Supernova’s ‘Trapped’ Jet Reveals Source of Fast X-ray Transient

This image shows the cosmic field in which the fast X-ray transient EP 250108a, and the supernova that followed it, were detected by Einstein Probe (EP) in early 2025. Using a combination of telescopes, including the W. M. Keck Observatory, a team of astronomers studied the evolving signal of EP 250108a/SN 2025kg to uncover details about its origin. Their analysis reveals that fast X-ray transients can result from the ‘failed’ explosive death of a massive star. Credit: International Gemini Observatory/NOIRLab/NSF/AURA.

Maunakea, Hawaiʻi – An international team of astrophysicists using W. M. Keck Observatory on Maunakea, Hawaiʻi Island have uncovered a possible origin of fast X-ray transients (FXTs) — mysterious, fleeting bursts of X-rays that have long puzzled astronomers.

Using a combination of telescopes around the globe and in space, the team studied the closest FXT associated with the explosive death of a massive star, or supernova, ever observed. A geyser of high-energy particles, or jet, trapped inside a supernova produced the FXT, the scientists discovered.

When jets burst through a massive star’s onion-like layers, they generate gamma-ray bursts (GRBs), the most powerful and luminous explosions in the universe. When the jets are stifled, however, they emit lower levels of energy, which astronomers can detect only from X-ray signals. The new observations now point to these “failed” jets as a source of the emission, explaining the historically elusive phenomena.

This finding marks a significant step in understanding the diverse landscape of cosmic explosions — bridging the gap among FXTs, GRBs and supernovae.

A pair of studies, led by Northwestern University and the University of Leicester in England, has been accepted by The Astrophysical Journal Letters.

“Since the 1970s, astronomers have detected FXTs — blasts of X-rays from distant galaxies that can last from seconds to hours,” said Northwestern’s Jillian Rastinejad, lead author of one of the studies. “But their origin sources have remained a long-standing mystery. Our work definitively shows that FXTs can originate from the explosive death of a massive star. It also supports a causal link between GRB-supernovae and FXT-supernovae, in which GRBs are produced by successful jets, and FXTs are produced by trapped weak jets.”

The team utilized the various time zones and locations of its members to gather and analyze the data, passing it along to the next time zone to make decisions on the next night of observations.

“The result? A massive and beautiful stream of data collected from facilities large and small, on the ground and in space, chronicling this event’s first month. It takes really special events to motivate such a global effort, and this FXT was one,” said Northwestern’s Wen-fai Fong, a senior author on the study.

This sequence of images shows the fading light of the supernova SN 2025kg, which followed the fast X-ray transient EP 250108a, a powerful blast of X-rays that was detected by Einstein Probe (EP) in early 2025. Using a combination of telescopes, including the W. M. Keck Observatory, a team of astronomers studied the evolving signal of EP 250108a/SN 2025kg to uncover details about its origin. Their analysis reveals that fast X-ray transients can result from the ‘failed’ explosive death of a massive star. Credit: International Gemini Observatory/NOIRLab/NSF/AURA.

Spectroscopy obtained from Keck Observatory’s Low-Resolution Imaging Spectrometer (LRIS) revealed that SN 2025kg is a Type Ic-BL supernova—an especially fast and powerful kind of stellar explosion. By analyzing the light, scientists measured how quickly the star’s material was ejected (nearly 19,000 kilometers per second or about 11,800 miles per second) and gained insight into the immense energy released during the blast.

“The fact that Keck Observatory was able to respond quickly to a transient of interest was pivotal to understanding the composition and speed of the supernova ejecta, and how much material was shed,” said Fong. “Its nimble capabilities were particularly important at later times when the source was fainter and only detectable with the most sensitive ground-based spectrographs.”

“This result highlights the important role Keck Observatory plays with observatories across the globe and in space,” added John O’Meara, chief scientist and deputy director at the observatory. “The international team has really pulled out all the stops to characterize and understand this new type of transient.”

“The fact that Keck Observatory was able to respond quickly to a transient of interest was pivotal to understanding the composition and speed of the supernova ejecta, and how much material was shed,” said Fong. “Its nimble capabilities were particularly important at later times when the source was fainter and only detectable with the most sensitive ground-based spectrographs.”

“This result highlights the important role Keck Observatory plays with observatories across the globe and in space,” added John O’Meara, chief scientist and deputy director at the observatory. “The international team has really pulled out all the stops to characterize and understand this new type of transient.”

An explosive neighbor

Although astronomers have detected FXTs for decades, the limited number of discoveries prevented detailed studies. But now, scientists have a new space-based tool, called the Einstein Probe, which is dedicated to the search. Launched in January 2024 by the Chinese Academy of Sciences in partnership with the European Space Agency and the Max Planck Institute for Extraterrestrial Physics, the Einstein Probe carries two scientific instruments, specially designed to observe X-ray sources.

“FXTs have long fascinated us but their study has relied on a small number of events that were discovered in serendipitous ways,” Fong said. “The Einstein Probe has revolutionized this field by increasing the number of known events by ten-fold in just a year of operations. Thus, it is not only filling in the previously sparse landscape of FXTs, but also making our picture of that landscape crisper, bringing facets of these explosions into focus that we had not imagined before.

Shortly after its launch, the Einstein Probe captured the most nearby FXT, associated with a supernova, to date. Dubbed EP 250108a, the FXT was located 2.8 billion light-years away from Earth, within the river-like constellation Eridanus. Its close proximity to Earth gave astronomers an unprecedented opportunity to observe the event’s evolution.

To track this evolving behavior, the team captured the event’s signal across multiple wavelengths. The Gemini South telescope at the International Gemini Observatory provided near-infrared data, the Gemini North telescope atop Maunakea provided optical data, the MMT Observatory in Arizona provided the infrared images, and the James Webb Space Telescope provided highly sensitive infrared data.

Failed jet, big breakthrough

By analyzing the rapidly evolving signal of EP 250108a, the scientists concluded the object is likely a “failed” GRB. Although EP 250108a is similar to a jet-driven explosion, its jets did not break through the outer layer of the dying star. Instead, the jets remained trapped inside.

“Through decades of scientific study, we know that jets can successfully plow through a dying star’s outer layers, and we view them as GRBs,” Rastinejad said. “In our study, we found this ‘trapped’ jet outcome is more common in massive star explosions than jets that successfully emerge from the star.”

The researchers now plan to use datasets provided by the Vera C. Rubin Observatory that will show how stars and their explosive deaths change over time. These insights could help reveal the inner workings of FXTs and many other exotic cosmic events.

Related Links:

• Science Paper by Rastinejad et. al

Source: W. M. Keck Observatory/News

---

Biggest Boom Since the Big Bang: Hawaiʻi-Based Astronomers Uncover the Most Energetic Explosions In The Universe Yet Discovered

Artist’s concept of the formation of Extreme Nuclear Transients (ENTs)
Credit: W. M. Keck Observatory / Adam Makarenko

Releasing more energy than 100 supernovae, Extreme Nuclear Transients (ENTs) are the most energetic transients yet observed

Maunakea, Hawaiʻi – Astronomers using data from the W. M. Keck Observatory on Maunakea, Hawaiʻi Island discovered the most energetic cosmic explosions discovered to date, naming the new class of events “extreme nuclear transients” (ENTs). These extraordinary phenomena occur when massive stars—at least three times heavier than our Sun—are torn apart after wandering too close to a supermassive black hole. Their disruption releases vast amounts of energy visible across enormous distances.

The team’s findings were detailed today in the journal Science Advances.

“We’ve observed stars getting ripped apart as tidal disruption events for over a decade, but these ENTs are different beasts, reaching brightnesses nearly ten times more than what we typically see,” said Jason Hinkle, who led the study as the final piece of his doctoral research at the University of Hawaiʻi’s Institute for Astronomy (IfA). “Not only are ENTs far brighter than normal tidal disruption events, but they remain luminous for years, far surpassing the energy output of even the brightest known supernova explosions.”

The immense total energy output of these ENTs are truly unprecedented. The most energetic ENT studied, named Gaia18cdj, emitted an astonishing 25 times more energy than the most energetic supernovae known. While typical supernovae emit as much energy as the Sun does in its 10 billion-year lifetime, ENTs radiate the energy of 100 Suns.

ENTs were first uncovered when Hinkle began a systematic search of public surveys for long-lived flares emanating from the centers of galaxies. He identified two unusual flares in data from the European Space Agency’s Gaia mission that were detected in 2016 and 2018.

“Gaia doesn’t tell you the physics of the event, just that something changed in brightness,” said Hinkle. The discovery launched a multi-year follow-up campaign to figure out what these sources were.

Meanwhile, a third event with similar properties was discovered in 2020 by the Zwicky Transient Facility (ZTF) and reported independently by two teams in 2023. Using data from the Keck Observatory Archive (KOA) for this new ZTF object showed it was similar to the two Gaia ENTs, adding strong support that ENTs are a distinct new class of extreme astrophysical events.

Drawing on observations from a wide array of ground- and space-based telescopes, the team determined these extraordinary events could not be supernovae because they release far more energy than any known stellar explosion. The sheer energy budget, combined with their smooth and prolonged light curves, firmly pointed to an alternative mechanism: accretion onto a supermassive black hole.

However, ENTs differ significantly from normal black hole accretion, when materials surrounding the black hole heat up and emit light and typically show irregular and unpredictable changes in brightness. The smooth and long-lived flares of ENTs indicate a distinct physical process—the gradual accretion of a disrupted star by a supermassive black hole.

Benjamin Shappee, Associate Professor at IfA and study co-author, emphasized the implications: “ENTs provide a valuable new tool for studying massive black holes in distant galaxies. Because they’re so bright, we can see them across vast cosmic distances—and in astronomy, looking far away means looking back in time. By observing these prolonged flares, we gain insights into black hole growth during a key era known as cosmic noon, when the universe was half its current age when galaxies were happening places—forming stars and feeding their supermassive black holes 10 times more vigorously than they do today.”

The rarity of ENTs, occurring at least 10 million times less frequently than supernovae, makes their detection challenging and dependent on sustained monitoring of the cosmos. Future observatories like the Vera C. Rubin Observatory and NASA’s Nancy Grace Roman Space Telescope promise to uncover many more of these spectacular events, revolutionizing our understanding of black hole activity in the distant, early universe.

“These ENTs don’t just mark the dramatic end of a massive star’s life,” stated Hinkle. “They illuminate the processes responsible for growing the largest black holes in the universe.”

Source: W. M. Keck Observatory/Science News

---

Related Links:

• Keck Observatory Archive (KOA)
• Science Paper by Jason Hinkle et al.
• NASA Press Release
• University of Hawaiʻi News

---

Media Contact:

Meagan O’Shea
moshea@keck.hawaii.edu

---

Gargantuan Black Hole Jets Are Biggest Seen Yet

An artist’s illustration of the longest black hole jet system ever observed. Nicknamed Porphyrion after a mythological Greek giant, these jets span roughly 7 megaparsecs, or 23 million light-years. That is equivalent to lining up 140 Milky Way galaxies back-to-back. Porphyrion dates back to a time when our universe was less than half its present age. During this early epoch, the wispy filaments that connect and feed galaxies, known as the cosmic web, were closer together than they are now. Consequently, this colossal jet pair extended across a larger portion of the cosmic web compared to similar jets in our nearby universe. Porphyrion’s discovery thus implies that jets in the early universe may have influenced the formation of galaxies to a greater extent than previously believed. Image credit: E. Wernquist / D. Nelson (IllustrisTNG Collaboration) / M. Oei

---

The jumbo jets blast hot plasma well beyond their own host galaxy

Maunakea, Hawaiʻi – Astronomers have spotted the biggest pair of black hole jets ever seen, spanning 23 million light-years in total length. That’s equivalent to lining up 140 Milky Way galaxies back to back.

“This pair is not just the size of a solar system, or a Milky Way; we are talking about 140 Milky Way diameters in total,” says Martijn Oei, a Caltech postdoctoral scholar and lead author of the new study. “The Milky Way would be a little dot in these two giant eruptions.”

The study, which includes data from W. M. Keck Observatory on Maunakea, Hawaiʻi, published online today in the journal Nature and will be featured on the cover of the print issue tomorrow, September 19.

The jet megastructure, nicknamed Porphyrion after a giant in Greek mythology, dates to a time when our universe was 6.3 billion years old, or less than half its present age of 13.8 billion years. These fierce outflows—with a total power output equivalent to trillions of suns—shoot out from above and below a supermassive black hole at the heart of a remote galaxy.

Prior to Porphyrion’s discovery, the largest confirmed jet system was Alcyoneus, also named after a giant in Greek mythology. Alcyoneus, which was discovered in 2022 by the same team that found Porphyrion, spans the equivalent of around 100 Milky Ways. For comparison, the well-known Centaurus A jets, the closest major jet system to Earth, spans 10 Milky Ways.

The latest finding suggests that these giant jet systems may have had a larger influence on the formation of galaxies in the young universe than previously believed. Porphyrion existed during an early epoch when the wispy filaments that connect and feed galaxies, known as the cosmic web, were closer together than they are now. That means enormous jets like Porphyrion reached across a greater portion of the cosmic web compared to jets in the local universe.

“Astronomers believe that galaxies and their central black holes co-evolve, and one key aspect of this is that jets can spread huge amounts of energy that affect the growth of their host galaxies and other galaxies near them,” says co-author George Djorgovski, professor of astronomy and data science at Caltech. “This discovery shows that their effects can extend much farther out than we thought.”

Lurking in the Past

To find the galaxy from which Porphyrion originated, the team used the Giant Metrewave Radio Telescope in India along with ancillary data from a project called Dark Energy Spectroscopic Instrument, which operates from Kitt Peak National Observatory in Arizona. The observations pinpointed the home of the jets to a hefty galaxy about 10 times more massive than our Milky Way.

The team then used the Keck Observatory to show that Porphyrion is 7.5 billion light-years from Earth.

“Up until now, these giant jet systems appeared to be a phenomenon of the recent universe,” Oei says. “If distant jets like these can reach the scale of the cosmic web, then every place in the universe may have been affected by black hole activity at some point in cosmic time,” Oei says.

Keck Observatory’s Low Resolution Imaging Spectrometer (LRIS) also revealed that Porphyrion emerged from what is called a radiative-mode active black hole, as opposed to one that is in a jet-mode state. When supermassive black holes become active—in other words, when their immense forces of gravity tug on and heat up surrounding material—they are thought to either emit energy in the form of radiation or jets. Radiative-mode black holes were more common in the young, or distant, universe, while jet-mode ones are more common in the present-day universe.

The fact that Porphyrion came from a radiative-mode black hole came as a surprise because astronomers did not know this mode could produce such huge and powerful jets. What is more, because Porphyrion lies in the distant universe where radiative-mode black holes abound, the finding implies there may be a lot more colossal jets left to be found.

Porphyrion: Largest Known Black Hole Jet System
Credit: Caltech - Vimeo

Ongoing Mysteries

How the jets can extend so far beyond their host galaxies without destabilizing is still unclear.

“Martijn’s work has shown us that there isn’t anything particularly special about the environments of these giant sources that causes them to reach those large sizes,” says Hardcastle, who is an expert in the physics of black hole jets. “My interpretation is that we need an unusually long-lived and stable accretion event around the central, supermassive black hole to allow it to be active for so long—about a billion years—and to ensure that the jets keep pointing in the same direction over all of that time. What we’re learning from the large number of giants is that this must be a relatively common occurrence.”

As a next step, Oei wants to better understand how these megastructures influence their surroundings. The jets spread cosmic rays, heat, heavy atoms, and magnetic fields throughout the space between galaxies.

Oei is specifically interested in finding out the extent to which giant jets spread magnetism.

“The magnetism on our planet allows life to thrive, so we want to understand how it came to be,” he says. “We know magnetism pervades the cosmic web, then makes its way into galaxies and stars, and eventually to planets, but the question is: Where does it start? Have these giant jets spread magnetism through the cosmos?”

Source: W. M. Keck Observatory/Science News

---

About LRIS

The Low Resolution Imaging Spectrometer (LRIS) is a very versatile and ultra-sensitive visible-wavelength imager and spectrograph built at the California Institute of Technology by a team led by Prof. Bev Oke and Prof. Judy Cohen and commissioned in 1993. Since then it has seen two major upgrades to further enhance its capabilities: the addition of a second, blue arm optimized for shorter wavelengths of light and the installation of detectors that are much more sensitive at the longest (red) wavelengths. Each arm is optimized for the wavelengths it covers. This large range of wavelength coverage, combined with the instrument’s high sensitivity, allows the study of everything from comets (which have interesting features in the ultraviolet part of the spectrum), to the blue light from star formation, to the red light of very distant objects. LRIS also records the spectra of up to 50 objects simultaneously, especially useful for studies of clusters of galaxies in the most distant reaches, and earliest times, of the universe. LRIS was used in observing distant supernovae by astronomers who received the Nobel Prize in Physics in 2011 for research determining that the universe was speeding up in its expansion.

About W. M. Keck Observatory

The W. M. Keck Observatory telescopes are among the most scientifically productive on Earth. The two 10-meter optical/infrared telescopes atop Maunakea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometers, and world-leading laser guide star adaptive optics systems. Some of the data presented herein were obtained at Keck Observatory, which is a private 501(c) 3 non-profit organization operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the Native Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

---

Faintest Known Star System Orbiting the Milky Way Discovered from Hawaiʻi

An image of uma3/u1, a tiny cluster of ancient stars captured by CFTH
Credit: CFHT/S. Gwyn

Maunakea, Hawaiʻi - A team of astronomers led by the University of Victoria and Yale University has detected an ancient star system traveling around our galaxy named Ursa Major III / UNIONS 1 (UMa3/U1) – the faintest and lowest-mass Milky Way satellite ever discovered, and possibly one of the most dark matter-dominated systems known.

The team conducted the study from Hawaiʻi using two Maunakea Observatories on Hawaiʻi Island – W. M. Keck Observatory and Canada-France-Hawaiʻi Telescope (CFHT) – as well as the University of Hawaiʻi Institute for Astronomy Pan-STARRS (Panoramic Survey Telescope and Rapid Response System) on Haleakalā, Maui; the findings are published in a recent edition of The Astrophysical Journal.

“UMa3/U1 is located in the Ursa Major (Great Bear) constellation, home of the Big Dipper. It is in our cosmic backyard, relatively speaking, at about 30,000 light-years from the Sun,” says Simon Smith, an astronomy graduate student at University of Victoria and lead author of the study. “UMa3/U1 had escaped detection until now due to its extremely low luminosity.”

Observations reveal the stellar system is tiny, with only about 60 stars that are over 10 billion years old spanning just 10 light years across. UMa3/U1 has an extremely low mass – at 16 times the mass of the Sun, it is 15 times less massive than the faintest suspected dwarf galaxy.

UMa3/U1 was first detected using data obtained from the Ultraviolet Near Infrared Optical Northern Survey (UNIONS) at CFHT and Pan-STARRS.

The team then studied the star system in finer detail using Keck Observatory’s Deep Imaging Multi-Object Spectrograph (DEIMOS) and confirmed UMa3/U1 is a gravitationally-bound system, either a dwarf galaxy or a star cluster.

“There are so few stars in UMa3/U1 that one might reasonably question whether it’s just a chance grouping of similar stars. Keck was critical in showing this is not the case,” says co-author Marla Geha, professor of astronomy and physics at Yale University. “Our DEIMOS measurements clearly show all the stars are moving through space at very similar velocities and appear to share similar chemistries.”

Hidden in this deep sky image (left) is Uma3/U1, a miniscule group of stars (right) bound together by their own gravity (and possibly even dark matter!) in orbit around the Milky Way. Credit: CFHT/S. Gwyn (right) / S. Smith (left)

“Excitingly, a tentative spread in velocities among the stars in the system may support the conclusion that UMa3/U1 is a dark matter-dominated galaxy – a tantalizing possibility we hope to scrutinize with more Keck observations,” says Yale University graduate student Will Cerny, the second author of the study.

How these stars have managed to stay a tight-knit group is remarkable. One possible explanation is that dark matter may be keeping them together.

“The object is so puny that its long-term survival is very surprising. One might have expected the harsh tidal forces from the Milky Way’s disk to have ripped the system apart by now, leaving no observable remnant,” says Cerny. “The fact that the system appears intact leads to two equally interesting possibilities. Either UMa3/U1 is a tiny galaxy stabilized by large amounts of dark matter, or it’s a star cluster we’ve observed at a very special time before its imminent demise.”

With the former scenario, achieving direct confirmation of UMa3/U1 as a faint, ancient, dark matter-dominated satellite star system would be an exciting feat because it would support a prediction in the leading theory for the universe’s origin. Under the Lambda Cold Dark Matter (LCDM) model, scientists hypothesize that when galaxies like the Milky Way first formed, they created a gravitational pull during their assembly process that attracted hundreds of satellite star systems which continue to orbit galaxies today.

A companion study on UMa3/U1’s implications on the LCDM theory has been accepted for publication in The Astrophysical Journal and is available in preprint format on arXiv.org.

“Whether future observations confirm or reject that this system contains a large amount of dark matter, we’re very excited by the possibility that this object could be the tip of the iceberg – that it could be the first example of a new class of extremely faint stellar systems that have eluded detection until now,” says Cerny.

Conclusive evidence of the presence or lack of dark matter in UMa3/U1 is key to determining whether the star system is a dwarf galaxy or a star cluster. Until its classification becomes clear, Ursa Major III / UNIONS 1 has two names. Ultra-faint Milky Way satellites are typically named after the constellation they are discovered in (in this case, Ursa Major) whereas ultra-faint star clusters are generally named after the survey project they were discovered in (UNIONS).

While this star system’s identity is still ambiguous, UMa3/U1 paves the way for new perspectives in cosmology.

“This discovery may challenge our understanding of galaxy formation and perhaps even the definition of a ‘galaxy’,” says Smith.

Source: W. M. Keck Observatory/News

---

About DEIMOS

The DEep Imaging and Multi-Object Spectrograph (DEIMOS) boasts the largest field of view (16.7arcmin by 5 arcmin) of any of the Keck Observatory instruments, and the largest number of pixels (64 Mpix). It is used primarily in its multi-object mode, obtaining simultaneous spectra of up to 130 galaxies or stars. Astronomers study fields of distant galaxies with DEIMOS, efficiently probing the most distant corners of the universe with high sensitivity.

---

About W. M. Keck Observatory

The W. M. Keck Observatory telescopes are among the most scientifically productive on Earth. The two 10-meter optical/infrared telescopes atop Maunakea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometers, and world-leading laser guide star adaptive optics systems. Some of the data presented herein were obtained at Keck Observatory, which is a private 501(c) 3 non-profit organization operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the Native Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

---

A Hundred Million Suns

SN 2023ixf occurred in a spiral arm of the pinwheel galaxy near several star-forming regions.
Credit: Travis Deyoe, Mount Lemmon SkyCenter, University of Arizona

Maunakea, Hawai – Accounts of supernovae – exploding stars – go back thousands of years, and while we know today these events create the building blocks of life itself, there are still unanswered questions about the conditions that cause a star to explode.

Researchers from the Weizmann Institute of Science have now made major headway in better understanding these fascinating phenomena. Using multiple telescopes, including W. M. Keck Observatory on Maunakea, Hawaiʻi Island, they were able to gather data from a once-in-a-lifetime supernova called SN 2023ixf. Their findings are published in today’s edition of the journal Nature.

Until recently, supernovae were considered rare with known occurrences in the Milky Way happening once a century at best, lighting up the night sky with the intensity of 100 million suns; the last observable explosion in our galaxy took place hundreds of years ago.

Advances in telescope technology have since helped identify supernovae in distant galaxies, supplying more data than was previously possible. Still, the same problem persists; since explosions can’t be predicted, astrophysicists are like space archeologists, usually arriving at the scene after the event and trying to piece together information from the remains.

“That’s what makes this particular supernova different,” says PhD student Erez Zimmerman of Prof. Avishay Gal-Yam’s group at Weizmann. “We were able – for the very first time – to closely follow a supernova while its light was emerging from the circumstellar material in which the exploding star was embedded.”

The discovery was equivalent to getting to the scene of the crime while the crime was still taking place.

A composite image taken with the Liverpool Telescope showing the location of SN 2023ixf, a red supergiant supernova (the most blue object in the rectangle) that occurred 22 million light-years from Earth in the Pinwheel Galaxy. Credit: E. Zimmerman et al., Weizmann Institute of Science/Liverpool Telescope.

The scientists admit they were lucky. Gal-Yam’s team applied for research time on NASA’s Hubble Space Telescope, hoping to gather ultraviolet (UV) spectral data on any supernova interacting with its environment. Instead, they got the chance to witness in real-time one of the closest supernovae in decades: a red supergiant exploding in a neighboring galaxy called Messier 101, also known as the Pinwheel Galaxy.

Koichi Itagaki, an amateur astronomer from Japan, discovered SN 2023ixf and reported it on a Friday night, which was in the middle of the weekend in Israel (the work week in Israel is Sunday-Thursday) and right before the weekend in Baltimore’s Space Telescope Science Institute – the operations center for the Hubble Telescope. Complicating things even further, it took place two days before Zimmerman’s wedding. But his team quickly conducted follow-up observations of the supernova, pulling an all-nighter on Friday and delivering the necessary measurements to NASA in the nick of time.

“It’s very rare, as a scientist, that you have to act so swiftly,” says Gal-Yam. “Most scientific projects don’t happen in the middle of the night, but the opportunity arose, and we had no choice but to respond accordingly.”

Not only did they succeed in getting Hubble to assume the right coordinates and angle for recording the necessary data, but because of the explosion’s relative proximity, it turned out Hubble had already made recordings in this sector of the universe many times before. Turning to the NASA archives, Gal-Yam’s team and many other groups were able to acquire data from before the star’s eventual demise – when it was still just a red supergiant in its final stages of life – thus creating the most complete portrait of a supernova ever: a composite of its last days and death.

Observations of SN 2023ixf consisted of UV and X-ray data from NASA’s Hubble and Swift satellites, as well as many of the best telescopes across the globe.

This included spectra captured using three of Keck Observatory’s instruments – the Keck Cosmic Web Imager (KCWI), Deep Imaging and Multi-Object Spectrograph (DEIMOS), and Low Resolution Imaging Spectrometer (LRIS) – with each instrument offering a unique view of the supernova and how it changed over time.

The compilation of high-quality space- and ground-based data enabled the researchers to map out the two outer layers of the exploding star and come up with an extraordinary hypothesis.

“Calculations of the circumstellar material emitted in the explosion, as well as this material’s density and mass before and after the supernova, create a discrepancy, which makes it very likely that the missing mass ended up in a black hole that was formed in the aftermath of the explosion – something that’s usually very hard to determine,” says PhD student Ido Irani of Gal-Yam’s team.

“Stars behave very erratically in their senior years,” says Gal-Yam. “They become unstable and we usually cannot be sure which complex processes occur within them because we always start the forensic process after the fact, when much of the data has already been lost.”

“This study presents a unique opportunity to better understand the mechanisms that lead to the conclusion of a star’s life and the eventual formation of something entirely new,” said Zimmerman.

Scientists may never find out what will happen to the matter that made up Messier 101’s former red supergiant. However, the later stages of the supernova are ongoing and new data are still coming in, which means this study, along with follow-up studies of SN 2023ixf, could provide more insight into these explosive events.

Source: W. M. Keck Observatory

---

About KCWI

The Keck Cosmic Web Imager (KCWI) is designed to provide visible band, integral field spectroscopy with moderate to high spectral resolution formats and excellent sky-subtraction. The astronomical seeing and large aperture of the telescope enables studies of the connection between galaxies and the gas in their dark matter halos, stellar relics, star clusters, and lensed galaxies. KCWI covers the blue side of the visible spectrum; the instrument also features the Keck Cosmic Reionization Mapper (KCRM), extending KCWI’s coverage to the red side of the visible spectrum. The combination of KCWI-blue and KCRM provides simultaneous high-efficiency spectral coverage across the entire visible spectrum. Support for KCWI was provided by the National Science Foundation, Heising-Simons Foundation, and Mt. Cuba Astronomical Foundation. Support for KCRM was provided by the National Science Foundation and Mt. Cuba Astronomical Foundation.

---

About DEIMOS

The DEep Imaging and Multi-Object Spectrograph (DEIMOS) boasts the largest field of view (16.7arcmin by 5 arcmin) of any of the Keck Observatory instruments, and the largest number of pixels (64 Mpix). It is used primarily in its multi-object mode, obtaining simultaneous spectra of up to 130 galaxies or stars. Astronomers study fields of distant galaxies with DEIMOS, efficiently probing the most distant corners of the universe with high sensitivity.

---

About LRIS

The Low Resolution Imaging Spectrometer (LRIS) is a very versatile and ultra-sensitive visible-wavelength imager and spectrograph built at the California Institute of Technology by a team led by Prof. Bev Oke and Prof. Judy Cohen and commissioned in 1993. Since then it has seen two major upgrades to further enhance its capabilities: the addition of a second, blue arm optimized for shorter wavelengths of light and the installation of detectors that are much more sensitive at the longest (red) wavelengths. Each arm is optimized for the wavelengths it covers. This large range of wavelength coverage, combined with the instrument’s high sensitivity, allows the study of everything from comets (which have interesting features in the ultraviolet part of the spectrum), to the blue light from star formation, to the red light of very distant objects. LRIS also records the spectra of up to 50 objects simultaneously, especially useful for studies of clusters of galaxies in the most distant reaches, and earliest times, of the universe. LRIS was used in observing distant supernovae by astronomers who received the Nobel Prize in Physics in 2011 for research determining that the universe was speeding up in its expansion.

---

About W. M. Keck Observatory/News

The W. M. Keck Observatory telescopes are among the most scientifically productive on Earth. The two 10-meter optical/infrared telescopes atop Maunakea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometers, and world-leading laser guide star adaptive optics systems. Some of the data presented herein were obtained at Keck Observatory, which is a private 501(c) 3 non-profit organization operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the Native Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

---

Astronomers Capture Direct Image of Ancient Galaxy Recycling Gas to Make New Stars

Artist’s illustration of mammoth-1, a massive ancient galaxy recycling gas to sustain its growth in the early universe.
Credit: Tsinghua University

Maunakea, Hawaiʻi – Astronomers have found direct evidence showing ancient galaxies were able to sustain star formation by recycling gas from previous stars to birth new generations of stars. This recycled gas could have been enough to supply all the material needed for galaxies in the early universe to grow, shedding new light on the evolution of galaxies and stars.

The findings, which include data from two Maunakea Observatories on Hawaiʻi Island – W. M. Keck Observatory and Subaru Telescope – are published in the journal Science.

Gas provides the material galaxies need to form new stars. When stars die in supernova explosions, they can expel gas out of a galaxy. To continue forming stars, a galaxy requires a steady supply of gas streaming into it. But it has been unclear if star formation is driven by a supply of pristine new gas, which consists mostly of hydrogen with a little helium – among the lightest elements in the universe – or if galaxies are able to recycle the gas from previous generations of supernovae, which would contain heavier elements produced by nuclear fusion in stars.

To answer this question, an international team of researchers led by Tsinghua University snapped a direct image of MAMMOTH-1, a massive nebula in a galaxy cluster that existed 11 billion years ago.

Using Keck Observatory’s Keck Cosmic Web Imager (KCWI) and Subaru Telescope, the team detected signs of hydrogen, helium, and carbon extending out to 300,000 light-years around MAMMOTH-1. The ratios of the elements are similar to what is seen in the Sun today; this is surprising for such an ancient protogalaxy, whose composition is expected to more closely resemble the pristine state of new gas.

---

Artist’s animation depicting direct observations of recycled gas spiraling into the MAMMOTH-1 protogalaxy, fueling more star formation. Credit: Tsinghua University

Source:  W. M. Keck Observatory/News

 

---

The team was also able to map the motion of the gas, which showed the gas enriched with heavy elements is flowing back into the galaxy, delivering about 700 times the mass of the Sun in recycled gas each year. This amounts to much more than what is needed to fuel the star formation rate seen in MAMMOTH-1, which is about 81 times the mass of the Sun each year, thus indicating that the recycled gas alone is enough to sustain star formation in the protogalaxy. “Our observations give a first hint that recycled inflows might be an ubiquitous supply mechanism for massive star-forming galaxies in the early universe,” said Zheng Cai of Tsinghua University, the Principal Investigator of this study and co-author of the paper.

---

About KCWI

The Keck Cosmic Web Imager (KCWI) is designed to provide visible band, integral field spectroscopy with moderate to high spectral resolution formats and excellent sky-subtraction. The astronomical seeing and large aperture of the telescope enables studies of the connection between galaxies and the gas in their dark matter halos, stellar relics, star clusters, and lensed galaxies. Support for this project was provided by the National Science Foundation, Heising-Simons Foundation, and Mt. Cuba Astronomical Foundation.

About W. M. Keck Observatory

The W. M. Keck Observatory telescopes are among the most scientifically productive on Earth. The two 10-meter optical/infrared telescopes atop Maunakea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometers, and world-leading laser guide star adaptive optics systems. Some of the data presented herein were obtained at Keck Observatory, which is a private 501(c) 3 non-profit organization operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the Native Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

---

First Detection of Radio Waves from a Type Ia Supernova

Artist's rendition of SN 2020eyj, a white dwarf star that went supernova after pulling material from a helium companion star. Credit: W. M. Keck Observatory/Adam Makarenko

Maunakea, Hawaiʻi – A team of astronomers led by Stockholm University has discovered an unusual Type Ia supernova – or thermonuclear supernova – called SN 2020eyj. Not only did they make the first detection of such a supernova in radio waves, follow-up observations from W. M. Keck Observatory on Maunakea, Hawaiʻi Island also showed strong emission lines of helium.

This marks the first confirmed Type Ia supernova triggered by a white dwarf star that pulled material from a companion star with an outer layer consisting primarily of helium; normally, in the rare cases where the material stripped from the outer layers of the donor star could be detected in spectra, this was mostly hydrogen.

Type Ia supernovae are important for astronomers since they are used to measure the expansion of the universe. However, the origin of these explosions has remained an open question. While it is established that the explosion is caused by a compact white dwarf star that somehow accretes too much matter from a companion star, the exact process and the nature of the progenitor is not known.

The new discovery of supernova SN 2020eyj is evidence the companion star was a helium star that had lost much of its material just prior to the explosion of the white dwarf.

The study, which includes data from Keck Observatory’s Low Resolution Imaging Spectrometer (LRIS), is published in today’s issue of the journal Nature.

First Detection of Radio Waves from a Type Ia Supernova from Keck Observatory on Vimeo.

Artist’s impression of SN2020eyj, a double star system with a compact white dwarf star accreting matter from a helium-rich donor companion, surrounded by dense and dusty circumstellar material. It was the interaction of the exploded star and the material left over from this companion that gave rise to the strong radio signal and the conspicuous helium lines in the optical spectra of SN 2020eyj. Credit: W. M. Keck Observatory/Adam Makarenko

“Once we saw the signatures of strong interaction with the material from the companion, we tried to also detect it in radio emission,” says Erik Kool, a postdoc at Stockholm University’s Department of Astronomy and lead author of the paper. “The detection in radio is the first one of a Type Ia supernova – something astronomers have tried to do for decades.”

Supernova 2020eyj was first spotted by the Zwicky Transient Facility at Palomar Observatory near San Diego where the Oskar Klein Centre at Stockholm University are members.

“The Nordic Optical Telescope on La Palma was fundamental for following up this supernova,” says Jesper Sollerman, a professor at Stockholm University’s Department of Astronomy and co-author of the paper. “As were spectra from the large Keck telescope in Hawaiʻi that immediately revealed the very unusual helium-dominated material around the exploded star.”

“This is clearly a very unusual Type Ia supernova, but still related to the ones we use to measure the expansion of the universe,” adds co-author Joel Johansson from the Department of Physics at Stockholm University. “While normal Type Ia supernovae appear to always explode with the same brightness, this supernova tells us that there are many different pathways to a white dwarf star explosion.”

Source: W.M.Keck Observatory/Science News

---

About LRIS

The Low Resolution Imaging Spectrometer (LRIS) is a very versatile and ultra-sensitive visible-wavelength imager and spectrograph built at the California Institute of Technology by a team led by Prof. Bev Oke and Prof. Judy Cohen and commissioned in 1993. Since then it has seen two major upgrades to further enhance its capabilities: the addition of a second, blue arm optimized for shorter wavelengths of light and the installation of detectors that are much more sensitive at the longest (red) wavelengths. Each arm is optimized for the wavelengths it covers. This large range of wavelength coverage, combined with the instrument’s high sensitivity, allows the study of everything from comets (which have interesting features in the ultraviolet part of the spectrum), to the blue light from star formation, to the red light of very distant objects. LRIS also records the spectra of up to 50 objects simultaneously, especially useful for studies of clusters of galaxies in the most distant reaches, and earliest times, of the universe. LRIS was used in observing distant supernovae by astronomers who received the Nobel Prize in Physics in 2011 for research determining that the universe was speeding up in its expansion.

---

About W. M. Keck Observatory

The W. M. Keck Observatory telescopes are among the most scientifically productive on Earth. The two 10-meter optical/infrared telescopes atop Maunakea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometers, and world-leading laser guide star adaptive optics systems. Some of the data presented herein were obtained at Keck Observatory, which is a private 501(c) 3 non-profit organization operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the Native Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

---

First Ever 3D Map of Messier 87 Galaxy Assembled

An image of the M87 galaxy captured with nasa's hubble space telescope.

Credit: NASA, ESA, Hubble Heritage Team (STScI/AURA); Acknowledgment: P. Cote (Herzberg Institute of Astrophysics), E. Baltz (Stanford University)

Maunakea, Hawaiʻi – A UC Berkeley-led team of astronomers has for the first time measured the three-dimensional shape of Messier 87 (M87), one of the biggest and closest elliptical galaxies to us. New data from W. M. Keck Observatory on Maunakea in Hawaiʻi show M87 isn’t perfectly symmetrical after all, but rather triaxial – similar to the uneven shape of a potato.

The study is published in The Astrophysical Journal Letters.

Located about 55 million light-years away from Earth in the constellation Virgo, M87 is close enough to see using binoculars or a small telescope. As with most celestial objects viewed from our vantage point, M87 appears flat.

The galaxy’s true form revealed itself through the lens of Keck Observatory’s cutting-edge instrument called the Keck Cosmic Web Imager (KCWI), which captures 3D data as opposed to the traditional 2D image or spectrum from conventional instruments.

The researchers used KCWI along with star brightness measurements of M87 from NASA’s Hubble Space Telescope to assemble a 3D view of the motion of stars orbiting M87’s supermassive black hole, named Pōwehi by Larry Kimura, a Hawaiian language professor at the University of Hawaiʻi at Hilo. This provided fresh insight into the galaxy’s shape and allowed the team to calculate with higher precision Pōwehi’s mass, which came out to about 5.4 billion times the mass of the Sun. Previous measurements taken in 2017 when the Event Horizon Telescope (EHT) snapped a direct image of Pōwehi found its mass to be about 6.5 billion solar masses.

Pōwehi means ‘embellished dark source of unending creation’ in Hawaiian and is the world’s first black hole to have its picture taken using EHT’s network of telescopes around the planet, including two Maunakea Observatories – the James Clerk Maxwell Telescope and the Submillimeter Array.

A photo of the huge elliptical galaxy M87 [left] is compared to its three-dimensional shape as gleaned from meticulous observations made with the Hubble and Keck telescopes [right]. Because the galaxy is too far away for astronomers to employ stereoscopic vision, they instead followed the motion of stars around the center of M87, like bees around a hive. This created a three-dimensional view of how stars are distributed within the galaxy. Credit: NASA, ESA, Joseph Olmsted (STScI), Frank Summers (STScI), Chung-Pei Ma (UC Berkeley)

While KCWI was unable to resolve the individual stars due to M87’s great distance from Earth, it was able to obtain spectra that revealed the range of the stars’ velocities as they whizzed around Pōwehi.

“It’s sort of like looking at a swarm of 100 billion bees that are going around in their own happy orbits,” said Chung-Pei Ma, a UC Berkeley professor of astronomy and of physics who led the research team. “Though we are looking at them from a distance and can’t discern individual bees, we are getting very detailed information about their collective velocities. It’s really the superb sensitivity of this spectrograph that allowed us to map out M87 so comprehensively.”

Ma, UC Berkeley graduate student and lead author of the study Emily Liepold, and Jonelle Walsh at Texas A&M University pointed the Keck II telescope at 62 locations across the galaxy and captured KCWI spectra of stars covering a region spanning 70,000 light years across. Gravity in the central 3,000 light-years of this region is largely dominated by Pōwehi. This marked the first time KCWI has been used to reconstruct the geometry of a distant galaxy.

“The Keck data are so good that we can measure the intrinsic shape of M87 along with the black hole at the same time,” said Ma. “We made the first measurement of the actual 3D shape of the galaxy. And since we allowed the swarm of bees to have a more general shape than just a sphere or disk, we have a more robust dynamical measurement of the mass of the central black hole that is governing the bees’ orbiting velocities.”

Ma’s team was also able to measure M87’s rotation, which clocks in at a relatively sedate 25 kilometers per second.

The new findings pave the way for an exciting investigation into M87 that wasn’t possible before – determining Pōwehi’s spin.

“Now that we know the direction of the net rotation of stars in M87 and have an updated mass of the black hole, we can combine this information with the amazing data from the EHT team to constrain the spin,” said Ma. “This may point toward a certain direction and range of spin for the black hole, which would be remarkable.”

Source: W. M. Keck Observatory

 

---

Learn more:

• “3D Picture of Galaxy M87 Helps Pin Down Mass of the Black Hole at its Core” – UC Berkeley Press Release April 13, 2023
• “Giant Galaxy Seen in 3D by NASA’s Hubble Space Telescope and Keck Observatory” – STScI Press Release, April 13, 2023

---

About KCWI

The Keck Cosmic Web Imager (KCWI) is designed to provide visible band, integral field spectroscopy with moderate to high spectral resolution formats and excellent sky-subtraction. The astronomical seeing and large aperture of the telescope enables studies of the connection between galaxies and the gas in their dark matter halos, stellar relics, star clusters, and lensed galaxies. Support for this project was provided by the National Science Foundation, Heising-Simons Foundation, and Mt. Cuba Astronomical Foundation.

About W. M. Keck Observatory

The W. M. Keck Observatory telescopes are among the most scientifically productive on Earth. The two 10-meter optical/infrared telescopes atop Maunakea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometers, and world-leading laser guide star adaptive optics systems. Some of the data presented herein were obtained at Keck Observatory, which is a private 501(c) 3 non-profit organization operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the Native Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

---

Tracing the Origins of Rare, Cosmic Explosions

A typical star-forming host galaxy where a short gamma-ray burst originated from.
Credit: W. M. Keck Observatory/Adam Makarenko

---

Astronomers Produce the Most Robust Catalog to Date of Short Gamma-Ray Burst Hosts

Maunakea, Hawaiʻi – A team of astronomers led by Northwestern University has created the most extensive inventory yet of the galaxies where short gamma-ray bursts (sGRBs) come from. Using several highly sensitive instruments at W. M. Keck Observatory on Maunakea, Hawaiʻi and other large observatories, combined with some of the most sophisticated galaxy modeling ever used in the field, the researchers pinpointed the galactic homes of 84 sGRBs.

“This is the largest catalog of sGRB host galaxies to ever exist, so we expect it to be the gold standard for many years to come,” said Anya Nugent, an astronomy graduate student at Northwestern University who led the research, observational efforts with Keck Observatory, and one of two publications about the study.

As an homage to the fact that sGRBs are among the brightest explosions in the universe, the team calls their catalog BRIGHT (Broadband Repository for Investigating Gamma-ray burst Host Traits) with all of their data and modeling products online for community use.

SGRBs are momentary flashes of intense gamma-ray light emitted when two neutron stars collide. While the gamma-rays last only seconds, the optical light can continue for hours before fading below detection, called an afterglow. SGRBs are some of the most luminous explosions in the universe with, at most, a dozen detected and pinpointed each year.

---

An artistic rendition of the diversity of short gamma-ray burst (sGRB) host environments, in large part discovered and characterized by Keck Observatory. SGRBs may occur in actively star-forming or dead galaxies, nearby or deep into the universe, and close or far from their host’s centers. All data is publicly available on the BRIGHT website (bright.ciera.northwestern.edu). Credit: W. M. Keck Observatory/Adam Makarenko

Since the discovery of sGRB afterglows in 2005 by NASA’s Neil Gehrels Swift Observatory, astronomers have spent the last 17 years trying to find out which galaxies these powerful bursts originated from, as the stars within a galaxy can give insight into the environmental conditions needed to produce these events and can connect them to their neutron star merger origins. Indeed, only one sGRB, GRB 170817A, has a confirmed neutron star merger origin, as it was detected just seconds after gravitational wave detectors observed the binary neutron star merger, GW170817.

“In a decade, the next generation of gravitational wave observatories will be able to detect neutron star mergers out to the same distances as we do sGRBs today. Thus, our catalog will serve as a benchmark for comparison to future detections of neutron star mergers,” said Wen-fai Fong, assistant professor of astronomy and physics at Northwestern University and lead author of one of the publications.

“Building this catalog and finally having enough host galaxies to see patterns and draw significant conclusions is exactly what the field needed to push our understanding of these fantastic events and what happens to stars after they die,” said Nugent.

Learning about sGRB host galaxies is crucial to understanding the blasts themselves and offers clues about the types of stars that created them as well as their distance from Earth. Since neutron star mergers create heavy elements like gold and platinum, the data will also deepen scientists’ understanding of when precious metals were first created in the universe.

The first paper in the study, which is published in The Astrophysical Journal, found that sGRBs occur at higher redshifts, or earlier times in the universe, than previously thought—and with greater distances from their hosts’ centers than understood before. Surprisingly, several of these explosions were found just outside their host galaxies as if they were “kicked out,” raising questions as to how they were able to travel that far.

Published in the same journal, the second research paper in the study probed the characteristics of 69 of the identified sGRB host galaxies. The findings suggest about 85 percent of them are young, actively star-forming galaxies — a stark contrast to earlier studies that characterized the population of sGRB host galaxies as relatively old and approaching death. This means neutron star systems may form in a broad range of environments and many of them have quick formation-to-merger timescales.

Keck Observatory’s Low Resolution Imaging Spectrometer (LRIS), DEep Imaging and Multi-Object Spectrograph (DEIMOS), and Multi-Object Spectrograph for Infrared Exploration (MOSFIRE) were crucial instruments in creating the catalog. Together, they allowed the team to capture deep imaging and spectroscopy of some of the faintest galaxies identified in the survey of sGRB hosts.

“It would simply not be possible to obtain distances to some of these galaxies, or even detect them at all, without the Keck Observatory,” Fong said. “In many cases, Keck enabled the first detection of a very faint host galaxy and ensured we did not misidentify any host galaxies.”

Many questions remain about how neutron stars merge and how long the process takes. But observing sGRBs and their host galaxies provides one of the best perspectives to answer them and can offer more data about neutron star mergers and their hosts at much farther distances, and more frequently, than current gravitational wave detectors. This new sGRB host catalog will therefore serve as a vital reference point in the coming decade to understand the full evolution of these systems over cosmic time. “The catalog can really make impacts beyond just a single class of transients like sGRBs,” said co-author Yuxin “Vic” Dong, an astronomy PhD student at Northwestern University. “With the wealth of data and results presented in the catalog, I believe a variety of research projects will make use of it, maybe even in ways we have yet not thought of.”

“I started observations for this project 10 years ago and it was so gratifying to be able to pass the torch onto the next generation of researchers,” said Fong. “It is one of my career’s greatest joys to see years of work come to life in this catalog, thanks to the young researchers who really took this study to the next level.”

The James Webb Space Telescope (JWST) is poised to further advance our understanding of neutron star mergers and how far back in time they began, as it will be able to detect the faintest host galaxies that exist at very early times in the universe.
 

“I’m most excited about the possibility of using JWST to probe deeper into the source of these rare, explosive events,” said Nugent. “JWST’s ability to observe faint galaxies in the universe could uncover more sGRB host galaxies that are currently evading detection, perhaps even revealing a missing population and a link to the early universe!”

Source:W. M. Keck Observatory

---

About LRIS

The Low Resolution Imaging Spectrometer (LRIS) is a very versatile and ultra-sensitive visible-wavelength imager and spectrograph built at the California Institute of Technology by a team led by Prof. Bev Oke and Prof. Judy Cohen and commissioned in 1993. Since then, it has seen two major upgrades to further enhance its capabilities: the addition of a second, blue arm optimized for shorter wavelengths of light and the installation of detectors that are much more sensitive at the longest (red) wavelengths. Each arm is optimized for the wavelengths it covers. This large range of wavelength coverage, combined with the instrument’s high sensitivity, allows the study of everything from comets (which have interesting features in the ultraviolet part of the spectrum), to the blue light from star formation, to the red light of very distant objects. LRIS also records the spectra of up to 50 objects simultaneously, especially useful for studies of clusters of galaxies in the most distant reaches, and earliest times, of the universe. LRIS was used in observing distant supernovae by astronomers who received the Nobel Prize in Physics in 2011 for research determining that the universe was speeding up in its expansion.

About DEIMOS

The DEep Imaging and Multi-Object Spectrograph (DEIMOS) boasts the largest field of view (16.7arcmin by 5 arcmin) of any of the Keck Observatory instruments, and the largest number of pixels (64 Mpix). It is used primarily in its multi-object mode, obtaining simultaneous spectra of up to 130 galaxies or stars. Astronomers study fields of distant galaxies with DEIMOS, efficiently probing the most distant corners of the universe with high sensitivity.

About MOSFIRE

The Multi-Object Spectrograph for Infrared Exploration (MOSFIRE), gathers thousands of spectra from objects spanning a variety of distances, environments and physical conditions. What makes this large, vacuum-cryogenic instrument unique is its ability to select up to 46 individual objects in the field of view and then record the infrared spectrum of all 46 objects simultaneously. When a new field is selected, a robotic mechanism inside the vacuum chamber reconfigures the distribution of tiny slits in the focal plane in under six minutes. Eight years in the making with First Light in 2012, MOSFIRE’s early performance results range from the discovery of ultra-cool, nearby substellar mass objects, to the detection of oxygen in young galaxies only two billion years after the Big Bang. MOSFIRE was made possible by funding provided by the National Science Foundation.  

 

About W. M. Keck Observatory

The W. M. Keck Observatory telescopes are among the most scientifically productive on Earth. The two 10-meter optical/infrared telescopes atop Maunakea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometers, and world-leading laser guide star adaptive optics systems. Some of the data presented herein were obtained at Keck Observatory, which is a private 501(c) 3 non-profit organization operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the Native Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

---

New Record: Nearest Known Black Hole to Earth Discovered

A bright, sun-like star orbiting the closest known black hole to earth, named gaia bh1. Credit: T. Müller (MPIA), PanSTARRS DR1 (K. C. Chambers et al. 2016), ESA/Gaia/DPAC (CC BY-SA 3.0 IGO)

Maunakea, Hawaiʻi – Astronomers using two Maunakea Observatories, W. M. Keck Observatory and the Gemini North telescope, have found the closest known black hole to our planet. Located a mere 1,560 light-years away from Earth in the constellation Ophiuchus, the black hole, named Gaia BH1, is three times closer to us than the previous record-holder.

The new study, which includes data from Keck Observatory’s High-Resolution Echelle Spectrometer (HIRES) and Echellette Spectrograph and Imager (ESI), is published in the journal Monthly Notices of the Royal Astronomical Society.

A research team led by the Max Planck Institute for Astronomy (MPIA) made the discovery by tracking Gaia BH1’s companion – a bright Sun-like star that orbits the black hole once every 185.6 days at about the same distance as the Earth orbits the Sun.

“Take the solar system, put a black hole where the Sun is, and the Sun where the Earth is, and you get this system,” said lead author Kareem El-Badry, an astrophysicist at MPIA and the Harvard & Smithsonian Center for Astrophysics. “While there have been many claimed detections of systems like this, almost all these discoveries have subsequently been refuted. This is the first unambiguous detection of a Sun-like star in a wide orbit around a stellar-mass black hole in our galaxy.”

Stellar-mass black holes form when dying massive stars collapse in on themselves. To find these dark, hard-to-detect objects, El-Badry’s team combed through data from the European Space Agency’s (ESA) Gaia spacecraft, which is designed to measure the motion of one billion stars in the Milky Way as they orbit around the center of our galaxy.

One star’s behavior caught the team’s attention; its orbit was larger than expected for its orbital period, suggesting the presence of a massive, unseen companion. For a more detailed look, the researchers conducted follow-up observations at several ground-based telescopes, including Gemini North and Keck Observatory in Hawaiʻi, and determined the star’s companion is a black hole that is 10 times more massive than the Sun.

“I have been searching for a system like Gaia BH1 for the last four years, trying all kinds of methods – but none of them worked,” said El-Badry. “It has been elating to see this search finally bear fruit.”

Learn more:

• Max Planck Institute for Astronomy Press Release
• International Gemini Observatory, operated by NSF’s NOIR Lab, Press Release

Zooming towards the black hole Gaia BH1. Background: region of the Milky Way galaxy; Panel 1: an image of the star orbiting the black hole; Panel 2: reconstructed orbit of the star; Panel 3: relativistic light-bending effects that would be visible if we could see star and black hole up close. Credit: T. Müller (MPIA), PanSTARRS DR1 (K. C. Chambers et al. 2016), ESA/Gaia/DPAC (CC BY-SA 3.0 IGO)

Source: W. M. Keck Observatory/News

---

About HIRES

The High-Resolution Echelle Spectrometer (HIRES) produces spectra of single objects at very high spectral resolution, yet covering a wide wavelength range. It does this by separating the light into many “stripes” of spectra stacked across a mosaic of three large CCD detectors. HIRES is famous for finding exoplanets. Astronomers also use HIRES to study important astrophysical phenomena like distant galaxies and quasars, and find cosmological clues about the structure of the early universe, just after the Big Bang.

About ESI

The Echellette Spectrograph and Imager (ESI) is a medium-resolution visible-light spectrograph that records spectra from 0.39 to 1.1 microns in each exposure. Built at UCO/Lick Observatory by a team led by Prof. Joe Miller, ESI also has a low-resolution mode and can image in a 2 x 8 arc min field of view. An upgrade provided an integral field unit that can provide spectra everywhere across a small, 5.7 x4.0 arc sec field. Astronomers have found a number of uses for ESI, from observing the cosmological effects of weak gravitational lensing to searching for the most metal-poor stars in our galaxy.

About W. M. Keck Observatory

 

The W. M. Keck Observatory telescopes are among the most scientifically productive on Earth. The two 10-meter optical/infrared telescopes atop Maunakea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometers, and world-leading laser guide star adaptive optics systems. Some of the data presented herein were obtained at Keck Observatory, which is a private 501(c) 3 non-profit organization operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the Native Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

---

Massive Stars’ Blasts Hitting Orion’s “Sword” Mapped in Unprecedented Detail Using Hawaiʻi Telescope

Infrared image of orion's photo-dissociation region captured by the Keck ii telescope
Credit: Habart et al./W. M. Keck Observatory

Maunakea, Hawaiʻi – Astronomers using W. M. Keck Observatory on Hawaiʻi Island have captured from Maunakea the most detailed and complete images ever taken of the zone where the famed constellation of Orion gets zapped with ultraviolet (UV) radiation from massive young stars.

This irradiated neutral zone, called a Photo-Dissociation Region (PDR), is located in the Orion Bar within the Orion Nebula, an active star-forming site found in the middle of the “sword” hanging from Orion’s “belt.” When viewed with the naked eye, the nebula is often mistaken for one of the stars in the constellation; when viewed with a telescope, the photogenic nebula is seen as a glowing gaseous stellar nursery located 1,350 light-years from Earth.

“It was thrilling being the first, together with my colleagues of the ‘PDRs4All’ James Webb Space Telescope team, to see the sharpest images of the Orion Bar ever taken in the near infrared,” said Carlos Alvarez, a staff astronomer at Keck Observatory and co-author of the study.

Because the Orion Nebula is the closest massive star formation region to us and may be similar to the environment in which our solar system was born, studying its PDR – the area that’s heated by starlight – is an ideal place to find clues as to how stars and planets are created.

“Observing photo-dissociation regions is like looking into our past,” said Emilie Habart, an Institut d’Astrophysique Spatiale associate professor at Paris-Saclay University and lead author of a paper on this study. “These regions are important because they allow us to understand how young stars influence the gas and dust cloud they are born in, particularly sites where stars, like the Sun, form.”

The study has been accepted for publication in the journal Astronomy & Astrophysics, and is available in preprint format on arXiv.org.

These pathfinder observations have assisted in the planning of the James Webb Space Telescope (JWST) Early Release Science (ERS) program PDRs4All: Radiative feedback of massive stars (ID1288). The PDRs4All program is described in a Publications of the Astronomical Society of the Pacific paper by Berné, Habart, Peeters et al. (2022).

Methodology

To probe Orion’s PDR, the PDRs4All team used Keck Observatory’s second generation Near-Infrared Camera (NIRC2) in combination with the Keck II telescope’s adaptive optics system. They successfully imaged the region with such extreme detail, the researchers were able to spatially resolve and distinguish the Orion Bar’s different substructures – such as ridges, filaments, globules, and proplyds (externally illuminated photoevaporating disks around young stars) – that formed as starlight blasted and sculpted the nebula’s mixture of gas and dust.

Left: Hubble Space Telescope mosaic of the Orion Bar. Credit: NASA/STScI/Rice Univ./C.O’Dell et al. The NIRC2 wide camera Field of View is shown in the yellow square. Right: Infrared heat map of the Orion Bar obtained with Keck Observatory’s NIRC2 instrument reveals substructures such as proplyds. Credit: Habart et al./W. M. Keck Observatory

---

“Never before have we been able to observe at a small scale how interstellar matter structures depend on their environments, particularly how planetary systems could form in environments strongly irradiated by massive stars,” said Habart. “This may allow us to better understand the heritage of the interstellar medium in planetary systems, namely our origins.”

Massive young stars emit large quantities of UV radiation that affect the physics and chemistry of their local environment; how this surge of energy the stars inject into their native cloud impacts and shapes star formation is not yet well known.

The new Keck Observatory images of the Orion Bar will help deepen astronomers’ understanding of this process because they reveal in detail where gas in its PDR changes from hot ionized gas, to warm atomic, to cold molecular gas. Mapping this conversion is important because the dense, cold molecular gas is the fuel needed for star formation.

Source:  W. M. Keck Observatory

---

What's Next

These new observations from Keck Observatory have informed plans for JWST observations of the Orion Bar, which is among JWST’s targets and is expected to be observed in the coming weeks.

“One of the most exciting aspects of this work is seeing Keck play a fundamental role in the JWST era,” said Alvarez. “JWST will be able to dive deeper into the Orion Bar and other PDRs, and Keck will be instrumental in validating JWST’s early science results. Together, the two telescopes can provide unique insight into the characteristics of the gas and chemical composition of PDRs, which will help us understand the nature of these fascinating star-blasted regions.”

---

About NIRC2

The Near-Infrared Camera, second generation (NIRC2) works in combination with the Keck II adaptive optics system to obtain very sharp images at near-infrared wavelengths, achieving spatial resolutions comparable to or better than those achieved by the Hubble Space Telescope at optical wavelengths. NIRC2 is probably best known for helping to provide definitive proof of a central massive black hole at the center of our galaxy. Astronomers also use NIRC2 to map surface features of solar system bodies, detect planets orbiting other stars, and study detailed morphology of distant galaxies.

About Adaptive Optics

W. M. Keck Observatory is a distinguished leader in the field of adaptive optics (AO), a breakthrough technology that removes the distortions caused by the turbulence in the Earth’s atmosphere.  Keck Observatory pioneered the astronomical use of both natural guide star (NGS) and laser guide star adaptive optics (LGS AO) and current systems now deliver images three to four times sharper than the Hubble Space Telescope at near-infrared wavelengths. AO has imaged the four massive planets orbiting the star HR8799, measured the mass of the giant black hole at the center of our Milky Way Galaxy, discovered new supernovae in distant galaxies, and identified the specific stars that were their progenitors. Support for this technology was generously provided by the Bob and Renee Parsons Foundation, Change Happens Foundation, Gordon and Betty Moore Foundation, Mt. Cuba Astronomical Foundation, NASA, NSF, and W. M. Keck Foundation.

About W. M. Keck Observatory

The W. M. Keck Observatory telescopes are among the most scientifically productive on Earth. The two 10-meter optical/infrared telescopes atop Maunakea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometers, and world-leading laser guide star adaptive optics systems. Some of the data presented herein were obtained at Keck Observatory, which is a private 501(c) 3 non-profit organization operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the Native Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

---