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

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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

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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

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Related Link(s)

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

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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

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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."

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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

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Contact:

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

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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

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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

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A Sharper Look at the First Image of a Black Hole

PR Image noirlab2310a
Comparison of EHT and EHT Reconstructed with PRIMO

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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

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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.”

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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.

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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

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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)

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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

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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

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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

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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

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Multi-wavelength Observations Reveal Impact of Black Hole on M87 Galaxy

A Black Hole and its Far-Reaching Effects
Credit: Sophia Dagnello; NRAO/AUI/NSF; CXC; EHT Collaboration

To better understand the black hole at the core of galaxy M87, the EHT Collaboration mounted a multi-wavelength observing campaign. Observations across the electromagnetic spectrum in radio, visible-light, ultraviolet, X-ray, and gamma-ray revealed the far-reaching impact of the supermassive black hole on its surroundings. Credit: EHT Collaboration; NASA/Swift; NASA/Fermi; Caltech-NuSTAR; CXC; CfA-VERITAS; MAGIC; HESS. Hi-res image

In 2019, a worldwide collaboration of scientists used a global collection of radio telescopes called the Event Horizon Telescope (EHT) to make the first-ever image of a black hole — the supermassive black hole at the core of the galaxy M87, some 55 million light-years from Earth. This long-sought achievement was an important scientific landmark. However, any image at a single wavelength can give only a partial picture of the entire phenomenon.

“We knew that the first direct image of a black hole would be groundbreaking,” said Kazuhiro Hada of the National Astronomical Observatory of Japan, a co-author on the new study. “But to get the most out of this remarkable image, we need to know everything we can about the black hole’s behavior at that time by observing over the entire electromagnetic spectrum.”

The tremendous gravitational pull of a supermassive black hole can power jets of particles that travel at nearly the speed of light across vast distances. The result produces electromagnetic radiation spanning the entire range from radio waves to visible light, to gamma rays.

In this video, results from each telescope across the observing campaign reveal previously unseen structures and the impact of the black hole on its surroundings in regions spanning one to 100,000 light-years across.

“Understanding the particle acceleration is really central to our understanding of both the EHT image as well as the jets, in all their ‘colors’,” said co-author Sera Markoff, from the University of Amsterdam. “These jets manage to transport energy released by the black hole out to scales larger than the host galaxy, like a huge power cord. Our results will help us calculate the amount of power carried, and the effect the black hole’s jets have on its environment.”

To expand their view of the region around the 6.5-million-solar-mass black hole, scientists mounted a multi-wavelength observing campaign, including 19 ground-and space-based observatories working at gamma-ray, X-ray, visible-light, and radio wavelengths. The study used the Atacama Large Millimeter/submillimeter Array (ALMA) and the National Science Foundation’s Very Long Baseline Array (VLBA).

“There are multiple groups eager to see if their models are a match for these rich observations, and we’re excited to see the whole community use this public data set to help us better understand the deep links between black holes and their jets,” said co-author Daryl Haggard of McGill University.

This new study, reported in The Astrophysical Journal Letters, provides a valuable resource for helping scientists understand the physics of how such monster black holes operate and strongly affect their surroundings.

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Dave Finley
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Scientific Paper: “Broadband Multi-wavelength Properties of M 87 During the 2017 Event Horizon Telescope Campaign,” Algaba, J.C. et al, The Astrophysical Journal Letters, 911, L11, April 14, 2021, doi: 3847/2041-8213/abef71

EHT Official Press Release

 

Source:  National Radio Astronomy Observatory (NRAO)/News

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New Images Reveal Magnetic Structures Near Supermassive Black Hole

View of the M87 supermassive black hole and jet

This composite image shows three radio-telescope views of the central region of the galaxy Messier 87 (M87), where a jet of fast-moving particles is ejected from the galaxy's core. In these images, the lines indicate polarization -- the alignment of the electric fields in the radio waves coming from the object. The polarization is a signature of the magnetic fields. The ALMA image shows the inner 6000 light-years of the jet. The image from the National Science Foundation's Very Long Baseline Array (VLBA) zooms down to show the inner one light-year of the jet, and the EHT image shows the region closest to the supermassive black hole at the galaxy's core. Labels indicate the observing frequency in GigaHertz (GHz) and the distance indicated by the scale bar below the frequency. Combined, these images allow astronomers to study the structure of magnetic fields from very close to the black hole to thousands of light-years outward from it. Credit: EHT Collaboration; Goddi et al., ALMA (ESO/NAOJ/NRAO); Kravchenko et al.; J. C. Algaba, I. Martí-Vidal, NRAO/AUI/NSF. Hi-Res File

ALMA image of M87 jet

This image shows a view of the jet in the galaxy Messier 87 (M87). The image was obtained with the Atacama Large Millimeter/submillimeter Array (ALMA), while observing as part of the Event Horizon Telescope (EHT). The image captures the part of the jet, with a size of 6000 light years, closer to the center of the galaxy. The lines mark the orientation of polarization, which is related to the magnetic field in the region imaged. This ALMA image indicates what the structure of the magnetic field along the jet looks like. Credit: Goddi et al., ALMA (ESO/NAOJ/NRAO). Hi-Res File

New EHT Image

The new image of the region around the supermassive black hole at the core of the galaxy M87, from the Event Horizon Telescope. Lines show polarization of the radio emission from the area closest to the black hole. Credit: EHT Collaboration. Hi-Res File

 

A new view of the region closest to the supermassive black hole at the center of the galaxy Messier 87 (M87) has shown important details of the magnetic fields close to the black hole and hints about how powerful jets of material can originate in that region.

A worldwide team of astronomers using the Event Horizon Telescope, a collection of eight telescopes, including the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, measured a signature of magnetic fields — called polarization — around the black hole. Polarization is the orientation of the electric fields in light and radio waves and it can indicate the presence and alignment of magnetic fields.

“We are now seeing the next crucial piece of evidence to understand how magnetic fields behave around black holes, and how activity in this very compact region of space can drive powerful jets,” said Monika Mościbrodzka, Coordinator of the EHT Polarimetry Working Group and Assistant Professor at Radboud University in the Netherlands.

New images with the EHT and ALMA allowed scientists to map magnetic field lines near the edge of M87’s black hole. That same black hole is the first ever to be imaged — by the EHT in 2019. That image revealed a bright ring-like structure with a dark central region — the black hole’s shadow. The newest images are a key to explaining how M87, 50 million light-years from Earth, can launch energetic jets from its core.

The black hole at M87’s center is more than 6 billion times more massive than the Sun. Material drawn inward forms a rotating disk — called an accretion disk — closely orbiting the black hole. Most of the material in the disk falls into the black hole, but some surrounding particles escape and are ejected far out into space in jets moving at nearly the speed of light.

“The newly published polarized images are key to understanding how the magnetic field allows the black hole to ‘eat’ matter and launch powerful jets,” said Andrew Chael, a NASA Hubble Fellow at the Princeton Center for Theoretical Science and the Princeton Gravity Initiative in the U.S.

The scientists compared the new images that showed the magnetic field structure just outside the black hole with computer simulations based on different theoretical models. They found that only models featuring strongly magnetized gas can explain what they are seeing at the event horizon.

“The observations suggest that the magnetic fields at the black hole’s edge are strong enough to push back on the hot gas and help it resist gravity’s pull. Only the gas that slips through the field can spiral inwards to the event horizon,” explained Jason Dexter, Assistant Professor at the University of Colorado Boulder and Coordinator of the EHT Theory Working Group.

To make the new observations, the scientists linked eight telescopes around the world — including ALMA — to create a virtual Earth-sized telescope, the EHT. The impressive resolution obtained with the EHT is equivalent to that needed to measure the length of a credit card on the surface of the Moon.

This resolution allowed the team to directly observe the black hole shadow and the ring of light around it, with the new image clearly showing that the ring is magnetized. The results are published in two papers in the Astrophysical Journal Letters by the EHT collaboration. The research involved more than 300 researchers from multiple organizations and universities worldwide.

A third paper also was published in the same volume of the Astrophysical Journal Letters, based on data from ALMA, lead by Ciriaco Goddi, a scientist at Radboud University and Leiden Observatory, the Netherlands.

“The combined information from the EHT and ALMA allowed scientists to investigate the role of magnetic fields from the vicinity of the event horizon to far beyond the core of the galaxy, along its powerful jets extending thousands of light-years,” Goddi said.

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

The EHT collaboration involves more than 300 researchers from Africa, Asia, Europe, North and South America. The international collaboration is working to capture the most detailed black hole images ever obtained by creating a virtual Earth-sized telescope. Supported by considerable international investment, the EHT links existing telescopes using novel systems — creating a fundamentally new instrument with the highest angular resolving power that has yet been achieved.

The individual telescopes involved are: ALMA, APEX, the Institut de Radioastronomie Millimetrique (IRAM) 30-meter Telescope, the IRAM NOEMA Observatory, the James Clerk Maxwell Telescope (JCMT), the Large Millimeter Telescope (LMT), the Submillimeter Array (SMA), the Submillimeter Telescope (SMT), the South Pole Telescope (SPT), the Kitt Peak Telescope, and the Greenland Telescope (GLT).

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-Universitaet Frankfurt, Institut de Radioastronomie Millimétrique, 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 Smithsonian Astrophysical Observatory.

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of 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.

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Scientific Papers:

Paper VII (The Astrophysical Journal Letters, Vol. 910, L12):

Paper VIII (The Astrophysical Journal Letters, Vol. 910, L13):

Related Paper, Goddi et al., Polarimetric properties of Event Horizon Telescope targets from ALMA, The Astrophysical Journal Letters, Vol. 910, in press, 24 March 2021:

 

Source: National Radio Astronomy Observatory (NRAO)/News

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The wobbling shadow of the M87* black hole

Snapshots of the M87* black hole obtained through imaging/geometric modeling, and the EHT array of telescopes from 2009 to 2017. The diameter of all rings is similar, but the location of the bright side varies.  Credits:  Image courtesy of M. Wielgus, D. Pesce, and the EHT Collaboration.

Analysis of Event Horizon Telescope observations from 2009 to 2017 reveals turbulent evolution of the M87* black hole image.

In 2019, the Event Horizon Telescope (EHT) Collaboration, including a team of MIT Haystack Observatory scientists, delivered the first image of a black hole, revealing M87* — the supermassive object in the center of the M87 galaxy. The EHT team has used the lessons learned last year to analyze the archival data sets from 2009 to 2013, some of which were not published before. The analysis reveals the behavior of the black hole image across multiple years, indicating persistence of the crescent-like shadow feature, but also variation of its orientation — the crescent appears to be wobbling. The full results appear today in The Astrophysical Journal in an article titled, “Monitoring the Morphology of M87* in 2009–2017 with the Event Horizon Telescope.”

The EHT is a global array of telescopes, performing synchronized observations using the technique of very long baseline interferometry. Together they form a virtual Earth-sized radio dish, providing a uniquely high image resolution. In 2009–13, M87* was observed by early-EHT prototype arrays, with telescopes located at three geographical sites from 2009 to 2012 and four sites in 2013. In 2017, the EHT reached maturity with telescopes located at five distinct geographical sites across the globe.

Datasets for this research were fully correlated at MIT Haystack Observatory. The 2009–2013 observations consist of less data than the ones performed in 2017, making it impossible to create an image. But the EHT team was able to use statistical modeling to look at changes in the appearance of M87* over time. In the modeling approach, the data are compared to a family of geometric templates, in this case rings of non-uniform brightness. A statistical framework is then employed to determine if the data are consistent with such models and to find the best-fitting model parameters.

“This is a beautiful example of creative data analysis. Extracting important new astrophysical understanding and squeezing new insight out of previous observations is an imaginative example of how scientists can maximally use the information content of such painstakingly collected data,” says Colin Lonsdale, director of MIT Haystack Observatory and chair of the EHT Collaboration Board. “The behavior of this event horizon scale structure over a period of years allows important additional constraints to be placed on the properties of this fascinating object.”

Expanding the analysis to the 2009–2017 observations, EHT scientists have shown that M87* adheres to theoretical expectations. The black hole’s shadow diameter has remained consistent with the prediction of Einstein’s theory of general relativity for a black hole of 6.5 billion solar masses.

“In this study, we show that the general morphology, or presence of an asymmetric ring, most likely persists on timescales of several years,” says Kazu Akiyama, research scientist at MIT Haystack Observatory and a participant in the project. “The consistency throughout multiple observational epochs gives us more confidence than ever about the nature of M87* and the origin of the shadow.”

Although the crescent diameter remained consistent, the EHT team found that the data were hiding a surprise: The ring is wobbling, and that means big news for scientists. For the first time, they can get a glimpse of the dynamical structure of the accretion flow so close to the black hole’s event horizon, in extreme gravity conditions. Studying this region holds the key to understanding phenomena such as relativistic jet launching, and will allow scientists to formulate new tests of the theory of general relativity.

The gas falling onto a black hole heats up to billions of degrees, ionizes, and becomes turbulent in the presence of magnetic fields. “Because the flow of matter is turbulent, the crescent appears to wobble with time,” says Maciek Wielgus of the Harvard and Smithsonian Center for Astrophysics, who is a Black Hole Initiative fellow, and lead author of the paper. “Actually, we see quite a lot of variation there, and not all theoretical models of accretion allow for so much wobbling. What it means is that we can start ruling out some of the models based on the observed source dynamics.”

“MIT Haystack Observatory was instrumental in organizing these early observations, correlating the massive amounts of data returned on large numbers of hard drives, and reducing the data,” says Vincent Fish, research scientist at Haystack Observatory. “While we were able to place important constraints on the size and nature of the emission in M87* at the time, the images made from the much better 2017 array data provided critical context for fully understanding what the earlier data were trying to tell us.”

Haystack scientist Geoff Crew adds, “After working on EHT technology for a decade, I’m gratified that M87* has been making equally good use of its time.”

 

 Nancy Wolfe Kotary | MIT Haystack Observatory

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