Astronomers Discover Fastest-Evolving Radio Signals Ever Observed from Black Hole Tearing Apart Star

Artist’s interpretation of two massive black holes (MBHs) within a galaxy. A tidal disruption event unfolds around the MBH that resides away from the galactic center and matter from a disrupted star swirls into a bright accretion disk, launching an energetic outflow and resulting in two bright radio flares. Credit: NSF/AUI/NSF NRAO/P.Vosteen

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An international team of astronomers has discovered the first radio-bright tidal disruption event (TDE) occurring outside a galaxy's center, combining data from the Atacama Large Millimeter/submillimeter Array (ALMA) and from the Very Large Array (VLA) of the U.S. National Science Foundation National Radio Astronomy Observatory (NSF NRAO), along with several partner telescopes. The event, designated AT 2024tvd, revealed the fastest-evolving radio signals ever observed from this type of cosmic catastrophe.

The discovery, led by principal investigators Itai Sfaradi and Raffaella Margutti of the University of California, Berkeley, and others, represents a significant breakthrough in understanding how massive black holes can hide in unexpected places throughout the universe.

"This is truly extraordinary," said Sfaradi, lead author of the study. "Not only is this the first time we've observed such bright radio emission from a tidal disruption event happening away from a galaxy's center, but it's also evolving faster than anything we've seen before."

Tidal disruption events occur when a star ventures too close to a massive black hole and is torn apart by the black hole's immense gravitational forces. While these events typically occur at the centers of galaxies where supermassive black holes reside, AT 2024tvd was discovered approximately 0.8 kiloparsecs (about 2,600 light-years) away from its host galaxy's center.

The international team observed the event in great detail using a network of radio telescopes that covered a wide range of wavelengths, from centimeters to millimeters. Their data revealed an exceptionally fast and unusual evolution never before seen in this kind of phenomenon. The event produced two separate bursts of radio waves that brightened and faded far more rapidly than any known tidal disruption event. The first burst increased in brightness over a very short period of time and then dimmed almost as quickly, while the second flared up and faded even faster. These dramatic changes occurred on timescales many times shorter than those astronomers typically observe, showing that this was an extraordinarily dynamic and short-lived event.

"The radio emission from AT 2024tvd evolves so rapidly that it stands out even among the most extreme cosmic events we know," explained co-principal investigator Raffaella Margutti. "These observations are revealing new physics about how material behaves when launched from the vicinity of black holes," added Kate Alexander, PI of the VLA Program and professor at the University of Arizona.

The discovery utilized an extensive network of radio telescopes, including NSF NRAO's VLA and ALMA, the Arcminute Micro-Kelvin Imager Large Array (AMI-LA), the Allen Telescope Array (ATA), and the Submillimeter Array (SMA). This multi-telescope approach allowed the team to track the event's evolution across a wide range of radio frequencies over approximately 300 days.

The research suggests that the rapid radio evolution results from at least one—and possibly two—outflows launched significantly after the initial stellar disruption. The team's analysis indicates these outflows were likely launched 80 and 170 days after the optical discovery, challenging traditional models of how tidal disruption events unfold.

"What makes this discovery even more remarkable is that it reveals a massive black hole that would otherwise be invisible to us," said Raffaella Margutti, "The only reason we can detect this wandering black hole is because it happened to tear apart a star and produce these incredibly bright radio signals."

The off-nuclear position of this TDE provides crucial insights into the population of massive black holes that may be wandering through galaxies or recoiling from past interactions. Current theories suggest such black holes could result from triple black hole interactions or be remnants from galaxy mergers.

The team's sophisticated analysis also marks the first time that both free-free absorption and inverse-Compton cooling have been considered together in modeling TDE radio emission, providing new tools for understanding these extreme events.

"This discovery opens up entirely new possibilities for finding hidden black holes throughout the universe," noted Itai Sfaradi. "With upcoming sky surveys, we may discover that these off-nuclear tidal disruption events are more common than we thought."

The research also revealed a potential connection between the launch of radio-emitting outflows and changes in the event's X-ray emission, suggesting a link to accretion processes around the black hole.

AT 2024tvd was initially discovered by the Zwicky Transient Facility on August 25, 2024, at optical wavelengths before follow-up observations revealed its radio brightness and off-nuclear nature.

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

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Additional Information

The findings are published in The Astrophysical Journal Letters,and you can read them HERE.

This text is based on the press release by the National Radio Astronomy Observatory (NRAO), aALMA partner on behalf of North America.

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Southern Observatory (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 National Science and Technology Council (NSTC) in Taiwan, 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 leaders,/divhip and management of ALMA's construction, commissioning, and operation.

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Contacts:

Nicolás Lira
Education and Public Outreach Officer
Joint ALMA Observatory, Santiago - Chile
Phone: +56 2 2467 6519
Cel: +56 9 9445 7726
Email: nicolas.lira@alma.cl

Jill Malusky
Public Information Officer
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Phone: +1 304-456-2236
Email: jmalusky@nrao.edu

Yuichi Matsuda
Education and Public Outreach Officer
NAOJ
Email: yuichi.matsuda@nao.ac.jp

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Black Hole Flare is Biggest and Most Distant Seen

This artist's concept depicts a supermassive black hole in the process of shredding a massive star—at least 30 times the mass of our Sun—to pieces. Scientists propose this is what happened around the distant black hole referred to as J2245+3743, which in 2018, brightened dramatically to create the brightest black hole flare ever recorded, shining with the light of 10 trillion suns. This is likely the most massive star-shredding event (formally called a tidal disruption event or TDE) ever observed and one of only a few to have occurred in an active galactic nucleus (AGN), which is an active supermassive black hole "feeding" off material in a surrounding disk. The stunning flare was discovered by the Zwicky Transient Facility (ZTF), based at Caltech's Palomar Observatory, and the Caltech-led Catalina Real-Time Transient Survey. Credit: Caltech/R. Hurt (IPAC)

The 48-inch Samuel Oschin Telescope at Palomar Observatory, where ZTF resides.
Credit: Palomar/Caltech

Matthew Graham
Credit: Nick Macdonald

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The flare, co-discovered by the Zwicky Transient Facility, may be the result of a mega black-hole meal

The most massive stars in the universe are destined to explode as brilliant supernova before collapsing into black holes. Yet one huge star appears to have never fulfilled its destiny; in a twist of irony, the star wandered too close to a gargantuan black hole, which gobbled it up, shredding the star to bits and pieces.

That is the most likely explanation to come from authors of a new Nature Astronomy report describing the most powerful and most distant flare of energy ever recorded from a supermassive black hole. The cosmic object was first observed in 2018 by the US National Science Foundation (NSF)-funded Zwicky Transient Facility (ZTF), based at Caltech's Palomar Observatory, and the Caltech-led Catalina Real-Time Transient Survey, which is also funded by NSF. The flare rapidly brightened by a factor of 40 over a period of months, and, at its peak, was 30 times more luminous than any previous black hole flare seen to date. At its brightest, the flare shined with the light of 10 trillion suns.

The supermassive black hole behind the flare is a type of accreting, or feeding, black hole called an active galactic nucleus (AGN). Referred to as J2245+3743, this AGN is estimated to be 500 million times more massive than our Sun. It resides 10 billion light-years away in the remote universe. Because light has a finite speed and takes time to reach us, astronomers observe distant events like this one in the past, when the universe was young.

"The energetics show this object is very far away and very bright," says study lead author Matthew Graham, research professor of astronomy at Caltech, as well as the project scientist for ZTF, and a co-principal investigator of the project. "This is unlike any AGN we've ever seen."

Astronomers are continuing to monitor the black hole flare though it is fading over time. In fact, in addition to witnessing the object in the past, time itself runs slower at the remote site of the black hole compared to our own experience of time. "It's a phenomenon called cosmological time dilation due to stretching of space and time. As the light travels across expanding space to reach us, its wavelength stretches as does time itself," Graham explains, noting that long-lived surveys like ZTF and Catalina are important to fully witness events in the past because, in this case, "seven years here is two years there. We are watching the event play back at quarter speed."

To determine what could cause such a dramatic burst of light in the cosmos, the researchers thoroughly examined a list of possibilities, concluding that the most likely culprit is a tidal disruption event (TDE). This phenomenon occurs when a supermassive black hole's gravity shears a star that comes too close, slowly consuming the star over time as it spirals into the black hole. The fact that the black hole flare J2245+3743 is still going indicates that we are witnessing a star not yet fully devoured but rather like "a fish only halfway down the whale's gullet," Graham says.

If the flare is from a TDE, the scientists estimate that the supermassive black hole gobbled a star with a mass at least 30 times greater than that of our Sun. The previous record holder for the largest candidate TDE, an event nicknamed Scary Barbie after its initial ZTF classification as ZTF20abrbeie, was not nearly as intense. That TDE, which is also thought to have originated from an AGN, was 30 times weaker than that of J2245+3743, and its doomed star is estimated to have been between three and 10 solar masses.

Stellar Snack Within a Black Hole's Disk

Most of the roughly 100 TDEs seen to date do not take place around AGN—massive structures that consist of supermassive black holes surrounded by large, swirling disks of material that feed the central black hole. The AGN burble along, flaring up with their own feeding activity, which can mask TDE bursts and makes them harder to find. The recent jumbo flare J2245+3743, on the other hand, was so large that it was easier to see.

However, at first, J2245+3743 did not seem to be anything special. In 2018, after the object was first spotted, the researchers used the 200-inch Hale Telescope at Caltech's Palomar Observatory to obtain a spectrum of the object's light, but it did not reveal anything unusual. In 2023, the team noticed the flare was decaying slower than expected, so they obtained another spectrum from the W. M. Keck Observatory in Hawai‘i, which indicated the extreme brightness of this particular AGN.

"At first, it was important to establish that this extreme object was truly this bright," explains co-author K. E. Saavik Ford, a professor at the City University of New York (CUNY) Graduate Center and Borough of Manhattan Community College and American Museum of Natural History (AMNH). It was possible, she says, that the object could have been beaming the light toward us rather than glowing in all directions, but data from NASA's former Wide-field Infrared Survey Explorer (WISE) mission helped rule that out. In the end, after other scenarios were also ruled out, the researchers concluded that J2245+3743 was indeed the brightest black hole flare ever recorded.

"If you convert our entire Sun to energy, using Albert Einstein's famous formula E = mc2, that's how much energy has been pouring out from this flare since we began observing it," Ford says.

Once the team established the unprecedented brightness of the event, they looked at what could possibly have caused it. "Supernovae are not bright enough to account for this," Ford says, referring to one possibility. Instead, the team's favored explanation is a supermassive black hole slowly ripping a huge star to death.

"Stars this massive are rare," Ford says, "but we think stars within the disk of an AGN can grow larger. The matter from the disk is dumped onto stars, causing them to grow in mass."

Finding a black hole meal with such mega proportions indicates that other events like this are likely taking place across the cosmos. The researchers hope to mine through more ZTF data to find others, and the NSF and Department of Energy's Vera C. Rubin Observatory may likewise find unusually large TDEs.

"We never would have found this rare event in the first place if it weren't for ZTF," Graham says. "We've been observing the sky with ZTF for seven years now, so when we see anything flare or change, we can see what it has done in the past and how it will evolve."

The Nature Astronomy study titled "An Extremely Luminous Flare Recorded from a Supermassive Black Hole" was funded by the NSF, the Simons Foundation, NASA, and the German Research Foundation. Other Caltech authors include Andrew Drake, Yuanze Ding (MS '25), Mansi Kasliwal (PhD '11), Sam Rose, Jean Somalwar (now a postdoc at UC Berkeley), George Djorgovski, Shri Kulkarni, and Ashish Mahabal; Tracy Chen and Steven Groom of Caltech's IPAC astronomy center; and Daniel Stern of NASA's Jet Propulsion Laboratory (which is managed by Caltech). Additional authors are Barry McKernan of CUNY Graduate Center and Borough of Manhattan Community Collegeand AMNH; Matteo Cantiello of the Simons Foundation's Flatiron Institute and Princeton University; Mike Koss of Eureka Scientific; Raffaella Margutti of UC Berkeley; Phil Wiseman of University of Southampton, UK; Patrik Veres of Ruhr University in Bochum, Germany; and Eric Bellm of the University of Washington.

Caltech's ZTF is funded by the NSF and an international collaboration of partners. Additional support comes from the Heising-Simons Foundation and from Caltech. ZTF data are processed and archived by Caltech's IPAC. NASA supports ZTF's search for near-Earth objects through the Near-Earth Object Observations program.

Written by Whitney Clavin

Source: Caltech/News

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Contact:

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

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Investigation of the First Radio-Bright Off-Nuclear Tidal Disruption Event

Illustration of a tidal disruption event.
Credit: DESY, Science Communication Lab

Catastrophic encounters between stars and massive black holes usually take place in the nuclei of galaxies, but not always. Researchers recently reported on the brightest-ever radio emission from an off-nuclear tidal disruption event caused by a wandering or recoiling black hole.

Signature of a Roaming Black Hole

Tidal disruption events occur when a star ventures too close to a massive black hole. The tidal forces of the black hole stretch the star until it’s partially or entirely disrupted, sometimes causing jets or outflows to spray from the shredded star. One thing that often distinguishes a tidal disruption event from the sea of other possible transients is the location, close to the nucleus of a galaxy.

But not all tidal disruption events happen in the center of a galaxy. In rare cases, a massive black hole roaming elsewhere in a galaxy may encounter a star, sending out a tell-tale signal in an unexpected location.

One such event is AT 2024tvd, which was discovered at optical wavelengths by the Zwicky Transient Facility. Though the initial identification placed it at the center of its host galaxy, follow-up observations suggested that it was in fact 2,600 light years from the center. What can radio observations tell us about this rare off-center event?

Radio observations of AT 2024tvd on two dates after its optical discovery. The tidal disruption event was not detected at 88 days post-discovery (left) and outshone the center of its host galaxy on 160 days post-discovery (right). Credit: Sfaradi et al. 2025

Radio Reconnaissance

Less than three months after AT 2024tvd was discovered, Itai Sfaradi (University of California, Berkeley) and collaborators launched a months-long radio-wavelength observing campaign using the Very Large Array, the Atacama Large Millimeter/submillimeter Array, the Arcminute Microkelvin Imager Large Array, the Allen Telescope Array, and the Submillimeter Array. Radio observations are critical for investigating jets and outflows from tidal disruption events. The observations, which spanned centimeter and millimeter wavelengths, revealed two emission peaks from the tidal disruption event. The first peak occurred roughly 131 days after the event was discovered, and the second followed at day 194.

About 40% of the tidal disruption events that have been identified at optical wavelengths show this kind of delayed brightening at radio wavelengths, but AT 2024tvd stands out as having the fastest radio evolution ever seen. Even among fairly fast-evolving flares, AT 2024tvd is unusual, having a brighter second peak than peer events.

Demonstration of the fast evolution of AT 2024tvd’s radio emission (red and orange stars) compared to other radio-bright tidal disruption events (other symbols). Credit: Sfaradi et al. 2025

Prompt or Delayed, Outflow or Jet?

To understand the origin of the fast-evolving, extremely bright radio emission from AT 2024tvd, Sfaradi’s team modeled the emission that would arise from outflows and jets. For both wide-angle outflows and narrow jets, the team considered both prompt — arising simultaneously with the event’s optical detection — and delayed sources.

The team’s modeling highlighted several possible scenarios. In the first, both bright radio peaks arose from a single outflow that was launched about 84 days after the star met its doom. The double-peaked behavior is due to the outflow interacting with a complex distribution of material surrounding the black hole. It’s also possible for the two peaks to arise from separate outflows or jets, one launched around 84 days and the other around either 170 or 190 days, depending on whether the second source is a mildly relativistic outflow or a relativistic jet.

Sfaradi and collaborators posited that AT 2024tvd’s unusual radio behavior could be due to its off-nuclear location, but they acknowledged that this event might simply occupy a region of tidal disruption event parameter space that had yet to be explored. Sensitive interferometric or polarimetric observations may reveal more about how AT 2024tvd interacts with its environment, helping to illuminate the nature of this rare event.

By Kerry Hensley

Citation

“The First Radio-Bright Off-Nuclear TDE 2024tvd Reveals the Fastest-Evolving Double-Peaked Radio Emission,” Itai Sfaradi et al 2025 ApJL 992 L18. doi:10.3847/2041-8213/ae0a26

Source: American Astronomical Society/AAS-Nova

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Did That Supermassive Black Hole Rip Apart a Star, or Is It Eating Lunch Like Normal?

Artist's impression of a tidal disruption event — the ripping apart of a star by a black hole
Credit: NASA/JPL-Caltech

Title: An Untargeted Search for Radio-Emitting Tidal Disruption Events in the VAST Pilot Survey
Authors: Hannah Dykaar et al.
First Author’s Institution: University of Toronto
Status: Published in ApJ

supermassive black holes in the centers of most galaxies are notoriously, and predictably, violent actors in the universe. While some, classified as active galactic nuclei, act like a drain on their host galaxies, swallowing anything and everything that falls into them, even dormant black holes will react destructively when provoked. Orbit too closely, and any galactic nucleus will break you apart like a first-year chemistry student bumping an unsuspecting beaker off the lab bench.

If an ill-fated star falls into a black hole, the system will briefly glow across the electromagnetic spectrum. When and where these mishaps, known as tidal disruption events (TDEs, shown in Figure 1), occur, as well as the exact physical processes causing the brief glow, are not well understood. TDEs have been detected overwhelmingly in galaxies that do not have active galactic nuclei and are calming down after an era of intense star formation, and current models of the TDE occurrence rate disagree with observations. We expect to see more types of galaxies, such as those with active galactic nuclei, that host TDEs at similar rates, but we don’t — however, we might just be looking in the wrong places, or rather, with the wrong set of eyes.

Figure 1: An artist’s impression of a tidal disruption event observed with X-ray and optical telescopes. Credit: X-ray: NASA/CXC/Queen’s Univ. Belfast/M. Nicholl et al.; Optical/IR: PanSTARRS, NSF/Legacy Survey/SDSS; Illustration: Soheb Mandhai / The Astro Phoenix; Image Processing: NASA/CXC/SAO/N. Wolk

Traditionally, TDEs have been identified by their optical, ultraviolet, or X-ray emission, but active galactic nuclei are surrounded by dust, which absorbs light at these wavelengths on its way to us. However, at radio wavelengths, the issue of dust obscuration fades, allowing us to uncover the TDEs that may be hiding. While radio emission has been observed from known TDEs, identifying TDEs in the radio comes with a major hurdle, presented by the pesky active galactic nuclei themselves; they are famously variable in radio emission, and they can serve as pretty convincing TDE imposters.

Searching for TDEs at Radio Wavelengths

Today’s authors decide to take on this challenge, armed with data from the Variable and Slow Transients (VAST) pilot survey, which observes large swaths of the sky at regular intervals to track variability on the order of days to months. VAST is optimized for observing TDEs, but unfortunately, it is also excellent at finding active galactic nuclei. How do we know what to look for, and how can we distinguish a TDE from an active galactic nucleus? Easy, we can just identify characteristics common to all the known radio-emitting TDEs in the VAST field of view — all one of them, that is. Surely, that won’t do. Instead, our authors simulate the evolution of TDEs as seen by VAST, which can only catch discrete snapshots of light at a specific radio wavelength. Their models of TDE radio emission assume one of three cases: either the TDE produces a relativistic jet directed at us (on-axis), directed away from us (off-axis), or none at all. The presence or absence of a jet, and its direction, determine the shape of the light curve, as shown in Figure 2.

Figure 2: This figure shows the change in radio brightness over time we expect to see from a galaxy during a TDE given different models. The shape of the radio flare depends strongly on whether the TDE results in a relativistic jet, and if so, whether the jet points toward us (on-axis) or not (off-axis). These simulated light curves were used to establish criteria for TDE candidacy, and compared with observations from the final sample to constrain the incidence rate of TDEs and likelihood of different jet geometries. Credit: Dykaar et al. 2024

From these simulations, the authors identify three overarching characteristics that wannabe TDEs must exhibit: first, they must be variable, signaling the flare of activity as the star crashes into the black hole; second, the flare should be sufficiently bright compared to the galaxy’s normal brightness; and third, the flare must last for more than one observation, to ensure it is not a spurious detection. Additionally, the authors find that the peak brightness of the TDE must be double the typical galaxy brightness to effectively rule out active galactic nucleus imposters, which do not tend to vary this drastically, as shown in Figure 3. Lastly, the TDE must actually occur near the center of a galaxy (the black hole locale), as confirmed by optical or infrared survey catalogs. In the VAST pilot survey, 12 sources meet these criteria.

Figure 3: To distinguish TDEs from active galactic nucleus imposters, the authors kept only sources that exhibited one dominant peak in their radio flux, shown by the blue windows. Sources with secondary peaks (shown by the purple windows) that were much smaller than the primary peak were allowed, as the secondary peak could reasonably be due to ambient active galactic nucleus activity. However, multiple comparable peaks are indicative of only intrinsic active galactic nucleus fluctuations, not a TDE. Credit: Dykaar et al. 2024

Following Up on TDE Candidates at Other Wavelengths

The authors next subject these TDE candidates to thorough multi-wavelength scrutiny using archival survey data. First, they investigated whether the candidates are associated with gamma-ray bursts, which are extremely luminous and energetic events that may accompany TDEs. Unfortunately, gamma rays are easily absorbed, making them notoriously difficult to trace back to their sources. (After all, the journey of a gamma ray through light-years of dust and gas to Earth is not unlike Odysseus’s return to Ithaca, and we all know how many made that journey unscathed.)

The authors found that all 12 sources were coincident with a gamma-ray burst, but all 12 sources were also coincident with multiple gamma-ray bursts (which is unlikely to be physical), as were randomized, TDE-free regions of the VAST sky. In other words, the gamma-ray burst association is inconclusive. Contemporary optical and infrared observations of the candidates revealed no corresponding flares, which leads to more questions. Are the sources simply too far away for their optical and infrared flares to be discernible, or could dust absorption be at play? Additionally, nearly all candidates maintained an increased radio flux after the TDE flare. This may indicate that the TDE occurred within an active galactic nucleus as it was transitioning to a higher radio flux state, that the TDE was followed by intense star formation, or both.

By comparing their candidates to the expected observational manifestations of their TDE models, the authors conclude that the candidate sources are consistent with TDEs that have relativistic jets. They also independently constrain the TDE incidence rate, which agrees with current theory. As our window into the variable radio universe expands with future observations, such as with the ongoing VAST survey, we will have a growing population of such radio-detected TDEs to study, and the ability to distinguish them from regular active galactic nuclei will be ever more valuable in our quest to understand them.

Source: American Astronomical Society/AAS-Nova

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Editor’s Note: Astrobites is a graduate-student-run organization that digests astrophysical literature for undergraduate students. As part of the partnership between the AAS and astrobites, we occasionally repost astrobites content here at AAS Nova. We hope you enjoy this post from astrobites; the original can be viewed at astrobites.org.

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About the author, Chloe Klare:

I’m a PhD student in Astronomy and Astrophysics at Penn State, with a physics doctoral minor. In my research, I’m looking for newly evolving synchrotron jets in active galactic nuclei (in the radio!).

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NASA's Hubble Pinpoints Roaming Massive Black Hole

Six panel illustration of Black Hole TDE AT2024tvd

This six-panel illustration of a tidal disruption event around a supermassive black hole shows the following: 1) A supermassive black hole is adrift inside a galaxy, its presence only detectable by gravitational lensing; 2) A wayward star gets swept up in the black hole's intense gravitational pull; 3) The star is stretched or "spaghettified" by gravitational tidal effects; 4) The star's remnants form a disk around the black hole; 5) There is a period of black hole accretion, pouring out radiation across the electromagnetic spectrum, from X-rays to radio wavelengths; and 6) The host galaxy, seen from afar, contains a bright flash of energy that is offset from the galaxy's nucleus, where an even more massive black hole dwells. Artwork: NASA, ESA, STScI, Ralf Crawford (STScI)

Like a scene out of a sci-fi movie, astronomers using NASA telescopes have found “Space Jaws.”

Lurking 600 million light-years away, within the inky black depths between stars, there is an invisible monster gulping down any wayward star that plummets toward it. The sneaky black hole betrayed its presence in a newly identified tidal disruption event (TDE) where a hapless star was ripped apart and swallowed in a spectacular burst of radiation. These disruption events are powerful probes of black hole physics, revealing the conditions necessary for launching jets and winds when a black hole is in the midst of consuming a star, and are seen as bright objects by telescopes.

The new TDE, called AT2024tvd, allowed astronomers to pinpoint a wandering supermassive black hole using NASA’s Hubble Space Telescope, with similar supporting observations from NASA’s Chandra X-Ray Observatory and the NRAO Very Large Array telescope that also showed that the black hole is offset from the center of the galaxy.

The paper will be published in an upcoming issue of The Astrophysical Journal Letters.

Surprisingly, this one million-solar-mass black hole doesn’t reside exactly in the center of the host galaxy, where supermassive black holes are typically found, and actively gobble up surrounding material. Out of approximately 100 TDE events recorded by optical sky surveys so far, this is the first time an offset TDE has been identified. The rest are associated with the central black holes of galaxies.

In fact, at the center of the host galaxy there is a different supermassive black hole weighing 100 million times the mass of the Sun. Hubble’s optical precision shows the TDE was only 2,600 light-years from the more massive black hole at the galaxy’s center. That’s just one-tenth the distance between our Sun and the Milky Way’s central supermassive black hole.

This bigger black hole spews out energy as it accretes infalling gas, and it is categorized as an active galactic nucleus. Strangely, the two supermassive black holes co-exist in the same galaxy, but are not gravitationally bound to each other as a binary pair. The smaller black hole may eventually spiral into the galaxy’s center to merge with the bigger black hole. But for now, it is too far separated to be gravitationally bound.

A TDE happens when an infalling star is stretched or “spaghettified” by a black hole’s immense gravitational tidal forces. The shredded stellar remnants are pulled into a circular orbit around the black hole. This generates shocks and outflows with high temperatures that can be seen in ultraviolet and visible light.

“AT2024tvd is the first offset TDE captured by optical sky surveys, and it opens up the entire possibility of uncovering this elusive population of wandering black holes with future sky surveys,” said lead study author Yuhan Yao of the University of California at Berkeley. “Right now, theorists haven't given much attention to offset TDEs. “I think this discovery will motivate scientists to look for more examples of this type of event.”

Black Hole TDE AT2024tvd

This is a Hubble Space Telescope image of galaxy located 600 million light-years away that is host to the telltale signature of a roaming supermassive black hole. Visible in the Hubble image is a tidal disruption event (TDE), an intense flash of radiation caused by the supermassive black hole eating a star. The TDE appears as an isolated blue point source of ultraviolet light, while the galaxy is colored orange in visible light. The source is one of the first examples of a TDE significantly offset from the host galaxy's core by 2,600 light-years – where an even more massive active black resides. Hubble's precise angular resolution clearly shows this offset and confirms independent observations made with NASA's Chandra X-ray observatory. The photo taken on January 16, 2025 with Hubble's WFC3 detector in UV and visible light wavelengths. Science: NASA, ESA, STScI, Yuhan Yao (UC Berkeley); Image Processing: Joseph DePasquale (STScI)

A Flash in the Night

The star-snacking black hole gave itself away when several ground-based sky survey telescopes observed a flare as bright as a supernova. But unlike a supernova, astronomers know that this came from a black hole snacking on a star because the flare was very hot, and showed broad emission lines of hydrogen, helium, carbon, nitrogen, and silicon. The Zwicky Transient Facility at Caltech’s Palomar Observatory, with its 1.2-meter telescope that surveys the entire northern sky every two days, first observed the event.

“Tidal disruption events hold great promise for illuminating the presence of massive black holes that we would otherwise not be able to detect,” said Ryan Chornock, associate adjunct professor at UC Berkeley and a member of the ZTF team. “Theorists have predicted that a population of massive black holes located away from the centers of galaxies must exist, but now we can use TDEs to find them.”

The flare was seemingly offset from the center of a bright massive galaxy as cataloged by Pan-STARRS (Panoramic Survey Telescope and Rapid Response System), the Sloan Digital Sky Survey, and the DESI Legacy Imaging Survey. To better determine that it was not at the galactic center, Yao’s team used NASA’s Chandra X-ray Observatory to confirm that X-rays from the flare site were also offset.

It took the resolving power of Hubble to settle any uncertainties. Hubble’s sensitivity to ultraviolet light also allows it to pinpoint the location of the TDE, which is much bluer than the rest of the galaxy.

Black Hole TDE AT2024tvd (Hubble + Chandra)

This is a combined Hubble Space Telescope/Chandra X-Ray Observatory image of galaxy located 600 million light-years away that is host to the telltale signature of a roaming supermassive black hole. Visible in the Hubble image is a tidbr> ultraviolet light, while the galaxy is colored orange in visible light. In addition, X-ray light is captured by Chandra as a blue haze that surrounds the TDE. Both Hub.ble and Chandra observations were combined to pinpoint the TDE's location, which is offset from the center of the galaxy, which appears as a bright orange-white blob.

Origin Unknown

The black hole responsible for the TDE is prowling inside the bulge of the massive galaxy. The black hole only becomes apparent every few tens of thousands of years when it “burps” from capturing a star, and then it goes quiet again until its next meal comes along.

How did the black hole get off-center? Previous theoretical studies have shown that black holes can be ejected out of the centers of galaxies because of three-body interactions, where the lowest-mass member gets kicked out. This may be the case here, given the stealthy black hole’s close proximity to the central black hole. “If the black hole went through a triple interaction with two other black holes in the galaxy’s core, it can still remain bound to the galaxy, orbiting around the central region,“ said Yao.

An alternative explanation is that the black hole is the surviving remnant of a smaller galaxy that merged with the host galaxy more than 1 billion years ago. If that is the case, the black hole might eventually spiral in to merge with the central active black hole sometime in the very far future. So at present, astronomers don’t know if it’s coming or going.

Erica Hammerstein, another UC Berkeley postdoctoral researcher, scrutinized the Hubble images as part of the study, but did not find any evidence of a past galaxy merger. But she explained, “There is already good evidence that galaxy mergers enhance TDE rates, but the presence of a second black hole in AT2024tvd’s host galaxy means that at some point in this galaxy’s past, a merger must have happened.”

Specialized for different kinds of light, observatories like Hubble and Chandra work together to pinpoint and better understand fleeting events like these. Future telescopes that will also be optimized for capturing transient events like this one include the National Science Foundation’s Vera C. Rubin Observatory and NASA’s upcoming Nancy Grace Roman Space Telescope. They will provide more opportunities for follow-up Hubble observations to zero in on a transient’s exact location.

Source: NASA's/Hubble Space Telescope

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Explore More:

• Monster Black Holes are Everywhere
• Hubble Focus: Black Holes – Into the Vortex e-Book
• Science Behind the Discoveries: Black Holes
• Hubble's Universe Uncovered: Black Holes

The Hubble Space Telescope has been operating for over three decades and continues to make ground-breaking discoveries that shape our fundamental understanding of the universe. Hubble is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope and mission operations. Lockheed Martin Space, based in Denver, also supports mission operations at Goddard. The Space Telescope Science Institute in Baltimore, which is operated by the Association of Universities for Research in Astronomy, conducts Hubble science operations for NASA.

ZTF is a public-private partnership, with equal support from the ZTF Partnership and from the U.S. National Science Foundation.

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NSF VLA Contributes Crucial Puzzle Piece to ‘Peculiar’ High Energy Transient

Illustration of a tidal disruption event
Credit: ESA/C. Carreau
Hi-Res File

An artist's concept of the Einstein probe
Credit: NSF/AUI/NSF NRAO/J.Hellerman
Hi-Res File

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Non-detection at radio wavelengths may prove to be the critical clue toward categorizing EP240408a as an entirely new phenomenon

High-energy transient signals are most often determined to be gamma-ray burst events, but the recently-launched Einstein Probe has expanded astronomers’ ability to quickly respond to similar signals occurring at X-ray wavelengths. Now, a multi-wavelength study of EP240408a concludes that while many of the signal’s characteristics might lead to the conclusion that it is a gamma-ray burst, the non-detection at radio wavelengths precludes that possibility. Instead, the international team of astronomers suggest that EP240408a is either a rare jetted tidal disruption event or, perhaps, an entirely new type of astronomical phenomenon. This was discovered in only the first two months of the commissioning phase.

Tidal disruption events (TDEs) occur when a star is shredded by a nearby black hole; these events are themselves rare, with fewer than 100 discovered so far. In even more rare cases, the black hole’s powerful tidal forces propel some of the shredded stellar material outward in high-velocity jets, which then interact with nearby clouds of dust and gas and shine brightly in X-ray and radio. Thus far, only four TDEs are known to have relativistic-velocity jets associated with them

An international team of astronomers led by Brendan O’Connor, an astronomer at Carnegie Mellon University, analyzed the signal from EP240408a across the span of wavelengths from radio to X-ray and concluded that this X-ray transient is—thus far—unique. “It ticks the boxes for a bunch of different kinds of phenomena, but it doesn’t tick all of the boxes for anything,” O’Connor summarizes. “And I think the radio non-detection is a massive box that we don’t know how to not tick.”

The team’s expansive follow-up campaign further characterized the X-ray emissions from EP240408a and identified a potential host galaxy in optical wavelengths. Crucially, however, O’Connor notes the non-detection in radio wavelengths as potentially the deciding factor in fully categorizing the source. Observations from the U.S. National Science Foundation Very Large Array (NSF VLA), operated by the U.S. National Science Foundation National Radio Astronomy Observatory (NSF NRAO), at 11 days, 158 days, and 258 days after EP240408a’s initial discovery indicated no radio emission from the source.

“I think where radio really fits in is that when we see something this bright, for this long, in X-rays, it usually has an extremely luminous radio counterpart. And here we see nothing, which is extremely peculiar,” O’Connor says.

After methodically eliminating a number of potential explanations including active galactic nuclei, fast blue optical transients, fast X-ray transients, and other variations of previously-characterized phenomena, O’Connor and his co-authors conclude that EP240408a is extragalactic in origin and is most likely a relativistically-jetted Tidal Disruption Event.

“Because of this new wide field view of the X-ray universe, there’s a diverse range of phenomena we can see that weren’t possible before. And it looks like this transient, EP 240408a, is new. It’s something that we don’t think we’ve seen before,” O’Connor says. “It’s falling in a range of energy, of wavelengths, that it can be detected at, and the time scales are so short, that it’s probably something that we’ve just missed before now.”

O’Connor emphasizes that the current lack of radio emissions is pivotal, but that follow-up observations in radio wavelengths will hopefully yield future detections as the material within the jets slows down to energies corresponding to radio—a process expected to occur on timescales of roughly 1000 days. Thus, follow-up radio observations with the NRAO VLA will be imperative.

Thus, EP240408a appears to be giving astronomers an in-between glimpse of a high-energy transient’s signal after its initial X-ray outburst but before its relativistic-speed jet flares in radio. “It seems to me that this is the most likely explanation for why we aren’t seeing radio emission. Hopefully, eventually, we will see a jet at radio wavelengths, either with the current setup of the VLA or the Next Generation VLA, and we can monitor it for years to come in order to learn even more about this explosion,” O’Connor muses;

“These results highlight the importance of multiwavelength observations in fully understanding the astronomical object,” says Joe Pesce, NSF Program Director for the NRAO. “The complete picture of what’s really happening requires a holistic study.”

An international team of astronomers were involved in the study, including Dheeraj Pasham at MIT, Igor Andreoni at the University of North Carolina Chapel Hill, Jeremy Hare at the Catholic University of America, Paz Beniamini at the Open University of Israel, and Eleonora Troja at the University of Rome Tor Vergata, among others. You can read the full scientific paper here.

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

Source: National Radio Astronomy Observatory (NRAO)/News

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Black Hole Fireworks: Tidal Disruption Events Light Up Supermassive Black Holes

An illustration of an accretion disk forming around a supermassive black hole in the wake of a tidal disruption event.
Adapted from NASA/Swift/Aurore Simonnet, Sonoma State University

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Title: Late-Time Radio Flares in Tidal Disruption Events
Authors: Tatsuya Matsumoto and Tsvi Piran
First Author’s Institution: Kyoto University
Status: Published in ApJ

Hungry (and Loud) Black Holes

Tidal disruption events arise when a star wanders too close to a supermassive black hole that then exerts a tidal force across the star, shredding it. These events are relatively rare: we have only discovered a few hundred. When the star is disrupted, about two-thirds of the material remains bound. The remaining material is ejected from the supermassive black hole into the “circumnuclear medium,” or the region immediately surrounding the supermassive black hole. We typically discover tidal disruption events from the optical emission resulting from the initial disruption, which lasts several weeks. However, tidal disruption events are known to be multi-wavelength events visible across the electromagnetic spectrum. Before optical tidal disruption events were discovered, almost all of the tidal disruption events were found in the X-ray, where the formation of an accretion disk around the supermassive black hole may be powering some high-energy activity. On the other end of the spectrum, the radio properties of tidal disruption events have proven to be unique. Today’s article aims to explain the radio light curves of tidal disruption events.

The radio emission from tidal disruption events is caused by the material that survives the disruption of the star and is ejected away from the supermassive black hole. This stellar material runs into the ambient density surrounding the supermassive black hole, causing shocks inside the material. These shocks give rise to synchrotron radiation, an emission caused by free electrons in a plasma spiraling around magnetic field lines. Directly related to the density and energy of the material, the synchrotron radiation is emitted across the radio spectrum, typically at frequencies lower than 10 GHz, making it an excellent choice for instruments like the Very Large Array.

Second Peak, Second Life?

Although we know about a third of the material from the star is ejected away from the supermassive black hole after the disruption, we do not understand how the black hole launches this material. For example, supermassive black holes in active galactic nuclei can launch powerful relativistic jets as they accrete massive amounts of material. Or, in a less energetic scenario, a jet does not have to be launched, and the outflows could be in all directions and essentially non-relativistic. In yet another situation, the delayed formation of an accretion disk may induce a relativistic jet to be launched much later than the initial disruption. To complicate matters further, it is almost certain that tidal disruption events do not originate from an underlying homogeneous population and that a spectrum of disruption scenarios results in many different ejecta geometries.

Today’s article uses the non-relativistic approach to model the tidal disruption event scenario. The authors model a shock quasi-spherically propagating first through a circumnuclear medium with a radially decreasing density and then through an interstellar medium with constant density. Using a standard set of code and modeling packages for synchrotron emission, they produce light curves for what this model should look like. In this model, there are two peaks caused by differing effects. The radio emission is “self-absorbed” in the first peak and transitions to optically thin, eventually peaking. By measuring the peak frequency and luminosity, we can estimate the radius of the outflow and local circumnuclear medium density. Then, depending on the spectral index of the circumnuclear medium’s radial density profile, the light curve will fall and eventually reach a minimum at the Bondi radius of the supermassive black hole. At this point, the radial density profile becomes flat (i.e., constant density interstellar medium), and the radio light curve will rise again as the shock wave sweeps up material. The brightness will continue to increase until the swept-up mass is comparable to the mass from the original ejected outflow. After the second peak, the radio brightness decreases indefinitely.

How does this model compare to some real scenarios? The authors of today’s article select two well-known events from the literature and gather radio observations to compare with their modeled light curves. When comparing AT2019dsg and AT2020vwl, the double-peaked feature is evident in both light curves, as seen in Figure 1. The authors note that while the rapid t³ initial rise is well explained for both sources, other radio-loud tidal disruption events, such as AT2018hyz, rise even faster like t⁵ and thus are better candidates for relativistic models. The authors state that further observations at even later times will enable improvements to this model and constrain their parameters.

Figure 1: The late-time C-band (6 GHz) radio light curves of AT2019dsg and AT2020vwl. These sources have some of the best data quality and quantity in the literature. The double-peaked feature of our authors’ model is evident in the light curves of both events. Credit: Matsumoto & Piran 2024

Original astrobite edited by Archana Aravindan

Source: American Astronomical Society/AAS-Nova

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About the author, Will Golay:

I am a graduate student in the Department of Astronomy at Harvard University and the Center for Astrophysics | Harvard & Smithsonian, advised by Edo Berger. I study radio emission from transient astrophysical objects like tidal disruption events.

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Editor’s Note: Astrobites is a graduate-student-run organization that digests astrophysical literature for undergraduate students. As part of the partnership between the AAS and astrobites, we occasionally repost astrobites content here at AAS Nova. We hope you enjoy this post from astrobites; the original can be viewed at astrobites.org.

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NuSTAR Reveals Black Hole Shredding a Star

A star is being consumed by a nearby supermassive black hole, in a rare event that astronomers call a tidal disruption event (TDE). What makes this event, AT2022cmc, even more rare is that as the black hole ripped the star apart, jets of material moving at almost the speed of light were launched. AT2022cmc, depicted here in an artist’s impression, was the first jetted-TDE discovered in over a decade and the first since the launch of NuSTAR. The sensitive, broadband X-ray observation by NuSTAR provided critical data for understanding the event. Image credit: ESO/M.Kornmesser

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NuSTAR unveiled crucial details for understanding one of the most energetic types of event in the universe. If a star comes too close to a supermassive black hole, it will be torn apart by the black hole’s tidal force. Fundamentally, the side of the star closer to the black hole feels a stronger gravitational pull than the far side of the star, much like people on Earth feel stronger gravity than an astronaut in the International Space Station. However, you’d have to imagine an astronaut so tall that their feet were on Earth while their head was in orbit. And the difference in gravitational field would also be much larger. When a star comes extremely close to the black hole, it becomes stretched and is pulled apart. The resulting stream of material loops around the black hole. Some stellar material is captured into orbit, creating an accretion disk around the black hole. This disk becomes quite bright. In a very rare subclass of events, a relativistic jet is also produced, creating another source of light. As the disk material is consumed by the black hole over the course of months to years, the event gradually fades.

Tidal disruption events, or TDEs for short, were first predicted in the 1970s, and first observed in the 1990s. Currently, approximately 100 TDEs are known, only four of which are of the rare jetted-TDE variety.

Just after midnight on February 11, 2022, the Zwicky Transient Facility at Palomar Observatory in Southern California detected a new transient source. Data obtained over the next two nights led to this new source, AT2022cmc, being flagged as unusual, rising and falling faster than a typical supernova. This inspired follow-up observations using telescopes around the planet and in space. Those data provided the distance and energetics of the system, ultimately classifying it as a jetted-TDE. This subclass of TDE is very bright at X-ray energies, and only four have been detected to date. The most recent jetted-TDE occurred more than a decade ago, prior to the launch of NuSTAR. NuSTAR is the first focusing high-energy, or hard X-ray telescope in orbit, providing two orders of magnitude improvement in sensitivity compared to previous instruments. NuSTAR significantly extends the range of X-ray energies that can be studied in detail for astrophysical phenomena. AT2022cmc provided the first opportunity to study this type of rare, X-ray bright, transient event and motivated three NuSTAR observations in the month after its discovery.

While the lower energy emission from jetted-TDEs is relatively well understood (e.g., at radio, optical, and UV energies), the location and mechanism producing the bright X-ray emission in jetted-TDEs is a topic of active debate. The most popular scenario is that the X-rays come from less energetic photons in the radio and optical bands being scattered by energetic relativistic electrons in the surrounding plasma up to X-ray energies. This scenario predicts that we should see the high-energy X-ray spectrum as a smooth extrapolation of the lower-energy X-ray spectrum. However, when NuSTAR observed AT2022cmc, it detected a pronounced break in the X-ray spectrum within the NuSTAR band. This break gives an important clue to the X-ray emission mechanisms of jetted-TDEs.

In a recent paper published in the Astrophysical Journal, Dr. Yuhan Yao of the University of California, Berkeley and her team report that the NuSTAR data and spectral break are consistent with a phenomenon known as synchrotron radiation, created as relativistic charged particles (i.e., electrons) move through a strong magnetic field. This is naturally expected from astrophysical jets, though the leading jetted-TDE models had predicted it to be subdominant to the up-scattered emission in jetted-TDEs. Modeling the X-ray data, Dr. Yao and her team were able to constrain the properties of the jet and determine what part of the jet is dominating its X-ray emission. They find that the jet is likely to be starved of protons, and instead is dominated by electrons moving in a highly magnetized jet.

AT2022cmc represents a significant leap in our understanding of relativistic jets in astrophysical phenomena. “The NuSTAR data challenge existing models and suggest that magnetic reconnection plays a key role in accelerating particles within these jets,” noted Dr. Yao. This result not only sheds light on the inner workings of TDEs but also has broader implications for understanding relativistic jets in other high-energy astrophysical sources, such as gamma-ray bursts. Dr. Yao explained, “overall, this work contributes to the ongoing quest to decipher the composition and acceleration mechanisms of relativistic jets in the Universe.”

Source: NASA's Nuclear Spectroscopic Telescope Array (NuSTAR)/News

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NASA's Roman Space Telescope Could Help Researchers Detect the Universe’s First Stars

Tidal Disruption of a Star (Artist’s Concept)
Credits: Illustration: Ralf Crawford (STScI)

Images

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The first stars to form in the universe were very different from our Sun. Known to astronomers (somewhat paradoxically) as Population III, or Pop III, stars, they were made almost entirely of hydrogen and helium. They are believed to have been much larger, hotter, and more massive than our Sun. As a result, Pop III stars use their fuel more quickly and have shorter lifespans.

Pop III stars, which came about in the first few hundred million years after the big bang, are crucial in understanding the development of the universe. These stars were the nuclear furnaces where the first elements heavier than helium, which astronomers call metals, were generated, and ultimately are the reason for the complex systems of galaxies in the current universe.

No Pop III stars are found around us today, so to learn about them we must look back to the early universe. NASA’s Nancy Grace Roman Space Telescope will provide a panoramic field of view 200 times larger than the infrared view of the sky from NASA’s Hubble Space Telescope and survey the sky 1,000 times faster. As a result, Roman may be a key tool for helping astronomers see this rare first generation of stars after it launches by May 2027.

Shredded Stars

The new approach will not seek intact stars. Instead, astronomers will hunt for signs of Pop III stars that have been shredded by black holes, creating a bright and energetic phenomenon known as a tidal disruption event (TDE).

If a star moves close enough to a black hole, the star will experience gravitational tides strong enough to completely disrupt it. Some of the material from the disrupted star then collects into an accretion disk, where complex physical processes cause it to glow brightly enough to be seen from billions of light-years away.

"Since we know that black holes likely exist at these early epochs, catching them as they’re devouring these first stars might offer us the best shot to indirectly detect Pop III stars," noted Priyamvada Natarajan of Yale University, a co-author of the study.

TDEs generate light in many wavelengths, including X-ray, radio, ultraviolet (UV), and optical light. The further we look into the early universe, where these early stars primarily reside, the more the optical and UV light is redshifted, or stretched by the expanding universe, into near-infrared wavelengths visible to Roman.

Not only does the wavelength of light stretch – so does the observed timescale of the TDE. Like an exploding star or supernova, a TDE is a transient event that increases quickly in brightness and then gradually decreases over time. But due to the large redshift of these events, a Pop III TDE would brighten over the course of hundreds to thousands of days, while its decline would last more than a decade.

“The evolution timescales of Pop III TDEs are very long, which is one feature that could distinguish a Pop III TDE from other transients including supernovas and TDEs of current-generation stars like our Sun,” said Rudrani Kar Chowdhury, postdoctoral fellow of the University of Hong Kong and first author of the study.

“Since they last for a longer time, a Pop III TDE might be easier to detect, but it might be harder to identify as a transient,” added co-author Jane Dai, professor of astrophysics at the University of Hong Kong. “Scientists would need to design the right survey strategy.”

A Coordinated Hunt

While NASA’s James Webb Space Telescope is powerful enough to detect and study TDEs in the early universe, its field of view is too small to make it an efficient TDE hunter. Of Roman’s core community surveys, the most promising for finding TDEs is the High Latitude Wide Area survey, which aims to cover approximately 2,000 square degrees of the sky outside of the plane of our galaxy.

“Roman can go very deep and yet cover a very big area of the sky. That's what's needed to detect a meaningful sample of these TDEs,” said Dai.

Webb would be useful for follow-up observations, however, particularly with its suite of spectroscopic tools. Once Roman detects these TDEs, Webb’s instruments could identify if any metals are present.

“Since these stars are only made up of hydrogen and helium, we will not see any metal lines in the spectrum of objects, whereas in the spectra of TDEs from regular stars we can see various metal lines,” Kar Chowdhury noted.

With this proposed strategy for identifying Pop III stars, there’s an opportunity to explore more of the universe’s mysteries, opening up numerous opportunities to better understand not only the early universe, but also galaxies closer to home.

This research has been published in the Astrophysical Journal Letters.

The Nancy Grace Roman Space Telescope is managed at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, with participation by NASA's Jet Propulsion Laboratory and Caltech/IPAC in Southern California, the Space Telescope Science Institute in Baltimore, and a science team comprising scientists from various research institutions. The primary industrial partners are BAE Systems, Inc. in Boulder, Colorado; L3Harris Technologies in Melbourne, Florida; and Teledyne Scientific & Imaging in Thousand Oaks, California.

Source: Space Telescope Science Institute (STScI)/Press Releases

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About This Release

Credits:

Media Contact:

Matthew Brown
Space Telescope Science Institute, Baltimore, Maryland

Christine Pulliam
Space Telescope Science Institute, Baltimore, Maryland

Science: Jane Dai (University of Hong Kong), Rudrani Kar Chowdhury (University of Hong Kong)

Permissions: Content Use Policy

Related Links and Documents

• Science Paper: Detecting Population III Stars through Tidal Disruption Events in the Era of JWST and Roman, PDF (1.44 MB)
• "Detecting Population III Stars through Tidal Disruption Events in the Era of JWST and Roman" by R. Kar Chowdhury et al.

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Sleeping Supermassive Black Holes Awakened Briefly by Shredded Stars

This image, captured by the Very Long Baseline Array (VLBA), shows the Compact Symmetric Object (CSO) known as J1734+0926. The red blobs are the ends of a powerful bipolar jet emanating from an unseen black hole.Credit: M.L. Lister/Purdue University

This illustration shows how Compact Symmetric Objects, or CSOs, likely form. When a single, massive star wanders too close to a black hole (left), it is devoured. This causes the black hole to shoot out an ultrafast, bipolar jet (center). The jet extends outward and its hot ends glow with radio emissions (right). Credit: B. Saxton/NRAO/AUI/NSF

This image, taken by the Very Long Baseline Array (VLBA), shows two supermassive black holes, which appear as the blobs with red strips. The black holes are in the center of an elliptical galaxy. Colors represent different spectral slopes in radio emission, with red showing the most dense regions surrounding the black holes. The black hole on the right has likely recently devoured a massive star, which caused it to shoot out two ultrafast jets. The ends of those jets appear as green blobs above and below the black hole. This object, called J0405+3803, is referred to as a Compact Symmetric Object (CSO), because its jets are relatively close-in (or compact), compared to other black holes with much larger jets.Credit: H.L. Maness/Grinnell College

Tony Readhead

Cosmic objects called Compact Symmetric Objects (CSOs) likely form when a single, massive star wanders too close to a supermassive black hole and is shredded to pieces. The process, highlighted in this animation, results in fierce bipolar jets that last up to 5,000 years. Credit: B. Saxton/NRAO/AUI/NSF

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Radio observations of Compact Symmetric Objects (CSOs) provide new clues about their origins

Readhead first suspected that CSOs might be fueled by TDEs back in the 1990s, but he says the idea went largely unnoticed by the scientific community. "The hypothesis was all but forgotten because years went by before observational evidence began to mount for TDEs," he says. At the time of his original hypothesis, only three CSOs had been found.

Fast forward to 2020. Readhead, who had paused his studies of CSOs to delve into different problems in radio astronomy, decided it was time to revisit the topic. He gathered some of his colleagues together on Zoom, and they decided to comb through literature and weed out objects that had been misclassified as CSOs. Over the next two years, the team investigated more than 3,000 CSO candidates, narrowing the group down to only dozens that had the criteria to be real CSOs.

Ultimately, a picture began to emerge of CSOs as an entirely distinct family with jets that die out much sooner than their gigantic brethren, such as those of the extremely powerful Cygnus A, a galaxy that shoots out extremely powerful jets that glow brightly at radio wavelengths. These jets stretch to distances of about 230,000 light-years in each direction and last tens of millions of years. In contrast, the CSO jets extend to about 1,500 light-years at most and die out by about 5,000 years.

According to the astronomers, the CSO jets likely form when a supermassive black hole snacks on not just any star, but a substantial one.

"The TDEs we've previously seen only lasted for a few years," Ravi says. "We think that the remarkable TDEs powering CSOs last far longer because the disrupted stars are very large in size, very massive, or both."

By analyzing the varied collection of CSO radio images, the researchers say they can trace how the objects age over time, almost like looking at a photo album of a CSO's life to observe how its jets evolve. The younger CSOs have shorter jets that are closer to the black holes, while the older objects have jets that extend further out from their black hole. Though most of the jets die out, the scientists estimate that one in 100 will go onto to become long-lived like those of Cygnus A. In those rare cases, the galaxies are likely merging with other galaxies, a turbulent process that provides a large quantity of fuel.

If the discoveries of Readhead and his team are confirmed with additional observations, the CSOs will provide a whole new avenue for studying how massive stars at the centers of galaxies interact with supermassive black holes.

"These objects are indeed a distinct population with their own distinct origin, and it is up to us now to learn more about them and how they came to be," Readhead says. "Being able to study these objects on timescales of years to decades rather than millions of years has opened the door to a whole new laboratory for studying supermassive black holes and the many unexpected and unpredictable surprises they hold."

The three studies are, "Compact Symmetric Objects - I Towards a Comprehensive Bona Fide Catalog," "Compact Symmetric Objects – II Confirmation of a Distinct Population of High-Luminosity Jetted Active Galaxies," and "Compact Symmetric Objects – III Evolution of the High-Luminosity Branch and a Possible Connection with Tidal Disruption Events." The studies were funded by NSF, NASA, Caltech, the Max Planck Institute for Radio Astronomy in Bonn, Germany, and the European Research Council.

Written by Whitney Clavin

Source: Caltech/News

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Contact:

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

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