Saturday, June 27, 2026

Hubble Details Early Galaxy Transforming Neighborhood

Detailed visible-light images from Hubble reveal that several bursts of younger stars cleared the space in and around galaxy MXDFz4.4. Astronomers have long sought evidence to explain this transition — and Hubble has provided the first example in this time period. Credit Image: NASA, ESA, CSA, STScI, Ilias Goovaerts (STScI), Marc Rafelski (STScI, JHU), Anton Koekemoer (STScI); Image Processing: Alyssa Pagan (STScI)

This illustration portrays galaxy MXDFz4.4 when it existed 1.4 billion years after the big bang. At this time, the universe was still a mix of opaque and transparent gas as the Era of Reionization was gradually ending. Credit Illustration: NASA, ESA, Leah Hustak (STScI)

This shows the galaxy MXDFz4.4, enlarged at right, in the Hubble Ultra Deep Field (HUDF), captured by both the Hubble Space Telescope’s Advanced Camera for Surveys (ACS) and the James Webb Space Telescope’s NIRCam (Near-Infrared Camera). Credit Image: NASA, ESA, CSA, STScI, Ilias Goovaerts (STScI), Marc Rafelski (STScI, JHU), Anton Koekemoer (STScI); Image Processing: Alyssa Pagan (STScI)

Ancient Galaxy Amazes Scientists
Credit: NASA's Goddard Space Flight Center; Lead Producer: Paul Morris


Astronomers using NASA’s Hubble Space Telescope have found something they never expected — ultraviolet light from a galaxy that existed just 1.4 billion years after the big bang. That galaxy contains tightly clustered young stars that produce ionizing light capable of transforming the opaque, neutral gas within and immediately around the galaxy, clearing our view. This suggests that similar galaxies in the early universe were responsible for clearing the neutral fog of hydrogen gas that once filled the cosmos.

A paper describing this discovery was published June 23 in the Astrophysical Journal.

The galaxy, cataloged MXDFz4.4, existed at the end of the Era of Reionization, a transformative period in our universe. During roughly the first billion years of the cosmos, the gas between stars and galaxies was opaque to energetic ultraviolet light. As time wore on, gas everywhere became transparent or ionized. The changeover was not like an on/off switch, but likely took hundreds of millions of years. Researchers are still collecting evidence to fully understand how this happened, which is why MXDFz4.4 sets a critical precedent.

“Observing a galaxy like this was thought to be impossible,” said lead author Ilias Goovaerts, a postdoctoral fellow at the Space Telescope Science Institute (STScI) in Baltimore. “Researchers expected the ‘fog’ or neutral hydrogen that filled the early universe would be too thick and obscure our view of its ionizing light. Hubble not only spotted that light, but it also helped reveal incredible details about the galaxy’s characteristics.”

Great light ‘escape’

Young, massive stars emit ultraviolet light capable of ionizing hydrogen atoms. As this light traveled for over 12 billion years to reach Hubble, space expanded, and the light stretched or redshifted into visible light. Hubble’s wavelength coverage, combined with the sensitivity and resolution of its space-based vantage point, makes it the only telescope capable of capturing this ultraviolet light from the early universe. “Astronomers have found many galaxies that existed at this point in the history of the universe, but we haven’t detected ionizing photons from any of them, making MXDFz4.4 one of a kind,” said Marc Rafelski, a co-author and Hubble deputy mission head at STScI.

Hubble’s long exposures, pulled from several existing surveys, revealed that the galaxy’s young, massive stars are the source of the ultraviolet light, which cleared the surrounding space. These stars formed in bursts within the last few million years of MXDFz4.4’s existence and are crammed together.

Amplifying this crowding effect, MXDFz4.4 is about 100 times smaller by area than our Milky Way galaxy, but is forming stars 10 times faster.

“A lot of young, hot, massive stars in a small space do a better job of blasting through opaque gas,” Goovaerts said. The researchers estimate that 50 to 100% of the young stars’ energetic ionizing light is escaping the surrounding gas.

Massive stars’ lifetimes also play a role, since they live for only a few million years. Many explode as supernovae, releasing gigantic amounts of energy and blowing colossal holes that allow even more light to escape.

Partnering with other observatories

Hubble could not do this alone. These conclusions are supported by survey data taken by NASA’s James Webb Space Telescope in near-infrared light and the MUSE eXtremely Deep Field or MXDF, the galaxy’s namesake, captured by the European Southern Observatory’s Very Large Telescope (VLT) in visible light.

The team used Webb’s data to determine the galaxy’s mass, analyze its older stars, and measure the galaxy’s star formation history. The galaxy’s older stars are less massive and cooler, and therefore not responsible for changing the gas around them.

Comparing Hubble and Webb data also showed that recent star formation happened in bursts. “Without Webb to clarify what we saw in Hubble’s images, we couldn’t make these conclusions,” Rafelski said.

Data from the VLT pinpointed when MXDFz4.4 existed: 1.4 billion years after the big bang. Before this discovery, researchers had only identified a galaxy emitting ionized light from a time when the universe was 1.6 billion years old. Only a few additional examples have been identified, and those existed when the universe was about 2 billion years old. MXDFz4.4 brings researchers closer to drawing firm conclusions about how the Era of Reionization unfolded.

Expanding what we know
Studying the Era of Reionization is a decades-old endeavor. Researchers use statistics about star populations in nearby galaxies, which we can observe in great detail, to make well-informed assumptions about what might be happening in galaxies in the early universe, in part because their star populations are too distant to resolve in any detail.

In 2023, researchers using Webb showed that galaxies’ stars emitted enough light to heat and ionize the gas around them 900 million years after the big bang. This was a breakthrough, but astronomers need galaxies like MXDFz4.4 to fully explain how the process happened, since it shows how the high-energy light from young stars managed to escape the gas and dust within the galaxy itself.

It’s possible other galaxies like MXDFz4.4 are waiting to be discovered.

“Hubble’s observations of MXDFz4.4 let us test our hypotheses much closer to the Era of Reionization than ever before,” Rafelski said. “Finding more galaxies, especially at slightly later cosmic times where larger samples are within reach, would let us refine these measurements and figure out what cleared our view as that era was ending.”

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



Details:

Last Updated: Jun 23, 2026
Editor: Andrea Gianopoulos
Location: NASA Goddard Space Flight Center

Contact Media:

Claire Andreoli
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
claire.andreoli@nasa.gov

Claire Blome, Christine Pulliam
Space Telescope Science Institute
Baltimore, Maryland

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NASA’s Webb Pinpoints Millions of Stars Within Cigar Galaxy

Scientists used NASA’s James Webb Space Telescope to image edge-on starburst galaxy Messier 82 and trace its evolutionary history. This Webb and Hubble composite image includes 16.5 million stars (blue-white), dust grains (red-orange), and ionized hydrogen gas (yellow). Credit Image: NASA, ESA, CSA, Adam Smercina (STScI, Tufts), Thomas Williams (University of Manchester); Image Processing: Alyssa Pagan (STScI)

NASA’s James Webb Space Telescope observed edge-on starburst galaxy Messier 82, peering through dust to reveal 16.5 million stars and the galaxy’s distended disk structure. Scientists seek to learn the galaxy’s evolutionary history with the Webb data. Credit Image: NASA, ESA, CSA, Adam Smercina (STScI, Tufts), Thomas Williams (University of Manchester); Image Processing: Alyssa Pagan (STScI)

Side-by-side comparison of a portion of starburst galaxy Messier 82 (M82) as seen by NASA’s Hubble (left) and James Webb (right) space telescopes. Hubble detailed M82’s gas and dust structure, while Webb pierced through the dust and resolved millions of stars in infrared light. Credit Image: NASA, ESA, CSA, Adam Smercina (STScI, Tufts), Thomas Williams (University of Manchester); Image Processing: Alyssa Pagan (STScI)

Annotated image of the starburst galaxy Messier 82 captured by Webb's NIRCam (Near-Infrared Camera) instrument, with compass arrows, a scale bar, and color key for reference. Credit Image: NASA, ESA, CSA, Adam Smercina (STScI, Tufts), Thomas Williams (University of Manchester); Image Processing: Alyssa Pagan (STScI)

NASA’s James Webb Space Telescope’s near-infrared observation of M82 is the most recent addition to overall data on this starburst galaxy. The Hubble Space Telescope is one observatory that has previously looked at M82, detailing the gas and dust structure seen in visible light. Credit Video: NASA, ESA, CSA, STScI, Alyssa Pagan (STScI)


Located 12 million light-years away and undergoing rapid star formation, edge-on spiral galaxy Messier 82 (M82) is a scientifically unique sight to behold, and now NASA’s James Webb Space Telescope has revealed previously unseen details.

M82’s intense star formation, thought to be the result of a galaxy merger, will be a short-lived event in astronomical terms, estimated to last a few hundred million years in its entirety. This temporary phase of extreme star formation relative to the galaxy’s mass, as well as its location in the local universe, are among the factors that make M82, also known as the Cigar galaxy, a one-of-a-kind environment to study.

A team of astronomers recently completed an imaging survey with the Webb telescope. This program entailed a total of 65 hours of observation time with Webb’s NIRCam (Near-Infrared Camera) instrument and revealed never-seen-before details of the starburst galaxy, including its distended disk structure and millions of individual stars. Webb’s high-resolution imaging, specifically of the main plane of the galactic disk, has unlocked vital information for astronomers as they seek to uncover M82’s formation history. Additionally, the Webb data will help scientists understand the current processes occurring within the starburst galaxy.

“M82 is a mess, but it’s a beautiful mess. We don’t fully understand what’s going on, especially concerning its evolutionary history. What could have triggered such an elevated rate of star formation? How long has this galaxy been driving plumes of material away from its center?” said principal investigator Adam Smercina, a NASA Hubble Fellow at the Space Telescope Science Institute in Baltimore, and incoming Assistant Professor at Tufts University in Massachusetts. “M82 is an ideal galaxy evolution laboratory because it has properties that allow us to probe important physical processes, such as how stars form in such environments and how that activity drives outflows. M82 provides a simultaneous window onto many astrophysical questions, in a way that no other galaxy in the local universe can.”

Prior to Webb, many observatories looked at the starburst galaxy, including NASA’s Hubble and retired Spitzer space telescopes. However, the sheer volume of dust within that galaxy limited the amount of information astronomers could acquire on M82 at high resolution. While Webb has previously looked at this galaxy, the duration of the new imaging survey, combined with the telescope’s infrared sensitivity, enabled it to pierce through the thick dust.

The telescope’s near-infrared-light view is a snapshot of a scene that has been evolving over a couple hundred million years. Webb’s image contains approximately 16.5 million individual stars dispersed throughout the galaxy. The light from these stellar sources is depicted as luminous blue granules. This is only a small portion of the total amount of stars astronomers think reside in a galaxy like M82, with the majority too faint to be seen.

“The sheer number of stars that we were able to resolve with Webb is incredible,” said team member Benjamin Williams of the University of Washington. “It’s a whole different world from what we’ve been able to see with other telescopes. All of these stars collectively provide a detailed fossil record of the formation and evolution of M82.”

Moving inward, the increase in brightness and the asymmetrical shape of the galactic disk hints at the spiral galaxy’s unique underlying structure. The differing radii between the two sides suggests that M82 has a distorted shape, which can happen during intense galaxy mergers.

“At first glance, the disk of the galaxy may seem less spectacular because Webb sees through the dust,” said team member Eric Bell of the University of Michigan. “But M82 is a delightfully complex system. Webb’s observations will help us address some ongoing mysteries, such as how star formation has moved within M82 over the last few billion years.”

Because of the extreme star formation within the galaxy, which is 10 times faster than the Milky Way galaxy’s star formation rate, stellar birth will eventually be disrupted. M82’s stellar frenzy is causing bipolar plumes of material to be ejected above and below the disk. Though it looks like a tumultuous region, the hourglass-shaped outflows appear to have a layered structure. The yellow tendrils of material closest to the galaxy’s disk represent ionized gas, whereas the orange material farther away depicts small dust grains. These grains are called polycyclic aromatic hydrocarbons and are helpful in tracing material in the space between the galaxy’s stars, also known as the interstellar medium.

The information collected as part of this Webb study is just one dataset scientists will analyze as they seek to piece together this starburst galaxy’s formation history.

“Galaxies are such intricate ecosystems that if you truly want to understand them, you have to pull datasets from different missions together,” said team member Kristen McQuinn of the Space Telescope Science Institute. “One mission cannot fully answer all of the questions we have about M82. Combining the data collected by different telescopes, like Webb and Hubble, is powerful. When you marry the datasets, you expand what you can probe, and the questions that you can pose are even more complex.”

The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).



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Last Updated: Jun 23, 2026
Location: NASA Goddard Space Flight Center

Contact Media:

Laura Betz
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
laura.e.betz@nasa.gov

Abigail Major
Space Telescope Science Institute
Baltimore, Maryland

Christine Pulliam
Space Telescope Science Institute
Baltimore, Maryland

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Friday, June 26, 2026

NASA’s Webb Finds Clues to Ancient, Distant Origin of Comet 3I/ATLAS

Researchers used the NIRSpec (Near-Infrared Spectrograph) instrument on NASA’s James Webb Space Telescope to map specific chemical contents of comet 3I/ATLAS as it moved away from the Sun. Credit Image: NASA, ESA, CSA, STScI, Martin Cordiner (CUA, NASA-GSFC); Image Processing: Alyssa Pagan (STScI)

These graphs lay out the significant difference in composition between the interstellar comet 3I/ATLAS and comets originating in our solar system. This very specific data helps researchers build a picture of the comet’s original planetary system. Credit Illustration: NASA, ESA, CSA, Martin Cordiner (CUA, NASA-GSFC), Leah Hustak (STScI)


As interstellar comet 3I/ATLAS began moving away from the Sun in December 2025, astronomers took the opportunity to turn NASA’s powerful James Webb Space Telescope in its direction and capture detailed measurements of its chemical components. The comet was freshly warmed from its closest pass by the Sun, and its ancient ice had been converted to a bright coma of gas ideal for observation.

Webb captured detailed data, including chemical ratios of carbon and deuterium, also known as heavy hydrogen, that are not found in solar system comets. The results surprised researchers. Working backward, astronomers used the components that make up comet 3I/ATLAS to understand the environment in which it formed.

A paper detailing the findings published June 22 in the journal Nature.

The comet’s name comes from its status as the third confirmed interstellar comet, meaning it originated outside the solar system, and the telescope that first spotted it, the NASA-funded ATLAS (Asteroid Terrestrial-impact Last Alert System).

“This was a unique opportunity to study an ancient object from the distant galaxy, probably pre-dating our Sun and solar system,” said astro-chemist Martin Cordiner of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and lead author of the study. “On the one hand, we get direct insight into that distant time and place, and on the other, we learn something about how unusual our own solar system may be.”

Cordiner and the research team joined astronomers from many sub-disciplines in taking the opportunity to get a look at 3I/ATLAS on its journey through the solar system. They received approval to interrupt Webb’s planned schedule of observations to make use of its NIRSpec (Near-Infrared Spectrograph) instrument to study the comet.

NIRSpec revealed exceptionally high levels of deuterium, about 30 times more than seen in solar system comets. This implies that 3I/ATLAS may have originated in a very cold system much earlier in the history of our galaxy. During its formation, the material that became incorporated into 3I/ATLAS was likely exposed to plenty of radiation, but not any long-term warmth that would have reprocessed its “heavy water” ice, with deuterium, into the type of H2O ice we are familiar with on Earth.

Additionally, NIRSpec showed only traces of carbon-13 compared to lighter-weight carbon-12. This also points to a very old origin for 3I/ATLAS, as stellar systems become enriched with carbon-13 over time as generations of stars are born and die in the galaxy. That is why there are higher levels of carbon-13 in our system, around our Sun, which formed relatively recently, 4.5 billion years ago.

The research team estimates that 3I/ATLAS could have formed as long as 10 to 12 billion years ago, during the universe’s “cosmic noon,” when star formation was at its height. Its young origin system was likely ensconced in a relatively cold, dense cloud. The abundance of heavy water shows that 3I/ATLAS spent its formative years in a deeply frozen state.

A separate study using the European Southern Observatory's Very Large Telescope, led by astronomer Cyrielle Opitom of the University of Edinburgh, complements Webb’s findings with an analysis of 3I/ATLAS’s carbon and nitrogen varieties in the form of the chemical cyanide. “For us as scientists, finding these rare isotopes is fascinating, but the bigger picture here is looking at the possibilities of prebiotic chemistry elsewhere in the galaxy,” said Stefanie Milam of NASA Goddard and co-author of the study with Cordiner. “So far, we know of only one place in the vast cosmos where chemical ingredients led to life – our solar system, our Earth. Analysis of these interstellar objects is a major step towards learning how common, or uncommon, the conditions for the evolution of life are in the universe.”

The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).



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Last Updated:: Jun 22, 2026
Location:: NASA Goddard Space Flight Center

Contact Media:

Laura Betz
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
laura.e.betz@nasa.gov

Leah Ramsay
Space Telescope Science Institute
Baltimore, Maryland

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Space Telescope Science Institute
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Thursday, June 25, 2026

Tracing a Neutrino Ghost to Distant “Shadow Blaster” Galaxy

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Composite of Gemini North and ALMA images of "Shadow Blaster"

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Gemini North image of the field around "Shadow Blaster"

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Gemini North and ALMA image of "Shadow Blaster"

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Gravitational lensing infographic

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ALMA image of "Shadow Blaster"

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James Clerk Maxwell Telescope

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The Submillimeter Array


Videos

Gravitational lensing animation
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Gravitational lensing animation

Gravitational lensing animation (Spanish)
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Gravitational lensing animation (Spanish)

Zooming into “Shadow Blaster” galaxy
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Zooming into “Shadow Blaster” galaxy


Gemini North telescope on Maunakea helps uncover strongest evidence yet that distant star-forming galaxies contribute to the production of one of the Universe’s most mysterious ghost particles

A team of astronomers has identified a remarkably bright, gravitationally-lensed, star-forming galaxy as the likely source of the high-energy neutrino event IC 210922A, detected by the IceCube Neutrino Observatory in 2021. The galaxy, nicknamed “Shadow Blaster,” is located about 11 billion light-years away, providing the most concrete observational evidence yet that populations of distant star-forming galaxies play a significant role in producing high-energy cosmic neutrinos.

Neutrinos are one of the fundamental particles of the Universe. They live a ghostly existence with no electric charge, very little mass, and extremely few interactions with matter. They are also the most abundant particles with mass in the Universe, and can be created through a variety of processes, such as the decay of heavy particles, nuclear reactions in the Sun, and the explosions of stars.

Instruments on Earth have detected high-energy neutrinos arriving from space since the 1960s, and identifying their origin has been a long-standing challenge in astronomy. While scientists have identified a small number of nearby neutrino sources [1], they cannot account for the total amount of neutrinos our instruments measure arriving from across the Universe, referred to as the cosmic neutrino background. Astronomers, therefore, suspect that other major source populations exist but remain hidden.

In a study published today in Nature Astronomy, a team led by Yuji Urata of MITOS Science Co., LTD. in Taiwan presents the analysis of a new neutrino source candidate — an extremely bright galaxy, JCMT0402−0424, nicknamed “Shadow Blaster.” This galaxy is located about 11 billion light-years away, has trillions of times the luminosity of the Sun in the infrared, and may provide the long-sought link between high-energy neutrino production and distant star-forming galaxies.

The discovery was made in part using observations from the International Gemini Observatory, partly funded by the U.S. National Science Foundation (NSF) and operated by NSF NOIRLab. The study also utilized observations from the James Clerk Maxwell Telescope (JCMT), operated by the East Asian Observatory, and the Submillimeter Array (SMA), a joint operation between the Center for Astrophysics | Harvard & Smithsonian and the Academia Sinica Institute of Astronomy and Astrophysics. All three of these telescopes are located on the summit of Maunakea in Hawai‘i.

In 2021, the NSF IceCube Neutrino Observatory in Antarctica alerted the scientific community to a high-energy neutrino event, dubbed IC 210922A, coming from a region of space in the direction of the constellation Eridanus. This alert triggered rapid follow-up observations across the electromagnetic spectrum to search for a counterpart signal that, if detected, could help identify the neutrino’s source.

Multiple teams of scientists conducted follow-up observations using a variety of telescopes and instruments. However, they all reported no convincing gamma-ray, X-ray, or optical counterpart, nor any gamma-ray burst, supernova, or tidal disruption event that could be associated with the alert [2].

Then, a couple of days after the initial alert, Urata and his team initiated observations with JCMT and SMA and discovered Shadow Blaster, whose location and brightness made it a promising candidate for the source of the signal. To investigate this galaxy further, the team organized follow-up observations with the Atacama Large Millimeter/submillimeter Array (ALMA), managed for North America by the NSF National Radio Astronomy Observatory, and they discovered that Shadow Blaster is located behind a strong gravitational lens[3].

Thanks to this lensing effect, the team would be able to study the internal structure of Shadow Blaster, which would otherwise be too distant and too faint to resolve in such detail. However, to use the lensing effect correctly and to understand how much the lens amplified the neutrino signal, they first needed to know the distance, nature, and mass distribution of the foreground galaxy. To decipher these details, they used two powerful instruments on Gemini North: the Gemini Multi-Object Spectrograph (GMOS) and the Gemini Near-InfraRed Spectrograph (GNIRS).

“The combined GMOS and GNIRS data helped us measure the distance to the lensing galaxy and determine that it is a massive elliptical galaxy. This information was crucial for estimating the lens mass distribution and constructing a model of the gravitational lens,” says Urata.

Combining the lens model with the ALMA imaging data revealed that the central region of Shadow Blaster contains an extremely compact core that is densely packed with gas and dust and forming new stars at an intense rate. Theoretical models predict that such an extreme environment can act as a natural particle accelerator, where energetic particles repeatedly collide with gas and produce neutrinos. Additionally, Shadow Blaster does not display any characteristics of possessing an active black hole. This strongly suggests that high-energy neutrinos can be produced not only by spectacular black-hole jets as scientists have observed in nearby galaxies, but also by the intense, densely packed star formation that is common in very distant galaxies.

“This breakthrough shows how particle detectors and telescopes become far more impactful when they work together, opening a powerful 'multi-messenger' window on the Universe,” says Martin Still, Program Director, NSF Office of Research Infrastructure. “By combining signals from particles and light, scientists can explore distant cosmic environments and events in unprecedented detail — revealing phenomena that were once only theoretical.”sts have observed in nearby galaxies, but also by the intense, densely packed star formation that is common in very distant galaxies.

Around 10 billion years ago, the Universe was populated with galaxies like Shadow Blaster that were actively forming stars. During this epoch, galaxies were theoretically producing large numbers of cosmic rays, which are high-energy streams of particles that can generate neutrinos. Yet obtaining observational evidence that links an individual neutrino event to such a distant galaxy has been extremely difficult since these galaxies are very far away and often deeply hidden behind thick layers of dust. Shadow Blaster's serendipitous location behind a gravitational lens makes finding this observational evidence much easier.

“Shadow Blaster possesses the kind of dense, gas-rich environment that theoretical models have long suggested could efficiently produce high-energy neutrinos,” says Urata. Combined with the absence of any more compelling counterpart despite extensive follow-up searches, Shadow Blaster is the most plausible candidate for the source of  IC 210922A. “If confirmed, Shadow Blaster would be the first-ever individual dusty star-forming galaxy directly linked to a high-energy neutrino event.”

Compact star-forming galaxies like Shadow Blaster may be numerous throughout the Universe. As a population, they may therefore contribute a significant fraction of the high-energy neutrino background that fills the cosmos. “Our analysis suggests that this population could contribute up to roughly 20% of the observed diffuse neutrino background measured by IceCube,” says Urata.



Notes

[1] Astrophysical neutrino sources, or candidate source associations, that have been identified include the Sun and Supernova 1987A at lower energies, and, at high energies, the blazar TXS 0506+056, the active galaxy Messier 77, the active galaxy PKS 1424+240, and diffuse emission from the plane of the Milky Way. Candidate high-energy associations have also been reported with tidal disruption events such as AT2019dsg and AT2019fdr.

[2] Facilities used for follow-up observations: NASA's Fermi Gamma-ray Space Telescope, ANTARES neutrino telescope, NASA's Neil Gehrels Swift Observatory, Zwicky Transient Facility, High-Altitude Water Cherenkov Observatory, and the Department of Energy-funded DESI Transients Survey. In particular, DESI “spare fibers” — fibers that can’t be matched to targets from the main DESI program on a given pointing — obtained spectra for 249 galaxies within the IceCube localization region.

[3] Gravitational lensing occurs when a very massive foreground galaxy bends spacetime, acting as a cosmic magnifying glass that enlarges and distorts the image of a more distant galaxy behind it. In this case, the gravitational lens amplified the brightness of Shadow Blaster from 2.7 trillion to 33 trillion times the luminosity of the Sun in infrared light.


More information

This research is presented in a paper titled “Compact dusty starbursts at cosmic noon linked to high-energy neutrinos,” appearing in Nature Astronomy. DOI: 10.1038/s41550-026-02884-9.

The team is composed of Y. Urata (MITOS Science Co., LTD/National Central University, Taiwan), K. Huang (Chung Yuan Christian University, Taiwan), B. Hatsukade (National Astronomical Observatory of Japan/The Graduate University for Advanced Studies/The University of Tokyo, Japan), M. Kasliwal (California Institute of Technology, USA), S. S. Kimura (Tohoku University, Japan), Y. Matsuda (National Astronomical Observatory of Japan/Ministry of Education, Culture, Sports, Science and Technology, Japan), Y. Miyamoto (Fukui University of Technology, Japan), H. Nagai (National Astronomical Observatory of Japan/The Graduate University for Advanced Studies, Japan), K. Nakanishi (National Astronomical Observatory of Japan/The Graduate University for Advanced Studies, Japan), and R. Stein (University of Maryland/NASA Goddard Space Flight Center, USA).

NSF NOIRLab, the U.S. National Science Foundation center for ground-based optical-infrared astronomy, operates the International Gemini Observatory (a facility of NSF, NRC–Canada, ANID–Chile, MCTIC–Brazil, MINCyT–Argentina, and KASI–Republic of Korea), NSF Kitt Peak National Observatory (KPNO), NSF Cerro Tololo Inter-American Observatory (CTIO), the Community Science and Data Center (CSDC), and NSF–DOE Vera C. Rubin Observatory (in cooperation with DOE’s SLAC National Accelerator Laboratory). It is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with NSF and is headquartered in Tucson, Arizona.

The scientific community is honored to have the opportunity to conduct astronomical research on I’oligam Du’ag (Kitt Peak) in Arizona, on Maunakea in Hawai‘i, and on Cerro Tololo and Cerro Pachón in Chile. We recognize and acknowledge the very significant cultural role and reverence of I’oligam Du’ag to the Tohono O’odham Nation, and Maunakea to the Kanaka Maoli (Native Hawaiians) community. The James Clerk Maxwell Telescope is operated by the East Asian Observatory, which is funded by the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA, Taiwan), the National Astronomical Research Institute of Thailand (NARIT), the Science and Technology Facilities Council (STFC, United Kingdom), and other partners.


Links


Contacts:

Yuji Urata
MITOS Science Co., Ltd
National Central University
Email: yjurata@gmail.com

Josie Fenske
Public Information Officer
NSF NOIRLab
Email: josie.fenske@noirlab.edu

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Wednesday, June 24, 2026

NASA's Chandra Finds Unexpected Fireworks in Aftermath of Stellar Explosions



  • Astronomers have uncovered a population of supernova remnants in a nearby galaxy that are unexpectedly changing in X-ray brightness.

  • Using Chandra data spanning 14 years, researchers found 22 supernova remnants that brighten and dim dramatically in X-rays.

  • Typically, supernova remnants over a hundred years old just steadily decrease their X-ray output over time.

  • The researchers think this unusual behavior comes from stellar companions to the supernovas that survived the explosions.


This graphic shows two of the X-ray sources in a nearby galaxy that are changing their brightness in surprising ways as described in our latest press release. By analyzing data from NASA’s Chandra X-ray Observatory that span over 14 years, researchers found over 20 previously identified supernova remnants — remains from stars that exploded — that vary unexpectedly in X-ray brightness in Messier 83 (M83). These represent roughly half of the X-ray sources associated with supernova remnants in their sample in M83.

The panel on the left contains a composite image of M83 with X-rays from Chandra (red, green, and blue) and optical light data from NASA’s Hubble Space Telescope (red, green, and blue). The two varying Chandra sources are circled in the composite image and close-up timelapse images of these sources are shown in the panels on the right.

This collection of varying sources is surprising because astronomers expect that about a hundred years after the explosion that created them, supernova remnants do not change their brightness dramatically. Rather, they typically fade in X-rays slowly over time. It would be unusual for M83 to have so many explode less than a century ago.

The most likely explanation given by the research team is that they uncovered a population of stellar survivors — stars that lived through their partner's destruction in a supernova explosion. In this scenario, each variable X-ray source began as a pair of massive stars orbiting each other. The more massive star collapsed and exploded as a supernova, leaving behind a black hole or ultra-dense neutron star. Its companion survived.

Galaxy M83 in X-ray and Optical Light. Credit: X-ray: NASA/CXC/SAO; Optical: NASA/ESA/AURA/STScI, Hubble Heritage Team, W. Blair (STScI/Johns Hopkins University) and R. O'Connell (University of Virginia); Image Processing: NASA/CXC/SAO/A. Jubett, L. Frattare and P. Edmonds

Chandra detects X-rays produced by infalling material that becomes superheated by the intense gravitational pull of the compact object. Such systems — known as high-mass X-ray binaries (HMXBs) — are among the most variable X-ray sources in the universe and may be the cause of the variations seen in M83’s supernova remnants. At the distance of M83, the supernova remnants appear as point sources even though they are much larger than the HMXBs they contain, implying that the two sources of X-rays cannot be separated in images.

Astronomers have known about HMXBs for decades, but the difference with this group in M83 is their connection to supernova remnants. Previously only a handful of supernova remnants associated with HMXBs were known across observations of all galaxies and so it is unprecedented to find more than twenty strong candidates in just one galaxy.

Galaxy M51 in X-ray and Optical Light. This is a composite image of the galaxy M51 combining data from NASA's Chandra X-ray Observatory (purple) with optical data (red, green and blue) taken with ground-based telescopes by a team of astrophotographers. A surprisingly high number of X-ray sources associated with supernova remnants in M51 show large changes in brightness, similar to the behavior seen in M83. Credit: Chandra X-ray Data: NASA/CXC/SAO; Astrobin/Optical Groundbased: C.Björk, T.Bähnck, S.Donoso, J.Gentillon, A. and D.Grelin, S.Guberski, R. Hall, T.Heuberger, J.Jacks, P.Kent, Br.Meyers, W.Ostling, N.Puig, T.Schaeffer, F.Schöfbänker, M.Vasilev

There is another possible explanation for the variability seen in the Chandra sources in M83. Rather than feeding off a companion star, the black hole or neutron star may be recapturing some of the material blasted outward in the original explosion. In a possible example of cosmic recycling, debris from the explosion falls back onto the very object the supernova created. The researchers suggest that both explanations could be happening in M83 with different sources in our sample having different origins.

These results were presented at the 248th meeting of the American Astronomical Society meeting in Pasadena, CA. In addition, a paper describing these results, led by Andrea Prestwich (Catholic University, Washington, DC), has been published in The Astrophysical Journal.

NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program. The Smithsonian Astrophysical Observatory's Chandra X-ray Center controls science operations from Cambridge, Massachusetts, and flight operations from Burlington, Massachusetts.

Quick Look: NASA's Chandra Finds Unexpected Fireworks in Aftermath of Stellar Explosions



Visual Description:

This release features a composite image of the nearby galaxy Messier 83, and short timelapse videos of two curious supernova remnants hidden inside.

In the composite image, Messier 83, or M83, is shown to have a spiral structure, viewed straight on. At the center is a brilliant white and yellow pool of light. From that light, spiral arms of hot pink cloud corkscrew out in wide, sweeping arches. The galaxy is covered in a faint grey haze, and flecked with red, green, blue, white, and yellow dots.

In an annotated version of the composite image, two tiny dots to our lower right of center are highlighted by white circles. These are two of the supernova remnants being considered by researchers. Each is examined further in a separate timelapse video.

Over a 14-year period from 2000 to 2014, astronomers pointed NASA’s X-ray observatory at the M83 galaxy. They discovered that about half of the X-ray sources believed to be supernova remnants, the aftermath of stellar explosions, were exhibiting dramatic changes in brightness. This result was entirely unexpected.

Those changes in brightness are highlighted in the timelapse videos. In each video, a series of static images flashes by, focused on one of the two X-ray sources once believed to be supernova remnants. In the videos, the X-ray sources appear as bright blue blobs with glowing cores. But in each image, taken months or years apart, the shapes change, as does the intensity of the blue color, and the brightness of the core. By presenting the substantively different images of the same objects one after another in quick succession, short timelapse videos are created.

The most likely explanation for the changes in brightness is that the team has uncovered a population of stellar survivors, stars that lived through an orbiting partner’s destruction in a supernova explosion. Material is being pulled from the surviving star onto the black hole or neutron star that formed in the supernova, a process known to cause rapid changes in X-ray brightness.


Fast Facts for M83:

Credit: X-ray: NASA/CXC/SAO; Optical: NASA/ESA/AURA/STScI, Hubble Heritage Team, W. Blair (STScI/Johns Hopkins University) and R. O'Connell (University of Virginia); Image Processing: NASA/CXC/SAO/A. Jubett, L. Frattare and P. Edmonds
Release Date: June 15, 2026
Scale: Image is about 9.5 arcmin (41,000 light-years) across.
Category: Normal Galaxies & Starburst Galaxies, Supernovas & Supernova Remnants
Coordinates (J2000): RA 13h 37m 00.80s | Dec -29° 51´ 58.60"
Constellation: Hydra
Observation Dates: 13 pointings between April 2000 and June 2014
Observation Time: 228 hours 2 minutes (9 days 12 hours 2 minutes)
Obs. ID: 793, 2064, 12992-12996, 13202, 13241, 13248, 14332, 14342, 16024
Instrument: ACIS
Also Known As: NGC 5236
References: Prestwich, A. et al., 2026, ApJ, 1004, 154.
Color Code: X-ray: red, green, blue; Optical: red, green, blue

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Tuesday, June 23, 2026

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).


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.




Related Links


Science Contacts:

Michael Keim
michael.keim@yale.edu

Pieter Van Dokkum
pieter.vandokkum@yale.edu

Media Contact:

Meagan O’Shea
moshea@keck.hawaii.edu


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 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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Monday, June 22, 2026

Radar Echoes From Europa Reveal Secrets Beneath the Ice

This artist's impression shows radar waves from the NASA Goldstone Solar System Radar pinging one of Jupiter’s moons, Europa. The radar waves penetrate Europa’s icy surface before bouncing back to be collected by the NSF Green Bank Telescope on Earth. Credit: NSF/AUI/NSF NRAO/P.Vosteen. Hi-Res File


Ateam of scientists has used NASA’s Goldstone Solar System Radar and the U.S. National Science Foundation Green Bank Telescope (NSF GBT) to carry out the most extensive radar study to date of Europa, the ocean world orbiting Jupiter. By repeatedly “pinging” Europa with 3.5‑centimeter radio waves between 2011 and 2024, the team measured how the moon reflects radar signals and confirmed that its icy surface scatters radio energy in an unusually strong and complex way not seen on rocky worlds.

Three of Jupiter’s big moons, Europa, Ganymede, and Callisto, are especially interesting to scientists because they have icy outer shells and are thought to hide oceans of liquid water underneath. Of these three, Europa is a prime target in the search for habitable environments beyond Earth. Geologic features provide clues to how the ice shell and underlying ocean interact, but these features only reveal what is happening at or near the surface. Explains Tunhui (Tina) Xie, a graduate student working with Professor Jean-Luc Margot at the University of California Los Angeles, “Radar delves below what is easily seen, because radio waves can penetrate into the ice, and carry information about its internal structure and purity.”

These new observations show that Europa’s radar “albedo”—a measure of how bright it appears to radar—is much higher than that of typical planets and asteroids. The returning radar signal is dominated by the same circular polarization as the transmitted beam, a hallmark of multiple scattering inside clean, porous ice. These properties strongly support an explanation known as the “coherent backscatter opposition effect,” in which radio waves bounce around within the ice before returning back to the telescope, dramatically boosting the echo.

Because the team observed Europa in a bistatic configuration—with Goldstone transmitting and both Goldstone and the NSF GBT receiving—they could also test how the coherent backscatter effect changes with the angle between transmitter, moon, and receiver. They found that Europa’s radar brightness stayed roughly constant even when the angle increased, implying that the bright backscatter “peak” must be broader than the range of angles they sampled, placing a limit on the depth that the radio waves diffused before being absorbed. This depth limit offers a new constraint on how transparent Europa’s ice is, and will help scientists interpret upcoming ice‑penetrating radar data from spacecraft now en route to study this moon in more detail.

These new ground‑based results fill a three‑decade gap since the last major radar study of Europa in the late 1980s and early 1990s. The researchers find strong agreement between their measurements and those earlier results, reinforcing the picture of Europa as an object with very high radar reflectivity and strongly “diffuse” scattering, rather than the mirror‑like reflections seen from many rocky surfaces. This consistency increases confidence that Europa’s radar properties are stable over time and that Earth‑based and spacecraft radar measurements can be interpreted within a unified physical framework.

Because the observing campaign spanned many years and viewing geometries, the team asked whether Europa’s radar brightness changed from one hemisphere to another, or with longitude. They found that Europa’s disk‑integrated radar properties are statistically consistent with remaining nearly constant as the moon rotates, which agreed with earlier observations.

However, when the authors divided the data into leading and trailing hemispheres and performed statistical tests, they saw a hint—though not statistically conclusive—that the trailing hemisphere could be slightly brighter in one polarization state. If confirmed with future data, that subtle difference could be related to how charged particles from Jupiter’s magnetosphere modify the ice or affect the formation of small‑scale surface structures that absorb or scatter radio waves. “Future planetary science and space flight missions, like NASA’s Europa Clipper, could benefit from this type of radar science,” shares Will Armentrout, a scientist with the NSF NRAO who supports radar projects. “As the Green Bank Telescope’s radar capabilities evolve, with new technologies currently under development, we’re looking forward to providing even more radar capabilities for the scientific community.”

This news is featured in a press conference at the American Astronomical Society’s 248th meeting on Tuesday, June 16th at 10:15am PDT. Find a recording from this presentation on the AAS Press Office YouTube channel.



About NRAO

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



This research was supported by the following grants:

Radio scattering properties of the icy Galilean satellites, NASA FINESST program, PI J.~L. Margot, 80NSSC26K0201, 2025–2028.

High-Precision Measurements of Planetary Rotation. NSF Astronomy and Astrophysics Research Grants, PI J.~L. Margot, 2408493, 2024–2027.

High-Precision Measurements of Planetary Rotation. NASA Solar System Observations Program, PI J.~L. Margot, 80NSSC19K0870, 2019–2022.

High-Precision Measurements of Planetary Rotation. NASA Planetary Astronomy Program, PI J.~L. Margot, NNX12AG34G, 2012–2016.


Press Contacts:

Jill Malusky
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Sunday, June 21, 2026

Celebrating the birth of new stars... and the VST!

Imagine for a moment you are lying back, gazing up at the red-orange celestial clouds in today’s Picture of the Week. What shapes do you see? A chicken pecking seeds on the ground, the head of a dragon, or something else entirely?

These pareidolia-inducing clouds are a pair of nebulae — collections of dust and gas in interstellar space — called Gum 10 and Gum 11. Visible mostly from the southern hemisphere, they are part of a larger complex, in which stars are born. Gum 10 is the brightest cloud that occupies most of the image, whereas Gum 11 is the fainter, detached cloud to the bottom-left. Their bright glow comes from a special interaction between hydrogen and the hot massive stars in each nebula. These stars emit ultraviolet light, which has enough energy to tear electrons away from their atoms, forming ions. These electrons eventually recombine with hydrogen ions, which causes the emission of the specific shade of red light seen in this image. The black lines in the nebula come from dust that blocks the light behind it.

This image was taken with the VLT Survey Telescope (VST), which celebrates the 15th anniversary of its first light today! The VST project was a joint venture between ESO and the Capodimonte Astronomical Observatory (OAC), part of the Italian National Institute for Astrophysics (INAF). Today the VST is solely managed by INAF and is hosted by ESO at its Paranal Observatory in Chile. The data behind this picture comes from a project called VPHAS+, which uses the VST to scan across the plane of our Milky Way galaxy, intended to better understand the lifecycle of stars.

Link

Credit: ESO/VPHAS+ team

Source: ESO/potw

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Saturday, June 20, 2026

NASA Webb, Hubble Reveal History of Relic of Milky Way’s Formation

This artist’s concept shows exoplanet HD 80606 b being “roasted” as its orbit approaches periastron, the point at which it is closest to its host star, which is similar to our Sun. Artwork: NASA, ESA, CSA, Joseph Olmsted (STScI)


One well-done gas giant, coming right up! That’s the latest from researchers analyzing NASA’s James Webb Space Telescope’s observations of HD 80606 b, an exoplanet four times the mass of Jupiter with an extremely elliptical orbit that sweeps close by its Sun-like star. The research team is presenting their study and preliminary findings Tuesday at the 248th meeting of the American Astronomical Society in Pasadena, California.

“Hot Jupiters are already considered some of the most extreme exoplanets we know of, but even among that population, HD 80606 b is one of the most extreme,” said Tiffany Kataria, the study’s principal investigator at NASA's Jet Propulsion Laboratory in Southern California. “We typically think of hot Jupiters as hot gas giants sitting right next to their stars, but this planet’s highly eccentric orbit creates a completely different beast.”

As the planet plunges close to its star, Webb shows its temperature skyrockets by 1,100 degrees Fahrenheit. Previous studies have shown that radical temperature swings can cause an exoplanet's chemistry and clouds to change in real time. According to the research team, the dynamic conditions of HD 80606 b make the planet an ideal target to observe these changes with Webb’s powerful instruments.

“Observing a planet like HD 80606 b is actually very efficient because its unusual orbit, with the corresponding swings in temperature and chemical composition, allow us to gather data under varying conditions in just hours and apply those findings to other hot Jupiters or more conventional exoplanets,” said Laura C. Mayorga, co-investigator on the study and an exoplanet astronomer at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland.

Measurements of temperature and chemical composition were done with spectroscopy, a technique scientists use to break light into its component colors to reveal information about the composition, temperature, motion, and physical properties of objects in space. The team used Webb’s MIRI (Mid-Infrared Instrument) for an extended observation of HD 80606 b before, during, and after its periastron, or closest pass by its star. During periastron, the planet also passed behind the star from Webb’s perspective in what’s known as a secondary eclipse. The observation was years in the planning, as scheduling the time to catch the planet at this point was complex given its extremely elliptical 111-day orbit, and Webb’s own restrictions on where it can look during specific times of the year, based on Earth’s position in orbit around the Sun.

Researchers say they have only begun to peel back the layers of an incredibly rich dataset, but they can clearly see a dramatic shift in the exoplanet’s temperature. “Webb has shown that the planet’s increase in temperature was even more extreme than we anticipated based on Spitzer data,” said Kataria.

In fact, the planet had already been dubbed the “roasted exoplanet” and even got its own poster in NASA’s popular series. NASA’s now-retired Spitzer Space Telescope laid the groundwork of infrared observations of HD 80606 b, showing that more detailed spectroscopic data from Webb would be especially compelling.

“Spitzer did amazing work on this exoplanet, and now Webb is building on that legacy by enabling us to drill down to distinguish specific chemical signatures like methane and carbon dioxide, which is just amazing progress,” said Ryan Challener, co-author and research associate at the Cornell Center for Astrophysics and Planetary Science. “There’s so much to learn from this one dataset here — we really are just getting started deciphering what Webb has to tell us.”

The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).



Details:

Last Updated: Jun 16, 2026
Location: NASA Goddard Space Flight Center

Contact Media:

Laura Betz
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
laura.e.betz@nasa.gov

Leah Ramsay
Space Telescope Science Institute
Baltimore, Maryland

Hannah Braun
Space Telescope Science Institute
Baltimore, Maryland

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From Dusk Till Dawn

Artist's impression of the exoplanet WASP-121 b. It belongs to the class of hot Jupiters. Due to its proximity to the central star, the planet's rotation is tidally locked to its orbit around it. As a result, one of WASP-121 b's hemispheres always faces the star, heating it to temperatures of up to 2500 degrees Celsius. The night side is always oriented towards cold space, which is why it is 1775 degrees Celsius cooler there. © Patricia Klein and MPIA


To the point:
  • Ultrahot exoplanet, atmospheric differences: Researchers discovered clear differences in the atmosphere between the morning and evening sides of the ultrahot gas planet WASP-121 b using the James Webb Space Telescope (JWST).

    •
  • Temperature and chemical variations: The evening side absorbs more infrared light due to higher temperatures caused by strong winds moving heat eastward, while water molecules decrease in the evening terminator due to high temperatures breaking them apart.

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  • Planetary rotation and observation method: WASP-121 b’s synchronous rotation reveals different atmospheric regions during transit, allowing scientists to analyse changes in light absorption over time and longitude.


Astronomers find variations between the morning and the evening conditions of an ultra-hot exoplanet.

Astronomers have revealed distinct differences in atmospheric conditions between the morning and evening transition zones of the ultra-hot gas planet WASP-121 b, which separate day from night, commonly called terminators. This achievement was only possible due to the unmatched sensitivity of the James Webb Space Telescope (JWST). Led by Cyril Gapp, a PhD student at the Max Planck Institute for Astronomy (MPIA) in Heidelberg, Germany, a team of researchers detected this phenomenon, which had previously been predicted by theoretical computations.

Confirmation of variations between dusk and dawn

The discovery corresponds to an asymmetry in the absorption of infrared light received from the host star, which is partially filtered through the planet’s atmosphere during its transit. The researchers interpret this as the result of non-uniform temperatures and chemical compositions in the exoplanet’s atmosphere.

With its unprecedented observational quality, JWST gives us the most detailed glimpses into distant planets to date: By measuring how star light absorption changes as WASP-121 b rotates, we probe its atmosphere longitude by longitude. Cyril Gapp, MPIA

The data indicate that the evening terminator absorbs more light than the morning side, consistent with the commonly accepted picture of powerful winds that transport intense heat from the day to the night side. Hot winds follow the planet’s rotation eastward, which heats the evening zone. With rising temperatures, this region is bound to expand, increasing the planet’s cross-section and allowing it to absorb stellar radiation more efficiently.

Besides a general slight reduction in brightness towards the end of the transit, the data obtained by JWST’s NIRSpec (Near-infrared spectrograph) instrument also reveal an increase in the carbon monoxide (CO) signal. However, this appears to be a temperature effect, not related to an increase in carbon monoxide molecules.

In contrast, the amount of water (H2O) in the atmosphere appears to drop, which the astronomers interpret as a real decrease in water molecules. The temperatures in the upper atmosphere are high enough to break water molecules into their constituents. This result again corroborates the existence of hot winds heating the evening terminator region.

Top view of the orbit of the exoplanet WASP-121 b around its star. The planet’s rotation is synchronized to its orbit, both taking about 30 hours to complete. As a result, the planet constantly faces the star with the same side producing distinct day and night sides. The transition zones between those hemispheres are the morning and evening regions. Due to the planet’s proximity to the central star of only 1.9 stellar diameters, the planet rotates by about 30 degrees during its transit. © MPIA (CC BY 4.0)

Two extreme sides of an ultra-hot planet

To detect these minute variations, the astronomers exploited a peculiar behaviour of hot gas planets. The proximity to their host stars slowly synchronizes their spin and orbital motion via tidal forces,such that eventually one rotation takes as long as one revolution. Finally, these planets exhibit two distinct hemispheres: a hot side constantly facing the star and an opposite, darker and cooler side.

“WASP-121 b is particularly extreme, with average temperatures on the dayside hemisphere being around 2770 Kelvin, while those on the nightside are closer to about 1000 Kelvin,” co-author Tom Evans-Soma from the University of Newcastle, Australia, explains. He previously determined the planet’s temperature range and is also affiliated with MPIA. These values translate to almost 2500 degrees Celsius, or about 4525 degrees Fahrenheit, on the dayside, and approximately 725 degrees Celsius, or 1340 degrees Fahrenheit, at night.

When astronomers observe such a planet transiting in front of a star, the planet rotates slightly between the points of ingress and egress, revealing different fractions of its atmosphere. While the planet mostly presents its night side, our point of view permits glimpses beyond the dusk and dawn towards the bright dayside, depending on the transit’s progress. The zone leading the planet’s orbit corresponds to the morning side, and the one trailing is the evening side.

Apart from recording the measured brightness variation over time, spectrographs break light into smaller components, which physicists call a spectrum, much as a prism produces a rainbow-like distribution of colours. Since atmospheric gases absorb light at distinct colours or wavelengths, a detailed analysis reveals their chemical composition.

Elapsed time converts to longitude

Hence, the variation along the direction of rotation translates into a time-dependent change of the filtered signal. In the case of WASP-121 b the rotation angle during a full transit amounts to about 30 degrees, which is sufficient to probe the morning (dawn) and evening (dusk) terminators with high precision in longitude.

Astronomers usually average the measurements over the entire transit to achieve a clearer signal. However, to determine how the signal changes during the planet’s trajectory across the star, Gapp and his colleagues allowed for a temporal variation while the planet rotates. By applying statistical methods, they found that their procedure provides a significantly better fit to the data, indicating that they indeed detected a significant variation.

Notable gaps in atmospheric models

To verify the measured temperatures that would cause local expansion, the astronomers ran models simulating heat distribution in the upper layers of a gas planet, depending on the planet's properties and the constellation of the planet and its host star. While these atmospheric models confirmed the asymmetric effect caused by spatial temperature variations, the data revealed a larger signal amplitude than the models predicted.

The astronomers suspected that cooling mechanisms at the morning terminator might be at work that the models didn’t account for. Previous studies have indicated that clouds may be present, albeit composed not of water droplets but of minerals such as silicates. Clouds can efficiently shield infrared light emitted from hot gaseous layers below, mimicking lower temperatures. Infamously, simulating the physics of clouds, condensation, and evaporation in a dynamic environment is hard. Therefore, physical models commonly applied to exoplanet atmospheres, such as the one used in this study, do not account for clouds, which can yield unrealistic results.

After tweaking the simulation to better approximate the effect of clouds on infrared radiation from deeper layers, the results were more consistent with observations. However, only more sophisticated models will be able to confidently confirm the presence of clouds.

A blueprint for future studies

Model updates will also improve future investigations using this method. The astronomers have already identified additional suitable targets within the required temperature range and rotation speed to successfully probe the terminator regions. This will help them establish a sample of ultrahot gas planets, revealing their longitudinal structure, and potentially discover similarities and differences among these extreme worlds.

Additional information

MPIA astronomers involved in this study were Cyril Gapp (also Heidelberg University), Thomas M. Evans-Soma (also University of Newcastle, Australia), and Eva-Maria Ahrer.

Other researchers were: Aurélien Falco (Sorbonne Université, Paris, France), David K. Sing (Johns Hopkins University, Baltimore, USA), Shashank Dholakia (University of Queensland, St. Lucia, Australia), Vivien Parmentier (Université de la Côte d’Azur, Nice, France), Jérémy Leconte (Université Bordeaux, France), and Guangwei Fu (Johns Hopkins University).

The JWST observations used in this study were conducted as part of GO program #1729 (PI: Thomas Evans-Soma, Co-PI: Tiffany Kataria) titled “A NIRSpec Phase Curve for the ultrahot Jupiter WASP-121b” and GTO program #1201 (PI: David Lafreniere) labelled “NIRISS Exploration of the Atmospheric diversity of Transiting exoplanets (NEAT).”

NIRSpec (Near Infrared Spectrograph) was built by European industry to the European Space Agency’s (ESA) specifications and managed by the ESA JWST Project at ESTEC (European Space Research and Technology Centre), the Netherlands. The prime contractor was Airbus Defence and Space in Ottobrunn, Germany. MPIA contributed to the development and manufacture of NIRSpec’s filter and grating wheels. The NIRSpec detector and micro-shutter array subsystems were provided by NASA’s Goddard Space Flight Center (GSFC).

The James Webb Space Telescope is the world’s leading observatory for space research. It is an international programme led by NASA and its partners ESA and CSA (Canadian Space Agency).



Contacs:

Dr. Markus Nielbock
Press and outreach officer
Tel: +49 6221 528-134
Email: pr@mpia.de
MPIA press team
Max Planck Institute for Astronomy, Heidelberg, Germany

Cyril Gapp
Tel: +49 6221 528-328
Email: gapp@mpia.de
Cyril Gapp / MPIA
Max Planck Institute for Astronomy, Heidelberg, Germany

Dr. Thomas M. Evans-Soma
Tel: +61 2 4055-3229
Email: tom.evans-soma@newcastle.edu.au
Homepage Thomas Evans-Soma
School of Information and Physical Sciences, The University of Newcastle, Callaghan, Australia
Max-Planck-Institut für Astronomie, Heidelberg, Deutschland


Original publication

Cyril Gapp, Aurélien Falco, Thomas M. Evans-Soma, et al. (incl. Eva-Maria Ahrer)
Atmospheric asymmetries in WASP-121 b revealed by rotational transits detected with JWST
Nature Astronomy (2026). DOI: 10.1038/s41550-026-02887-6

Source


Orbit of WASP-121 b around its host star (Video)
This animation illustrates the orbit of the exoplanet WASP-121 b around its host star, as well as its tidal locking. The perspective shifts from a top-down view of the orbit to the alignment during observation. During the transit, it becomes apparent that at the beginning and the end of the passage, a portion of the planet's illuminated dayside appears as a narrow crescent. T. Müller (MPIA/HdA)


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mpia-pm_wasp121b_2026_animation1080p (8.3 MB)

mpia-pm_wasp121b_2026_animation4k 21.22 MB

mpia-pm_wasp121b_2026_fig1_de 455.47 kB

mpia-pm_wasp121b_2026_fig1_en 455.92 kB

mpia-pr_wasp-121b_mikal-evans_2022_teaser 1.6 MB

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