Youngest Exoplanet Yet Discovered Found Hiding in Keck Observatory Data

Elias 2-24 b

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Astronomers confirm a giant planet still forming around its young star, offering a rare glimpse into how planetary systems take shape

Maunakea, Hawaiʻi -Astronomers have confirmed the youngest exoplanet detected so far, offering a rare glimpse into the earliest stages of planetary formation. The planet, known as Elias 2-24 b, is still actively gathering material from the disk of gas and dust surrounding its young host star, allowing scientists to study a giant planet while it is still growing.

The study, led by Diego Portales University in Chile and published in The Astrophysical Journal Letters, combines observations from W. M. Keck Observatory, the Atacama Large Millimeter/submillimeter Array (ALMA), and the European Southern Observatory’s Very Large Telescope (VLT). The findings support the core accretion model of giant planet formation and provide strong evidence linking gaps in protoplanetary disks to planets forming within them.

“What makes Elias 2-24 b so remarkable is its age,” said Andrea Bernardi, a doctoral student at Diego Portales University and lead author of the study. “This is the youngest planet detected so far, and because it is still actively accreting material from its surroundings, we’re able to observe a stage of planet formation that is rarely seen directly.”

Seeing a Planet in the Making

Young stars are often surrounded by rotating disks of gas and dust known as protoplanetary disks. Over time, material within these disks collects and grows into planets.

In recent years, ALMA has produced striking images of these disks, revealing rings and dark gaps in the surrounding material. Many astronomers suspected that emerging planets were carving those gaps as they formed, but direct evidence remained limited.

Elias 2-24 b provides one of the clearest examples yet of a planet occupying one of these gaps.

Elias 5 4k 5 (Artist’s animation depicting Elias 2-24 b)

“We can now connect the presence of gaps in protoplanetary disks to the presence of planets with much greater confidence,” Bernardi said. “This discovery provides direct evidence that these structures can be produced by planets forming within the disk.”

The finding also supports a specific stage of the core accretion model, the leading theory of giant planet formation. According to the team’s analysis, the planet is currently undergoing a brief but critical growth phase during which it rapidly accumulates gas from the surrounding disk and builds its atmosphere.

“In a way, we’re observing a much younger version of a planetary system like our own,” said Lucas Cieza, co-author of the study and professor at Universidad Diego Portales. “Because our solar system is billions of years old, we can only reconstruct how it formed. Systems like Elias 2-24 b allow us to study that process while it is still underway.”

Alice Zurlo, a professor at Universidad Diego Portales and one of the study’s authors, conducted the initial research on the system in 2018. “This planet is a rare gem, as it is currently undergoing a stage of its evolution for which theoretical models still struggle to reliably predict its mass, entropy, and, consequently, its expected luminosity,” said Zurlo. “This system will therefore provide key insights once we are able to further constrain its dynamical mass, helping us refine and recalibrate evolutionary models for young planets.”

A Decade-Long Search and a Discovery in the Archive

The discovery began with observations conducted at Keck Observatory in 2018.

That year, Alice Zurlo, then part of the research team studying young stars with structured protoplanetary disks, observed Elias 2-24 with Keck’s Near Infrared Camera 2 (NIRC2). At the time, the observations revealed a faint signal, but not enough evidence to identify it as a planet.

Years later, Bernardi returned to the data through the Keck Observatory Archive (KOA), a NASA-funded partnership between Keck Observatory and the NASA Exoplanet Science Institute (NExScI) at Caltech/IPAC. The archive serves all data taken at Keck Observatory, making it available for new scientific research long after the observations were originally obtained.

By reanalyzing the 2018 observations with new data-processing techniques, Bernardi identified a signal consistent with a forming planet. Additional archival Keck observations obtained in 2020, together with independent observations from the VLT and supporting evidence from ALMA, helped confirm the discovery.

“This object sits right at the limit of what current technology can detect,” said Cieza. “It was the combination of observations from multiple observatories that allowed us to show the planet is really there.”

The discovery also highlights the scientific value of preserving astronomical observations for future researchers.

“Astronomical data can have a remarkably long shelf life,” said Keck Observatory Chief Scientist John O’Meara. “The observations existed for years, but new techniques, improved models, and a fresh look at the data revealed something extraordinary. KOA allows scientists to return to those observations and ask new questions, sometimes uncovering discoveries that weren’t possible when the data were first collected.”

Looking Ahead

The research team continues to study the planet and hopes to obtain spectroscopy and other measurements that could reveal more about its atmosphere, temperature, mass, and ongoing accretion.

For now, Elias 2-24 b offers a rare opportunity to witness a giant planet in the midst of formation.

“This system has become a laboratory for understanding how planets form,” Cieza said. “Every new observation helps us piece together one of the most complex puzzles in modern astrophysics, the origin of planetary systems like our own.”

Source: W.M. Keck Observatory/News

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Related Link:

Science Paper | NASA Release

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Science Contact:

Andrea Bernardi
andrea.bernardi@mail.udp.cl

Media Contact:

Meagan O’Shea
moshea@keck.hawaii.edu

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A Wave of Ancient Quasars from the Dawn of the Universe

15 of the 31 quasars discovered, the small dots at the center of each tile, with their names and redshift (z). Credit: ESA/Euclid/Euclid Consortium/NASA, image processing by the Euclid Science Ground Segment and Antoine Basset (CNES).

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Keck Observatory and ESA’s Euclid mission double the known population, including the two most distant quasars ever found

Maunakea, Hawaiʻi – Astronomers using the W. M. Keck Observatory on Maunakea, Hawaiʻi Island, have confirmed two-thirds (21 of 31) of the most ancient quasars from the Euclid mission, including two of the most distant ever observed.

Quasars represent a brief phase in a galaxy’s life during which large amounts of material spiral into the central supermassive black hole, releasing enormous amounts of energy. In this phase, the galaxy’s nucleus can become one of the brightest persistent sources in the Universe.

Astronomers have been hunting for the Universe’s earliest quasars for decades. These celestial archives reveal conditions in the earliest days of the cosmos, including how the first supermassive black holes and galaxies took shape. But accessing them isn’t easy. Quasars from this era are difficult to find: they are elusive, as few galaxies had time to grow large enough, and their light has traveled for more than 13 billion years to reach us, arriving faint and stretched into infrared wavelengths, where it can resemble nearby cool stars.

“We see these quasars as they were during the Universe’s infancy,” says Daming Yang, lead author of the study and graduate student at Leiden University in the Netherlands. “By finding and studying them, we can better understand how these enormous systems formed and grew so quickly – one of the greatest mysteries in astrophysics.”

The study, led by an international team in the Euclid consortium, is published in today’s issue of Astronomy & Astrophysics.

Confirming Ancient Quasars

The 31 quasars reported here were selected from ESA’s Euclid Wide Survey, which will cover more than one-third of the total sky once complete. While the Euclid mission identified promising candidates, confirming them required follow-up spectroscopy from ground-based observatories.

To confirm these quasars spanning redshifts from 6.5 and beyond, the team used three instruments at Keck Observatory, covering a broad wavelength range: the Multi-Object Spectrograph for Infrared Exploration (MOSFIRE), the Low Resolution Imaging Spectrometer (LRIS), and the Keck Cosmic Web Imager (KCWI). With these instruments, the team analyzed the light from more than 100 candidates in the northern sky, searching each one for a telltale signature: a sharp drop in brightness known as the Lyman-alpha break. This cutoff is imprinted by hydrogen gas that pervaded the early universe, which absorbed the quasar’s light at specific wavelengths before it could reach us. The precise location of that drop confirms the object as a genuine quasar and pins down its distance.

The challenge is that these quasars appear incredibly faint due to their extreme distances, so detecting this signal requires the combination of highly sensitive instruments and the light-gathering capability of the world’s largest ground-based telescopes, such as Keck Observatory.

An elusive and distant population

Before Euclid, astronomers had identified only a handful of quasars at redshift 7 or higher after decades of searching — a measure of distance tied to how light stretches as the universe expands — corresponding to the first 770 million years after the Big Bang. Finding more and pushing further into the early universe is extraordinarily challenging for several reasons: so early in cosmic history, very few galaxies had grown large enough to power them; those that existed are so far away that their light has been travelling for over 13 billion years, arriving incredibly dim; and over that vast journey, the light has been stretched into infrared wavelengths, invisible to traditional optical telescopes.

The mission has already uncovered 12 new quasars above redshift 7, more than doubling the known population. For the first time, astronomers have a large enough sample to study these ancient quasars not as individual curiosities but as a population, building the first statistical picture of how supermassive black holes formed and grew in the Universe’s earliest epochs.

The two most ancient of the batch, EUCL J172902.75+641018.1 and EUCL J125308.55+705432.3, have redshifts of 7.77 and 7.69, respectively, setting a new record for the most ancient quasars ever found. Both lie more than 13 billion light-years away and emerged during the Universe’s first 670 million years.

Building a quasar chronicle

A multi-wavelength follow-up study of all high redshift quasars is currently underway. Using a collection of ground and space-based telescopes the team is constructing a quasar chronicle that will trace how supermassive black holes and their host galaxies evolved over the first billion years of cosmic history, and how reionization unfolded.

“We have a real sample at such high redshift for the first time, and we can finally start answering the questions that were unanswerable before,” said Yang.

“Every one of these 31 quasars is a new sightline into the early Universe, and the follow up science is just beginning” added Joseph Hennawi, co-author and professor at the University of California, Santa Barbara.

As the ESA Euclid space telescope continues to scan new sky, the probability of finding the first quasars beyond redshift 8 increases. A redshift 8 quasar would be shining when the Universe was less than about 630 million years old and would also place the strongest direct constraints yet on how early supermassive black holes could have formed and grown.

A Wave of Ancient Quasars Discovered from the Dawn of the Universe
Artist’s animation depicting a wave of ancient quasars discovered from the dawn of the universe.
Credit: W. M. Keck Observatory / Adam Makarenko. Image of Keck Observatory by Andrew Hara.

Source: W.M. Keck Observatory/News

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Astronomers Discover Third Galaxy Without Dark Matter

A close-up Hubble image of DF9 is shown beneath a wider view of the surrounding NGC 1052 region. Blue boxes highlight a line of related galaxies, including DF2 and DF4. Red outlines show where Keck Observatory’s KCWI instrument collected data, while yellow circles mark galaxy clusters whose motions have already been measured. Both images are oriented along the direction of the galactic structure. (Credit: Keim et al./DECaLS/HST).

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Findings strengthen evidence for a violent galactic collision that may have separated ordinary matter from dark matter

Maunakea, Hawaiʻi – Astronomers using W. M. Keck Observatory on Maunakea, Hawaiʻi Island, have discovered the third known galaxy apparently lacking dark matter, part of a strange linear structure that may have formed during a violent collision between galaxies.

The discovery strengthens evidence for a rare and previously unseen process in which ordinary matter becomes separated from dark matter, offering astronomers a powerful new way to study one of the universe’s greatest mysteries.

The galaxy, known as DF9, lies alongside two other unusual galaxies — DF2 and DF4 — which previously stunned astronomers because they appeared to contain little to no dark matter. New observations show that DF9 also lacks dark matter and is part of the same narrow line of faint, diffuse galaxies stretching across space.

“Almost every galaxy in the universe is dominated by dark matter. But DF2, DF4, and now DF9 appear to be extraordinary exceptions,” said Michael Keim, researcher and lead author of the study. “These findings provide some of the clearest evidence yet that these galaxies formed together in a violent event that separated ordinary matter from dark matter.”

The study, led by Yale University, is published today in The Astrophysical Journal.

A New Clue in the Dark Matter Mystery

Yale astronomers have played a central role in the discovery of dark matter-deficient galaxies since the first identification of DF2 and DF4 by astronomer Pieter van Dokkum and his team, who also used Keck Observatory observations to help confirm their unusual nature.

The discovery of DF9 strengthens the case that all three galaxies formed together during the same violent event, likely a high-speed collision between galaxies. Such a system has never been observed before and is reshaping astronomers’ understanding of how galaxies form.

Researchers believe the collision may have stripped gas away from its surrounding dark matter, allowing new galaxies to form from ordinary matter alone.

“The finding provides compelling evidence that dark matter behaves as a physical substance rather than the effect of an alternative theory of gravity, particularly at the dwarf-galaxy scale where those theories are most heavily debated,” added van Dokkum, co-author on the study.

Measuring the Invisible

The team used Keck Observatory’s Keck Cosmic Web Imager (KCWI) to measure the motions of stars inside DF9 by analyzing the light emitted across different wavelengths.

Those measurements revealed that DF9 has a mass of only about 100 million Suns, consistent entirely with the galaxy’s visible matter. If the galaxy contained a typical amount of dark matter, astronomers would expect it to be about 100 times more massive.

“KCWI’s exceptionally high precision enabled us to measure DF9’s extraordinarily low mass with the accuracy needed to demonstrate its lack of dark matter,” said Keim.

Building on these observations, future studies using both existing and upcoming observatories will enable the team to search for gas that may have been left behind in the collision and to constrain the gas content of the galaxies themselves.

Astronomers Discover Third Galaxy Without Dark Matter

Source: W.M. Keck Observatory/News

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Related Links

• Scientific Paper
• Yale University Release

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Science Contacts:

Michael Keim
michael.keim@yale.edu

Pieter Van Dokkum
pieter.vandokkum@yale.edu

Media Contact:

Meagan O’Shea
moshea@keck.hawaii.edu

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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.

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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 Hawaiʻi 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. For more information, visit: www.keckobservatory.org

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Keck Observatory observations help constrain a long-predicted pathway for black hole formation

Birth of a black hole: These images and animation shows a shell of thick gas and dust (red) expelled from the outer layers of a star as its core collapsed into a black hole. The inner regions show a heated sphere of gas continuing to fall into the black hole that is hidden inside the hot gas. Credit: Keith Miller, Caltech/IPAC – SELab. Video

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Maunakea, Hawaiʻi – Astronomers using W. M. Keck Observatory on Maunakea, Hawaiʻi Island contributed key observations to the identification of a rare stellar death in which a massive star appears to have collapsed directly into a black hole without first exploding as a supernova. The event occurred in the Andromeda galaxy and provides strong observational support for a long-theorized but rarely confirmed route to black hole formation.

The study, led by researchers at Columbia University, is published in today’s issue of the journal Science and combines archival space-based data with targeted ground-based follow-up observations from multiple observatories.

“This has probably been the most surprising discovery of my life,” said Kishalay De, professor of astronomy at Columbia University and lead author of the study. “The evidence of the disappearance of the star was lying in public archival data, and nobody noticed it for years until we picked it out.”

A quiet stellar death in Andromeda

The object, designated M31-2014-DS1, was a supergiant star located about 2.5 million light-years from Earth in the Andromeda galaxy. When it formed, the star was roughly 13 times the mass of the Sun. Over its lifetime, powerful stellar winds stripped away much of that mass, leaving it with about five times the mass of the Sun at the end of its life.

Archival observations from NASA’s NEOWISE mission revealed that the star gradually brightened in infrared light over several years before fading dramatically and disappearing from view. Unlike a typical supernova, the event showed no evidence of a powerful outward explosion. Instead, it left behind a shell of dust and a faint infrared glow.

“The dramatic and sustained fadig of this star is very unusual, and suggests a supernova failed to occur, leading to the collapse of the star’s core directly into a black hole,” De said.

Critical follow up from the ground

To better constrain the nature of the event, the team conducted follow-up observations using the Near-Infrared Echellette Spectrograph (NIRES) on the Keck II Telescope, with observing time awarded via the NASA-Keck partnership.

Prior to the Keck observations, there were no ground-based infrared spectra of the source at sufficient sensitivity to test whether the star had truly faded at infrared wavelengths.

NIRES is optimized for studying extremely faint infrared sources and isparticularly well suited to probing dusty stellar remnants. The data placed important limits on the temperature, composition, and evolution of the material left behind after the star disappeared, including faint emissio from material expelled by the star, helping rule out alternative explanations such as an unusual supernova or intrinsic stellar variability.

“It was only with Keck’s sensitivity in the near infrared that we could confirm the star had truly faded at all wavelengths,” De said. “Even with NIRES, the source was barely detected, which allowed us to rule out normal hints of stellar variability or dust obscuration and strengthened the case that the star had genuinely disappeared.”

The Keck observations were analyzed alongside data from space-based telescopes and other ground-based facilities as part of a coordinated, multi-wavelength campaign.

A Rare View into Direct Collapse

Astronomers have long known that black holes originate from massive stars, but direct observational evidence of that transformation has been scarce. While gravitational-wave detections have revealed black hole mergers across the universe, they do not show how those black holes initially formed.

Only one other candidate direct-collapse event has been reported previously, but it was significantly more distant and fainter, leaving its interpretation uncertain. The relative proximity of Andromeda and the quality of the available data make M31-2014-DS1 a particularly compelling case.

“We’ve known that black holes must come from stars,” said Morgan MacLeod, lecturer in astronomy at Harvard University and co-author of the study. “With events like this, we’re getting to watch it happen, and are learning a huge amount about how that process works along the way.”

Looking ahead

The findings suggest that direct collapse may be a more common outcome for massive stars than previously assumed. Future infrared surveys, combined with sensitive ground-based facilities like Keck Observatory, are expected to uncover additional examples and further clarify the physical conditions that determine how massive stars end their lives.

Source: W.M. Keck Observatory/Science News

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Related Links:

• Columbia Press Release


• Flatiron Institute Press Release


• Science Paper

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About NIRES

The Near-Infrared Echellette Spectrograph (NIRES) is a prism cross-dispersed near-infrared spectrograph built at the California Institute of Technology by a team led by Chief Instrument Scientist Keith Matthews and Prof. Tom Soifer. Commissioned in 2018, NIRES covers a large wavelength range at moderate spectral resolution for use on the Keck II telescope and observes extremely faint red objects found with the Spitzer and WISE infrared space telescopes, as well as brown dwarfs, high-redshift galaxies, and quasars. Support for this technology was generously provided by the 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 Hawaiʻi 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. For more information, visit: www.keckobservatory.org

Astronomers Reveal Hidden Lives of the Early Universe’s Ultramassive Galaxies

A new multi-wavelength study shows that some ultramassive galaxies shut down star formation early, while others remain active but hidden by dust

Maunakea, Hawaiʻi – An international team of astronomers has uncovered multiple evolutionary paths for the universe’s most massive galaxies. Observations of ultramassive galaxies, each containing more than 100 billion stars, show that less than two billion years after the Big Bang, some had already stopped forming stars and lost their dust, while others continued forming stars hidden behind thick dust clouds. Because dusty, star-forming galaxies can appear red and inactive, distinguishing truly “dead” galaxies from those still forming stars has long been a challenge—making the discovery of genuinely quiescent systems at such early times especially surprising.

“By combining multi-wavelength observations, we can tell which galaxies truly have limited ongoing star formation and which are still active but heavily hidden by dust,” said Wenjun Chang, lead author and graduate student at the University of California, Riverside. “Our far-infrared and (sub)millimeter measurements allow us to constrain how much dust these early massive galaxies contain.”

The study, led by Chang under the mentorship of Gillian Wilson, Vice Chancellor for Research, Innovation and Economic Development and Professor of Physics at the University of California, Merced, was presented at a media briefing during the 247th meeting of the American Astronomical Society on January 5, 2026, in Phoenix, Arizona.

Peering Through Cosmic Dust with Multi-Wavelength Observations

The findings come from MAGAZ3NE (the MAssive Galaxies at z ~ 3 NEar-infrared Survey), a long-running collaboration that uses spectroscopy and multi-wavelength observations to investigate how the most massive galaxies formed and evolved.

The team used more than 30 nights of Keck Observatory’s spectroscopy obtained through the Multi-Object Spectrograph for Infrared Exploration (MOSFIRE) instrument, which provided the precise redshifts and stellar mass measurements needed to interpret the multi-wavelength data.

Combining Keck Observatory optical data with longer-wavelength far-infrared and radio observations from the Atacama Large Millimeter/submillimeter Array (ALMA) and the Karl G. Jansky Very Large Array (VLA) enabled the researchers to test whether massive galaxies previously classified as quiescent were truly inactive or instead hosting star formation or nuclear activity that is obscured at optical and near-infrared wavelengths.

“While optical and near-infrared data alone can severely underestimate obscured star formation in dusty massive galaxies, ALMA probes far-infrared wavelengths allowing improved constraints on the nature of these galaxies,” said Dr. Benjamin Forrest, a researcher at the University of California, Davis, who played a central role in the development of the MAGAZ3NE survey and its multi-wavelength analysis of ultramassive galaxies, and led the proposal that resulted in many of the ALMA observations used in this study.

“What is striking is not just that we can detect hidden activity, but that we see such diversity among galaxies with similar masses at the same epoch,” Wilson said. “That tells us that the shutdown of star formation in the most massive galaxies was neither uniform nor simple, and it places important new constraints on our understanding of galaxy formation and evolution in the early Universe.”

Rethinking How the Most Massive Galaxies Evolve

Understanding how massive galaxies stop forming stars is key to explaining why today’s universe looks the way it does. The team’s research helps clarify whether ultramassive galaxies in the early universe are ‘dusty or dead’ – their answer is not one or the other. The results show that most of the ultramassive galaxies studied are genuinely quiescent, indicating a rapid and efficient shutdown of star formation.

Within this quiescent population, several systems are among the most dust-poor massive galaxies ever identified at these early cosmic times. The remaining two galaxies exhibit residual dust emission, with one showing evidence for ongoing but heavily obscured star formation, and the other caught in the process of quenching. These results offer a rare glimpse into the diverse evolutionary paths taken by the universe’s most massive galaxies.

“What excites me most about this work is that we are able to study an extremely rare population in the universe by combining data from as many telescopes as possible,” said Chang. “By bringing together optical, near-infrared, and far-infrared observations, we can build a much more complete picture of what ultra-massive galaxies really look like at these early cosmic times.”

Members of the MAGAZ3NE collaboration involved in this work include Dr. Ian McConachie, postdoctoral researcher at the University of Wisconsin–Madison; Professor Allison Noble of Arizona State University; Professor Tracy Webb of McGill University; Professor Adam Muzzin of York University, Canada; Professor Michael Cooper of the University of California, Irvine; Professor Gabriela Canalizo of the University of California, Riverside; Professor Danilo Marchesini of Tufts University; Dr. Percy Gomez, Staff Astronomer at the W. M. Keck Observatory; Dr. Stephanie Urbano Stawinski of the University of California, Santa Barbara.

Source: W.M. Keck Observatory/Science News

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Contacts:

Wenjun Chang
UC Riverside
Email: wchan148@ucr.edu

Gillian Wilson
UC Merced
Email: gwilson@ucmerced.edu

Benjamin Forrest
UC Davis
Email: bforrest@ucdavis.ed

AAS Press: Susanna Kohler
Email: susanna.kohler@aas.org

Media Contact: Meagan O’Shea

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Related Links:

UC Merced Pess Release - NRAO Press Release - Science Paper

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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 Hawaiʻi 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. For more information, visit: www.keckobservatory.org

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Astronomers Sharpen the Universe’s Expansion Rate, Deepening a Cosmic Mystery

Researchers using time-delay cosmography independently confirmed that the universe’s current rate of expansion, known as the Hubble constant (H₀), does not match values predicted from measurements from the universe when it was much younger. This “Hubble tension” may point to new physics governing the universe. Credit: W. M. Keck Observatory / Adam Makarenko

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New results strengthen the “Hubble tension,” hinting at the need for rethinking our model of the universe

Maunakea, Hawaiʻi – A team of astronomers using a variety of ground and space-based telescopes including the W. M. Keck Observatory on Maunakea, Hawaiʻi Island, have made one of the most precise independent measurements yet of how fast the universe is expanding, further deepening the divide on one of the biggest mysteries in modern cosmology.

Using data gathered from Keck Observatory’s Cosmic Web Imager (KCWI) as well as NASA’s James Webb Space Telescope (JWST), the Hubble Space Telescope (HST) the Very Large Telescope (VLT), and European Organisation for Astronomical Research in the Southern Hemisphere (ESO) researchers have independently confirmed that the universe’s current rate of expansion, known as the Hubble constant (H₀), does not match values predicted from measurements from the universe when it was much younger.

The finding strengthens what scientists call the “Hubble tension,” a cosmic disagreement that may point to new physics governing the universe.

“What many scientists are hoping is that this may be the beginning of a new cosmological model,” said Tommaso Treu, Distinguished Professor of Physics and Astronomy at the University of California Los Angeles and one of the authors of the study published in Astronomy and Astrophysics.

“This is the dream of every physicist. Find something wrong in our understanding so we can discover something new and profound,” added Simon Birrer, Assistant Professor of Physics at the Stony Brook University and one of the corresponding authors of the study.

A Constant in Question Questioned Constantly

Coined by astronomer Edwin Hubble, who first calculated it in 1929, the Hubble Constant is the rate at which the universe expands. This number reveals not only the universe’s current speed of growth, but also its age and history. Yet nearly a century later, scientists still can’t agree on its exact value. The Hubble Constant can be measured in two ways, one probing the universe at early times and another probing the universe at times near today. The early universe probe, which uses cosmological models to indirectly provide the current expansion rate of the universe, favors an expansion rate of ~67 km/s/Mpc; and the late (nearby) universe probe, which measures the local universe as it exists today favors an expansion rate of 73 km/s/Mpc. Measurements based on the nearby universe differ from predictions drawn from the early universe, resulting in what is famously known as the Hubble Tension.

Confirming this tension would force scientists to rethink the very makeup of the cosmos; perhaps revealing new particles, or evidence for an “early dark energy” phase that briefly accelerated expansion after the Big Bang. Because the implications are so profound, astronomers stress the importance of multiple independent methods to cross-check the result.

“This is significant in that cosmology as we know it may be broken,” said John O’Meara, Chief Scientist and Deputy Director of Keck Observatory. “If it is true that the Hubble Tension isn’t a mistake in the measurements, we will have to come up with new physics.”

New Way to Measure the Universe

To make this precise measurement, the team used a method called time-delay cosmography. Much like a funhouse mirror bends and distorts reflections, massive galaxies bend the light of more distant galaxies and quasars, producing multiple images of the same object.

When the distant object’s brightness changes, astronomers can measure how long it takes those changes to appear in each image. Those “time delays” act like cosmic yardsticks — allowing scientists to calculate distances across the universe and, ultimately, determine how fast it’s expanding.

KCWI’s powerful spectroscopy was essential to the measurement. By observing the motion of stars within the lensing galaxies, the instrument revealed how massive those galaxies are and how strongly they bend light, critical information for pinning down the Hubble Constant.

The Quest Continues

The team’s measurement currently achieves 4.5% precision — an extraordinary feat, but not yet enough to confirm the discrepancy beyond doubt. The next goal is to refine that precision to better than 1.5%, a level of certainty “probably more precise than most people know how tall they are,” noted Martin Millon, postdoctoral fellow at ETH Zurich and the third corresponding author of the study.

Artist Interpretation of TDCOSMO 2025 (Video)

Source: W.M. Keck Observatory/Science News

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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 Adaptive Optics (AO)

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 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 Hawaiʻi 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.

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Astronomers reveal tasty insights into exoplanet formation using SPAM

The NIRC2 image of dust around a young star named HD34282 (left) produced using an algorithm to construct images from aperture masking interferometry data. The light from the star is removed and its location is marked with a star symbol in all panels. The model that reproduces the data (middle) includes a circular inner structure around the star, which may be an envelope of dust. There is also a large protoplanetary disk around both the star and the inner structure. Between the inner structure and the protoplanetary disk is a ~40 AU gap, where planets may be forming. On the right is the image of the model after it is passed through the algorithm used on the left. This is done to test if the model can visually reproduce the data. Credit: Christina Vides / University of California Irvine / W. M. Keck Observatory.

The name SPAM is a registered trademark of Hormel Foods, LLC. This release and image are not sponsored or endorsed by Hormel Foods. Credit: W. M. Keck Observatory / Ilihia Gionson.

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Study serves up the closest-ever view of a planet-forming disk around young star HD 34282

Maunakea, Hawaiʻi – Astronomers using W. M. Keck Observatory on Maunakea, Hawaiʻi Island have taken the closest-ever look at the dusty regions where planets form, offering new insight into the earliest stages of planetary birth.

HD 34282 is one of thirty objects observed thus far as part of The Search for Protoplanets with Aperture Masking, affectionately referred to as SPAM.

“We all want to know where we came from and how our solar system formed,” said Christina Vides, a graduate student at the University of California Irvine and lead author of the study published in The Astrophysical Journal. “By studying systems like this, we can watch planet formation in action and learn what conditions give rise to worlds like our own.”

Peering Into Planet Nurseries

The team used Keck Observatory’s Near-Infrared Camera (NIRC2) which enables astronomers to see closer to a star than traditional imaging methods permit.

Their target, HD 34282, is a young star about 400 light-years away, surrounded by a thick ring of dust and gas—a “transition disk” thought to be sculpted by growing planets.

With Keck Observatory’s advanced instrumentation and adaptive optics, Vides and the team captured the most detailed view yet of the inner regions of HD 34282’s disk, revealing clumpy structures and brightness patterns that hint at possible planet-forming activity.

Although no confirmed protoplanet was detected, the observations provided the closest constraints yet on where a young planet could be hiding, as well as estimates of the star’s mass and accretion rate—key clues for modeling how its surrounding material might evolve into planets.

The Rarest of Discoveries

Early detection of protoplanets is exceptionally rare and technically challenging.

PDS 70 b and PDS 70 c are the only two confirmed protoplanets that have ever been imaged directly. Both were discovered in 2020 by Caltech observers also using Keck Observatory’s NIRC2 instrument.

Each new observation builds on that legacy, bringing astronomers closer to understanding how planetary systems emerge from swirling disks of gas and dust.

“This work is pushing the boundaries of what we can see,” said Vides. “Keck’s adaptive optics and masking capabilities make it possible to resolve features just a few astronomical units from the star—regions that are otherwise completely invisible.”

What’s Next

The team will continue using Keck’s advanced instruments to study other young stars with promising disks and compile more data for SPAM. The team is also preparing for observations using future instrumentation like SCALES, a next-generation high-contrast imager now being developed for Keck Observatory, which will expand the search for protoplanets in unprecedented detail.

“Every new system we study helps us understand a little more about how planets form and evolve,” said Vides. “It’s incredible that we can point a telescope at a young star hundreds of light-years away and actually see the conditions that could give rise to new worlds.”

Download Youtube video here

Source: W.M. Keck Observatory/Science News
Science Paper

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Astronomers Tune Into the Music of a Nearby Star Unlocking a Surprising Discovery

HD219134 system

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By analyzing subtle stellar vibrations, researchers using the Keck Planet Finder uncovered hidden interior structures that challenge long-standing models

Maunakea, Hawaiʻi – Astronomers using W. M. Keck Observatory on Maunakea, Hawaiʻi Island have listened to the music of a nearby star, uncovering surprises that shake our understanding of how stars work.

The study used Keck Observatory’s latest cutting-edge instrument, the Keck Planet Finder (KFP), to detect oscillations rippling through a star. The findings, published today in the The Astrophysical Journal, open a new window into the interiors of stars that were once thought too quiet to probe.

A Stellar Symphony

Although we cannot directly hear them with our own ears, stars are not silent. Like musical instruments, stars resonate with natural frequencies that astronomers can “hear” with the right tools. This field of research — known as asteroseismology — allows scientists to use these frequencies to probe the interiors of stars, just as earthquakes help scientists learn about Earth’s interior.

“The vibrations of a star are like its unique song,” said Yaguang Li, lead author and researcher at the University of Hawaiʻi at Mānoa. “By listening to those oscillations, we can precisely determine how massive a star is, how large it is, and how old it is.”

Until now, “stellar songs” had mostly been recorded from stars hotter than the Sun, using NASA space telescopes like Kepler and TESS. But the oscillations of HD 219134 — a cooler, orange-colored star just 21 light-years away — are too subtle to pick up using brightness variations that are probed by space-based telescopes.

Keck Observatory’s KPF instrument precisely measures the motion of the stellar surface towards and away from the observer. Over four consecutive nights, the team used KPF to collect over 2,000 ultra-precise velocity measurements of the star — enabling them to catch the star’s vibrations in action. This is the first asteroseismic inference of the age and radius for a cool star using KPF.

“KPF’s fast readout mode makes it perfectly suited for detecting oscillations in cool stars,” added Li, “and it is the only spectrograph on Mauna Kea currently capable of making this type of discovery.”

Artist’s concept of the HD219134 system. Sound waves propagating through the stellar interior were used to measure its age and size, and characterize the planets orbiting the star. Credit: openAI, based on original artwork from Gabriel Perez Diaz/Instituto de Astrofísica de Canarias. The 10-second audio clip transforms the oscillations of HD219134 measured using the Keck Planet Finder into audible sound. The star pulses roughly every four minutes. When sped up by a factor of ~250,000, its internal vibrations shift into the range of human hearing. By “listening” to starlight in this way, astronomers can explore the hidden structure and dynamics beneath the star’s surface.

A 10-Billion-Year-Old Time Capsule

Using the oscillations detected in HD 219134, the team determined its age to be 10.2 billion years, more than twice the age of our Sun. This makes it one of the oldest main-sequence stars with an age determined using asteroseismology.

This measurement is more than just a curiosity—it has major implications for how we understand stellar aging. Astronomers use a method called gyrochronology to estimate stellar ages based on how quickly they spin. Young stars rotate rapidly, but they gradually slow down as they lose angular momentum over time—much like spinning tops that wind down.

But something curious happens with stars like HD 219134: their spin-down seems to stall at older ages. The new asteroseismic age allows scientists to anchor models at the old end of the stellar timeline, helping to refine how we estimate the ages of countless other stars.

“This is like finding a long-lost tuning fork for stellar clocks,” said Dr. Yaguang Li. “It gives us a reference point to calibrate how stars spin down over billions of years.”

A Puzzle in the Star’s Size

Surprisingly, the team also discovered that HD 219134 appears smaller than expected. While other measurements using interferometry — a technique that measures a star’s size by observing it with multiple telescopes — gave a radius about 4% larger, the asteroseismic measurement suggests a more compact star.

This difference is puzzling and challenges assumptions in stellar modeling—especially for cooler stars like HD 219134. Whether the discrepancy is due to unrecognized atmospheric effects, magnetic fields, or deeper modeling issues remains an open question.

The star HD 219134 is not alone — it hosts a family of at least five planets, including two rocky, super-Earth-sized worlds that transit across the star’s face. With a more precise measurement of the star’s size, the team was able to refine the sizes and densities of these planets. Their updated values confirm that these worlds likely have Earth-like compositions, with solid, rocky surfaces.

Stellar Sounds and the Search for Life

Instruments like the Keck Planet Finder will enable measurements for other stars like HD 219134, which will become the focus for searching for life on other planets in the coming decades using future NASA Missions such as the Habitable Worlds Observatory.

“When we find life on another planet, we will want to know how old that life is.” said Dr. Daniel Huber, a co-author on the study. “Listening to the sounds of its star will tell us the answer.”

Paper DOI: 10.3847/1538-4357/adc737

 

Source: W.M. Observatory/Science News

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Media Contact

Meagan O’Shea
moshea@keck.hawaii.edu

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About KPF

The Keck Planet Finder (KPF) is a high-resolution optical spectrometer designed to study exoplanets identified through the behavior of their host stars using the Doppler Technique – a method that can detect stars moving back and forth at a rate of less than 30 centimeters per second. KPF has the ability to study smaller, Earth-like planets orbiting nearby bright stars and the ability to characterize transiting planets from missions such as TESS, Kepler, and PLATO, measuring their masses and orbital properties. Support for KPF was provided by the National Science Foundation, the Heising-Simons Foundation, W. M. Keck Foundation, Simons Foundation, Mt. Cuba Astronomical Foundation, the Jet Propulsion Laboratory, which is managed by Caltech for NASA, private donors, and W. M. Keck Observatory, Caltech, University of California, and University of Hawaiʻi.

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. For more information, visit: www.keckobservatory.org

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Famed WR 104 “Pinwheel” Star Reveals Another Surprise (and Some Relief)

An artist’s concept of the famous Wolf-Rayet 104 “pinwheel star,” previously nicknamed the “Death Star.” New research conducted from Maunakea, Hawaiʻi using three Keck Observatory instruments reveals the orbit of the two stars are angled 30 or 40 degrees away from us, sparing Earth from a potential gamma-ray burst (GRB). Credit: W. M. Keck Observatory/Adam Makarenko

An artist’s animation of WR 104, first discovered at Keck Observatory in 1999. It consists of two stars orbiting each other; a Wolf-Rayet star that produces a powerful, carbon-rich wind (depicted in yellow), and an OB star that creates a wind mostly made of hydrogen (depicted in blue). When the winds collide, they whip up a hydrocarbon “dust” spiral. Credit: W. M. Keck Observatory/Adam Makarenko

An infrared image of WR 104 captured by Keck Observatory’s NIRC instrument in 1998
Credit: U.C. Berkeley Space Sciences Laboratory/W. M. Keck Observatory

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A new spin on decades of W. M. Keck Observatory research

Maunakea, Hawaiʻi – A recent study reveals the famous Wolf-Rayet 104 “pinwheel star” holds more mystery but is even less likely to be the potential ‘Death Star’ it was once thought to be.

Research by W. M. Keck Observatory Instrument Scientist and astronomer Grant Hill finally confirms what has been suspected for years: WR 104 has at its heart a pair of massive stars orbiting each other with a period of about 8 months and the collision between their powerful winds gives rise to its rotating pinwheel of dust that glows in the infrared, and spins with the same period.

The pinwheel structure of WR 104 was discovered at Keck Observatory in 1999 and the remarkable images of it turning in the sky astonished astronomers. One of the two stars that were suspected to orbit each other – a Wolf-Rayet star– is a massive, evolved star that produces a powerful wind highly enriched with carbon. The second star – a less evolved but even more massive OB star – has a strong wind that is still mostly hydrogen. Collisions between winds like these are thought to allow hydrocarbons to form, often referred to as “dust” by astronomers. When discovered, WR 104 also made headlines as a potential gamma-ray burst (GRB) that could be aimed right at us. Models of the pinwheel images indicated it was rotating in the plane of the sky as if we were looking directly down on someone spinning a streaming garden hose over their head. That could mean the rotational poles of the two stars might be pointed in our direction as well. When one of the stars ends its life as a supernova the explosion might be energetic enough to create a GRB that would beam in the polar directions. Since it is located right here in our own Galaxy, and seemed to be aimed right at us, at the time, WR 104 gained a second nickname – the ‘Death Star’.

Hill’s research, published in the Monthly Notices of the Royal Astronomical Society, is based on spectroscopy using three of Keck Observatory’s instruments – the Low Resolution Imaging Spectrometer (LRIS), the Echellette Spectrograph and Imager (ESI), and the Near-Infrared Spectrograph (NIRSPEC). With these spectra, he was able to measure velocities for the two stars, calculate their orbit and identify features in the spectra arising from the colliding winds. There turned out to be a very big surprise in store though.

“Our view of the pinwheel dust spiral from Earth absolutely looks face-on (spinning in the plane of the sky), and it seemed like a pretty safe assumption that the two stars are orbiting the same way” says Hill. “When I started this project, I thought the main focus would be the colliding winds and a face-on orbit was a given. Instead, I found something very unexpected. The orbit is tilted at least 30 or 40 degrees out of the plane of the sky.”

While a relief for those worried about a nearby GRB pointed right at us, this represents a real curveball. How can the dust spiral and the orbit be tilted so much to each other? Are there more physics that needs to be considered when modelling the formation of the dust plume?

“This is such a great example of how with astronomy we often begin a study and the universe surprises us with mysteries we didn’t expect” muses Hill. “We may answer some questions but create more. In the end, that is sometimes how we learn more about physics and the universe we live in. In this case, WR 104 is not done surprising us yet!”

Source: W.M. Keck ObservatoryScience News

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About NIRSPEC

The Near-Infrared Spectrograph (NIRSPEC) is a unique, cross-dispersed echelle spectrograph that captures spectra of objects over a large range of infrared wavelengths at high spectral resolution. Built at the UCLA Infrared Laboratory by a team led by Prof. Ian McLean, the instrument is used for radial velocity studies of cool stars, abundance measurements of stars and their environs, planetary science, and many other scientific programs. A second mode provides low spectral resolution but high sensitivity and is popular for studies of distant galaxies and very cool low-mass stars. NIRSPEC can also be used with Keck II’s adaptive optics (AO)system to combine the powers of the high spatial resolution of AO with the high spectral resolution of NIRSPEC. Support for this project was provided by the Heising-Simons Foundation.

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 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. For more information, visit: www.keckobservatory.org

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NASA's Hubble Finds Kuiper Belt Duo May Be Trio

This artist’s concept depicts one of the possible scenarios for the 148780 Altjira system in the solar system’s Kuiper Belt. It is likely a hierarchical triple formation, in which two very close companions are orbited by a third member at a greater distance. Credit:NASA, ESA, Joseph Olmsted (STScI).

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Maunakea, Hawaiʻi – A team of researchers using data from W. M. Keck Observatory on Maunakea, Hawaiʻi Island and NASA’s Hubble Space Telescope have discovered what is likely a stable trio of icy space rocks in the solar system’s Kuiper Belt.

If confirmed as the second such three-body system found in the region, the 148780 Altjira system suggests there could be similar triples waiting to be discovered, which would support a particular theory of our solar system’s history and the formation of Kuiper Belt objects (KBOs).

The study, led by Brigham Young University, is published in today’s issue of the journal The Planetary Science Journal.

“The universe is filled with a range of three-body systems, including the closest stars to Earth, the Alpha Centauri star system, and we’re finding that the Kuiper Belt may be no exception,” said the study’s lead author Maia Nelsen, a physics and astronomy graduate of Brigham Young University in Provo, Utah.

Known since 1992, KBOs are primitive icy remnants from the early solar system found beyond the orbit of Neptune. To date, over 3,000 KBOs have been cataloged, and scientists estimate there could be several hundred thousand more that measure over 10 miles in diameter. The largest KBO is dwarf planet Pluto.

The team used a series of Keck Observatory NIRC2 narrow-field infrared camera data between 2006 and 2020 to model Altjira in different configurations.

“This discovery is scientifically fascinating because we don’t know how to distinguish between different models of how this part of the solar system formed, and the existence of triple systems helps rule one model out,” said John O’Meara, Keck Observatory Chief Scientist and Deputy Director. “With AO, we can be as sharp an eye on the sky as a space telescope, complimenting Hubble’s strengths.”

The Hubble finding is crucial support for a KBO formation theory, in which three small rocky bodies would not be the result of collision in a busy Kuiper Belt, but instead form as a trio directly from the gravitational collapse of matter in the disk of material surrounding the newly formed Sun, around 4.5 billion years ago. It’s well known that stars form by gravitational collapse of gas, commonly as pairs or triples, but that idea that cosmic objects like those in the Kuiper Belt form in a similar way is still under investigation.

The Altjira system is located in the outer reaches of the solar system, 3.7 billion miles away, or 44 times the distance between Earth and the Sun. Hubble images show two KBOs located about 4,700 miles (7,600 kilometers) apart. However, researchers say that repeated observations of the objects’ unique co-orbital motion indicate the inner object is actually two bodies that are so close together they can’t be distinguished at such a great distance.

“With objects this small and far away, the separation between the two inner members of the system is a fraction of a pixel on Hubble’s camera, so you have to use non-imaging methods to discover that it’s a triple,” said Nelsen

That is where Keck Observatory’s unique capabilities comes into play. “Keck Observatory is the one ground-based telescope that was able to do high-quality enough observations of Altjira for our study. All of our other observations were from HST, but those alone were not enough of an observational baseline for our models,” said Nelsen. “The extra points from Keck Observatory made for a better and more statistically robust result giving more credence to the strength of the hierarchical triple orientation of Altjira.

“In this case, its 10-meter mirror, coupled with its laser guide star adaptive optics system, provided small scales on the sky, which is what you need to do this type of work,” added O’Meara.

To conduct this research, scientists gathered a 17-year observational baseline of data from Keck Observatory and Hubble, watching the orbit of the Altjira system’s outer object.

“Over time, we saw the orientation of the outer object’s orbit change, indicating that the inner object was either very elongated or actually two separate objects,” said Darin Ragozzine, also of Brigham Young University, a co-author of the Altjira study.

Currently, there are about 40 identified binary objects in the Kuiper Belt. Now, with two of these systems likely triples, the researchers say it is more likely they are looking not at an oddball, but instead a population of three-body systems, formed by the same circumstances. However, building up that evidence takes time and repeated observations.

The only Kuiper Belt objects that have been explored in detail are Pluto and the smaller object Arrokoth, which NASA’s New Horizons mission visited in 2015 and 2019, respectively. New Horizons showed that Arrokoth is a contact binary, which for KBOs means that two objects that have moved closer and closer to one another are now touching and/or have merged, often resulting in a peanut shape. Ragozzine describes Altjira as a “cousin” of Arrokoth, a member of the same group of Kuiper Belt objects. They estimate Altjira is 10 times larger than Arrokoth, however, at 124 miles (200 kilometers) wide.

While there is no mission planned to fly by Altjira to get Arrokoth-level detail, Nelsen said there is a different upcoming opportunity for further study of the intriguing system.

Altjira has entered an eclipsing season, where the outer body passes in front of the central body. This will last for the next ten years, giving scientists a great opportunity to learn more about it,” Nelsen said. NASA’s James Webb Space Telescope is also joining in on the study of Altjira as it will check if the components look the same in its upcoming Cycle 3 observations.

Source: W.M. Keck Observatory/Science News

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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 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. For more information, visit: www.keckobservatory.org.

This artist’s concept depicts one of the possible scenarios for the 148780 Altjira system in the solar system’s Kuiper Belt. It is likely a hierarchical triple formation, in which two very close companions are orbited by a third member at a greater distance. NASA, ESA, Joseph Olmsted (STScI).

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Dandelion Supernova Revealed in 3-D

An artist’s concept of a supernova remnant called Pa 30—the leftover remains of a supernova explosion that was witnessed from Earth in the year 1181. Unusual filaments of sulfur protrude beyond a dusty shell of ejected material. The remains of the original star that exploded, now a hot inflated star which may cool to become a white dwarf, are seen at the center of the remnant. The Keck Cosmic Web Imager (KCWI) at the W. M. Keck Observatory in Hawai‘i has mapped the strange filaments in 3-D and shown that they are flying outward at approximately 1,000 kilometers per second. Credit: W. M. Keck Observatory/Adam Makarenko

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New observations probe a sphere of filaments around a dead star

Maunakea, Hawaiʻi – For nearly six months during the year 1181, people looked up to the skies to find a new star glittering in the constellation Cassiopeia. Chinese and Japanese astronomers recorded the rare event, an explosion of a star, or supernova. In the centuries since, astronomers have searched for the remains of the blast, but it was not until 2013 that they were finally found. As part of a citizen scientist project, amateur astronomer Dana Patchick—who had sifted through images taken by the now-retired Wide-field Infrared Survey Explorer, or WISE—found a nebula at the site where the supernova had occurred.

Further observations convinced astronomers that this nebula, called Pa 30, was in fact the leftover ejected material from the 1181 supernova. Later, in 2023, astronomers discovered strange filaments within the supernova remnant, which resemble the wispy tendrils of a dandelion flower.

Now, with the help of the Caltech-built Keck Cosmic Web Imager (KCWI) at the W. M. Keck Observatory on Maunakea, Hawai‘i Island, astronomers have, for the first time, mapped the location of those unusual filaments in three dimensions in addition to the speed at which they are streaming outward from the site of the blast.

“A standard image of the supernova remnant would be like a static photo of a fireworks display,” says Caltech professor of physics Christopher Martin, who led the team that built KCWI. “KCWI gives us something more like a ‘movie’ since we can measure the motion of the explosion’s embers as they streak outward from the central explosion.”

Martin is a co-author of a new paper reporting the findings published today in The Astrophysical Journal Letters. The study is led by Tim Cunningham, a NASA Hubble Fellow at the Center for Astrophysics |Harvard & Smithsonian (CfA), and the co-lead author is Ilaria Caiazzo, a former Caltech postdoctoral scholar who recently became an assistant professor at the Institute of Science and Technology Austria.

3-D Look at Unusual Remains of a Historical Supernova

In 1181, astronomers in China and Japan recorded a new star in the sky, a rare supernova explosion. The remains of that supernova, called SN 1181, are depicted here in this artist’s animation, which flies around the remnant as it appears today in one moment in time. The corpse of the star that detonated, a hot and inflated “zombie” star, is seen within a dusty shell of ejected material. Beyond the dusty shell, bright radial filaments of sulfur extend three light-years out from their point of origin. The Keck Cosmic Web Imager (KCWI) at the W. M. Keck Observatory has mapped these filaments in 3-D and shown that they are flying outward at approximately 1,000 kilometers per second. Credit: W. M. Keck Observatory/Adam Makarenko

The 1181 supernova is thought to have occurred when a thermonuclear explosion was triggered on a dense dead star called a white dwarf. Typically, the white dwarf would be completely destroyed in this type of explosion, but in this case some of the star survived, leaving behind a sort of “zombie star.” This type of partial explosion is called a Type Iax supernova. “Because this was a failed explosion, it was fainter than normal supernovae, which has been shown to be consistent with the historical records,” Caiazzo says.

Material ejected in the 1181 explosion makes up the Pa 30 nebula that astronomers observe today. While the scientists know that the peculiar filaments, which glow with light from sulfur, were also generated by the supernova, they do not know how and when they formed.

To probe the three-dimensional structure of the supernova remnant, the astronomers turned to KCWI, an instrument that can capture multiwavelength, or spectral, information for every pixel in an image. This is like breaking apart the light captured in every pixel into a rainbow of colors. The spectral information enabled the team to measure the motions of the filaments poking out from the center of the explosion and ultimately create a 3D map of the structure. The filament material that is flying toward us shifted toward the blue higher-energy portion end of the visible spectrum (blue-shifted), while light from material moving away from us shifted toward the red end of the spectrum (red-shifted).

This is analogous to the Doppler shift one can hear as a blaring firetruck races by. As the vehicle moves toward us, the sound waves from its horn become squeezed into higher frequencies; as the truck moves away from us, the sound waves become elongated to lower frequencies.

Specifically, this study used the “red arm” of the KCWI instrument, which was installed at Keck Observatory last summer. KCWI consists of two halves: One captures light wavelengths at the blue end of the visible spectrum, and the other half covers the red end in addition to infrared light. “The addition of the red arm more than doubled the spectral coverage of KCWI and made these observations possible,” says Caltech graduate student and co-author Nikolaus Prusinski. “This 3D map comprises the most sensitive spatial and spectral measurements of Pa 30 to date and holds the current record for the largest contiguous region surveyed with the red channel.”

The results showed that the filament material in the supernova is flying outward from the site of the explosion at approximately 1,000 kilometers per second.

“We find the material in the filaments is expanding ballistically,” says Cunningham. “This means that the material has not been slowed down nor sped up since the explosion. From the measured velocities, looking back in time, you can pinpoint the explosion to almost exactly the year 1181.”

The 3D information also revealed a large cavity inside the spindly, spherical structure in addition to some evidence that the supernova explosion of 1181 occurred asymmetrically.

As to how the filaments formed after the blast, the scientists are still puzzled. “A reverse shock wave may be condensing surrounding dust into filaments, but we don’t know yet,” says Cunningham. “The morphology of this object is very strange and fascinating.”

Source: W.M. Keck Observatory/Science News

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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.

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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.

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