New Even Horizon Telescope Results Trace M87 Jet Back to Its Black Hole

A Hubble Space Telescope image of the giant elliptical galaxy M87 with its blowtorch-like jet. The visible part of this giant stream of particles spans around 3000 light-years. © NASA, ESA, A. Lessing (Stanford University), E. Baltz (Stanford University), M. Shara (AMNH), J. DePasquale (STScI)

At 230 GHz (bottom), data from the EHT reveal the fine structure of the ring surrounding the supermassive black. © Bottom: Saurabh et al.: “Probing jet base emission of M87* with the 2021 Event Horizon Telescope observations”, Astronomy & Astrophysics 705 (2026), Figure 6. Upper Right: Lu, R.-S. et al.: “A ring-like accretion structure in M87 connecting its black hole and jet”. Nature 616 (2023), Figure 1

Selected sites from the 2021 EHT observing campaign, highlighting additional stations: the 12−m Kitt Peak (KP) Telescope, USA and the NOrthern Extended Millimeter Array (NOEMA), France. This introduces two critical intermediate-length baselines to the Submillimeter Telescope (SMT), USA and IRAM 30−m, Spain, providing sensitivity to emission structures close to the base of the jet. © Saurabh/MPIfR

---

To the point:

• Recently published data from the Event Horizon Telescope (EHT) of the galaxy Messier 87 facilitate new insights into the direct environment of the central supermassive black hole.

• Measured differences in the radio light on different spatial scales can be explained by the presence of an as of yet undetected jet at frequencies of 230 Gigahertz at spatial scales comparable to the size of the black hole.

• The most likely location of the jet base is determined through detailed modeling.

---

Observations with the Event Horizon Telescope enable researchers to localize the likely base of the central outflow in a massive galaxy

Some galaxies eject powerful streams of charged particles—jets—from their centers into space. The prominent jet of Messier 87 (M87) in the constellation Virgo is visible over distances of 3000 light-years and can be observed over the full electromagnetic spectrum. It is powered by the central engine, the supermassive black hole at the heart of the galaxy with a mass of around six billion times that of our Sun. The exact location around the black hole where the jets originate is still unknown. Using observations from the Event Horizon Telescope (EHT) from 2021, an international research team led by Saurabh (Max Planck Institute for Radio Astronomy, MPIfR), Hendrik Müller (National Radio Astronomy Observatory, NRAO) and Sebastiano von Fellenberg (formerly at MPIfR, currently at the Canadian Institute for Theoretical Astrophysics, CITA) has found first hints of the jet base in M87. The results are published in the current issue of the journal Astronomy & Astrophysics.

Observing different scales

M87*, the supermassive black hole at the center of the galaxy M87, is about 55 million light years (5 × 10²⁰ kilometers) away from Earth. In 2019, the first images of its shadow and the glowing ring of hot gas around it went around the world. In order to resolve these structures, radio telescopes around the world must be combined into a single virtual telescope such as the EHT. This technique is called Very Long Baseline Interferometry (VLBI). The images produced in this way are sensitive to emission on different scales, depending on the distances between telescopes (baselines): With long baselines of several thousand kilometers, the smallest structures—such as the luminous ring—around M87* can be depicted. Short baselines of a few hundred meters, on the other hand, reveal emission emanating from much larger spatial scales in M87 (the extended jet), but are blind to details near the black hole. Intermediate baselines of a few hundred to a few thousand kilometers are the important link. They can be used to establish a connection between the material around the black hole and the jet. Precisely these intermediate baselines enabled the research team to determine the probable position of the jet base. "This study represents an early step toward connecting theoretical ideas about jet launching with direct observations. Identifying where the jet may originate and how it connects to the black hole’s shadow, adds a key piece to the puzzle and points toward a better understanding of how the central engine operates", explains Saurabh.

The decisive difference

The researchers find hints to the base of the jet by comparing the measured radio intensity on different spatial scales: On short to intermediate baselines, the measured intensity is higher compared to that on long baselines. This indicates that what is observed with long baselines—the luminous ring of hot gas around the black hole—is not solely responsible for the detected radio emission. Instead, the current data show that part of the missing emission is captured on intermediate baselines. One possibility is the jet, which has not yet been observed at a radio frequency of 230 gigahertz (GHz) with the EHT.

EHT observations from 2017 and 2018 lacked the intermediate baselines to detect it. However, with the recently published data, Saurabh's team was able to show with numerous model calculations that part of the missing emission can be best explained by an additional compact region. From our perspective, this region is about 0.09 light-years away from M87* and associated with the base of the jet. The position of the region appears to coincide with the southern arm of a radio jet discovered at a different frequency (86 GHz) in 2018. "We have observed the inner part of the jet of M87 with global VLBI experiments for many years, with ever increasing resolution, and finally managed to resolve the black hole shadow in 2019. It is amazing to see that we are gradually moving towards combining these breakthrough observations across multiple frequencies and complete the picture of the jet launching region", says Hendrik Müller.

What’s next?

The current study shows that these interesting structures around M87* become visible at radio frequencies of 230 GHz with intermediate baselines. However, further observations with the EHT will be necessary to further constrain the morphology of the jet. These observations will then make it possible to not only deduce structures such as the jet base, but to image them. This opens up new possibilities for probing the direct environment of supermassive black holes and for testing theories of black hole physics. "Newly observed data—now being correlated and calibrated with support from MPIfR—will soon add back the Large Millimetre Telescope in Mexico. This will bring an even sharper view of the jet‑launching region within reach", says Sebastiano von Fellenberg.

Source: Max Planck for Radio Astronomy/Press Releases

---

Additional Information

The following scientists affiliated to the MPIfR are coauthors of this publication: Saurabh, Sebastiano D. von Fellenberg, Michael Janssen, Thomas P. Krichbaum, Dhanya G. Nair, Walter Alef, Rebecca Azulay, Uwe Bach, Anne-Kathrin Baczko, Silke Britzen, Gregory Desvignes, Sergio A. Dzib, Ralph P. Eatough, Christian M. Fromm, Ramesh Karuppusamy, Joana A. Kramer, Michael Kramer, Jun Liu, Andrei P. Lobanov, Ru-Sen Lu, Nicholas R. MacDonald, Nicola Marchili, Karl M. Menten, Cornelia Müller, Georgios Filippos Paraschos, Alexander Plavin, Eduardo Ros, Helge Rottmann, Alan L. Roy, Tuomas Savolainen, Lijing Shao, Pablo Torne, Efthalia Traianou, Jan Wagner, Robert Wharton, Gunther Witzel, Jompoj Wongphexhauxsorn, J. Anton Zensus, and Guang-Yao Zhao.

---

Contacts:

Mr. Saurabh
Tel: +49 228 525-366
saurabh@mpifr-bonn.mpg.de
Max Planck Institute for Radio Astronomy, Bonn

Dr. Hendrick Müller
Tel: +1 626 781-0043
hmuller@nrao.edu
National Radio Astronomy Observatory (NRAO), USA

Dr. Sebastiano von Fellenberg
Tel: +1 437 328-5547
sfellenberg@utoronto.ca
Canadian Institute for Theoretical Astrophysics (CITA), University of Toronto, Canada

Dr. Nina Brinkmann
Press and Public Relations
Tel: +49 228 525-399
brinkmann@mpifr-bonn.mpg.de
Max Planck Institute for Radio Astronomy, Bonn

---

Original publication

Saurabh et al.
Probing jet base emission of M87* with the 2021 Event Horizon Telescope observations
Astronomy & Astrophysics 705 (2026)
[doi.org/10.1051/0004-6361/202557022]

---

Parallel Press Release

CITA Press Release
From the Canadian Institute for Theoretical Astrophysics

Saurabh/MPIfR

Animation (open in full screen)

---

Images

• eht_closure_phase_triangles 1.56 MB


• m87_possible_jet_base 1.13 MB


• m87_possible_jet_base_blank 1.11 MB

---

Event Horizon Telescope images reveal new dark matter detection method

Simulated images of the supermassive black hole M87*. Left panel shows radiation from astrophysical plasma and right panel illustrates potential emission from dark matter annihilation. Credit: Yifan Chen.

---

According to a new Physical Review Letters study, black holes could help solve the dark matter mystery. The shadowy regions in black hole images captured by the Event Horizon Telescope can act as ultra-sensitive detectors for the invisible material that makes up most of the universe's matter.

Dark matter makes up roughly 85% of the universe's matter, but scientists still don't know what it actually is. While researchers have proposed countless ways to detect it, this study introduces black hole imaging as a fresh detection method—one that comes with some distinct benefits.

The Event Horizon Telescope's stunning images of supermassive black holes have revealed more than just the geometry of spacetime; they've opened an unexpected window into the search for dark matter.

Phys.org spoke to co-authors Jing Shu from Peking University and Yifan Chen from the Niels Bohr Institute. "I have always been fascinated by instruments like the Event Horizon Telescope (EHT), which allow us to probe the extreme environments around supermassive black holes and challenge the boundaries of known physical laws," Shu said.

Chen added, "I've been fascinated by the idea of using black holes as detectors for new particles. Their extreme gravity makes them natural concentrators of matter, creating a unique meeting point for particle physics, gravity, and astrophysical observation."

The research team focused on a striking feature of black hole images: the shadow region that appears dark in EHT observations of M87* and Sagittarius A*.

A cosmic darkroom

The Event Horizon Telescope is a global network of radio observatories working in concert to achieve Earth-sized resolution through Very Long Baseline Interferometry. Working at a frequency of 230 GHz, the telescope captures synchrotron radiation—light produced when electrons spiral along the intense magnetic field lines near supermassive black holes.

To understand what they're seeing, astrophysicists run complex computer simulations.

The magnetically arrested disk (MAD) model has consistently delivered the best agreement with EHT observations. The MAD model depicts strong magnetic fields penetrating the accretion disk, where they both regulate the flow of infalling matter and power jets that erupt perpendicular to the disk.

Crucially, the MAD model explains why black hole shadows appear dark: most electrons reside in the accretion disk, while the jet regions above and below are relatively particle-poor, creating a sharp contrast in the images.

"Ordinary astrophysical plasma is often expelled by powerful jets, leaving the shadow region especially faint," Chen explained. "Dark matter, however, could continuously inject new particles that radiate in this region."

Because dark matter is expected to concentrate densely near the black hole's center, even faint annihilation signals could stand out against this low astrophysical background, making the shadow an ideal testing ground.

Modeling dark matter

The gravitational pull of supermassive black holes causes dark matter to concentrate dramatically in their vicinity, forming what physicists call a "dark matter spike." These regions achieve densities orders of magnitude higher than anywhere else in the galaxy.

Since dark matter annihilation rates depend on density squared, these enhanced densities could produce detectable signals—if the annihilation occurs at all.

The research team developed a sophisticated framework that builds directly on the MAD model by adding dark matter physics to the astrophysical baseline.

The team applied general relativistic magnetohydrodynamic (GRMHD) simulations along with detailed particle propagation modeling. With this framework, they could model how electrons and positrons from hypothetical dark matter annihilation would behave in the magnetic field structures extracted from the MAD model.

Unlike previous studies that relied on simplified spherical models, this approach uses the realistic, asymmetric magnetic field configurations extracted from the MAD simulations—the same fields that shape the astrophysical emission we observe.

"What we see in black hole images is not the black hole itself, but light emitted by ordinary electrons in the surrounding accretion disk, whose behavior we can model using well-known physics," Shu said.

"If dark matter particles were annihilating near the black hole, they would produce extra electrons and positrons whose radiation looks slightly different from the normal emission."

The critical distinction emerges in spatial distribution. In the MAD model, electrons concentrate in the accretion disk with sparse populations in the jet regions—creating the dark shadow.

But electrons and positrons from dark matter annihilation would be distributed more uniformly throughout both disk and jet regions, because dark matter annihilation continuously supplies particles even where astrophysical processes produce few electrons.

The team examined two annihilation channels—bottom quark-antiquark pairs and electron-positron pairs—across dark matter masses ranging from sub-GeV to approximately 10 TeV.

For each scenario, they calculated the resulting synchrotron radiation and generated synthetic black hole images that combined both astrophysical emission (from MAD) and potential dark matter signals.

Morphology as a probe

The researchers' approach to exploiting the morphology of the black hole images rather than just the total brightness makes the work stand out.

They required that dark matter annihilation signals remain below astrophysical emission at every point in the image, particularly within the inner shadow region.

"By comparing these predictions with real EHT images at the 'darkroom,' we can search for subtle signals that may reveal dark matter," Shu said.

This morphological approach proves significantly more powerful than previous constraints based on total intensity alone. The analysis excludes substantial regions of previously unexplored parameter space, setting limits on annihilation cross sections down to approximately 10-27 cm³/s for current EHT observations.

"Our exclusions based on current EHT observations already probe large regions of previously unexplored parameter space, surpassing other searches that assume similar density profiles," Chen said.

The constraints remain robust against astrophysical uncertainties, including variations in black hole spin and plasma temperature parameters—factors that typically introduce significant uncertainties in indirect dark matter searches.

Future prospects The true power of this approach will be realized with anticipated EHT upgrades. Future improvements promise to increase dynamic range by nearly 100 times and achieve angular resolution equivalent to approximately one gravitational radius, enabling them to probe deeper into the darkest regions of the shadow.

"The key upgrade is improving the telescope's dynamic range, which is its ability to reveal very faint details right next to extremely bright features," Chen explained.

"A common example is the 'high dynamic range' (HDR) mode on many smartphones, which uses advanced processing to bring out details in both dark shadows and bright highlights in the same image."

These enhancements could enable detection of dark matter with annihilation cross sections near the thermal relic value, a theoretically well-motivated target, for masses up to approximately 10 TeV.

Looking ahead, the researchers envision several directions for expanding this research.

"The black hole shadow is not just a static image; it is a dynamic, multi-layered laboratory," Shu said. "Beyond the intensity maps, polarization data from the EHT also open new windows, because polarization encodes how magnetic fields and plasma shape the radiation."

Multi-frequency observations will also prove crucial, according to Shu. Different radiation mechanisms scale differently with frequency, allowing researchers to determine the source of radiation—essentially using multiple colors to distinguish dark matter signals from astrophysical backgrounds.

by Tejasri Gururaj, Phys.org

Source: Phys.org/Space News/Astronomy

---

More information: Yifan Chen et al, Illuminating Black Hole Shadows with Dark Matter Annihilation, Physical Review Letters (2025). DOI: 10.1103/yxqg-363n.

Journal information: Physical Review Letters

---

Written for you by our author Tejasri Gururaj, edited by Gaby Clark, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journali.sm alive. If this reporting matters to you, please consider a donation (especially monthly). You'll get an ad-free account as a thank-you.

---

Re-analysis of Data from Milky Way Central Supermassive Black Hole Observations

Radio image of Sagittarius A* in the center of the Milky Way Galaxy, obtained from this re-analysis. The structure is elongated from east to west. The east side is bright and the west side is dark, which the research team interprets to mean that the east side is moving towards us. Credit: Miyoshi et al.

A research team led by Assistant Professor Makoto Miyoshi of the National Astronomical Observatory of Japan (NAOJ) has independently re-analyzed observation data of the supermassive black hole at the center of the Milky Way Galaxy obtained and published by the international joint observation project Event Horizon Telescope (EHT). They found that the structure is slightly elongated in the east-west direction. This research takes a new look at the publicly available EHT data and demonstrates the scientific process in which the certainty of the answer increases as different researchers continue to examine and discuss a theory.

The Milky Way Galaxy, in which we live, contains more than 100 billion sun-like stars. There are countless such large galaxies in the Universe, most of which are thought to have supermassive black holes at their centers with masses millions to billions of times that of the Sun. The Milky Way Galaxy also has a supermassive black hole at its center, called Sagittarius A* (A star). The black hole swallows everything, including light, making it impossible to see the supermassive black hole itself, but analysis of stars circling the black hole at high speed indicates that Sagittarius A* has a mass approximately 4 million times that of the Sun. By closely observing its surroundings, we can obtain clues to the nature of the invisible black hole.

The EHT observed Sagittarius A* in 2017 with a network of eight ground-based radio telescopes using a technique known as radio interferometry to combine the results from the various telescopes. The results of these observations were published in 2022, including an image of a bright ring structure surrounding a central dark region, indicating the presence of a black hole.

In contrast to typical photography, data from observations linking several widely-separated radio telescopes contain many gaps in the completeness, so special algorithms are used to construct an image from the data. In this research, the team applied widely-used traditional methods to EHT data, as opposed to the EHT’s own original analysis method. Miyoshi explains, “Our image is slightly elongated in the east-west direction, and the eastern half is brighter than the western half. We think this appearance means the accretion disk surrounding the black hole is rotating.”

The EHT’s observational data and analysis methods are freely available, and many researchers have validated the results of EHT analysis. This research is also part of these regular verification activities. Radio interferometry connecting telescopes across the globe is a developing technology, and research on data analysis and image processing is ongoing, incorporating knowledge from statistics and other related disciplines. The structures presented in this research differ from the results of the EHT team, but both are plausible structures derived from the data using the respective methods. The EHT plays an important role in black hole research by soliciting independent verification and providing open data for verification. It is hoped that a more reliable picture of Sagittarius A* will emerge from active discussion by researchers based on improved analysis methods and data from follow-up observations carried out since 2018.

Source: National Astronomical Observatory of Japan (NAOJ)/News/Science

---

Detailed Article(s)

The Supermassive Black Hole at the Galactic Center — EHT Observational Data re-analysed and High-velocity rotating Accretion Disk found?

JASMINE Project

---

Release Information

Researcher(s) Involved in this Release
Makoto Miyoshi (National Astronomical Observatory of Japan)
Yoshiaki Kato (Japan Meteorological Agency)
Junichiro Makino (Kobe University)

Coordinated Release Organization(s)
National Astronomical Observatory of Japan
Royal Astronomical Society

Paper(s)

Makoto Miyoshi et al. “An Independent Hybrid Imaging of Sgr A* from the Data in EHT 2017 Observations”, in Monthly Notices of the Royal Astronomical Society, DOI: 10.1093/mnras/stae1158

---

Related Link(s)

• Astronomers reveal first image of the black hole at the heart of our galaxy (May 12, 2022)

---

Cosmic Simulation Reveals How Black Holes Grow and Evolve

This still from the simulation shows a supermassive black hole, or quasar, surrounded by a swirling disk of material called an accretion disk. Credit: Caltech/Phil Hopkins group

An earlier still from the simulation shows a tangle of merging galaxies.
Credit: Caltech/Phil Hopkins group

Hopkins Group: Simulation Zooms Into Black Hole

The new simulation flies into a tangle of merging galaxies, ultimately zooming into an active supermassive black hole, or quasar, surrounded by a swirling disk of material called an accretion disk. A filamentary stream of gas has been wound up into the disk, funneling gas in at a rate sufficient to fuel the brightest known quasars in the universe. Near the end of the simulation, magnetic fields rip away the angular momentum from the rotating disk, which allows material to spiral in further and further until it reaches the event horizon of the black hole, where it can't escape. During this simulation, which represents one moment in time, the scale zooms in by a factor of a billion. The colors show the density of the gas, with brighter colors representing higher densities. Credit: Caltech/Phil Hopkins group

---

A team of astrophysicists led by Caltech has managed for the first time to simulate the journey of primordial gas dating from the early universe to the stage at which it becomes swept up in a disk of material fueling a single supermassive black hole. The new computer simulation upends ideas about such disks that astronomers have held since the 1970s and paves the way for new discoveries about how black holes and galaxies grow and evolve.

"Our new simulation marks the culmination of several years of work from two large collaborations started here at Caltech," says Phil Hopkins, the Ira S. Bowen Professor of Theoretical Astrophysics.

The first collaboration, nicknamed FIRE (Feedback in Realistic Environments), has focused on the larger scales in the universe, studying questions such as how galaxies form and what happens when galaxies collide. The other, dubbed STARFORGE, was designed to examine much smaller scales, including how stars form in individual clouds of gas. "But there was this big gap between the two," Hopkins explains. "Now, for the first time, we have bridged that gap." To do that, the researchers had to build a simulation with a resolution that is more than 1,000 times greater than the previous best in the field.

To the team's surprise, as reported in The Open Journal of Astrophysics, the simulation revealed that magnetic fields play a much larger role than previously believed in forming and shaping the huge disks of material that swirl around and feed the supermassive black holes. "Our theories told us the disks should be flat like crepes," Hopkins says. "But we knew this wasn't right because astronomical observations reveal that the disks are actually fluffy—more like an angel cake. Our simulation helped us understand that magnetic fields are propping up the disk material, making it fluffier."

---

Cosmic Simulation Reveals How Black Holes Grow and Evolve

Visualizing the Activity Around Supermassive Black Holes Using "Super Zoom-Ins"

In the new simulation, the researchers performed what they call a "super zoom-in" on a single supermassive black hole, a monstrous object that lies at the heart of many galaxies, including our own Milky Way. These ravenous, mysterious bodies contain anywhere from thousands to billions of times the mass of the Sun, and thus exert a huge effect on anything that comes near.

Astronomers have known for decades that as gas and dust are pulled in by the tremendous gravity of these black holes, they are not immediately sucked in. Instead, the material first forms a rapidly swirling disk called an accretion disk. And as the material is just about to fall in, it radiates a huge amount of energy, shining with a brilliance unmatched by just about anything in the universe. But much is still not known about these active supermassive black holes, called quasars, and how the disks that feed them form and behave.

While disks around supermassive black holes have been imaged previously—the Event Horizon Telescope imaged disks circling black holes at the heart of our own galaxy in 2022 and Messier 87 in 2019—these disks are much closer and more tame than the ones that churn around quasars. To visualize what happens around these more active and distant black holes, astrophysicists turn to supercomputer simulations. They feed information about the physics at work in these galactic settings—everything from the basic equations that govern gravity to how to treat dark matter and stars—into thousands of computing processors that work in parallel. This input includes many algorithms, or series of instructions, for the computers to follow to recreate complicated phenomena. So, for example, the computers know that once gas becomes dense enough, a star forms. But the process is not that straightforward.

"If you just say gravity pulls everything down and then eventually the gas forms a star and stars just build up, you'll get everything wildly wrong," Hopkins explains. After all, stars do many things that affect their surroundings. They shine radiation that can heat up or push surrounding gas. They blow winds like the solar wind created by our own Sun, which can sweep up material. They explode as supernovae, sometimes launching material clear out of galaxies or changing the chemistry of their surroundings. So, the computers must know all the ins and outs of this "stellar feedback" as well, as it regulates how many stars a galaxy can actually form.

Building a Simulation that Spans Multiple Scales

But at these larger scales, the set of physics that are most important to include and what approximations can be made differ from those at smaller scales. For example, on the galactic scale, the complicated details of how atoms and molecules behave are extremely important and must be built into any simulation. However, scientists agree that when simulations focus on the more immediate area around a black hole, molecular chemistry can be mostly ignored because the gas there is too hot for atoms and molecules to exist. Instead, what is exists there is hot ionized plasma.

Creating a simulation that could cover all the relevant scales down to the level of a single accretion disk around a supermassive black hole was a huge computational challenge—one that also required a code that could handle all the physics. "There were some codes that had the physics that you needed to do the small-scale part of the problem and some codes that had the physics that you needed to do the larger, cosmological part of the problem, but nothing that had both," Hopkins says.

The Caltech-led team used a code they call GIZMO for both the large- and small-scale simulation projects. Importantly, they built the FIRE project so that all the physics they added to it could work with the STARFORGE project, and vice versa. "We built it in a very modular way, so that you could flip on and off any of the pieces of physics that you wanted for a given problem, but they were all cross compatible," Hopkins says.

This allowed the scientists in the latest work to simulate a black hole that is about 10 million times the mass of our Sun, beginning in the early universe. The simulation then zooms in on that black hole at a moment when a giant stream of material is torn off a cloud of star-forming gas and begins to swirl around the supermassive black hole. The simulation can continue zooming in, resolving a finer area at each step as it follows the gas on its way toward the hole.

Surprisingly Fluffy, Magnetic Disks

"In our simulation, we see this accretion disk form around the black hole," Hopkins says. "We would have been very excited if we had just seen that accretion disk, but what was very surprising was that the simulated disk doesn't look like what we've thought for decades it should look like." In two seminal papers from the 1970s that described the accretion disks fueling supermassive black holes, scientists assumed that thermal pressure—the change in pressure caused by the changing temperature of the gas in the disks—played the dominant role in preventing such disks from collapsing under the tremendous gravity they experience close to the black hole. They acknowledged that magnetic fields might play a minor role in helping to shore up the disks. In contrast, the new simulation found that the pressure from the magnetic fields of such disks was actually 10,000 times greater than the pressure from the heat of the gas.

"So, the disks are almost completely controlled by the magnetic fields," Hopkins says. "The magnetic fields serve many functions, one of which is to prop up the disks and make the material puffy."

This realization changes a host of predictions scientists can make about such accretion disks, such as their mass, how dense and thick they should be, how fast material should be able to move from them into a black hole, and even their geometry (such as whether the disks can be lopsided).

Looking forward, Hopkins hopes this new ability to bridge the gap in scales for cosmological simulations will open many new avenues of research. For example, what happens in detail when two galaxies merge? What types of stars form in the dense regions of galaxies where conditions are unlike those in our Sun's neighborhood? What might the first generation of stars in the universe have looked like? "There's just so much to do," he says.

The new simulation is detailed in a paper entitled "FORGE'd in FIRE: Resolving the End of Star Formation and Structure of AGN Accretion Disks from Cosmological Initial Conditions," which appears in The Open Journal of Astrophysics. Additional authors on the paper include Michael Grudic (PhD '19) of Carnegie Observatories, Kung-Yi Su (PhD '19) of Harvard University, Sarah Wellons of Wesleyan University, Daniel Angles-Alcazar of the University of Connecticut and the Flatiron Institute, Ulrich Steinwandel of the Flatiron Institute, David Guszeinov (PhD '18) of the University of Texas at Austin, Norman Murray (BS '79) of the University of Toronto, Claude-Andre Faucher-Giguere of Northwestern University, Eliot Quatert of Princeton University, and Dusan Keres of UC San Diego. Hopkins's work was supported by funding from the National Science Foundation and NASA.

Written by Kimm Fesenmaier

Source: Caltech/News

---

Contact:

Whitney Clavin
(626) 395‑1944
wclavin@caltech.edu

---

A Supermassive Black Hole’s Strong Magnetic Fields are Revealed in a New Light

A computer simulation of a disk of plasma around the supermassive black hole at the center of the M87 galaxy. A new analysis of the circularly polarized, or spiraling light, in EHT observations shows that magnetic fields near the black hole are strong. These magnetic fields push back on infalling matter and help launch jets of matter at velocities near the speed of light out. Credit: George Wong. Hi-Res File

The Event Horizon Telescope (EHT) collaboration has published new results that describe for the first time how light from the edge of the supermassive black hole M87* spirals as it escapes the black hole’s intense gravity, a signature known as circular polarization. The way light’s electric field prefers to rotate clockwise or counterclockwise as it travels carries information about the magnetic field and types of high-energy particles around the black hole. The new paper, published today in Astrophysical Journal Letters, supports earlier findings from the EHT that the magnetic field near the M87* black hole is strong enough to occasionally stop the black hole from swallowing up nearby matter.

The Atacama Large Millimeter/submillimeter Array (ALMA) is the world’s most powerful millimeter/ submillimeter telescope, and a key instrument for the EHT. The spiraling light at the heart of this research is actually made up of low frequency radio waves—light that can’t be seen by the human eye or optical telescopes, but can be observed by the many radio telescopes, including ALMA, working together across the EHT.

“Circular polarization is the final signal we looked for in the EHT’s first observations of the M87 black hole, and it was by far the hardest to analyze,” says  Andrew Chael, an associate research scholar at the Gravity Initiative at Princeton University, who coordinated the project.  “These new results give us confidence that our picture of a strong magnetic field permeating the hot gas surrounding the black hole is the right one. The unprecedented EHT observations are allowing us to answer long-standing questions about how black holes consume matter and launch jets outside their host galaxies.”

In 2019, the EHT released its first image of a ring of hot plasma close to the event horizon of M87*.  In 2021, EHT scientists released an image showing the directions of the oscillating electric fields across the image. Known as linear polarization, this result was the first sign that the magnetic fields close to the black hole were ordered and strong. The new measurements of the circular polarization – which indicate how light’s electric fields spiral around the linear direction from the 2021 analysis – provide yet more conclusive evidence for these strong magnetic fields.

ALMA provided both data and calibration for these results, and served as the array reference antenna for the EHT. Without the much greater sensitivity of ALMA as the reference antenna, circular polarization could not have been detected.

Source: National Radio Astronomy Observatory (NRAO)/News

---

About ALMA & NRAO

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Organisation for Astronomical Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the Ministry of Science and Technology (MOST) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

The National Radio Astronomy Observatory (NRAO) is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

 

Scientific Paper

---

A Sharper Look at the First Image of a Black Hole

PR Image noirlab2310a
Comparison of EHT and EHT Reconstructed with PRIMO

---

Videos

PR Video noirlab2310a

Cosmoview Episode 66: A Sharper Look at the First Image of a Black Hole 

 

PR Video noirlab2310b

Transition Between Original and PRIMO Images 

 

PR Video noirlab2310c

Cosmoview Episodio 66: Científicos logran mejorar la nitidez de la primera imagen de un agujero negro

---

Machine learning reconstructs new image of Messier 87 from Event Horizon Telescope data

A team of researchers, including an astronomer with NSF’s NOIRLab, has developed a new machine-learning technique to enhance the fidelity and sharpness of radio interferometry images. To demonstrate the power of their new approach, which is called PRIMO, the team created a new, high-fidelity version of the iconic Event Horizon Telescope's image of the supermassive black hole at the center of Messier 87, a giant elliptical galaxy located 55 million light-years from Earth.

The iconic image of the supermassive black hole at the center of Messier 87 has received its first official makeover, thanks to a new machine-learning technique known as PRIMO. This new image better illustrates the full extent of the object’s dark central region and the surprisingly narrow outer ring. To achieve this result, a team of researchers used the original 2017 data obtained by the Event Horizon Telescope (EHT) collaboration and created a new image that, for the first time, represents the full resolution of the EHT. [1]

PRIMO, which stands for principal-component interferometric modeling, was developed by EHT members Lia Medeiros (Institute for Advanced Study), Dimitrios Psaltis (Georgia Tech), Tod Lauer (NSF’s NOIRLab), and Feryal Ozel (Georgia Tech). A paper describing their work is published in The Astrophysical Journal Letters. 

In 2017 the EHT collaboration used a network of seven radio telescopes at different locations around the world to form an Earth-sized virtual telescope with the power and resolution capable of observing the “shadow” of a black hole’s event horizon. [2] Though this technique allowed astronomers to see remarkably fine details, it lacked the collecting power of an actual Earth-sized telescope, leaving gaps in the data. The researchers’ new machine-learning technique helped fill in those gaps. 

“With our new machine-learning technique, PRIMO, we were able to achieve the maximum resolution of the current array,” says lead author Lia Medeiros. “Since we cannot study black holes up close, the detail in an image plays a critical role in our ability to understand its behavior. The width of the ring in the image is now smaller by about a factor of two, which will be a powerful constraint for our theoretical models and tests of gravity.” 

PRIMO relies on a branch of machine learning known as dictionary learning, which teaches computers certain rules by exposing them to thousands of examples. The power of this type of machine learning has been demonstrated in numerous ways, from creating Renaissance-style  works of art to completing the unfinished work of Beethoven. 

Applying PRIMO to the EHT image of Messier 87, computers analyzed over 30,000 high-fidelity simulated images of gas accreting onto a black hole to look for common patterns in the images. The results were then blended to provide a highly accurate representation of the EHT observations, simultaneously providing a high-fidelity estimate of the missing structure of the image. A paper pertaining to the algorithm itself was published previously in The Astrophysical Journal on 3 February 2023.

“PRIMO is a new approach to the difficult task of constructing images from EHT observations,” said Lauer. “It provides a way to compensate for the missing information about the object being observed, which is required to generate the image that would have been seen using a single gigantic radio telescope the size of the Earth.”

The team confirmed that the newly rendered image is consistent with the EHT data and with theoretical expectations, including the bright ring of emission expected to be produced by hot gas falling into the black hole. 

The new image should lead to more accurate determinations of the mass of the Messier 87 black hole and the physical parameters that determine its present appearance. The data also provide an opportunity for researchers to place greater constraints on alternatives to the event horizon (based on the darker central brightness depression) and perform more robust tests of gravity (based on the narrower ring size). PRIMO can also be applied to additional EHT observations, including those of Sagittarius A*, the central black hole in our own Milky Way Galaxy.

“The 2019 image was just the beginning,” said Medeiros. “If a picture is worth a thousand words, the data underlying that image have many more stories to tell. PRIMO will continue to be a critical tool in extracting such insights.”

---

More Information

[1] One of the telescopes comprising the EHT, the South Pole Telescope, was not part of the Messier 87 observation. Since that time, the EHT has added additional telescopes to the array. 

[2]  The shadow of a black hole is the closest we can come to an image of the black hole itself, a completely dark object from which light cannot escape. In the case of Messier 87, the black hole’s boundary — the event horizon from which the EHT takes its name — is around 2.5 times smaller than the shadow it casts and measures just under 40 billion kilometers across.

Development of the PRIMO algorithm was enabled through the support of a National Science Foundation Astronomy and Astrophysics Postdoctoral Fellowship.

NSF’s NOIRLab, the US center for ground-based optical-infrared astronomy, operates the International Gemini Observatory (a facility of NSF, NRC–Canada, ANID–Chile, MCTIC–Brazil, MINCyT–Argentina, and KASI–Republic of Korea), Kitt Peak National Observatory (KPNO), Cerro Tololo Inter-American Observatory (CTIO), the Community Science and Data Center (CSDC), and Vera C. Rubin Observatory (operated in cooperation with the Department of Energy’s SLAC National Accelerator Laboratory). It is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with NSF and is headquartered in Tucson, Arizona. The astronomical community is honored to have the opportunity to conduct astronomical research on Iolkam Du’ag (Kitt Peak) in Arizona, on Maunakea in Hawai‘i, and on Cerro Tololo and Cerro Pachón in Chile. We recognize and acknowledge the very significant cultural role and reverence that these sites have to the Tohono O’odham Nation, to the Native Hawaiian community, and to the local communities in Chile, respectively.

---

Links

• The Astrophysical Journal Letters paper “The Image of the M87 Black Hole Reconstructed with PRIMO.”
• Event Horizon Telescope collaboration
• Institute for Advanced Study press release

---

Contacts:

Tod Lauer
NSF’s NOIRLab
Email: tod.lauer@noirlab.edu

Charles Blue
NSF’s NOIRLab
Tel: +1 202 236 6324
Email: charles.blue@noirlab.edu

Source: NSF’s National Optical-Infrared Astronomy Research Laboratory (NOIRLab)

---

Independent Reanalysis of the M87 Galactic Center Radio Observational Data

Radio images obtained from the reanalysis, showing the center of the elliptical galaxy M87. The upper left panel shows a close-up around the black hole, depicting the “core” (the red, round spot in the lower center) and “knots” (elongated spots on the center right and lower right). The wide-field image shows the jet extending diagonally to the upper right. The red spot on the right edge is a not real structured but an artifact created by the imaging method. (For details, please refer to the original paper.) (Credit: Miyoshi et al.) Original size (227KB)

An independent reanalysis of the Event Horizon Telescope (EHT)’s observational data for the center of the elliptical galaxy M87 has produced images with different features, according to a new study. This study is part of the research process in modern science, in which observational data and analysis methods are open to the public and reviewed and discussed in various communities of researchers to produce more credible results.

The radio observational data for the center of the elliptical galaxy M87 that were obtained by the Event Horizon Telescope in April 2017 and the methods by which the data were analyzed have been accessible to the public worldwide. Researchers not involved in the EHT have been independently reanalyzing these data and methods, thereby validating the results presented by the EHT. In fact, various teams have published their detailed reanalysis results in research papers.

A research team consisting of Makoto Miyoshi (Assistant Professor at NAOJ), Yoshiaki Kato (Contract Researcher at RIKEN at the time of the study), and Junichiro Makino (Professor at Kobe University) reanalyzed the M87 data with standard tools and investigated the nature of the data. Instead of the ring structure observed by the EHT, the resultant images show a “core” at the galactic center, in addition to the astrophysical jet extending from the core and “knots” apparently forming part of the jet. Many supermassive black holes emit astrophysical jets; the one extending from the center of M87 has been known for more than 100 years, having been studied on many occasions. The research team believes that it is the base of this jet that their analysis has resolved. The team points out that the 40-micro-arcsecond (1/25,000th of an arcsecond) ring structure seen in the EHT image is likely a result of the lack of sufficient data to resolve 40 micro-arcsecond structures, as compared to the data for the structures of other sizes, because of the fewer number of telescopes involved in the EHT observations at that time.

This study demonstrates the importance of the sensible, normal process that modern science should follow, with independent research teams reviewing observational data and analysis methods. Further data reanalysis, method examination, and planned follow-up observations are expected to provide more credible insights into M87’s center and the structure of the jet blasting out from the galactic center.

The study appeared as Miyoshi M. et al. “The Jet and Resolved Features of the Central Supermassive Black Hole of M87 Observed with the Event Horizon Telescope (EHT)” in the Astrophysical Journal on June 30, 2022.

Related Links

• Astronomers Capture First Image of a Black Hole — Japanese researchers contribute to paradigm-shifting observations of the gargantuan black hole at the heart of distant galaxy Messier 87
• Imaging Reanalyses of EHT Data

Source: National Astronomical Observatory of Japan (NAOJ)/Science

---

Milky Way’s Black Hole Was “Birth Cry” of Radio Astronomy

A Very Large Array image of the Milky Way's central region. The bright spot marked by the circle is Sagittarius A*, where our galaxy's central black hole is located. Credit: NRAO/AUI/NSF. Hi-Res File

Karl Jansky, standing by the highly directional antenna he used to locate the sources of radio static, including that coming from the center of our Milky Way galaxy. Credit: NRAO/AUI/NSF. Hi-res image

The first image of the supermassive black hole at the center of our Milky Way galaxy brings radio astronomy back to its celestial birthplace. The Event Horizon Telescope (EHT), a worldwide collection of millimeter-wave radio telescopes, made the new, landmark image of the same region from which came the first cosmic radio waves ever detected. That detection, by Bell Telephone Laboratories engineer Karl Jansky in 1932, was the beginning of radio astronomy.

The new EHT image is the culmination of a long history of Milky Way research starting with Galileo Galilei, who used his telescope in 1610 to discover that our galaxy, which appears like clouds to the naked eye, actually is composed of stars. In 1785, British astronomer William Herschel produced a rudimentary map of the Milky Way.

In 1918, American astronomer Harlow Shapley located the Milky Way’s center by using the newly discovered distance-measuring tool provided by Cepheid variable stars to determine that a halo of globular star clusters that surrounds the Milky Way is centered on a region in the constellation Sagittarius. That region is obscured from visible-light telescopes by thick clouds of gas and dust.

Jansky was hired by Bell Laboratories in 1928 and given the task of determining the sources of noise that interfered with short-wave radio telephone communications. He designed a highly directional antenna and by 1932 had identified a number of noise sources. However, one mystery remained — “a very steady hiss type static the origin of which is not known.”

The time of day when this hiss appeared changed with the seasons. At the suggestion of an astronomer friend, Jansky consulted some astronomy textbooks and in December of 1932 concluded that the strange hiss is coming “from outside the solar system.” He announced this in a paper he presented at a Washington, D.C. meeting in April of 1933. His announcement was reported on the front page of the New York Times on May 5, 1933.

Ten days later, Jansky was interviewed on a nationwide radio network and said he had located the position in the sky of the noise he had found, and “that seems to confirm Dr. Shapley’s calculation that the radio waves seem to come from the center of gravity of our galaxy.”

That region later would be called Sagittarius A, as the brightest source of radio emission in that constellation. In 1951, Australian radio astronomers further narrowed down the emission’s origin as the galaxy’s center.

In 1974, Bruce Balick and Robert Brown used the National Radio Astronomy Observatory’s Green Bank Interferometer to discover a very bright and compact object to which Brown later attached the name Sagittarius A* (adding the asterisk). A black hole became the leading explanation for what powers the bright radio emission of the object, abbreviated Sgr A*. In 1994, infrared and submillimeter studies estimated the object’s mass at 3 million times that of the Sun.

In 2002, a team led by Reinhard Genzel of the Max Planck Institute for Extraterrestrial Physics reported on a 10-year study of the orbital motion of a star called S2 near Sgr A*. That study concluded that the central object is more than 4 million times more massive than the Sun.

In 2009, another team reported on further observations of stellar orbits in the region and concluded that the central object probably is a black hole because no other phenomenon is known that can pack that much mass into such a small space. This work and other studies of Sgr A* earned the 2020 Nobel Prize in Physics for Genzel and Andrea Ghez of UCLA for producing “the most convincing evidence yet of a supermassive black hole at the center of the Milky Way.”

The EHT Collaboration’s production of an image consistent with the theoretical predictions of what should be seen around a black hole makes the case even more convincing today.

 

About the author:

Dave Finley is Public Information Officer for NRAO in Socorro, New Mexico, where he handles media relations for the VLA and VLBA. He is a former editor and writer for The Miami Herald, and edited that paper's science & medicine section. He later did documentation, training, and business development for two supercomputer centers. Author of one book and editor of another, he has lectured on astronomy and other topics at universities, clubs, conventions, and on cruise ships. He is an amateur radio operator and a private pilot. He is a past president of The Albuquerque Astronomical Society, the Socorro Amateur Radio Association, the Socorro County Chamber of Commerce, and is a former squadron commander in the Civil Air Patrol. He is a veteran of the U.S. Marine Corps.

Source: National Radio Astronomy Observatory (NRAO)/News

---

NASA’s Webb Will Join Forces with the Event Horizon Telescope to Reveal the Milky Way’s Supermassive Black Hole

An enormous swirling vortex of hot gas glows with infrared light, marking the approximate location of the supermassive black hole at the heart of our Milky Way galaxy. This multiwavelength composite image includes near-infrared light captured by NASA’s Hubble Space Telescope, and was the sharpest infrared image ever made of the galactic center region when it was released in 2009. Dynamic flickering flares in the region immediately surrounding the black hole, named Sagittarius A*, have complicated the efforts of the Event Horizon Telescope (EHT) collaboration to create a closer, more detailed image. While the black hole itself does not emit light and so cannot be detected by a telescope, the EHT team is working to capture it by getting a clear image of the hot glowing gas and dust directly surrounding it. NASA’s upcoming James Webb Space Telescope, scheduled to launch in December 2021, will combine Hubble’s resolution with even more infrared light detection. In its first year of science operations, Webb will join with EHT in observing Sagittarius A*, lending its infrared data for comparison to EHT’s radio data, making it easier to determine when bright flares are present, producing a sharper overall image of the region. In the composite image shown here, colors represent different wavelengths of light. Hubble’s near-infrared observations are shown in yellow, revealing hundreds of thousands of stars, stellar nurseries, and heated gas. The deeper infrared observations of NASA’s Spitzer Space Telescope are shown in red, revealing even more stars and gas clouds. Light detected by NASA’s Chandra X-ray Observatory is shown in blue and violet, indicating where gas is heated to millions of degrees by stellar explosions and by outflows from the supermassive black hole. Credits: NASA, ESA, SSC, CXC, STScI.  Hi-res image

On isolated mountaintops across the planet, scientists await word that tonight is the night: The complex coordination between dozens of telescopes on the ground and in space is complete, the weather is clear, tech issues have been addressed—the metaphorical stars are aligned. It is time to look at the supermassive black hole at the heart of our Milky Way galaxy.

This “scheduling Sudoku,” as the astronomers call it, happens each day of an observing campaign by the Event Horizon Telescope (EHT) collaboration, and they will soon have a new player to factor in; NASA’s James Webb Space Telescope will be joining the effort. During Webb’s first slate of observations, astronomers will use its infrared imaging power to address some of the unique and persistent challenges presented by the Milky Way’s black hole, named Sagittarius A* (Sgr A*; the asterisk is pronounced as “star”).

In 2017, EHT used the combined imaging power of eight radio telescope facilities across the planet to capture the historic first view of the region immediately surrounding a supermassive black hole, in the galaxy M87. Sgr A* is closer but dimmer than M87’s black hole, and unique flickering flares in the material surrounding it alter the pattern of light on an hourly basis, presenting challenges for astronomers.

“Our galaxy’s supermassive black hole is the only one known to have this kind of flaring, and while that has made capturing an image of the region very difficult, it also makes Sagittarius A* even more scientifically interesting,” said astronomer Farhad Yusef-Zadeh, a professor at Northwestern University and principal investigator on the Webb program to observe Sgr A*.

The flares are due to the temporary but intense acceleration of particles around the black hole to much higher energies, with corresponding light emission. A huge advantage to observing Sgr A* with Webb is the capability of capturing data in two infrared wavelengths (F210M and F480M) simultaneously and continuously, from the telescope’s location beyond the Moon. Webb will have an uninterrupted view, observing cycles of flaring and calm that the EHT team can use for reference with their own data, resulting in a cleaner image.

The source or mechanism that causes Sgr A*’s flares is highly debated. Answers as to how Sgr A*’s flares begin, peak, and dissipate could have far-reaching implications for the future study of black holes, as well as particle and plasma physics, and even flares from the Sun.

“Black holes are just cool,” said Sera Markoff, an astronomer on the Webb Sgr A* research team and currently vice chairperson of EHT’s Science Council. “The reason that scientists and space agencies across the world put so much effort into studying black holes is because they are the most extreme environments in the known universe, where we can put our fundamental theories, like general relativity, to a practical test.”

Heated gas swirls around the region of the Milky Way galaxy’s supermassive black hole, illuminated in near-infrared light captured by NASA’s Hubble Space Telescope. Released in 2009 to celebrate the International Year of Astronomy, this was the sharpest infrared image ever made of the galactic center region. NASA’s upcoming James Webb Space Telescope, scheduled to launch in December 2021, will continue this research, pairing Hubble-strength resolution with even more infrared-detecting capability. Of particular interest for astronomers will be Webb’s observations of flares in the area, which have not been observed around any other supermassive black hole and the cause of which is unknown. The flares have complicated the Event Horizon Telescope (EHT) collaboration’s quest to capture an image of the area immediately surrounding the black hole, and Webb’s infrared data is expected to help greatly in producing a clean image.Credits: NASA, ESA, STScI, Q. Daniel Wang (UMass). Hi-res image

Black holes, predicted by Albert Einstein as part of his general theory of relativity, are in a sense the opposite of what their name implies—rather than an empty hole in space, black holes are the most dense, tightly-packed regions of matter known. A black hole’s gravitational field is so strong that it warps the fabric of space around itself, and any material that gets too close is bound there forever, along with any light the material emits. This is why black holes appear “black.” Any light detected by telescopes is not actually from the black hole itself, but the area surrounding it. Scientists call the ultimate inner edge of that light the event horizon, which is where the EHT collaboration gets its name.

The EHT image of M87 was the first direct visual proof that Einstein’s black hole prediction was correct. Black holes continue to be a proving ground for Einstein’s theory, and scientists hope carefully scheduled multi-wavelength observations of Sgr A* by EHT, Webb, X-ray, and other observatories will narrow the margin of error on general relativity calculations, or perhaps point to new realms of physics we don’t currently understand.

As exciting as the prospect of new understanding and/or new physics may be, both Markoff and Zadeh noted that this is only the beginning. “It’s a process. We will likely have more questions than answers at first,” Markoff said. The Sgr A* research team plans to apply for more time with Webb in future years, to witness additional flaring events and build up a knowledge base, determining patterns from seemingly random flares. Knowledge gained from studying Sgr A* will then be applied to other black holes, to learn what is fundamental to their nature versus what makes one black hole unique.

So the stressful scheduling Sudoku will continue for some time, but the astronomers agree it’s worth the effort. “It’s the noblest thing humans can do, searching for truth,” Zadeh said. “It’s in our nature. We want to know how the universe works, because we are part of the universe. Black holes could hold clues to some of these big questions.”

NASA’s Webb telescope will serve as the premier space science observatory for the next decade and explore every phase of cosmic history—from within our solar system to the most distant observable galaxies in the early universe, and everything in between. Webb will reveal new and unexpected discoveries, and help humanity understand the origins of the universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.

By Leah Ramsay
Space Telescope Science Institute, Baltimore, Md.

Editor: Lynn Jenner

Source: NASA/Blacks Holes

---

EHT pinpoints dark heart of the nearest radio galaxy

Distance scales uncovered in the Centaurus A jet. The top left image shows how the jet disperses into gas clouds that emit radio waves, captured by the ATCA and Parkes observatories. The top right panel displays a color composite image, with a 40x zoom compared to the first panel to match the size of the galaxy itself. Submillimeter emission from the jet and dust in the galaxy measured by the LABOCA/APEX instrument is shown in orange. X-ray emission from the jet measured by the Chandra spacecraft is shown in blue. Visible white light from the stars in the galaxy has been captured by the MPG/ESO 2.2-metre telescope. The next panel below shows a 165000x zoom image of the inner radio jet obtained with the TANAMI telescopes. The bottom panel depicts the new highest resolution image of the jet launching region obtained with the EHT at millimeter wavelengths with a 60000000x zoom in telescope resolution. Indicated scale bars are shown in light years and light days. One light year is equal to the distance that light travels within one year: about nine trillion kilometers. In comparison, the distance to the nearest-known star from our Sun is approximately four light years. One light day is equal to the distance that light travels within one day: about six times the distance between the Sun and Neptune. Credit: Radboud University; CSIRO/ATNF/I.Feain et al., R.Morganti et al., N.Junkes et al.; ESO/WFI; MPIfR/ESO/APEX/A. Weiss et al.; NASA/CXC/CfA/R. Kraft et al.; TANAMI/C. Mueller et al.; EHT/M. Janssen et al. Hi-res image

Highest resolution image of Centaurus A obtained with the Event Horizon Telescope on top of a color composite image of the entire galaxy. Credit: Radboud University; ESO/WFI; MPIfR/ESO/APEX/A. Weiss et al.; NASA/CXC/CfA/R. Kraft et al.; EHT/M. Janssen et al. Hi-res image

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.

The new image shows that the jet launched by Centaurus A is brighter at the edges compared to the center. This phenomenon is known from other jets, but has never been seen so pronouncedly before. “Now we are able to rule out theoretical jet models that are unable to reproduce this edge-brightening. It’s a striking feature that will help us better understand jets produced by black holes”, says Matthias Kadler, TANAMI leader and professor for astrophysics at the University of Würzburg in Germany.

Future observations

With the new EHT observations of the CentaurusA jet, the likely location of the black hole has been identified at the launching point of the jet. Based on this location, the researchers predict that future observations at an even shorter wavelength and higher resolution would be able to photograph the central black hole of Centaurus A. This will require the use of space-based satellite observatories.

“These data are from the same observing campaign that delivered the famous image of the black hole in M87. The new results show that the EHT provides a treasure trove of data on the rich variety of black holes and there is still more to come”, says Heino Falcke, EHT board member and professor for Astrophysics at Radboud University.

Additional Information

To observe the Centaurus A galaxy with this unprecedentedly sharp resolution at a wavelength of 1.3 mm, the EHT collaboration used Very Long Baseline Interferometry (VLBI), the same technique with which the famous image of the black hole in M87 was made. An alliance of eight telescopes around the world, of which ALMA is the most sensitive element, joined together to create the virtual Earth-sized Event Horizon Telescope. The EHT collaboration involves more than 300 researchers from Africa, Asia, Europe, North and South America.

The EHT consortium consists of 13 stakeholder institutes: the Academia Sinica Institute of Astronomy and Astrophysics, the University of Arizona, the University of Chicago, the East Asian Observatory, Goethe University Frankfurt, Institut de Radioastronomie Millimétrique (MPG/CNRS/IGN), Large Millimeter Telescope, Max Planck Institute for Radio Astronomy, MIT Haystack Observatory, National Astronomical Observatory of Japan, Perimeter Institute for Theoretical Physics, Radboud University and the Center for Astrophysics | Harvard & Smithsonian.

TANAMI (Tracking Active Galactic Nuclei with Austral Milliarcsecond Interferometry) is a multiwavelength program to monitor relativistic jets in active galactic nuclei of the Southern Sky. This program has been monitoring Centaurus A with VLBI at centimeter-wavelengths since the mid 2000s. The TANAMI array consists of nine radio telescopes located on four continents observing at wavelengths of 4 cm and 1.3 cm.

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Organisation for Astronomical Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the Ministry of Science and Technology (MOST) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

Scientific Paper 

Source:   Atacama Large Millimeter/submillimeter Array (ALMA)/Press Releases

---

Contacts

Valeria Foncea

Education and Public Outreach Manager

Joint ALMA Observatory Santiago - Chile

Phone: +56 2 2467 6258

Cell phone: +56 9 7587 1963

Email: valeria.foncea@alma.cl

Masaaki Hiramatsu

Education and Public Outreach Officer, NAOJ Chile

Observatory, Tokyo - Japan

Phone: +81 422 34 3630

Email: hiramatsu.masaaki@nao.ac.jp

Bárbara Ferreira

ESO Public Information Officer

Garching bei München, Germany

Phone: +49 89 3200 6670

Email: pio@eso.org

Amy C. Oliver

Public Information & News Manager

National Radio Astronomical Observatory (NRAO), USA

Phone: +1 434 242 9584

Email: aoliver@nrao.edu

---