclassified as a radio galaxy with a blazar at its centre.

Changes in the direction of jets have been described in the past, for example with X-shaped radio galaxies. This is the first time that such a phenomenon has been observed where it does not suggest the presence of two different phases of jet activity from its morphology observed at radio frequencies -- the direction change appears to have taken place in the same nuclear outburst originating from the AGN.

To find out more about this mysterious galaxy, astronomers had to observe it across a wide range of the electromagnetic spectrum. PBC J2333.9-2343 was observed with radio, optical, infrared, x-ray, ultraviolet and gamma ray telescopes. Data was obtained from the German 100m-Radio Telescope Effelsberg at the Max Planck Institute for Radio Astronomy, the Yale University 1.3m-SMARTS optical telescope, and the Penn State Neil Gehrels Swift Observatory.

The team then compared the properties of PBC J2333.9-2343 with large samples of blazars and non-blazar galaxies provided by the ALeRCE (Automatic Learning for the Rapid Classification of Events) project in Chile with data from the Zwicky Transient Facility (ZTF) and the Asteroid Terrestrial-impact Last Alert System (ATLAS).

Using the observational data, the team concluded that this galaxy has a bright blazar in the centre, with two lobes in the outer areas of the jet. The lobes that are observed are related to the old jets and are no longer being fed by the emission from the nucleus, so these lobes are relics of past radio activity. The AGN no longer drives the lobes as seen in typical radio galaxies.

The team do not yet know what caused the drastic change in direction of the jets. They speculate that it could have been a merging event with another galaxy or any other relatively large object, or a strong burst of activity in the galactic nucleus after a dormant period.

Dr Lorena Hernández-García, lead author of the paper and researcher at the Millenium Institute of Astrophysics, says "We started to study this galaxy as it showed peculiar properties. Our hypothesis was that the relativistic jet of its supermassive black hole had changed its direction, and to confirm that idea we had to carry out a lot of observations."

Read more at Science Daily

Rare sighting of luminous jet spewed by supermassive black hole

What happens when a dying star flies too close to a supermassive black hole?

According to University of Maryland astronomer Igor Andreoni, several things happen: first, the star is violently ripped apart by the black hole's gravitational tidal forces -- similar to how the Moon pulls tides on Earth but with greater strength. Then, pieces of the star are captured into a swiftly spinning disk orbiting the black hole. Finally, the black hole consumes what remains of the doomed star in the disk. This is what astronomers call a tidal disruption event (TDE).

But in some extremely rare cases, the supermassive black hole launches "relativistic jets" -- beams of matter traveling close to the speed of light -- after destroying a star. Andreoni, who is a postdoctoral associate in the Department of Astronomy at UMD and NASA Goddard Space Flight Center, discovered one such case with his team in the Zwicky Transient Facility (ZTF) survey in February 2022. After the group publicly announced the sighting, the event was named "AT2022cmc." The team published its findings in the journal Nature on November 30, 2022.

"The last time scientists discovered one of these jets was well over a decade ago," said Michael Coughlin, an assistant professor of astronomy at the University of Minnesota Twin Cities and co-lead on the project. "From the data we have, we can estimate that relativistic jets are launched in only 1% of these destructive events, making AT2022cmc an extremely rare occurrence. In fact, the luminous flash from the event is among the brightest ever observed."

Before AT2022cmc, the only two previously known jetted TDEs were discovered through gamma-ray space missions, which detect the highest-energy forms of radiation produced by these jets. As the last such discovery was made in 2012, new methods were required to find more events of this nature. To help address that need, Andreoni and his team implemented a novel, "big picture" tactic to find AT2022cmc: ground-based optical surveys, or general maps of the sky without specific observational targets. Using ZTF, a wide-field sky survey taken by the Samuel Oschin Telescope in California, the team was able to identify and uniquely study the otherwise dormant-looking black hole.

"We developed an open-source data pipeline to store and mine important information from the ZTF survey and alert us about atypical events in real time," Andreoni explained. "The rapid analysis of ZTF data, the equivalent to a million pages of information every night, allowed us to quickly identify the TDE with relativistic jets and make follow-up observations that revealed an exceptionally high luminosity across the electromagnetic spectrum, from the X-rays to the millimeter and radio."

Follow up observations with many observatories confirmed that AT2022cmc was fading rapidly and the ESO Very Large Telescope revealed that AT2022cmc was at cosmological distance, 8.5 billion light years away.

Hubble Space Telescope optical/infrared images and radio observations from the Very Large Array pinpointed the location of AT2022cmc with extreme precision. The researchers believe that AT2022cmc was at the center of a galaxy that is not yet visible because the light from AT2022cmc outshone it, but future space observations with Hubble or James Webb Space Telescopes may unveil the galaxy when the transient eventually disappears.

It is still a mystery why some TDEs launch jets while others do not seem to. From their observations, Andreoni and his team concluded that the black holes in AT2022cmc and other similarly jetted TDEs are likely spinning rapidly so as to power the extremely luminous jets. This suggests that a rapid black hole spin may be one necessary ingredient for jet launching -- an idea that brings researchers closer to understanding the physics of supermassive black holes at the center of galaxies billions of light years away.

Read more at Science Daily

Elusive, dusty inner region of distant galaxy

An international team of scientists has achieved the milestone of directly observing the long-sought, innermost dusty ring around a supermassive black hole, at a right angle to its emerging jet. Such a structure was thought to exist in the nucleus of galaxies but had been difficult to observe directly because intervening material obscured our line of sight.

Now the inner disk is detected using the highest spatial resolution in the infrared wavelengths ever done for an extragalactic object. The new discovery was just published in The Astrophysical Journal.

"This is a very exciting step forward to view the inner region of a distant galaxy with such fine detail," said Gail Schaefer, Associate Director of the Center for High Angular Resolution Astronomy (CHARA) Array.

A supermassive black hole is thought to exist at the center of every large galaxy. As material in the surrounding region gets pulled toward the center, the gas forms a hot and bright disk-like structure. In some cases, a jet emerges from the vicinity of the black hole in a direction at a right angle to the disk. However, this flat structure, which is essentially the 'engine' of this active supermassive black hole system, has never been directly seen because it's too small to be captured by conventional telescopes.

One way to approach this key structure is to directly see an outer 'dusty ring' -- interstellar gas contains dust grains, tiny solid particles made of heavy elements, which can only survive in the outer region where temperature is low enough (< ~1500K -- otherwise metals evaporate). The heated dust emits thermal infrared radiation, and thus would look like an outer ring around the black hole, if the central system indeed has a flat structure. The detection of its structure would be a key step to delineate how the central engine works.

Attempts to see this structure from edge-on directions are difficult, because the system is obscured by the same dust acting as an absorber of light. Instead, in the new investigation the team focused on a system with a face-on view, the brightest such object in the nearby universe. However, the detection needed very high spatial resolution in the infrared wavelengths, and at the same time, a large array of telescopes that is laid out suitably to observe objects at different orientations.

The Georgia State University CHARA Array interferometer at the Mount Wilson Observatory in California is the only facility which meets both of these requirements. The Array consists of 6 telescopes, each of which has a 1-meter diameter mirror, that are combined to achieve the spatial resolution of a much larger telescope. While each individual telescope is relatively small, the array layout is optimized to observe objects in a variety of angles and with large distances between telescopes. This achieves a very high spatial resolution capability. The CHARA Array actually has the sharpest eyes in the world in infrared wavelengths.

With the CHARA Array, the team finally detected the dusty ring, at a right angle to the emerging jet in the center of the galaxy called NGC 4151.

"We've been hoping to see this structure in a bare nucleus object for a long, long time," says Makoto Kishimoto, principal investigator of the project at Kyoto Sangyo University.

A big boost was that each telescope has recently added a new system called "adaptive optics."

Matt Anderson, a postdoctoral researcher at the CHARA Array who played a critical role in conducting the observations, says "This greatly increased the injection rate of the light, compensating for the relatively small collecting mirror to observe the extragalactic target, which is much fainter than the stellar targets typically observed in our Galaxy."

Over the last nearly 40 years, researchers in the field believed that this dusty ring is a key to understanding different characteristics of accreting supermassive blackhole systems. The properties we observe depend on whether we have an obscured, edge-on view or clear, face-on view of the nucleus of the active galaxy. The detection of this ring-like structure validates this model.

Furthermore, the detection probably is not just an indication of a flat structure. Additional studies have been showing that the structure seen at slightly longer infrared wavelengths, corresponding to an even larger outer region, seems elongated along the jet, and not at a right angle to it. This has been interpreted as an indication for a dusty wind being blown out toward the jet direction. The present finding that the inner structure looks flat and perpendicular to the jet, is an important link to the windy structure and its interaction with the rest of the galaxy surrounding the active black hole system.

Read more at Science Daily

Black hole discovered firing jets at neighboring galaxy

With the help of citizen scientists, a team of astronomers has discovered a unique black hole spewing a fiery jet at another galaxy. The black hole is hosted by a galaxy around one billion light years away from Earth named RAD12. The work was published today in Monthly Notices of the Royal Astronomical Society (Letters).

Galaxies are typically divided into two major classes based on their morphology: spirals and ellipticals. Spirals have optically-blue looking spiral arms with an abundance of cold gas and dust. In spiral galaxies, new stars form at an average rate of one Sun-like star per year. In contrast elliptical galaxies appear yellowish and lack distinct features such as spiral arms.

Star formation in elliptical galaxies is very scarce; it is still a mystery to astronomers as to why the elliptical galaxies we see today have not been forming new stars for billions of years. Evidence suggests that supermassive or 'monster' black holes are responsible. These 'monster' black holes spew gigantic jets made of electrons moving at very high speeds at other galaxies, depleting the fuel required for future star formation: cold gas and dust.

The unique nature of RAD12 had been observed in 2013 using optical data from the Sloan Digitised Sky Survey (SDSS) and radio data from the Very Large Array (FIRST survey). However, follow-up observation with the Giant Meterwave Radio Telescope (GMRT) in India was required to confirm its truly exotic nature: The black hole in RAD12 appears to be ejecting the jet only towards a neighbouring galaxy, named RAD12-B. In all cases, jets are ejected in pairs, moving in opposite directions at relativistic speeds. Why only one jet is seen coming from RAD12 remains a puzzle to astronomers.

A conical stem of young plasma is seen being ejected from the centre and reaches far beyond the visible stars of RAD12. The GMRT observations revealed that the fainter and older plasma extends far beyond the central conical stem and flares out like the cap of a mushroom (seen in red in the tricolour image). The whole structure is 440 thousand light years long, which is much larger than the host galaxy itself.

RAD12 is unlike anything known so far; this is the first time a jet has been observed to collide with a large galaxy like RAD12-B. Astronomers are now one step closer to understanding the impact of such interactions on elliptical galaxies, which may leave them with little cold gas for future star formation.

Read more at Science Daily

X-shaped radio galaxies might form more simply than expected

When astronomers use radio telescopes to gaze into the night sky, they typically see elliptical-shaped galaxies, with twin jets blasting from either side of their central supermassive black hole. But every once in a while -- less than 10% of the time -- astronomers might spot something special and rare: An X-shaped radio galaxy, with four jets extending far into space.

Although these mysterious X-shaped radio galaxies have confounded astrophysicists for two decades, a new Northwestern University study sheds new insight into how they form -- and its surprisingly simple. The study also found that X-shaped radio galaxies might be more common than previously thought.

The study will be published on Aug. 29 in the Astrophysical Journal Letters. It marks the first large-scale galaxy accretion simulation that tracks the galactic gas far from the supermassive black hole all the way toward it.

Simple conditions lead to messy result

Using new simulations, the Northwestern astrophysicists implemented simple conditions to model the feeding of a supermassive black hole and the organic formation of its jets and accretion disk. When the researchers ran the simulation, the simple conditions organically and unexpectedly led to the formation of an X-shaped radio galaxy.

Surprisingly, the researchers found that the galaxy's characteristic X-shape resulted from the interaction between the jets and the gas falling into the black hole. Early in the simulation, the infalling gas deflected the newly formed jets, which turned on and off, erratically wobbled and inflated pairs of cavities in different directions to resemble an X-shape. Eventually, however, the jets became strong enough to push through the gas. At this point, the jets stabilized, stopped wobbling and propagated along one axis.

"We found that even with simple symmetric initial conditions, you can have quite a messy result," said Northwestern's Aretaios Lalakos, who led the study. "A popular explanation of X-shaped radio galaxies is that two galaxies collide, causing their supermassive black holes to merge, which changes the spin of the remnant black hole and the direction of the jet. Another idea is that the jet's shape is altered as it interacts with large-scale gas enveloping an isolated supermassive black hole. Now, we have revealed, for the first time, that X-shaped radio galaxies can, in fact, be formed in a much simpler way."

Lalakos is a graduate student in Northwestern's Weinberg College of Arts and Sciences and a member of the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA). He is co-advised by paper coauthor Sasha Tchekhovskoy, an assistant professor of physics and astronomy at Northwestern and key member of CIERA, and Ore Gottlieb, a CIERA postdoctoral fellow.

An accidental X-shape

Although radio galaxies emit visible light, they also encompass large regions of radio emission. Perhaps the most famous radio galaxy is M87, one of the most massive galaxies in the universe, which was further popularized in 2019 when the Event Horizon Telescope imaged its central supermassive blackhole. First coined in 1992, X-shaped radio galaxies make up less than 10% of all radio galaxies.

When Lalakos set out to model a black hole, he did not expect to simulate an X-shaped galaxy. Instead, he aimed to measure the amount of mass eaten by a black hole. He inputted simple astronomical conditions into the simulation and let it run. Lalakos did not initially recognize the importance of the emerging X-shape, but Tchekhovskoy reacted with enthusiastic fervor.

"He said, 'Dude, this is very important! This is an X-shape!'" Lalakos said. "He told me that astronomers have observed this in real life and didn't know how they formed. We created it in a way that no one had even speculated before."

In previous simulations, other astrophysicists have attempted to create X-shaped structures artificially in order study how they arise. But Lalakos' simulation organically led to the X-shape.

"In my simulation, I tried to assume nothing," Lalakos said. "Usually, researchers put a black hole in the middle of a simulation grid and place a large, already-formed gaseous disk around it, and then they may add ambient gas outside the disk. In this study, the simulation starts without a disk, but soon one forms as the rotating gas gets closer to the black hole. This disk then feeds the black hole and creates jets. I made the simplest assumptions possible, so the whole outcome was a surprise. This is the first time anyone has seen X-shaped morphology in simulations from very simple initial conditions."

'Not lucky enough to see them'

Because the X-shape only emerged early in the simulation -- until the jets strengthened and stabilized -- Lalakos believes X-shaped radio galaxies might appear more frequently, but last a very short time, in the universe than previously thought.

"They might arise every time the black hole gets new gas and starts eating again," he said. "So they might be happening frequently, but we might not be lucky enough to see them because they only happen for as long as the power of the jet is too weak to push the gas away."

Next, Lalakos plans to continue running simulations to better understand how these X-shapes arise. He looks forward to experimenting with the size of the accretion disks and spins of central black holes. In other simulations, Lalakos included accretion disks that were almost non-existent all the way up to extremely large -- none led to the elusive X-shape.

"For most of the universe, it's impossible to zoom in right at the center and see what's happening very near a black hole," Lalakos said. "And even the things we can observe, we are constrained by time. If the supermassive black hole is already formed, we cannot observe its evolution because human lifetime is too short. In most cases, we rely on simulations to understand what happens near a black hole."

Read more at Science Daily

Supermassive blackhole influences star formation

A European team of astronomers led by Professor Kalliopi Dasyra of the National and Kapodistrian University of Athens, Greece, under participation of Dr. Thomas Bisbas, University of Cologne modelled several emission lines in Atacama Large Millimeter Array (ALMA) and Very Large Telescope (VLT) observations to measure the gas pressure in both jet-impacted clouds and ambient clouds. With these unprecedented measurements, published recently in Nature Astronomy, they discovered that the jets significantly change the internal and external pressure of molecular clouds in their path. Depending on which of the two pressures changes the most, both compression of clouds and triggering of star formation and dissipation of clouds and delaying of star formation are possible in the same galaxy. "Our results show that supermassive black holes, even though they are located at the centers of galaxies, could affect star formation in a galaxy-wide manner" said Professor Dasyra, adding that "studying the impact of pressure changes in the stability of clouds was key to the success of this project. Once few stars actually form in a wind, it is usually very hard to detect their signal on top of the signal of all other stars in the galaxy hosting the wind."

It is believed that supermassive black holes lie at the centers of most galaxies in our Universe. When particles that were infalling onto these black holes are trapped by magnetic fields, they can be ejected outwards and travel far inside galaxies in the form of enormous and powerful jets of plasma. These jets are often perpendicular to galactic disks. In IC 5063 however, a galaxy 156 million light years away, the jets are actually propagating within the disk, interacting with cold and dense molecular gas clouds. From this interaction, compression of jet-impacted clouds is theorized to be possible, leading to gravitational instabilities and eventually star formation due to the gas condensation.

For the experiment, the team used the emission of carbon monoxide (CO) and formyl cation (HCO+) provided by ALMA, and the emission of ionized sulfur and ionized nitrogen provided by VLT. They then used advanced and innovative astrochemical algorithms to pinpoint the environmental conditions in the outflow and in the surrounding medium. These environmental conditions contain information about the strength of the far-ultraviolet radiation of stars, the rate at which relativistic charged particles ionize the gas, and the mechanical energy deposited on the gas by the jets. Narrowing down these conditions revealed the densities and gas temperatures descriptive of different parts of this galaxy, which were then used to provide pressures.

"We have performed many thousands of astrochemical simulations to cover a wide range of possibilities that may exist in IC 5063" said co-author Dr. Thomas Bisbas, DFG Fellow of the University of Cologne and former postdoctoral researcher at the National Observatory of Athens. A challenging part of the work was to meticulously identify as many physical constraints as possible to the examined range that each parameter could have. "This way, we could get the optimal combination of physical parameters of clouds at different locations of the galaxy," said co-author Mr. Georgios Filippos Paraschos, Ph.D. student at the Max Planck Institute for Radio Astronomy in Bonn and former Master's student at the National and Kapodistrian University of Athens.

Read more at Science Daily

Mini-jet found near Milky Way's supermassive black hole

Our Milky Way's central black hole has a leak. This supermassive black hole looks like it still has the vestiges of a blowtorch-like jet dating back several thousand years. NASA's Hubble Space Telescope hasn't photographed the phantom jet but has helped find circumstantial evidence that it is still pushing feebly into a huge hydrogen cloud and then splattering, like the narrow stream from a hose aimed into a pile of sand.

This is further evidence that the black hole, with a mass of 4.1 million Suns, is not a sleeping monster but periodically hiccups as stars and gas clouds fall into it. Black holes draw some material into a swirling, orbiting accretion disk where some of the infalling material is swept up into outflowing jets that are collimated by the black hole's powerful magnetic fields. The narrow "searchlight beams" are accompanied by a flood of deadly ionizing radiation.

"The central black hole is dynamically variable and is currently powered down," said Gerald Cecil of the University of North Carolina in Chapel Hill. Cecil pieced together, like a jigsaw puzzle, multiwavelength observations from a variety of telescopes that suggest the black hole burps out mini-jets every time it swallows something hefty, like a gas cloud. His multinational team's research has just been published in the Astrophysical Journal.

In 2013 evidence for a stubby southern jet near the black hole came from X-rays detected by NASA's Chandra X-ray Observatory and radio waves detected by the Jansky Very Large Array telescope in Socorro, New Mexico. This jet too appears to be plowing into gas near the black hole.

Cecil was curious if there was a northern counter-jet as well. He first looked at archival spectra of such molecules as methyl alcohol and carbon monosulfide from the ALMA Observatory in Chile (Atacama Large Millimeter/Submillimeter Array), which uses millimeter wavelengths to peer through the veils of dust between us and the galactic core. ALMA reveals an expanding, narrow linear feature in molecular gas that can be traced back at least 15 light-years to the black hole.

By connecting the dots, Cecil next found in Hubble infrared-wavelength images a glowing, inflating bubble of hot gas that aligns to the jet at a distance of at least 35 light-years from the black hole. His team suggests that the black hole jet has plowed into it, inflating the bubble. These two residual effects of the fading jet are the only visual evidence of it impacting molecular gas.

As it blows through the gas the jet hits material and bends along multiple streams. "The streams percolate out of the Milky Way's dense gas disk," said co-author Alex Wagner of Tsukuba University in Japan. "The jet diverges from a pencil beam into tendrils, like that of an octopus." This outflow creates a series of expanding bubbles that extend out to at least 500 light-years. This larger "soap bubble" structure has been mapped at various wavelengths by other telescopes.

Wagner and Cecil next ran supercomputer models of jet outflows in a simulated Milky Way disk, which reproduced the observations. "Like in archeology, you dig and dig to find older and older artifacts until you come upon remnants of a grand civilization," said Cecil. Wagner's conclusion: "Our central black hole clearly surged in luminosity at least 1 millionfold in the last million years. That sufficed for a jet to punch into the Galactic halo."

Previous observations by Hubble and other telescopes found evidence that the Milky Way's black hole had an outburst about 2-4 million years ago. That was energetic enough to create an immense pair of bubbles towering above our galaxy that glow in gamma-rays. They were first discovered by NASA's Fermi Gamma-ray Space Telescope in 2010 and are surrounded by X-ray bubbles that were discovered in 2003 by the ROSAT satellite and mapped fully in 2020 by the eROSITA satellite.

Hubble ultraviolet-light spectra have been used to measure the expansion velocity and composition of the ballooning lobes. Hubble spectra later found that the burst was so powerful that it lit up a gaseous structure, called the Magellanic stream, at about 200,000 light-years from the galactic center. Gas is glowing from that event even today.

To get a better idea of what's going on, Cecil looked at Hubble and radio images of another galaxy with a black hole outflow. Located 47 million light-years away, the active spiral galaxy NGC 1068 has a string of bubble features aligned along an outflow from the very active black hole at its center. Cecil found that the scales of the radio and X-ray structures emerging from both NGC 1068 and our Milky Way are very similar. "A bow shock bubble at the top of the NGC 1068 outflow coincides with the scale of the Fermi bubble start in the Milky Way. NGC 1068 may be showing us what the Milky Way was doing during its major power surge several million years ago."

The residual jet feature is close enough to the Milky Way's black hole that it would become much more prominent only a few decades after the black hole powers up again. Cecil notes that "the black hole need only increase its luminosity by a hundredfold over that time to refill the jet channel with emitting particles. It would be cool to see how far the jet gets in that outburst. To reach into the Fermi gamma-ray bubbles would require that the jet sustain for hundreds of thousands of years because those bubbles are each 50,000 light years across!"

Read more at Science Daily

Jet from giant galaxy M87: Computer modelling explains black hole observations

The galaxy Messier 87 (M87) is located 55 million light years away from Earth in the Virgo constellation. It is a giant galaxy with 12,000 globular clusters, making the Milky Way's 200 globular clusters appear modest in comparison. A black hole of six and a half billion sun masses is harboured at the centre of M87. It is the first black hole for which an image exists, created in 2019 by the international research collaboration Event Horizon Telescope.

This black hole (M87*) shoots a jet of plasma at near the speed of light, a so-called relativistic jet, on a scale of 6,000 light years. The tremendous energy needed to power this jet probably originates from the gravitational pull of the black hole, but how a jet like this comes about and what keeps it stable across the enormous distance is not yet fully understood.

The black hole M87* attracts matter that rotates in a disc in ever smaller orbits until it is swallowed by the black hole. The jet is launched from the centre of the accretion disc surrounding M87, and theoretical physicists at Goethe University, together with scientists from Europe, USA and China, have now modelled this region in great detail.

They used highly sophisticated three-dimensional supercomputer simulations that use the staggering amount of a million CPU hours per simulation and had to simultaneously solve the equations of general relativity by Albert Einstein, the equations of electromagnetism by James Maxwell, and the equations of fluid dynamics by Leonhard Euler.

The result was a model in which the values calculated for the temperatures, the matter densities and the magnetic fields correspond remarkably well with what deduced from the astronomical observations. On this basis, scientists were able to track the complex motion of photons in the curved spacetime of the innermost region of the jet and translate this into radio images. They were then able to compare these computer modelled images with the observations made using numerous radio telescopes and satellites over the past three decades.

Dr Alejandro Cruz-Osorio, lead author of the study, comments: "Our theoretical model of the electromagnetic emission and of the jet morphology of M87 matches surprisingly well with the observations in the radio, optical and infrared spectra. This tells us that the supermassive black hole M87* is probably highly rotating and that the plasma is strongly magnetized in the jet, accelerating particles out to scales of thousands of light years."

Read more at Science Daily

Dark heart of the nearest radio galaxy

An international team anchored by the Event Horizon Telescope (EHT) Collaboration, which is known for capturing the first image of a black hole in the galaxy Messier 87, has now imaged the heart of the nearby radio galaxy Centaurus A in unprecedented detail. The astronomers pinpoint the location of the central supermassive black hole and reveal how a gigantic jet is being born. Most remarkably, only the outer edges of the jet seem to emit radiation, which challenges our theoretical models of jets. This work, led by Michael Janssen from the Max Planck Institute for Radio Astronomy in Bonn and Radboud University Nijmegen is published in Nature Astronomy on July 19th.

At radio wavelengths, Centaurus A emerges as one of the largest and brightest objects in the night sky. After it was identified as one of the first known extragalactic radio sources in 1949, Centaurus A has been studied extensively across the entire electromagnetic spectrum by a variety of radio, infrared, optical, X-ray, and gamma-ray observatories. At the center of Centaurus A lies a black hole with the mass of 55 million suns, which is right between the mass scales of the Messier 87 black hole (six and a half billion suns) and the one in the center of our own galaxy (about four million suns).

In a new paper in Nature Astronomy, data from the 2017 EHT observations have been analyzed to image Centaurus A in unprecedented detail. "This allows us for the first time to see and study an extragalactic radio jet on scales smaller than the distance light travels in one day. We see up close and personally how a monstrously gigantic jet launched by a supermassive black hole is being born," says astronomer Michael Janssen.

Compared to all previous high-resolution observations, the jet launched in Centaurus A is imaged at a tenfold higher frequency and sixteen times sharper resolution. With the resolving power of the EHT, we can now link the vast scales of the source, which are as big as 16 times the angular diameter of the Moon on the sky, to their origin near the black hole in a region of merely the width of an apple on the Moon when projected on the sky. That is a magnification factor of one billion.

Understanding jets

Supermassive black holes residing in the center of galaxies like Centaurus A are feeding off gas and dust that is attracted by their enormous gravitational pull. This process releases massive amounts of energy and the galaxy is said to become 'active'. Most matter lying close to the edge of the black hole falls in. However, some of the surrounding particles escape moments before capture and are blown far out into space: Jets -- one of the most mysterious and energetic features of galaxies -- are born.

Astronomers have relied on different models of how matter behaves near the black hole to better understand this process. But they still do not know exactly how jets are launched from its central region and how they can extend over scales that are larger than their host galaxies without dispersing out. The EHT aims to resolve this mystery.

Read more at Science Daily

Researchers identify where giant jets from black holes discharge their energy

 The supermassive black holes at the centers of galaxies are the most massive objects in the universe. They range from about 1 million to upwards of 10 billion times the mass of the Sun. Some of these black holes also blast out gigantic, super-heated jets of plasma at nearly the speed of light. The primary way that the jets discharge this powerful motion energy is by converting it into extremely high-energy gamma rays. However, UMBC physics Ph.D. candidate Adam Leah Harvey says, "How exactly this radiation is created is an open question."

The jet has to discharge its energy somewhere, and previous work doesn't agree where. The prime candidates are two regions made of gas and light that encircle black holes, called the broad-line region and the molecular torus.

A black hole's jet has the potential to convert visible and infrared light in either region to high-energy gamma rays by giving away some of its energy. Harvey's new NASA-funded research sheds light on this controversy by offering strong evidence that the jets mostly release energy in the molecular torus, and not in the broad-line region. The study was published in Nature Communications and co-authored by UMBC physicists Markos Georganopoulos and Eileen Meyer.

Far out

The broad-line region is closer to the center of a black hole, at a distance of about 0.3 light-years. The molecular torus is much farther out -- more than 3 light-years. While all of these distances seem huge to a non-astronomer, the new work "tells us that we're getting energy dissipation far away from the black hole at the relevant scales," Harvey explains.

"The implications are extremely important for our understanding of jets launched by black holes," Harvey says. Which region primarily absorbs the jet's energy offers clues to how the jets initially form, pick up speed, and become column-shaped. For example, "It indicates that the jet is not accelerated enough at smaller scales to start to dissipate energy," Harvey says.

Other researchers have proposed contradictory ideas about the jets' structure and behavior. Because of the trusted methods Harvey used in their new work, however, they expect the results to be broadly accepted in the scientific community. "The results basically help to constrain those possibilities -- those different models -- of jet formation."

On solid footing

To come to their conclusions, Harvey applied a standard statistical technique called "bootstrapping" to data from 62 observations of black hole jets. "A lot of what came before this paper has been very model-dependent. Other papers have made a lot of very specific assumptions, whereas our method is extremely general," Harvey explains. "There isn't much to undermine the analysis. It's well-understood methods, and just using observational data. So the result should be correct."

A quantity called the seed factor was central to the analysis. The seed factor indicates where the light waves that the jet converts to gamma rays come from. If the conversion happens at the molecular torus, one seed factor is expected. If it happens at the broad-line region, the seed factor will be different.

Georganopolous, associate professor of physics and one of Harvey's advisors, originally developed the seed factor concept, but "applying the idea of the seed factor had to wait for someone with a lot of perseverance, and this someone was Adam Leah," Georganopolous says.

Harvey calculated the seed factors for all 62 observations. They found that the seed factors fell in a normal distribution aligned almost perfectly around the expected value for the molecular torus. That result strongly suggests that the energy from the jet is discharging into light waves in the molecular torus, and not in the broad-line region.

Tangents and searches

Harvey shares that the support of their mentors, Georganopoulos and Meyer, assistant professor of physics, was instrumental to the project's success. "I think that without them letting me go off on a lot of tangents and searches of how to do things, this would have never gotten to the level that it's at," Harvey says. "Because they allowed me to really dig into it, I was able to pull out a lot more from this project."

Harvey identifies as an "observational astronomer," but adds, "I'm really more of a data scientist and a statistician than I am a physicist." And the statistics has been the most exciting part of this work, they say.

Read more at Science Daily

Newborn jets in distant galaxies

 Astronomers using data from the ongoing VLA Sky Survey (VLASS) have found a number of distant galaxies with supermassive black holes at their cores that have launched powerful, radio-emitting jets of material within the past two decades or so. The scientists compared data from VLASS with data from an earlier survey that also used the National Science Foundation's Karl G. Jansky Very Large Array (VLA) to reach their conclusion.

"We found galaxies that showed no evidence of jets before but now show clear indications of having young, compact jets," said Dr. Kristina Nyland, who is an NRC postdoctoral fellow in residence at the Naval Research Laboratory.

"Jets like these can strongly affect the growth and evolution of their galaxies, but we still don't understand all of the details. Catching newborn jets with surveys like VLASS provides a measure of the role of powerful radio jets in shaping the lives of the galaxies over billions of years," Nyland said.

VLASS is a project that will survey the sky visible from the VLA -- about 80 percent of the entire sky -- three times over seven years. The observations began in 2017 and the first of the three scans now is complete. Nyland and her colleagues compared data from this scan with data from the FIRST survey that used the VLA to observe a smaller portion of the sky between 1993 and 2011.

They found about 2,000 objects that appear in the VLASS images, but were not detected in the earlier FIRST survey. From these, they selected 26 objects that previously were categorized as galaxies with active nuclei -- powered by supermassive black holes -- by optical and infrared observations. The FIRST observations of the 26 objects had been made between 1994 and 2001. The VLASS observations were made in 2019. The intervals between observations of the objects thus ranged from 18 to 25 years.

They chose 14 of these galaxies for more detailed observations with the VLA. These observations provided higher-resolution images and also were done at multiple radio frequencies to get a more complete understanding of the objects' characteristics.

"The data from these detailed observations tell us that the most likely cause of the difference in radio brightness between the FIRST and the VLASS observations is that the 'engines' at the cores of these galaxies have launched new jets since the FIRST observations were made," explained Dillon Dong, from Caltech.

The black holes at the cores of galaxies are known to interact with the galaxies themselves, and the two evolve together. The jets launched from the regions near the black holes can affect the amount of star formation within the galaxy.

"Radio jets provide natural laboratories for learning about the extreme physics of supermassive black holes, whose formation and growth are believed to be intrinsically linked to that of the galaxy centers in which they reside," said Pallavi Patil, of the University of Virginia.

"Jets as young as the ones discovered in our study can provide us with a rare opportunity to gain new insights on how these interactions between the jets and their surroundings work," Nyland said.

"VLASS has proven to be a key tool for discovering such jets, and we eagerly await the results of its next two observing epochs," said Mark Lacy, of the National Radio Astronomy Observatory.

Read more at Science Daily