Friday, January 17, 2025

Sticks and Stones: The Molecular Clouds in the Heart of the Milky Way

The Central Molecular Zone (CMZ) at the heart of the Milky Way holds a lot of gas. It contains about 60 million solar masses of molecular gas in complexes of giant molecular clouds (GMCs), structures where stars usually form. Because of the presence of Sag. A*, the Milky Way’s supermassive black hole (SMBH), the CMZ is an extreme environment. The gas in the CMZ is ten times more dense, turbulent, and heated than gas elsewhere in the galaxy.

How do star-forming GMCs behave in such an extreme environment?

Researchers have found a novel way to study two of the GMCs in the CMZ. The clouds are named “Sticks” and “Stones” and astronomers have used decades of X-ray observations from the Chandra X-ray Observatory to probe the 3D structures of the pair of clouds.

University of Connecticut Physics Researcher Danya Alboslani and postdoctoral researcher Dr. Samantha Brunker are both with the Milky Way Laboratory at the University of Connecticut. They’ve produced two manuscripts presenting their new X-ray tomography method and their results. Brunker is the lead author of “3D MC I: X-ray Tomography Begins to Unravel the 3-D Structure of a Molecular Cloud in our Galaxy’s Center,” and Alboslani is the lead author of “3D MC II: X ray echoes reveal a clumpy molecular cloud in the CMZ.” Brunker and Alboslani are also co-authors on each paper. Alboslani also presented her results at the recent 245th Meeting of the American Astronomical Society.

When gas from elsewhere in the galaxy reaches Sgr A*, it forms an accretion ring around the SMBH. As the gas heats up, it releases X-rays. These X-ray emission are only intermittent, and in the past, some of these episodes have been very intense. The X-ray travel outward in all directions, and while we didn’t have the capability to observe them, they interacted with GMCs near the CMZ. The clouds first absorbed them the re-emitted them in a phenomenon called fluorescence.

“The cloud absorbs the X-rays that are coming from Sgr A* then re-emits X-rays in all directions. Some of these X-rays are coming towards us, and there is this very specific energy level, the 6.4 electron volt neutral iron line, that has been found to correlate with the dense parts of molecular gas,” says Alboslani. “If you imagine a black hole in the center producing these X-rays which radiate outwards and eventually interact with a molecular cloud in the CMZ, over time, it will highlight different parts of the cloud, so what we’re seeing is a scan of the cloud.”

The Central Molecular Zone; the Heart of the Milky Way. Image Credit: Henshaw / MPIA
The Central Molecular Zone; the Heart of the Milky Way. Image Credit: Henshaw / MPIA

The center of the galaxy is choked with dust that obscures our view of the region. Visible light is blocked, but the powerful X-rays emitted by Sgr A* during accretion events are visible.

Typically, astronomers only see two dimensions of objects in space. According to Battersby, their new X-Ray tomography method allows them to measure the GMCs’ third dimension. Battersby explains that while we typically only see two spatial dimensions of objects in space, the X-ray tomography method allows us to measure the third dimension of the cloud. It’s because we see the X-rays illuminate individual slices of the cloud over time. “We can use the time delay between illuminations to calculate the third spatial dimension because X-rays travel at the speed of light,” Battersby explains.

The Chandra X-Ray Observatory has been observing these X-rays for two decades, and as it observes them it sees different “slices” of the clouds, just like medical tomography. The slices are then built up into a 3D image. These are the first 3D maps of star-forming clouds in such an extreme environment.

This figure from Brunker's paper illustrates how the X-ray tomography works. Each coloured line represents a different "slice" of the cloud from a specific year. Image Credit: Brunker et al. 2025.
This figure from Brunker’s paper on the “Sticks” cloud illustrates how the X-ray tomography works. Each coloured line represents a different “slice” of the cloud from a specific year. Image Credit: Brunker et al. 2025.

The X-ray tomography method has one weakness. The X-ray observations aren’t continuous, so there are gaps. There are also some structures visible in submillimeter wavelengths that aren’t seen in X-rays. To get around that, the pair of researchers used data from the ALMA and the Herschel Space Observatory to compare the structures seen in the X-ray echoes to those seen in other wavelengths. The structures that are missing in X-rays but visible in submillimeter wavelengths can also be used to constrain the duratio of X-ray flares that illuminated the clouds.

“We can estimate the sizes of the molecular structures that we do not see in the X-ray,“ says Brunker, “and from there we can place constraints on the duration of the X-ray flare by modeling what we would be able to observe for a range of flare lengths. The model that reproduced observations with similar sized ‘missing structures’ indicated that the X-ray flare couldn’t have been much longer than 4-5 months.”

This figure from Brunker's paper shows ALMA observations, which show the presence of H2CO (formaldehyde) combined with Chandra's X-ray observations. Blue is X-rays and pink is ALMA data. Purple is where they overlap. Each panel is from a different year. Image Credit: Brunker et al. 2025.
This figure from Brunker’s paper shows ALMA observations, which show the presence of H2CO (formaldehyde) combined with Chandra’s X-ray observations. Blue is X-rays and pink is ALMA data. Purple is where they overlap. Each panel is from a different year. Image Credit: Brunker et al. 2025.

“The overall morphological agreement, and in particular, the association of the densest regions in both X-ray and molecular line data is striking and is the first time it has been shown on such a small scale,” says Brunker.

Detecting a third dimension of the clouds in this extreme environment could open new avenues of discovery.

“While we learn a lot about molecular clouds from data collected in 2D, the added third dimension allows for a more detailed understanding of the physics of how new stars are born,” says Battersby. “Additionally, these observations place key constraints on the global geometry of our Galaxy’s Center as well as the past flaring activity of Sgr A*, central open questions in modern astrophysics.”

When it comes to how new stars from, there are many unanswered questions. While we know turbulence in GMCs can inhibit star formation, the exact mechanism is unkown. Astronomers are also uncertain how environmental factors affect star formation. There are many others and some of them can be answered by watching how GMCs behave in extreme environments.

There are also many questions regarding Sgr A*’s X-ray flaring. Astronomers aren’t certain how factors like magnetic reconnection events near the black hole and hot spots in the accretion flow affect X-ray flaring. They also aren’t certain why X-ray flaring occurs in random intervals. That’s just a sample of unanswered questions that could be addressed by studying GMCs in the galactic centre.

If all large galaxies contain SMBHs, which seems increasingly likely, then all large galaxies have CMZs that are extreme environments. The CMZs and the SMBHs are the heart of galaxies, and astrophysicists are keen to understand the processes that play out there, and if stars are able to form there.

“We can study processes in the Milky Way’s Central Molecular Zone (CMZ) and use our findings to learn about other extreme environments. While many distant galaxies have similar environments, they are too far away to study in detail. By learning more about our own Galaxy, we also learn about these distant galaxies that cannot be resolved with today’s telescopes,” says Alboslani.

Alboslani presents her results in this video from AAS 245. Her presentation begins at the 32:40 mark.

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Thursday, January 16, 2025

A Flexible, Adaptable Space Metamaterial

Researchers have discovered how to make a new kind of metamaterial reconfigure itself without tangling itself up in knots, opening up the possibility of a broad array of space applications.

Metamaterials are a hot topic in engineering. These are materials inspired from biological systems. Many living structures start from simple, repeatable patterns that then grow into large, complex structures. The resulting structures can then have properties that the small subcomponents don’t. For example, individual bone cells or coral polyp skeletons aren’t very strong, but when they work together they can support huge animals or gigantic underwater colonies.

One promising kind of metamaterial is known as a Totimorphic lattice. This lattice starts from a triangular shaped structure. On one side is a fixed beam with a ball joint in the center. An arm attaches to that ball joint, and the other end of the arm is attached to the ends of the fixed beam with two springs. Many of these shapes attached together can morph into a wide variety of shapes and structures, all with very minimal input, giving the Totimorphic lattice incredible flexibility.

In a recent paper, scientists with the European Space Agency’s Advanced Concepts Team found a way to reconfigure Totimorphic lattices without having them tangle up on themselves. They discovered this using a series of computer simulations, creating an optimization problem for the algorithm to solve. With the algorithm in hand, they could then take any configuration of the lattice and change it to another in an optimal, efficient way.

The researchers showed off their technique with two examples. The first was a simple habitat structure that could change its shape and stiffness, which could allow future astronauts to deploy the same kind of metamaterial to build a variety of structures, and reconfigure them as mission needs changed.

The second example was a flexible space telescope that could change its focal length by adapting the curvature of its lens. This would enable a single launch, with a single vehicle, to serve a variety of observing needs.

As of right now, this is all hypothetical. Totimorphic lattices don’t exist in practice, only as curious mathematical objects. But this research is crucial for advancing humanity into space. The cost and difficulty of launching materials into space mean that we need flexible, adaptable structures that are cheap to launch and easy to deploy.

This research is yet another example of how we can draw inspiration from nature, in this case investigating the surprising properties of metamaterials, to bring ourselves into a future in space.

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SpaceX Catches Booster But Loses Ship in Starship Test Flight

SpaceX’s seventh flight test of its massive Starship launch system brought good news as well as not-so-great news.

The good news? The Super Heavy booster successfully flew itself back to the Texas launch site and was caught above the ground by the launch tower’s chopstick-style mechanical arms. That’s only the second “Mechazilla” catch to be done during the Starship test program. The bad news is that the upper stage, known as Ship 33, was lost during its ascent.

“Starship experienced a rapid unscheduled disassembly during its ascent burn. Teams will continue to review data from today’s flight test to better understand root cause,” SpaceX said in a post-mission posting to X. “With a test like this, success comes from what we learn, and today’s flight will help us improve Starship’s reliability.”

Today’s test marked the first use of an upper stage that was upgraded with a redesign of the avionics, the propulsion system and the forward control flaps. Ship 33’s heat shield featured next-generation protective tiles as well as a backup layer of heat-resistant material. SpaceX had removed some of the tiles for this flight as a stress test for the heat shield.

During the webcast, an onscreen graphic suggested that Ship experienced engine problems during its ascent. “We saw engines dropping out on telemetry,” launch commentator Dan Huot said.

After Ship’s breakup, eyewitnesses posted videos showing a glittering hail of debris falling to Earth. Reuters reported that at least 20 commercial aircraft had to divert to different airports or alter their course to dodge the debris.

In response to an emailed inquiry, the Federal Aviation Administration said it was aware of the anomaly that occurred during today’s flight test and would be assessing the operation. “The FAA briefly slowed and diverted aircraft around the area where space vehicle debris was falling,” the agency said via email. “Normal operations have resumed.”

If Ship had made it to space, it would have deployed 10 Starlink simulators that were about the same size and weight as SpaceX’s Starlink broadband satellites. This was meant to test the procedure that SpaceX plans to use to put scores of Starlink satellites into low Earth orbit during a single Starship mission.

At the end of the flight test, Ship would have made a controlled re-entry and splashdown into the Indian Ocean.

Starship is the world’s most powerful launch system, with the booster’s 33 methane-fueled Raptor engines providing liftoff thrust of 16.7 million pounds. That’s more than twice the thrust of the Apollo-era Saturn V rocket, and almost twice the thrust of NASA’s Space Launch System, which was first launched in 2022 for the uncrewed Artemis I moon mission.

When fully stacked, Starship stands 403 feet (123 meters) tall. The system is meant to be fully reusable. Flight tests began in 2023, and SpaceX has made gradual progress. The first successful catch of the Super Heavy booster thrilled observers last October — and like that catch, today’s catch drew cheers from SpaceX employees watching the launch.

This year, SpaceX aims to demonstrate full reuse of Super Heavy and Ship, and promises to fly “increasingly ambitious missions.” The Starship system would be used for large-scale satellite deployments — and eventually for missions beyond Earth orbit. A customized version of Starship is slated to serve as a crewed lunar landing system for NASA’s Artemis III mission, which is currently scheduled for no earlier than mid-2027.

SpaceX founder Elon Musk envisions sending Starships on missions to Mars, perhaps starting in 2026. “These will be uncrewed to test the reliability of landing intact on Mars,” he said last September in a posting to X, the social-media platform that he owns.

“If those landings go well, then the first crewed flights to Mars will be in 4 years,” Musk said. “Flight rate will grow exponentially from there, with the goal of building a self-sustaining city in about 20 years.”

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The Most Accurate View of the Milky Way

We can judge the value of any scientific endeavour based on how much of our knowledge it overturns or transforms. By that metric, the ESA’s Gaia mission is a resounding success. The spacecraft gave us a precise, 3D map of our Milky Way galaxy and has forced us to abandon old ideas and replace them with compelling new ones.

Currently, we’re marking the end of the Gaia mission, our best effort to understand the Milky Way. Gaia is an astrometry mission that’s built an impressive map of the Milky Way by taking three trillion observations of two billion individual objects in the galaxy, most of them stars, over an 11-year period. Measuring the same objects repeatedly means Gaia’s map is 3D and shows the proper motion of stars throughout the galaxy. Rather than a static map, it reveals the galaxy’s kinetic history and some of the changes it’s gone through.

Gaia showed us our galaxy's turbulent history, including the streams of stars stemming from past disruptive events. Image Credit: ESA/Gaia/DPAC, Stefan Payne-Wardenaar
Gaia showed us our galaxy’s turbulent history, including the streams of stars stemming from past disruptive events. Image Credit: ESA/Gaia/DPAC, Stefan Payne-Wardenaar

We’ve waited a long time for such a detailed look at our galaxy.

Radio astronomy, which gained momentum in the 1950s, helped us understand the structure of the Milky Way. Radio telescopes could see through intervening dust clouds and detect the distribution of hydrogen in the galaxy. In 1952, astronomers began the first major radio survey of the Milky Way. Astronomers theorized that the galaxy had a spiral structure, and finally, they detected the spiral arms, revealing the Milky Way’s basic structure.

In a 1958 paper, the authors wrote that “The distribution of the hydrogen evidently shows great irregularities. Nevertheless, several arms can be followed over considerable lengths.”

This figure shows the hydrogen distribution in the plane of the Milky Way's disk. Though it appears outdated to our modern eyes, it was exciting at the time. Image Credit: From "The galactic system as a spiral nebula" by Oort et al. 1958.
This figure shows the hydrogen distribution in the plane of the Milky Way’s disk. Though it appears outdated to our modern eyes and isn’t visually intuitive, it was exciting at the time. Image Credit: From “The galactic system as a spiral nebula” by Oort et al. 1958.

Astronomers also used RR Lyrae and Cepheids, two types of variable stars with known intrinsic brightnesses (standard candles), to calculate their distances. This allowed them to trace the Milky Way’s structure. Globular clusters also helped astronomers map the Milky Way.

In the 1980s, infrared telescopes like NASA’s IRAS peered through cosmic dust to help find features like the Milky Way’s central bar. Then, in 1989, the ESA’s Hipparcos mission was launched. Hipparcos was an astrometry mission and was Gaia’s predecessor. Though not nearly as precise, and though it only measured 100,000 stars, it was finally able to measure their proper motions. It revealed more details of the Milky Way and helped confirm its barred spiral form. It also provided some insights into our galaxy’s history and evolution.

But astronomers craved more detailed knowledge. Gaia was launched in 2013 to meet this need, and it’s been a total success.

Gaia is a tribute to ingenuity. We’re effectively trapped inside the Milky Way, and no spacecraft can get beyond it to capture an external view of the galaxy. Gaia has given us that view without ever leaving L2.

While many prior efforts to trace the Milky Way’s structure depended on sampling select stellar populations, Gaia precisely measured the position and motion of almost two billion stars throughout the galaxy.

Gaia's map of the Milky Way has become iconic. This image is constructed from Gaia data that's mapping two billion of the galaxy's stars. It also mapped stars in the Large and Small Magellanic clouds. Image Credit: ESA/Gaia/DPAC
Gaia’s map of the Milky Way has become iconic. This image is constructed from Gaia data that’s mapping two billion of the galaxy’s stars. It also mapped stars in the Large and Small Magellanic clouds. Image Credit: ESA/Gaia/DPAC

Gaia’s work has culminated in artist impressions of the Milky Way based on its voluminous data. These impressions show that the Milky Way has multiple arms and that they’re not as prominent as we thought.

Gaia’s observations have given us a much more detailed and precise look at the Milky Way’s spiral arms. It has identified previously unknown structures in the arms, including fossil arms in the outer disk. These could be remnants of past tidal arms or distortions in the disk, or remnants of ancient interactions with other galaxies. Gaia has also found many previously unknown filamentary structures at the disk’s edge.

The Gaia mission has also allowed us to finally see our galaxy from the side. We’ve learned that the galactic disk has a slight wave to it. Astronomers think this was caused by a smaller galaxy interacting with the Milky Way. The Sagittarius Dwarf Spheroidal galaxy could be responsible for it.

The Sagittarius Dwarf Spheroidal Galaxy has been orbiting the Milky Way for billions of years. According to astronomers, the three known collisions between this dwarf galaxy and the Milky Way have triggered major episodes of star formation, one of which may have given rise to our Solar System. Image Credit: ESA/Gaia
The Sagittarius Dwarf Spheroidal Galaxy has been orbiting the Milky Way for billions of years. According to astronomers, the three known collisions between this dwarf galaxy and the Milky Way have triggered major episodes of star formation, one of which may have given rise to our Solar System. Image Credit: ESA/Gaia

Alongside the compelling science, artists have created illustrations based on Gaia data that really hit home. The stunning side view of our galaxy is one of the most accurate views of the Milky Way we’ve ever seen.

This artist's reconstruction of Gaia data shows the Milky Way's central bulge, galactic disk, and outer reaches. Image Credit: ESA/Gaia/DPAC, Stefan Payne-Wardenaar
This artist’s reconstruction of Gaia data shows the Milky Way’s central bulge, galactic disk, and outer reaches. Image Credit: ESA/Gaia/DPAC, Stefan Payne-Wardenaar

Gaia has updated our understanding of the galaxy we live in and brought its history to life. Even if it had no more to offer beyond today, it would still be an outstanding, successful mission. But even though its mission is over, we still don’t have all of its data.

Its final data release, DR5, will be available by the end of 2030.

Who knows what else the mission will show us about our home, the Milky Way galaxy.

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Webb and ALMA Team Up to Study Primeval Galaxy

One of the most exciting developments in modern astronomy is how astronomers can now observe and study the earliest galaxies in the Universe. This is due to next-generation observatories like the James Webb Space Telescope (JWST), with its sophisticated suite of infrared instruments and spectrometers, and advances in interferometry – a technique that combines multiple sources of light to get a clearer picture of astronomical objects. Thanks to these observations, astronomers can learn more about how the earliest galaxies in the Universe evolved to become what we see today.

Using Webb and the Atacama Large Millimeter/submillimeter Array (ALMA), an international team led by researchers from the National Astronomical Observatory of Japan (NAOJ) successfully detected atomic transitions coming from galaxy GHZ2 (aka. GLASS-z12), located 13.4 billion light-years away. Their study not only set a new record for the farthest detection of these elements This is the first time such emissions have been detected in galaxies more than 13 billion light-years away and offers the first direct insights into the properties of the earliest galaxies in the Universe.

The galaxy was first identified in July 2022 by the Grism Lens-Amplified Survey from Space (GLASS) observing program using the JWST’s Near-Infrared Camera (NIRCam). A month later, follow-up observations by ALMA confirmed that the galaxy had a spectrographic redshift of more than z = 12, making it one of the earliest and most distant galaxies ever observed. The exquisite observations by both observatories have allowed astronomers to gain fresh insights into the nature of the earliest galaxies in the Universe.

The Atacama Large Millimeter/submillimeter Array (ALMA). Credit: C. Padilla, NRAO/AUI/NSF

Jorge Zavala, an astronomer at the East Asian ALMA Regional Center at the NAOJ, was the lead author of this study. As he explained in an ALMA-NAOJ press release:

“We pointed the more than forty 12-m antennas of the Atacama Large Millimeter/submillimeter Array (ALMA) and the 6.5-m James Webb Space Telescope (JWST) for several hours at a sky position that would appear totally empty to the naked human eye, aiming to catch a signal from one of the most distant astronomical objects known to date. And [we] successfully detected the emission from excited atoms of different elements such as Hydrogen and Oxygen from an epoch never reached before.”

Confirming and characterizing the physical properties of distant galaxies is vital to testing our current theories of galaxy formation and evolution. However, insight into their internal physics requires detailed and sensitive astronomical observations and spectroscopy – the absorption and emission of light by matter- allowing scientists to detect specific chemical elements and compounds. Naturally, these observations were challenging for the earliest galaxies, given that they are the most distant astronomical objects ever studied.

Nevertheless, the ALMA observations detected the emission line associated with doubly ionized oxygen (O III), confirming that the galaxy existed about 367 million years after the Big Bang. Combined with data obtained by Webb’s Near-Infrared Spectrograph (NIRSpec) and Mid-Infrared Instrument (MIRI) instruments, the team was able to characterize this object effectively. Based on their observations, the team discovered that GHZ2 was experiencing extreme bursts of star formation 13.4 billion years ago under conditions that differ considerably from what astronomers have seen in star-forming galaxies over the past few decades.

For instance, the relative abundance of heavier elements in this galaxy (metallicity) is significantly lower than that of most galaxies studied. This was expected given the dearth of heavier elements during the early Universe when Population III stars existed, which were overwhelmingly composed of hydrogen and helium. These stars were massive, hot, and short-lived, lasting only a few million years before they went supernova. Similarly, the team attributed GHZ2’s high luminosity to its Population III stars, which are absent from more evolved galaxies.

The scattered stars of the globular cluster NGC 6355 are strewn across this image from the NASA/ESA Hubble Space Telescope. Credit: ESA/Hubble & NASA, E. Noyola, R. Cohen

This luminosity is amplified by the fact that GHZ2, which is a few hundred million times the mass of the Sun, occupies a region of around 100 parsecs (~325 light-years). This indicates that the galaxy has a high stellar density similar to that of Globular Clusters observed in the Milky Way and neighboring galaxies. Other similarities include low metallicity, the anomalous abundances of certain chemicals, high star formation rates, high stellar mass surface density, and more. As such, studying galaxies like GHZ2 could help astronomers explain the origin of globular clusters, which remains a mystery.

Said Tom Bakx, a researcher at Chalmers University, these observations could pave the way for future studies of ancient galaxies that reveal the earliest phases of galaxy formation:

“This study is a crown on the multi-year endeavor to understand galaxies in the early Universe. The analysis of multiple emission lines enabled several key tests of galaxy properties, and demonstrates the excellent capabilities of ALMA through an exciting, powerful synergy with other telescopes like the JWST.”

Further Reading: ALMA, AJL

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Wednesday, January 15, 2025

Recent Observations Challenge our Understanding of Giant Black Holes

Black holes are among the most mysterious and powerful objects in the Universe. These behemoths form when sufficiently massive stars reach the end of their life cycle and experience gravitational collapse, shedding their outer layers in a supernova. Their existence was illustrated by the work of German astronomer Karl Schwarzschild and Indian-American physicist Subrahmanyan Chandrasekhar as a consequence of Einstein’s Theory of General Relativity. By the 1970s, astronomers confirmed that supermassive black holes (SMBHs) reside at the center of massive galaxies and play a vital role in their evolution.

However, only in recent years were the first images of black holes acquired by the Event Horizon Telescope (EHT). These and other observations have revealed things about black holes that have challenged preconceived notions. In a recent study led by a team from MIT, astronomers observed oscillations that suggested an SMBH in a neighboring galaxy was consuming a white dwarf. But instead of pulling it apart, as astronomical models predict, their observations suggest the white dwarf was slowing down as it descended into the black hole – something astronomers have never seen before!

The study was led by Megan Masterson, a PhD student from the MIT Kavli Institute for Astrophysics and Space Research. She was joined by researchers from the Nucleo de Astronomia de la Facultad de Ingenieria, the Kavli Institute for Astronomy and Astrophysics (KIAA-PU), the Center for Space Science and Technology (CSST), and the Joint Space-Science Institute at the University of Maryland Baltimore County (UMBC), the Centro de Astrobiologia (CAB), the Cahill Center for Astronomy and Astrophysics, the Harvard & Smithsonian Center for Astrophysics (CfA), NASA’s Goddard Space Flight Center, and multiple universities.

From what astronomers have learned about black holes, these gravitational behemoths are surrounded by infalling matter (gas, dust, and even light) that form swirling, bright disks. This material and energy is accelerated to near the speed of light, causing it to release heat and radiation (mostly in the ultraviolet) as it slowly accretes onto the black hole’s “face.” These UV rays interact with a cloud of electrically charged plasma (the corona) surrounding the black hole, which boosts the rays’ into the X-ray wavelength.

Since 2011, NASA’s XMM-Newton has been observing 1ES 1927+654, a galaxy located 236 million light-years away in the constellation Draco with a black hole of 1.4 million Solar masses Suns at its center. In 2018, the X-ray corona mysteriously disappeared, followed by a radio outburst and a rise in its X-ray output—what is known as Quasi-periodic oscillations (QPO). UMBC associate professor Eileen Meyer, a co-author of this latest study, also recently released a paper describing these radio outbursts.

“In 2018, the black hole began changing its properties right before our eyes, with a major optical, ultraviolet, and X-ray outburst,” she said in a NASA press release. “Many teams have been keeping a close eye on it ever since.” Meyer presented her team’s findings at the 245th meeting of the American Astronomical Society (AAS), which took place from January 12th to 16th, 2025, in National Harbor, Maryland. By 2021, the corona reappeared, and the black hole seemed to return to its normal state for about a year.

However, from February to May 2024, radio data revealed what appeared to be jets of ionized gas extending for about half a light-year from either side of the SMBH. “The launch of a black hole jet has never been observed before in real time,” Meyer noted. “We think the outflow began earlier, when the X-rays increased prior to the radio flare, and the jet was screened from our view by hot gas until it broke out early last year.” A related paper about the jet co-authored by Meyer and Masterson was also presented at the 245th AAS.

Artist’s impression of the ESA’s XMM-Newton mission in space. Credit: ESA-C. Carreau

In addition, observations gathered in April 2023 showed a months-long increase in low-energy X-rays, which indicated a strong and unexpected radio flare was underway. Intense observations were mounted in response by the Very Long Baseline Array (VLBA) and other facilities, including XMM-Newton. Thanks to the XMM-Newton observations, Masterson found that the black hole exhibited extremely rapid X-ray variations of 10% between July 2022 and March 2024. These oscillations are typically very hard to detect around SMBHs, suggesting that a massive object was rapidly orbiting the SMBH and slowly being consumed.

“One way to produce these oscillations is with an object orbiting within the black hole’s accretion disk. In this scenario, each rise and fall of the X-rays represents one orbital cycle,” Masterson said. Additional calculations also showed that the object is probably a white dwarf of about 0.1 solar masses orbiting at a velocity of about 333 million km/h (207 million mph). Ordinarily, astronomers would expect the orbital period to shorten, producing gravitational waves (GWs) that drain the object’s orbital energy and bring it closer to the black hole’s outer boundary (the event horizon).

However, the same observations conducted between 2022 and 2024 showed the fluctuation period dropped from 18 minutes to 7, and the velocity increased to half the speed of light (540 million km/h; 360 million mph). Then, something truly odd and unexpected followed: the oscillations stabilized. As Masterson explained:

“We were shocked by this at first. But we realized that as the object moved closer to the black hole, its strong gravitational pull could begin to strip matter from the companion. This mass loss could offset the energy removed by gravitational waves, halting the companion’s inward motion.”

Artist’s impression of two neutron stars at the point at which they merge and explode as a kilonova. Credit: University of Warwick/Mark Garlick

This theory is consistent with what astronomers have observed with white dwarf binaries spiraling toward each other and destined to merge. As they got closer to each other, instead of remaining intact, one would begin to pull matter off the other, which slowed down the approach of the two objects. While this could be the case here, there is no established theory for explaining what Masterson, Meyer, and their colleagues observed. However, their model makes a key prediction that could be tested when the ESA’s Laser Interferometer Space Antenna (LISA) launches in the 2030s.

“We predict that if there is a white dwarf in orbit around this supermassive black hole, LISA should see it,” says Megan. The preprint of Masterson and her team’s paper recently appeared online and will be published in Nature on February 15th, 2025.

Further Reading: ESA, NASA, arXiv, AJL

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An Even Ghostlier Neutrino May Rule the Universe

Strange “right-handed” neutrinos may be responsible for all the matter in the universe, according to new research.

Why is the universe filled with something other than nothing? Almost all fundamental interactions in physics are exactly symmetrical, meaning that they produce just as much matter as they do antimatter. But the universe is filled with only matter, with antimatter only appearing in the occasional high-energy process.

Obviously something happened to tip the balance, but what?

New research suggests that the answer may lie in the ghostly little particles known as neutrinos.

Neutrinos are beyond strange. There are three varieties, and they each have almost no mass. Additionally, they are also all “left-handed”, which means that their internal spins orient in only one direction as they travel. This is unlike all the other particles, which can orient in both directions.

Physicists suspect that there may be other kinds of neutrinos out there, ones that as yet remain undetected. These “right-handed” neutrinos would be much more massive than the more familiar left-handed ones.

Back in the early universe, these two kinds of neutrinos would have mixed together more freely. But as the cosmos expanded and cooled, this even symmetry broke, rendering the heavy right-handed neutrinos invisible. In the process, the symmetry breaking would separate matter from antimatter.

This could be the exact mechanism needed to explain that primordial mystery of the universe. But the right-handed neutrinos have one more trick up their sleeves.

The researchers behind the paper propose that the right-handed neutrinos didn’t completely disappear from the cosmic scene. Instead, they mixed together to form yet another new entity: the Majoran, a hypothetical kind of particle that is its own anti-particle. The Majoran would still inhabit the cosmos, surviving as a relic of those ancient times.

A massive, invisible particle just hanging around the cosmos? That would be an ideal candidate for dark matter, the mysterious substance that makes up the mass of almost every galaxy.

This means that the interactions between different kinds of neutrinos could explain why all observed neutrinos are left-handed, why there is more matter than antimatter, and why the universe is filled with dark matter.

This is all hypothetical, but definitely worth pursuing. And if we ever discover evidence for right-handed neutrinos, we just might be on the right track to solving a number of cosmological mysteries.

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