Black holes – Canadian Institute for Theoretical Astrophysics

CITA Researcher Helps Locate the “Missing Link” in Giant Black Hole’s Power Source

citaadmin — Wed, 28 Jan 2026 13:00:14 +0000

CITA Researcher Helps Locate the “Missing Link” in Giant Black Hole’s Power Source

January 28, 2026

New data from the Event Horizon Telescope (EHT) has provided scientists with a first-of-its-kind look at the “exhaust pipe” of a supermassive black hole.

James Webb Space Telescope (JWST) + NIRCam RBG image of the giant elliptical galaxy M87. The stream of the glowing torch represents the jet. The visible part spans around 3000 light-years. Credits: Jan Röder, Maciek Wielgus, Joseph B. Jensen, Gagandeep S. Anand, R. Brent Tully, 2025.

, a postdoctoral researcher at the Canadian Institute for Theoretical Astrophysics (CITA), is part of an international team that has identified the likely starting point of a massive cosmic jet — a powerful stream of particles being blasted out from the heart of the galaxy Messier 87 (M87).

The discovery, published today in the journal Astronomy & Astrophysics, contributes to the uncovering of a major mystery in space science: exactly where black holes launch these 5,000-light-year-long streams of energy into the universe.

Finding the Engine Room

At the center of the M87 galaxy lies a black hole with a mass six billion times that of our Sun. While black holes are famous for pulling matter in, they also act as massive engines that eject streams of charged particles—known as “jets”—at nearly the speed of light.

“By identifying where the jet originates and how it connects to the black hole’s shadow, we are adding key pieces to the puzzle,” says Saurabh, the study’s lead author from the Max Planck Institute for Radio Astronomy.

The “Middle View” Discovery

To see this, the team used the Event Horizon Telescope, a global network of radio dishes that work together to create a single virtual telescope the size of the Earth. In the past, the radio observations have provided two different views of M87:

The pre-2021 EHT observations provided the Extreme Close-Up: A “zoomed-in” view showing the famous glowing ring of hot gas around the black hole’s shadow.
Lower frequency radio observations provided the Wide Angle: A “zoomed-out” view showing the long, thin jet stretching across the galaxy.

The “missing link” has always been the area in between—the transition where the glowing ring becomes the jet. By analyzing new data from 2021, von Fellenberg and his colleagues utilized “intermediate” telescope distances to see this middle ground for the first time.

They discovered that the glowing ring alone couldn’t explain all the light they were seeing. Through detailed computer modeling, they found that the “missing light” matches a specific spot about 0.09 light-years away from the black hole. This, they believe, is the place of origin of the black hole’s jet.

A New Era of Black Hole Imaging

The contribution from CITA and the international team marks a shift from simply theorizing about black holes to observing their direct environment. To capture this elusive region, the team relied on a technique called “calibration”—a complex process of cleaning up raw data from the Earth-sized virtual telescope. Sebastiano von Fellenberg of CITA led the calibration for the 2021 M87* observations. By precisely correcting for atmospheric interference and slight hardware differences between telescopes scattered across the globe, he essentially “cleared the static,” allowing the team to see the faint signals of the jet’s origin that were previously hidden.

“Newly observed data—now being processed with support from our international partners—will soon include even more telescopes and thus intermediate baselines,” says Sebastiano von Fellenberg of CITA. “This will bring an even sharper view of the jet launching region within reach. We aren’t just calculating where these structures are anymore; we are moving toward being able to image them directly.”

Observations from 2018 (left), conducted with the Global mm-VLBI Array (GMVA) at frequencies of 86 GHz, show not only the ring around the supermassive black hole M87*, but also a jet that splits into a northern and southern component. At higher frequencies of 230 GHz (right), the EHT data show fine details of the ring, but cannot yet image the jet. A compact region that coincides with the southern part of the jet at 86 GHz best explains the missing radiation at 230 GHz observed at different spatial scales. Figure credit: (Lu. et al. 2023 + Saurabh et al. 2026)

Professor Bart Ripperda, who leads a research group at CITA that studies the causes for the ejection of these powerful streams of charged particles, also explains:

“The jets are theorized to be launched tapping the rotational energy of the black hole through electromagnetism, such that they are a laboratory where general relativity and quantum electrodynamics (the two most successful theories of the 20th century) act together. Seeing how jets are launched so close to the event horizon of the black hole is a major step in the understanding of black holes!”

Observational data, such as the one presented in , allows scientists to test their theories on how gravity and magnetism interact in the most extreme environments in the universe, bringing us one step closer to understanding the “engines” that shape entire galaxies.

Original publication: Saurabh et al. Probing jet base emission of M87* with the 2021 Event Horizon Telescope observations, Astronomy & Astrophysics 705 (2026), DOI:

What do black hole collisions look like?

citaadmin — Tue, 28 Oct 2025 11:58:23 +0000

In OJ 287, the secondary black hole repeatedly plunges through the disk surrounding the primary black hole, roughly once every 12 years. As time goes on, the oval-shaped orbit slowly shifts forward so that the black hole collides with different parts of the disk. Each impact disrupts the disk and produces hot bubbles that generate the bursts of light that we observe.

CITA researchers have the calculations and simulations to explain mysterious flashes from the galaxy OJ 287

Roughly twice every 12 years, from 3.5 billion light years away, the light equivalent of one trillion suns flashes in the night sky and then fades away over the next few months. It’s a phenomenon that astronomers have been documenting since the late 1880s, originating in a galaxy known as OJ 287. For more than 40 years, astronomers have attributed the oddly regular bursting behaviour to be caused by a pair of extremely massive black holes on a collision course. In theory, supermassive binary pairs are expected to be common – but this is the only system where there is clear evidence for one.

“Supermassive binary pairs like these provide a rare opportunity to investigate how galaxies merge and grow over time,” says Sean Ressler, a postdoctoral researcher at the Canadian Institute for Theoretical Physics (CITA). Ressler led a recent in The Astrophysical Journal Letters that presents the first ever simulations of OJ 287. His three co-authors include Luciano Combi, CITA National fellow at Perimeter institute and the University of Guelph, Bart Ripperda at CITA, and Xinyu Li, Tsinghua University.

Beyond ‘pen and paper’ estimates

For the OJ 287 pair, the primary black hole is one of the largest known, at about 18 billion times the mass of Earth’s sun. It’s surrounded by a disk of gas falling inwards toward its event horizon. The secondary black hole, a mere 150 million times the mass of Earth’s sun, repeatedly collides with this disk, creating an explosion of light.

It’s an explanation that mostly relies on simple ‘pen and paper’ estimates of how the black holes interact with the surrounding gas. Combi notes the team’s paper presents the first-ever simulations of OJ 287 as a whole. Unlike previous estimates, their work was able to study how the disk reacts to the repeated collisions, how the ejected gas interacts with the secondary black hole, and how the secondary black hole twists and amplifies magnetic fields that surround the disk to drive outflows.

“These simulations take into account the complicated interaction between extreme gravity, electrodynamics, and fluid dynamics in order to rigorously test whether or not the model can actually explain the observed outbursts,” says Combi. “This is the first time the gas (which produces the light) around the binary hole has been simulated all together.”

Simulation-based images and animations

The team has used its simulations to create based on foundational physical understanding that truly bring the system at the centre of OJ 287 to life.

“For years the idea of a smaller mass black hole colliding with the disk of a larger mass black hole has inspired stunning visualizations and artistic renderings, but now we have some compelling animations that are based on more complex calculations,” says Ressler.

The simulations generally confirm the idea that the collision of the secondary black hole with the disk can generate enough energy to account for the observed burst of light. The collisions are also seen to modify the structure of the disk, warping it and creating transient spiral patterns that fall inward.

“These calculations should really be treated as a first step towards fully realistic simulations,” Ressler says. “We still need to include the effects of how the flashes of light are produced and then get bent by the extreme gravity of the black holes. We also made a few simplifications to make the simulations more feasible, but in the end, we expect to remove these simplifications and account for the behaviour of light. This is a step towards a fully coherent picture of the system.”

The connection to gravitational waves

Because the gravity around these two massive black holes is so intense, they also cause ripples in space and time called gravitational waves. Although this will ultimately drive them to a full-on collision, it won’t happen for another 10,000 years. In the meantime, there is an effort to detect these ripples by monitoring a set of pulsating stars, called pulsar timing arrays, that act like cosmic clocks. With the next generation of radio telescopes, the sensitivity at which we can monitor changes in space and time with pulsar timing arrays will eventually grow to such an extent that they could pick up on gravitational waves emitted by the OJ 287 system.

As CITA faculty member Bart Ripperda notes, “combining the information that we would get from these gravitational waves with the information we get from traditional telescopes will lead to major breakthroughs in our understanding of gravity, black holes, and how galaxies grow over time. Realistic simulations will be crucial in predicting electromagnetic signatures from the plasma physics near the event horizon.”

*“Black Hole Collisions With Thin Accretion Disks: OJ 287 and Small-Mass-Ratio Supermassive Black Hole Binary Candidates”,��,��,��,��,��The Astrophysical Journal Letters, October 28, 2025: .

This news story was published by the Perimeter Institute. Read it

Neutron Stars & Black Holes: Astrophysical Laboratories for Nuclear Physics and Nuclear Yardsticks for Astrophysical Phenomena

citaadmin — Thu, 29 May 2025 21:34:07 +0000

Neutron Stars & Black Holes: Astrophysical Laboratories for Nuclear Physics and Nuclear Yardsticks for Astrophysical Phenomena

Reed Essick (University of Toronto) — May 29, 2025

Abstract

The physics of compact objects, such as Neutron Stars and Black Holes, remains at the forefront of astronomical theory and experiment. In particular, there is significant uncertainty in the nuclear physics that governs the cores of Neutron Stars and sculpts the entire population of stellar remnants. I will discuss how to use theoretical insights about the behaviour of these exotic objects, together with cutting-edge inference techniques, to improve constraints from multi-messenger observations. Similarly, I will show a few examples of how improved theoretical understanding of compact object properties can inform our understanding of a broad range of astrophysical phenomena. I will discuss the current state of the field, with a focus on insights enabled by the technology I’ve developed, what we are likely to learn over the coming years, and promising paths towards deep physical insights about the behaviour of supranuclear matter and dynamic, strong-field gravity.

Flaring Activity of the Black Hole at the Center of the Galaxy

citaadmin — Wed, 16 Apr 2025 17:54:12 +0000

Flaring Activity of the Black Hole at the Center of the Galaxy

Farhad Yusef-Zadeh (Northwestern University) — April 7, 2025

Abstract

It is clear that an under-luminous supermassive black hole (Sgr A*) with a mass of 4.2 million solar mass lies at the center of the Galaxy. Precise measurements taken at radio and infrared wavelengths over the last two decades have led to this conclusion. The recent studies indicate deviations from Keplerian motion of a star orbiting the black hole, the precession of an orbiting star, and an image of the shadow of the black hole. These measurements are consistent with the predictions of the Einstein’s general theory of relativity. I will present highlights of recent James Webb Space Telescope (JWST) observations to study the flaring activity of the black hole. The variability of the black hole probes the process of the accretion flow at a distance of few Schwarszchild radius before running across the event horizon. These observations indicate that the flux of Sgr A* is fluctuating constantly punctuated with multiple synchrotron flares per day. I will argue that two distinct populations of particles produce bright and faint synchrotron variable emission. As for the origin of the infrared flares, a number of recent simulations suggest that flares are ejected plasmoids from the accretion disk due to the reconnection of the magnetic field lines. Time permitting, I will also discuss the relationship between radio/submm, X-ray and infrared variable emission.

Magnetized Plasma around Merging Black Holes Shines and Burst like the Corona of the Sun

citaadmin — Wed, 22 Jan 2025 20:55:42 +0000

What happens when the supermassive black holes at the centre of galaxies collide?

This is the question explored in a new article by CITA Postdoctoral fellow Sean Ressler, CITA faculty Bart Ripperda, CITA National Fellow Luciano Combi (University of Guelph/Perimeter Institute), and Caltech faculty Elias Most that just came out in .

At the centre of almost every large galaxy in the Universe is a supermassive black hole that has helped shape its evolution throughout its lifetime. When two galaxies collide, the massive black holes in their center can form a binary system surrounded by strongly magnetized gas. As outlined in their paper, the authors perform novel computer simulations of binary black holes in a magnetized plasma showing that the system can shine and burst in a similar way as the corona of the sun.

Three-dimensional visualization of the magnetic field in the simulation during a “bridge” eruption event. Green lines denote the magnetic field that connects the two black holes while the yellow lines represent magnetic fields that have “broken off” in a violent flaring event. (Created by Sean Ressler)

Supermassive binary black holes in galactic centres are particularly important for studying the most extreme gravitational events in the universe. As potential multimessenger sources of both gravitational waves and electromagnetic radiation, binaries can be “seen” as light (electromagnetic radiation) and, in coming years, will also be “heard” through the ripples in space and time called gravitational waves. Space-based detectors targeting these waves will offer additional insight into these systems that can be combined with more traditional observations to deepen our understanding of such unique environments.

“It is an exhilarating time to be studying these supermassive binary systems because we are truly only in the early stages of modeling their interactions with surrounding matter; each step forward is groundbreaking. As a community we have spent most of our time modeling single black hole sources (like those that have recently been imaged by the Event Horizon Telescope) and in a way this is the next step. The ground was laid by a handful of pioneering simulations, but we are now able to start pushing towards more realistic regimes and making robust predictions about what we might see,” shares first author and CITA Postdoctoral fellow Dr. Sean Ressler.

Since gravitational wave detectors are not able to precisely locate these supermassive objects, it is imperative to have solid predictions about how such binary systems would appear in the sky. To make such predictions, the authors use high-performance numerical simulations of hot, magnetized gas around binary black holes to identify two ways in which galaxies containing such binaries may shine differently than galaxies containing a single supermassive black hole. The first way involves the collision of the two jets: beams of ultra-fast, highly magnetized outflow accelerated by the rotation of each black hole. These collisions are very similar to how loops of magnetic field poking through the surface of the sun often collide and generate solar flares. The second way involves “bridges” of magnetic field lines that can spontaneously form between the two black holes. As the black holes orbit around each other, these bridges get severely twisted until they ultimately snap, releasing a large amount of energy associated with a burst of light. This is similar to the so-called “coronal mass ejections” in the sun, where bridges form between two moving spots on the solar surface.

“For me, it was most exciting to see the same mechanisms that cause extreme events in the sun show up in binary black hole systems. On the one hand, you have the most well-studied and (if I may say) important object in space, and on the other, you have something that seems to have appeared straight out of a sci-fi. But physics is universal, so even the most extreme or remotest parts of the universe are governed by the same physical laws as our local solar system. In fact, this is not the first time that black hole astronomers have learned something from solar astronomers!”, continues Dr. Ressler.

These findings will help future missions identify supermassive black hole binary pairs and link gravitational wave sources with visual counterparts in the sky. As another one of the contributors, CITA National Fellow Luciano Combi, affirms:

“Our new state-of-the-art simulations led and developed by Dr. Ressler represent a major step forward in modeling the plasma around supermassive binary black holes. Thanks to our team’s diverse expertise in magnetohydrodynamics, plasma physics, and curved spacetime, we have devised a few novel emission mechanisms occurring around binaries; surprisingly, these are analogous to phenomena occurring in our sun! Our hope is that these theoretical results will help detect pairs of giant black holes lurking in the center of galaxies.”

The video sequence above contains a three-dimensional visualization of the two jets in the simulation (in orange and yellow) as they spiral around each other and collide, potentially releasing a large amount of energy in the form of light. (Created by Sean Ressler)

Sean M. Ressler,��Luciano Combi,��Bart Ripperda, Elias R. Most, , ,��,��, DOI 10.3847/2041-8213/ad9eb5, Published 2025 January 22

Contact:
Lyuba Encheva
Communications and Events, CITA
lyuba@cita.utoronto.ca

Beyond the first wave: understanding binary neutron star and black hole formation channels

citaadmin — Mon, 23 Dec 2024 19:59:34 +0000

Beyond the first wave: understanding binary neutron star and black hole formation channels

Lieke Van Son (Harvard University) — November 25, 2024

Abstract

After the first waves of gravitational-wave detections, it often seems as though we are left with more questions than answers. The hope of finding “one formation channel to rule them all” has given way to “one channel for every system.” This shift is not necessarily a drawback: moving away from a single unifying framework allows us to focus on specific properties—such as mass ranges—and connect observed features to their progenitors.

In this talk, I will focus on lower-mass compact objects and discuss key findings on which recent studies are converging, such as: why binary neutron stars are expected to form through only a single channel, and why binary black hole formation is metallicity dependent, while binary neutron star formation is not (or much less so). I will explore the “if” and “why” behind each of these findings, their broader implications for merger predictions and cosmology, and how we can test them with upcoming gravitational-wave and electromagnetic observations.

Electromagnetic and Gravitational Wave Signals from Merging Black Holes and Neutron Stars

citaadmin — Thu, 08 Dec 2016 02:20:05 +0000

Given the increasing sensitivity of existing gravitational wave detectors, we expect gravitational waves from neutron star mergers to be observed in the coming years. In order to extract as much information as possible from these observations, reliable models of the gravitational wave and electromagnetic signals powered by mergers are necessary. In this talk, I will discuss our efforts to study binary mergers using general relativistic simulations. I will in particular focus on recently developed gravitational wave models which account for tidal effects in neutron stars, on the electromagnetic transients powered by radioactive decays in the matter ejected by neutron star mergers, and on the outcome of nucleosynthesis in that ejecta. Tidal effects in neutron star mergers can provide us with information about the size of neutron stars, an important observable in nuclear physics, while radioactively powered transients can offer both improved localization of the merger events and additional information about the properties of the merging objects.

Details

Francois Foucart

Lawrence Berkeley National Lab

December 8, 2016