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Webb studies moon-forming disc around massive planet CT Cha B

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The James Webb Space Telescope studies the potential moon-forming disc around the massive exoplanet CT Cha B This is an illustration of a young planet with a surrounding disc of dust and gas, potentially forming moons. The planet, which appears red, is shown at lower right, enveloped by a cloudy disc. The host star appears at upper left, and glows yellow, with its own reddish disc of debris. The black background of space is speckled with stars. At the bottom of the illustration, graphics of molecules are listed in the following order: Acetylene, Carbon Dioxide, Ethane, Benzene, Hydrogen cyanide.

Webb studies moon-forming disc around massive planet CT Cha B

The disc offers insight into how the moons of solar system gas giants like Jupiter might have formed.

The NASA/ESA/CSA James Webb Space Telescope has provided the first direct measurements of the chemical and physical properties of a potential moon-forming disc encircling a large exoplanet. The carbon-rich disc surrounding the world called CT Cha B, which is located 625 light years away from Earth, is a possible construction yard for moons, although no moons are detected in the Webb data.

Our Solar System contains eight major planets, and more than 400 known moons orbiting six of these planets. Where did they all come from? There are multiple formation mechanisms. The case for large moons, like the four Galilean satellites around Jupiter, is that they condensed out of a dust and gas disc encircling the planet when it formed. But that would have happened over 4 billion years ago, and there is scant forensic evidence today.

Webb has now provided the first direct view of material in a disc around a large exoplanet. An international team of astronomers have uncovered a carbon-rich disc encircling the world called CT Cha b, which is located 625 light-years away from Earth.

The young star the planet orbits is only 2 million years old and still accreting circumstellar material. However, the circumplanetary disc discovered by Webb is not part of the larger accretion disc around the central star. The two objects are 74 billion kilometres apart.

Observing planet and moon formation is fundamental to understanding the evolution of planetary systems across our galaxy. Moons likely outnumber planets, and some might be habitats for life as we know it. But we are now only entering an era where we can witness their formation.

This discovery fosters a better understanding of planet and moon formation, say researchers. Webb’s data is invaluable for making comparisons to our Solar System’s birth over 4 billion years ago.

“We can see evidence of the disc around the companion, and we can study the chemistry for the first time. We’re not just witnessing moon formation – we’re also witnessing this planet’s formation,” said co-lead author Sierra Grant of the Carnegie Institution for Science in Washington, D.C., USA.

“We are seeing what material is accreting to build the planet and moons,” added main lead author Gabriele Cugno of the University of Zurich in Switzerland and member of the National Centre of Competence in Research PlanetS.

Dissecting starlight

Infrared observations of CT Cha b were made with Webb’s MIRI (Mid-Infrared Instrument) using its medium resolution spectrograph. An initial look into Webb’s archival data revealed signs of molecules within the circumplanetary disc, which motivated a deeper dive into the data. Because the planet’s faint signal is buried in the glare of the host star, the researchers had to disentangle the light of the star from the planet using high-contrast methods.

“We saw molecules at the location of the planet, and so we knew that there was stuff in there worth digging for and spending a year trying to tease out of the data. It really took a lot of perseverance,” said Grant.

Ultimately, the team discovered seven carbon-bearing molecules within the planet’s disc, including acetylene (C2H2) and benzene (C6H6). This carbon-rich chemistry is in stark contrast to the chemistry seen in the disc around the host star, where the researchers found water but no carbon. The difference between the two discs offers evidence for their rapid chemical evolution over only 2 million years.

Genesis of moons

A circumplanetary disc of debris has long been hypothesized as the birthplace of Jupiter’s four major moons. These Galilean satellites must have condensed out of such a flattened disc billions of years ago, as evident in their co-planar orbits about Jupiter. The two outermost Galilean moons, Ganymede and Callisto, are 50% water ice. But they presumably have rocky cores, perhaps made of carbon or silicon.

“We want to learn more about how our Solar System formed moons. This means that we need to look at other systems that are still under construction. We’re trying to understand how it all works,” said Cugno. “How do these moons come to be? What are the ingredients? What physical processes are at play, and over what timescales? Webb allows us to witness the drama of moon formation and investigate these questions observationally for the first time.”

In the coming year, the team will use Webb to perform a comprehensive survey of similar objects to better understand the diversity of physical and chemical properties in the discs around young planets.

This is an illustration of a young planet with a surrounding disc of dust and gas, potentially forming moons. The planet, which appears red, is shown at lower right, enveloped by a cloudy disc. The host star appears at upper left, and glows yellow, with its own reddish disc of debris. The black background of space is speckled with stars. At the bottom of the illustration, graphics of molecules are listed in the following order: Acetylene, Carbon Dioxide, Ethane, Benzene, Hydrogen cyanide.
The James Webb Space Telescope studies the potential moon-forming disc around the massive exoplanet CT Cha B. An artistic rendering of a dust and gas disc encircling the young exoplanet, CT Cha b, 625 light-years from Earth. Spectroscopic data from the NASA/ESA/CSA James Webb Space Telescope suggest the disc contains the raw materials for moon formation. The planet appears at lower right, while its host star and surrounding protoplanetary disc are visible in the background.
Credit: NASA, ESA, CSA, STScI, G. Cugno (University of Zürich, NCCR PlanetS), S. Grant (Carnegie Institution for Science), J, Olmsted (STScI), L. Hustak (STScI)

Bibliographic information:

Gabriele Cugno and Sierra L. Grant 2025, ApJL 991 L46, DOI: 10.3847/2041-8213/ae0290

 

Press release from ESA Webb.

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Webb explores Sagittarius B2 (Sgr B2) molecular cloud, the largest star-forming cloud in the Milky Way

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Sagittarius B2 (Sgr B2) molecular cloud A wide view of a region of space filled with stars and clumps of orange clouds.

Webb explores Sagittarius B2, the largest star-forming cloud in the Milky Way

The NASA/ESA/CSA James Webb Space Telescope has revealed a colourful array of massive stars and glowing cosmic dust in the Sagittarius B2 (Sgr B2) molecular cloud, the most massive and active star-forming region in our Milky Way galaxy.

A wide view of a region of space filled with stars and clumps of orange clouds.
Stars, gas and cosmic dust in the Sagittarius B2 molecular cloud glow in near-infrared light, captured by Webb’s NIRCam (Near-Infrared Camera). In this light, astronomers see more of the region’s diverse, colourful stars, but less of its gas and dust structure. Webb’s instruments each provide astronomers with important information that help build a more complete picture of what is happening in this intriguing portion of the centre of our galaxy.
Credit: NASA, ESA, CSA, STScI, A. Ginsburg (University of Florida), N. Budaiev (University of Florida), T. Yoo (University of Florida). Image processing: A. Pagan (STScI)

Sagittarius B2 is the Milky Way galaxy’s most massive and active star forming cloud, producing half of the stars created in the galactic centre region despite having only 10 percent of the area’s star-making material. Now, Webb has revealed stunning new views of the region, using both its near-infrared and mid-infrared instruments, to capture both its colourful stars and gaseous stellar nurseries in unprecedented detail.

Sagittarius B2 is located only a few hundred light-years from the supermassive black hole at the heart of the galaxy called Sagittarius A*, a region densely packed with stars, star-forming clouds, and complex magnetic fields. The infrared light that Webb detects is able to pass through some of the area’s thick clouds to reveal young stars and the warm dust surrounding them. Astronomers think that analysis of Webb’s data will help unravel enduring mysteries of the star formation process, and why Sagittarius B2 is forming so many more stars than the rest of the galactic centre.

However, one of the most notable aspects of Webb’s images of Sagittarius B2 are the portions that remain dark. These ironically empty-looking areas of space are actually so dense with gas and dust that even Webb cannot see through them. These thick clouds are the raw material of future stars and a cocoon for those still too young to shine.

Cosmic clouds of pink and purple, some with bright centres, are surrounded by dark areas that appear like black space dotted with bright blue stars. A group of small clouds to the right is more red than any other area of the image.
Webb’s MIRI (Mid-Infrared Instrument) shows the Sagittarius B2 (Sgr B2) region in mid-infrared light, with warm dust glowing brightly. To the right is one clump of clouds that captured astronomers’ attention. It is redder than the rest of the clouds in the image and corresponds to an area that other telescopes have shown to be one of the most molecularly rich regions known. Additional analysis of this intriguing region could yield important insights into why Sgr B2 is so much more productive in making stars than the rest of the galactic centre. Only the brightest stars in this region emit mid-infrared light that can be picked up by Webb’s MIRI instrument, which is why this image has so many fewer stars than that captured by Webb’s NIRCam (Near-Infrared Camera). The darkest areas of the image are not empty space but areas where cosmic dust and gas are so dense that light cannot penetrate them to reach the telescope.
Credit: NASA, ESA, CSA, STScI, A. Ginsburg (University of Florida), N. Budaiev (University of Florida), T. Yoo (University of Florida). Image processing: A. Pagan (STScI)

The high resolution and mid-infrared sensitivity of Webb’s MIRI (Mid-Infrared Instrument) revealed this region in unprecedented detail, including glowing cosmic dust heated by very young massive stars. The reddest area, known as Sagittarius B2 North, (note: north is to the right in these Webb images) is one of the most molecularly rich regions known, but astronomers have never seen it with such clarity.

Sagittarius B2 (Sgr B2) molecular cloud Cosmic clouds of pink and purple, some with bright centres, are surrounded by dark areas that appear like black space dotted with bright blue stars. A small cloud to the lower right is more red than any other area of the image. At the top right are compass arrows indicating the orientation of the image on the sky. The north arrow points to just past 3 o’clock, and the east arrow points to just past 12 o’clock. At the lower right is a scale bar labeled 5 light-years. The length of the scale bar is about 7 times the total width of the image. Below the image is a colour key showing which filters were used to create the image and which visible-light colour is assigned to each filter. From left to right, the filters are: F770W in blue, F1280W in green, and F2550W is red.
This image of the Sagittarius B2 (Sgr B2) molecular cloud, captured by Webb’s MIRI (Mid-Infrared Instrument) includes compass arrows, scale bar, and colour key for reference. To create this image, mid-infrared wavelengths of light have been translated into visible-light colours. The colour key at the bottom shows which MIRI filters were used, and which visible-light colour was assigned to that filter. The north and east compass arrows show the orientation of the image on the sky. Note that the relationship between north and east on the sky (as seen from below) is flipped relative to direction arrows on a map of the ground (as seen from above).
Credit: NASA, ESA, CSA, STScI, A. Ginsburg (University of Florida), N. Budaiev (University of Florida), T. Yoo (University of Florida). Image processing: A. Pagan (STScI)

The difference longer wavelengths of light make, even within the infrared spectrum, are stark when comparing the images from Webb’s MIRI and NIRCam (Near-Infrared Camera) instruments. Glowing gas and dust appear dramatically in mid-infrared light, while all but the brightest stars disappear from view.

In contrast to MIRI, colourful stars steal the show in Webb’s NIRCam image, punctuated occasionally by bright clouds of gas and dust. Further research into these stars will reveal details of their masses and ages, which will help astronomers better understand the process of star formation in this dense, active galactic centre region. Has it been going on for millions of years? Or has some unknown process triggered it only recently?

Sagittarius B2 (Sgr B2) molecular cloud A region of space filled with stars and clumps of orange clouds. At the top right are compass arrows indicating the orientation of the image on the sky. The north arrow points to 3 o’clock, and the east arrow points to 12 o’clock. At the lower right is a scale bar labeled 10 light-years. The length of the scale bar is about 5 times the total width of the image. Below the image is a colour key showing which filters were used to create the image and which visible-light colour is assigned to each filter. From left to right, the filters are: F150W, F182M, and F187N are blue; F212N and F210M are cyan; F300M and F360M are green; F405N is yellow; F410M is light orange; F466N and F480M are orange.
This image of the Sagittarius B2 (Sgr B2) molecular cloud, captured by Webb’s NIRCam (Near-Infrared Camera) instrument includes compass arrows, scale bar, and colour key for reference. To create this image, near-infrared wavelengths of light have been translated into visible-light colours. The colour key at the bottom shows which NIRCam filters were used, and which visible-light colour was assigned to that filter. The north and east compass arrows show the orientation of the image on the sky. Note that the relationship between north and east on the sky (as seen from below) is flipped relative to direction arrows on a map of the ground (as seen from above).
Credit: NASA, ESA, CSA, STScI, A. Ginsburg (University of Florida), N. Budaiev (University of Florida), T. Yoo (University of Florida). Image processing: A. Pagan (STScI)

Astronomers hope Webb will shed light on why star formation in the galactic centre is so disproportionate. Though the region is stocked with plenty of gaseous raw material, on the whole it is not nearly as productive as Sagittarius B2. While Sagittarius B2 has only 10 percent of the galactic centre’s gas, it produces 50 percent of its stars.

Bibliographic information:

Nazar Budaiev, Adam Ginsburg, Ashley T. Barnes, Desmond Jeff, Taehwa Yoo, Cara Battersby, Alyssa Bulatek, Xing Lu, Elisabeth A.C. Mills, Daniel L. Walker, JWST’s first view of the most vigorously star-forming cloud in the Galactic center — Sagittarius B2, DOI: https://doi.org/10.48550/arXiv.2509.11771

Press release from ESA Webb.

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Hubble sees white dwarf WD 1647+375 eating piece of Pluto-like extrasolar planetesimal

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An illustration showing a glowing white object in the upper left corner. This object is encircled by hundreds of thin, concentric, pale-yellow rings on an angle from bottom left to top right. The rings are palest closest to the central, glowing white object. A curving trail of gray, rock-like fragments marches across the right side, through the thin rings and joins the rings at far right. The eight largest fragments of varying sizes appear in the foreground. These objects have white, comet-like tails streaking away from the glowing white object in the rings’ center. The curving trail of fragments bends toward the glowing white object. At the bottom left corner is the label Artist’s Concept. Thanks to the Hubble Space Telescope, a new study reports the accretion of an icy extrasolar planetesimal on to white dwarf WD 1647+375

Hubble sees white dwarf eating piece of Pluto-like object: a new study reports the accretion of an icy extrasolar planetesimal on to WD 1647+375

In our nearby stellar neighbourhood, a burned-out star is snacking on a fragment of a Pluto-like object. With its unique ultraviolet capability, only the NASA/ESA Hubble Space Telescope could identify that this meal is taking place.

The stellar remnant is a white dwarf about half the mass of our Sun, but that is densely packed into a body about the size of Earth. Scientists think the dwarf’s immense gravity pulled in and tore apart an icy Pluto analogue from the system’s own version of the Kuiper Belt, an icy ring of debris that encircles our Solar System. The findings were reported on 18 September 2025 in the Monthly Notices of the Royal Astronomical Society.

An international team of astronomers were able to determine this carnage by analysing the chemical composition of the doomed object as its pieces fell onto the white dwarf. In particular, they detected “volatiles” (substances with low boiling points) including carbon, sulphur, nitrogen, and a high oxygen content that suggests the strong presence of water.

“We were surprised,” said Snehalata Sahu of the University of Warwick in the United Kingdom. Sahu led the data analysis of a Hubble survey of white dwarfs. “We did not expect to find water or other icy content. This is because the comets and Kuiper Belt-like objects are thrown out of their planetary systems early, as their stars evolve into white dwarfs. But here, we are detecting this very volatile-rich material. This is surprising for astronomers studying white dwarfs as well as exoplanets, planets outside our Solar System.”

Only with Hubble

Using Hubble’s Cosmic Origins Spectrograph, the team found that the fragments were composed of nearly two thirds water ice. The fact that they detected so much ice meant that the pieces were part of a very massive object that formed far out in the star system’s icy Kuiper Belt analogue. Using Hubble data, scientists calculated that the object was bigger than typical comets and may be a fragment of an exo-Pluto.

They also detected a large fraction of nitrogen – the highest ever detected in white dwarf debris systems.

“We know that Pluto’s surface is covered with nitrogen ices,” said Sahu. “We think that the white dwarf accreted fragments of the crust and mantle of a dwarf planet.”

Accretion of these volatile-rich objects by white dwarfs is very difficult to detect in visible light. These volatile elements can only be detected with Hubble’s unique ultraviolet light sensitivity. In optical light, the white dwarf would appear ordinary.

About 260 light-years away, the white dwarf is a relatively close cosmic neighbor. In the past, when it was a Sun-like star, it would have been expected to host planets and an analogue to our Kuiper Belt.

Like seeing our Sun in the future

Billions of years from now, when our Sun burns out and collapses to a white dwarf, Kuiper Belt objects will be pulled in by the stellar remnant’s immense gravity.

“These planetesimals will then be disrupted and accreted,” said Sahu. “If an alien observer looks into our Solar System in the far future, they might see the same kind of remains we see today around this white dwarf.”

The team hopes to use the NASA/ESA/CSA James Webb Space Telescope to detect molecular features of volatiles such as water vapour and carbonates by observing this white dwarf in infrared light. By further studying white dwarfs, scientists can better understand the frequency and composition of these volatile-rich accretion events.

Sahu is also following the recent discovery of the interstellar comet 3I/ATLAS. She is eager to learn its chemical composition, especially its fraction of water. 

“These types of studies will help us learn more about planet formation. They can also help us understand how water is delivered to rocky planets,” said Sahu.

Boris Gänsicke, of the University of Warwick and a visitor at Spain’s Instituto de Astrofisica de Canarias, was the principal investigator of the Hubble program that led to this discovery.

“We observed over 500 white dwarfs with Hubble. We’ve already learned so much about the building blocks and fragments of planets, but I’ve been absolutely thrilled that we now identified a system that resembles the objects in the frigid outer edges of our solar system,” said Gänsicke. “Measuring the composition of an exo-Pluto is an important contribution toward our understanding of the formation and evolution of these bodies.”

An illustration showing a glowing white object in the upper left corner. This object is encircled by hundreds of thin, concentric, pale-yellow rings on an angle from bottom left to top right. The rings are palest closest to the central, glowing white object. A curving trail of gray, rock-like fragments marches across the right side, through the thin rings and joins the rings at far right. The eight largest fragments of varying sizes appear in the foreground. These objects have white, comet-like tails streaking away from the glowing white object in the rings’ center. The curving trail of fragments bends toward the glowing white object. At the bottom left corner is the label Artist’s Concept.
Thanks to the Hubble Space Telescope, a new study reports the accretion of an icy extrasolar planetesimal on to white dwarf WD 1647+375. This artist’s concept shows a white dwarf surrounded by a large debris disc. Debris from pieces of a captured, Pluto-like object is falling onto the white dwarf.
Credit: T. Pyle (Caltech, NASA’s Jet Propulsion Laboratory)

Bibliographic information:

Snehalata Sahu, Boris T Gänsicke, Jamie T Williams, Detlev G Koester, Jay Farihi, Steven J Desch, Nicola Pietro Gentile Fusillo, Dimitri Veras, Sean N Raymond, Maria Teresa Belmonte, Discovery of an icy and nitrogen-rich extrasolar planetesimal, Monthly Notices of the Royal Astronomical Society, Volume 543, Issue 1, October 2025, Pages 223–232, https://doi.org/10.1093/mnras/staf1424

Press release from ESA Hubble

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Webb observes Sharpless 2-284, a Herbig-Haro object, an immense stellar jet on outskirts of our Milky Way

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Gaseous yellow-orange filaments look like a rose seen from the side and tilted slightly from upper left to lower right, slightly higher than the center of the frame. Extending from the rose to upper left and lower right are gaseous outflows that appear as red lobes that have an overall shape of tall, narrow triangles with rounded tips. Each red triangle is made up of wavy, irregular lines. Dozens of stars are scattered across the field. One particularly bright white star with eight diffraction spikes is located at the top of the yellow rose. Another bright blue star with even more prominent diffraction spikes is to its lower left. The background of space is black.

Webb observes Sharpless 2-284, a Herbig-Haro object, an immense stellar jet on outskirts of our Milky Way

Way out toward the edge of our Milky Way galaxy, a young star that is still forming is sending out a birth announcement to the Universe in the form of a celebratory looking firework. These seething twin jets of hot gasses are blazing across 8 light-years – twice the distance between our Sun and the nearest star system. Superheated gases falling onto the massive star are blasted back into space along the star’s rotational axis and powerful magnetic fields confine the jets to narrow beams. The NASA/ESA/CSA James Webb Space Telescope witnessed the spectacle in infrared light. The jets are plowing into interstellar dust and gas, creating fascinating details captured only by Webb.

Gaseous yellow-orange filaments look like a rose seen from the side and tilted slightly from upper left to lower right, slightly higher than the center of the frame. Extending from the rose to upper left and lower right are gaseous outflows that appear as red lobes that have an overall shape of tall, narrow triangles with rounded tips. Each red triangle is made up of wavy, irregular lines. Dozens of stars are scattered across the field. One particularly bright white star with eight diffraction spikes is located at the top of the yellow rose. Another bright blue star with even more prominent diffraction spikes is to its lower left. The background of space is black.
The NASA/ESA/CSA James Webb Space Telescope recently imaged an extremely large stellar jet at the outskirts of our Milky Way galaxy in the proto-cluster Sh2-284. This Herbig-Haro (HH) object, jets of plasma shooting out from newly formed stars, is 8 light-years across. This is about double the distance from our Sun to its closest neighboring star system, Alpha Centauri.
Its detection provides evidence that HH jets scale with the mass of their parent stars—the more massive the stellar engine driving the plasma, the larger the resulting jet.
Credit: NASA, ESA, CSA, STScI, Y. Cheng (NAOJ), J. DePasquale (STScI)

A blowtorch of seething gasses erupting from a volcanically growing monster star has been captured by Webb. Stretching across 8 light-years, the length of the stellar eruption is approximately twice the distance between our Sun and the nearby Alpha Centauri system. The size and strength of this particular stellar jet, known as Sharpless 2-284 (Sh2-284 for short), qualifies it as rare, say researchers.

The outflow is streaking across space at hundreds of thousands of kilometres per hour. The central protostar, weighing as much as ten of our Suns, is located 15,000 light-years away in the outer reaches of our galaxy.

The Webb discovery was serendipitous. “We didn’t really know there was a massive star with this kind of super-jet out there before the observation. Such a spectacular outflow of molecular hydrogen from a massive star is rare in other regions of our galaxy,” said lead author Yu Cheng of the National Astronomical Observatory of Japan.

This unique class of stellar fireworks, called Herbig-Haro (HH) objects, are highly collimated jets of plasma shooting out from newly forming stars. Such jetted outflows are a star’s spectacular “birth announcement” to the Universe. Some of the infalling gas building up around the central star is blasted along the star’s spin axis, likely under the influence of magnetic fields.

Today, well over 300 HH objects have been observed, but mainly from low-mass stars. These spindle-like jets offer clues into the nature of newly forming stars. The energetics, narrowness, and evolutionary time scales of HH objects all serve to constrain models of the environment and physical properties of the young stellar object powering the outflow.

“I was really surprised at the order, symmetry, and size of the jet when we first looked at it,” said co-author Jonathan Tan of the University of Virginia in Charlottesville and Chalmers University of Technology in Gothenburg, Sweden.

Its detection offers evidence that HH jets must scale up with the mass of the star powering them. The more massive the stellar engine propelling the plasma, the larger the gusher’s size.

The jet’s detailed filamentary structure, captured by Webb’s crisp resolution in infrared light, is evidence the jet is plowing into interstellar dust and gas. This creates separate knots, bow shocks, and linear chains.

The tips of the jet, lying in opposite directions, encapsulate the history of the star’s formation. “Originally the material was close into the star, but over 100,000 years the tips were propagating out, and then the stuff behind is a younger outflow,” said Tan.

Outlier

At nearly twice the distance from the galactic center as our Sun, the host proto-cluster that’s home to the voracious jet is on the periphery of our Milky Way galaxy.

Within the cluster, a few hundred stars are still forming. Being in the galactic hinterlands means the stars are deficient in heavier elements beyond hydrogen and helium. This is measured as metallicity, which gradually increases over cosmic time as each passing stellar generation expels end products of nuclear fusion through winds and supernovae. The low metallicity of Sh2-284 is a reflection of its relatively pristine nature, making it a local analog for the environments in the early universe that were also deficient in heavier elements.

“Webb’s exquisite data have also shown us that relatively more stars seem to form at lower masses in Sh2-284 than in closer, more metal-rich clusters,” said co-author Morten Andersen, of the European Southern Observatory, and lead author of a second paper on the Webb data. “This cluster is an excellent region to help us understand star formation throughout the Universe.”

“Massive stars, like the one found inside this cluster, have very important influences on the evolution of galaxies. Our discovery is shedding light on the formation mechanism of massive stars in low metallicity environments, so we can use this massive star as a laboratory to study what was going on in earlier cosmic history,” added Cheng.

Unrolling stellar tapestry

Stellar jets, which are powered by the gravitational energy released as a star grows in mass, encode the formation history of the protostar.

“Webb’s new images are telling us that the formation of massive stars in such environments could proceed via a relatively stable disc around the star that is expected in theoretical models of star formation known as core accretion,” said Tan. “Once we found a massive star launching these jets, we realised we could use the Webb observations to test theories of massive star formation. We developed new theoretical core accretion models that were fit to the data, to basically tell us what kind of star is in the center. These models imply that the star is about 10 times the mass of the Sun and is still growing and has been powering this outflow.”

For more than 30 years, astronomers have disagreed about how massive stars form. Some think a massive star requires a very chaotic process, called competitive accretion.

In the competitive accretion model, material falls in from many different directions so that the orientation of the disc changes over time. The outflow is launched perpendicularly, above and below the disc, and so would also appear to twist and turn in different directions.

“However, what we’ve seen here, because we’ve got the whole history – a tapestry of the story – is that the opposite sides of the jets are nearly 180 degrees apart from each other. That tells us that this central disc is held steady and validates a prediction of the core accretion theory,” said Tan.

Where there’s one massive star, there could be others in this outer frontier of the Milky Way. Other massive stars may not yet have reached the point of firing off Roman-candle-style outflows. Data from the Atacama Large Millimeter Array in Chile, also presented in this study, has found another dense stellar core that could be in an earlier stage of construction.

The paper has been accepted for publication in The Astrophysical Journal.

Image titled “James Webb Space Telescope; Stellar Jet; SH2-284,” with compass arrows, scale bar, and color key. Gaseous yellow-orange filaments look like a rose seen from the side and tilted slightly from upper left to lower right, slightly higher than the center of the frame. Extending from the rose to upper left and lower right are gaseous outflows that appear as red lobes that have an overall shape of tall, narrow triangles with rounded tips. At the bottom left are compass arrows indicating the orientation of the image on the sky. The east arrow points toward 10 o’clock. The north arrow points in the 2 o’clock direction. At the bottom left is a scale bar labeled 1.1 light-years, 15 arcsec. The length of the scale bar is about one sixth of the total image. Below the image is a color key showing which NIRCam filters were used to create the image and which visible-light color is assigned to each filter. From left to right: F162M and 182M are blue, F200W and F356W are green, and F405N and F470N are red.
This image of the stellar jet in Sh2-284, captured by the NASA/ESA/CSA James Webb Space Telescope’s NIRCam (Near-Infrared Camera), shows compass arrows, scale bar, and color key for reference.
The north and east compass arrows show the orientation of the image on the sky. Note that the relationship between north and east on the sky (as seen from below) is flipped to the direction arrows on a map of the ground (as seen from above).
The scale bar is labeled in light-years, which is the distance that light travels in one Earth-year, and arcsec (It takes 1.1 years for light to travel a distance equal to the length of the scale bar.) One light-year is equal to about 5.88 trillion miles or 9.46 trillion kilometers.
This image shows invisible near-infrared wavelengths of light that have been translated into visible-light colors. The color key shows which NIRCam filters were used when collecting the light. The color of each filter name is the visible light color used to represent the infrared light that passes through that filter.
Credit: NASA, ESA, CSA, STScI, Y. Cheng (NAOJ), J. DePasquale (STScI)

Press release from ESA Webb.

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Pismis 24: a glittering glimpse of starbirth

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In what appears as a celestial dreamscape, a blue and black sky filled with brilliant stars covers about two thirds of the image. The stars are different sizes and shades of white, beige, yellow, and light orange. Across the bottom third of the scene is a craggy, mountain-like vista with spire-like peaks and deep, seemingly misty valleys. These so-called mountains appear in varying shades of orange, yellow, and brown. Above their soaring spires is a wispy, ethereal white cloud that stretched horizontally across the scene. Steam appears to rise from the mountaintops and join with this cloud. At the top, right corner of the image, a swath of orange and brown structure cuts diagonally across the sky.

Pismis 24: a glittering glimpse of starbirth

This sparkling scene of star birth was captured by the NASA/ESA/CSA James Webb Space Telescope. What appears to be a craggy, starlit mountaintop kissed by wispy clouds is actually a cosmic dust-scape being eaten away by the blistering winds and radiation of nearby, massive, infant stars.

Called Pismis 24, this young star cluster resides in the core of the nearby Lobster Nebula, approximately 5,500 light-years from Earth in the constellation Scorpius. Home to a vibrant stellar nursery and one of the closest sites of massive star birth, Pismis 24 provides rare insight into large and massive stars. This region is one of the best places to explore the properties of hot young stars and how they evolve.

In what appears as a celestial dreamscape, a blue and black sky filled with brilliant stars covers about two thirds of the image. The stars are different sizes and shades of white, beige, yellow, and light orange. Across the bottom third of the scene is a craggy, mountain-like vista with spire-like peaks and deep, seemingly misty valleys. These so-called mountains appear in varying shades of orange, yellow, and brown. Above their soaring spires is a wispy, ethereal white cloud that stretched horizontally across the scene. Steam appears to rise from the mountaintops and join with this cloud. At the top, right corner of the image, a swath of orange and brown structure cuts diagonally across the sky.
This sparkling scene of star birth was captured by the NASA/ESA/CSA James Webb Space Telescope. What appears to be a craggy, starlit mountaintop kissed by wispy clouds is actually a cosmic dust-scape being eaten away by the blistering winds and radiation of nearby, massive, infant stars.
Called Pismis 24, this young star cluster resides in the core of the nearby Lobster Nebula, approximately 5,500 light-years from Earth in the constellation Scorpius. Home to a vibrant stellar nursery and one of the closest sites of massive star birth, Pismis 24 provides rare insight into large and massive stars. This region is one of the best places to explore the properties of hot young stars and how they evolve. Credit: NASA, ESA, CSA, and STScI, A. Pagan (STScI)

At the heart of this glittering cluster is the brilliant Pismis 24-1. It is at the centre of a clump of stars above the jagged orange peaks, and the tallest spire is pointing directly toward it. Pismis 24-1 appears as a gigantic single star, and it was once thought to be the most massive known stars. Scientists have since learned that it is composed of at least two stars, though they cannot be resolved in this image. At 74 and 66 solar masses, respectively, the two known stars are still among the most massive and luminous stars ever seen.

Captured in infrared light by Webb’s NIRCam (Near-Infrared Camera), this image reveals thousands of jewel-like stars of varying sizes and colors. The largest and most brilliant ones with the six-point diffraction spikes are the most massive stars in the cluster. Hundreds to thousands of smaller members of the cluster appear as white, yellow, and red, depending on their stellar type and the amount of dust enshrouding them. Webb also shows us tens of thousands of stars behind the cluster that are part of the Milky Way galaxy.

Super-hot, infant stars (some almost 8 times the temperature of the Sun) blast out scorching radiation and punishing winds that are sculpting a cavity into the wall of the star-forming nebula. That nebula extends far beyond NIRCam’s field of view. Only small portions of it are visible at the bottom and top right of the image. Streamers of hot, ionized gas flow off the ridges of the nebula, and wispy veils of gas and dust, illuminated by starlight, float around its towering peaks. Dramatic spires jut from the glowing wall of gas, resisting the relentless radiation and winds. They are like fingers pointing toward the hot, young stars that have sculpted them. The fierce forces shaping and compressing these spires cause new stars to form within them. The tallest spire spans about 5.4 light-years from its tip to the bottom of the image. More than 200 of our solar systems out to Neptune’s orbit could fit into the width its tip, which is 0.14 light-years. In this image, the color cyan indicates hot or ionised hydrogen gas being heated up by the massive young stars. Dust molecules similar to smoke here on Earth are represented in orange. Red signifies cooler, denser molecular hydrogen. The darker the red, the denser the gas. Black denotes the densest gas, which is not emitting light. The wispy white features are dust and gas that are scattering starlight.

Webb image of Pismis 24 with compass arrows, scale bar, and color key. Image shows brilliant stars against a blue and black sky covering about two thirds of the image. Across the bottom third is a craggy, mountain-like vista with soaring peaks and deep, seemingly misty valleys. A wispy white cloud stretches horizontally across the mountaintops. At bottom left, compass arrows indicate the orientation of the image on the sky. The north arrow points downward in the 6 o’clock direction. The east arrow points in the 3 o’clock direction. At lower right is a scale bar labeled 1 light-year. The length of the bar is a about one-eighth the total width of the image. Below the image is a color key showing which NIRCam filters were used to create the image and which visible-light color is assigned to each filter. From left to right, filters are: F090W is blue; F187N is blue-green; F200W is yellow-green; F335M is orange; and F470N is red.
This sparkling scene of star birth was captured by the NASA/ESA/CSA James Webb Space Telescope. What appears to be a craggy, starlit mountaintop kissed by wispy clouds is actually a cosmic dust-scape being eaten away by the blistering winds and radiation of nearby, massive, infant stars.
Called Pismis 24, this young star cluster resides in the core of the nearby Lobster Nebula, approximately 5,500 light-years from Earth in the constellation Scorpius. Home to a vibrant stellar nursery and one of the closest sites of massive star birth, Pismis 24 provides rare insight into large and massive stars. This region is one of the best places to explore the properties of hot young stars and how they evolve.
Credit: NASA, ESA, CSA, and STScI, A. Pagan (STScI)

Press release from ESA Webb.

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Webb narrows atmospheric possibilities for Earth-sized exoplanet TRAPPIST-1 d

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The James Webb Space Telescope narrows atmospheric possibilities for Earth-sized rocky exoplanet TRAPPIST-1 d. Illustration of a planet silhouetted in front of a star. The star shows a large eruption on one side and more wisps of red coming from its southern hemisphere. Two more planets appear in the background.

Webb narrows atmospheric possibilities for Earth-sized exoplanet TRAPPIST-1 d

The exoplanet TRAPPIST-1 d intrigues astronomers looking for possibly habitable worlds beyond our solar system because it is similar in size to Earth, rocky, and resides in an area around its star where liquid water on its surface is theoretically possible. But according to a new study using data from the NASA/ESA/CSA James Webb Space Telescope, it does not have an Earth-like atmosphere.

A protective atmosphere, a friendly Sun, and lots of liquid water — Earth is a special place. Using the unprecedented capabilities of the Webb, astronomers are on a mission to determine just how special, and rare, our home planet is. Can this temperate environment exist elsewhere, even around a different type of star? The TRAPPIST-1 system provides a tantalizing opportunity to explore this question, as it contains seven Earth-sized worlds orbiting the most common type of star in the galaxy: a red dwarf.

“Ultimately, we want to know if something like the environment we enjoy on Earth can exist elsewhere, and under what conditions. While the James Webb Space Telescope is giving us the ability to explore this question in Earth-sized planets for the first time, at this point we can rule out TRAPPIST-1 d from a list of potential Earth twins or cousins,”

said Caroline Piaulet-Ghorayeb of the University of Chicago and Trottier Institute for Research on Exoplanets (IREx) at Université de Montréal, lead author of the study published in The Astrophysical Journal.

Planet TRAPPIST-1 d

The TRAPPIST-1 system is located 40 light-years away and was revealed as the record-holder for most Earth-sized rocky planets around a single star in 2017, thanks to data from NASA’s retired Spitzer Space Telescope and other observatories. Due to that star being a dim, relatively cold red dwarf, the “habitable zone” – where the planet’s temperature may be just right, such that liquid surface water is possible – lies much closer to the star than in our solar system. TRAPPIST-1 d, the third planet from the red dwarf star, lies on the cusp of that temperate zone, yet its distance to its star is only 2 percent of Earth’s distance from the Sun. TRAPPIST-1 d completes an entire orbit around its star, its year, in only four Earth days.

Webb’s NIRSpec (Near-Infrared Spectrograph) instrument did not detect molecules from TRAPPIST-1 d that are common in Earth’s atmosphere, like water, methane, or carbon dioxide. However, Piaulet-Ghorayeb outlined several possibilities for the exoplanet that remain open for follow-up study.

“There are a few potential reasons why we don’t detect an atmosphere around TRAPPIST-1 d. It could have an extremely thin atmosphere that is difficult to detect, somewhat like Mars. Alternatively, it could have very thick, high-altitude clouds that are blocking our detection of specific atmospheric signatures — something more like Venus. Or, it could be a barren rock, with no atmosphere at all,” Piaulet-Ghorayeb said.

The star TRAPPIST-1

No matter what the case may be for TRAPPIST-1 d, it’s tough being a planet in orbit around a red dwarf star. TRAPPIST-1, the host star of the system, is known to be volatile, often releasing flares of high-energy radiation with the potential to strip off the atmospheres of its small planets, especially those orbiting most closely. Nevertheless, scientists are motivated to seek signs of atmospheres on the TRAPPIST-1 planets because red dwarf stars are the most common stars in our galaxy. If planets can hold on to an atmosphere here, under waves of harsh stellar radiation, they could, as the saying goes, make it anywhere.

“Webb’s sensitive infrared instruments are allowing us to delve into the atmospheres of these smaller, colder planets for the first time,” said Björn Benneke of IREx at Université de Montréal, a co-author of the study. “We’re really just getting started using Webb to look for atmospheres on Earth-sized planets, and to define the line between planets that can hold onto an atmosphere, and those that cannot.”

The outer TRAPPIST-1 planets

Webb observations of the outer TRAPPIST-1 planets are ongoing, which hold both potential and peril. On the one hand, Benneke said, planets e, f, g, and h may have better chances of having atmospheres because they are further away from the energetic eruptions of their host star. However, their distance and colder environment will make atmospheric signatures more difficult to detect, even with Webb’s infrared instruments.

“All hope is not lost for atmospheres around the TRAPPIST-1 planets,” Piaulet-Ghorayeb said. “While we didn’t find a big, bold atmospheric signature at planet d, there is still potential for the outer planets to be holding onto a lot of water and other atmospheric components.”

“Our detective work is just beginning. While TRAPPIST-1 d may prove a barren rock illuminated by a cruel red star, the outer planets TRAPPIST-1e, f, g, and h, may yet possess thick atmospheres,” added Ryan MacDonald, a co-author of the paper, now at the University of St Andrews in the United Kingdom, and previously at the University of Michigan. “Thanks to Webb we now know that TRAPPIST-1 d is a far cry from a hospitable world. We’re learning that the Earth is even more special in the cosmos.”

Illustration of a planet silhouetted in front of a star. The star shows a large eruption on one side and more wisps of red coming from its southern hemisphere. Two more planets appear in the background.
The James Webb Space Telescope narrows atmospheric possibilities for Earth-sized rocky exoplanet TRAPPIST-1 d. This artist’s concept depicts planet TRAPPIST-1 d passing in front of its turbulent star, with other members of the closely packed system shown in the background.
The TRAPPIST-1 system is intriguing to scientists for a few reasons. Not only does the system have seven Earth-sized rocky worlds, but its star is a red dwarf, the most common type of star in the Milky Way galaxy. If an Earth-sized world can maintain an atmosphere here, and thus have the potential for liquid surface water, the chance of finding similar worlds throughout the galaxy is much higher. In studying the TRAPPIST-1 planets, scientists are determining the best methods for separating starlight from potential atmospheric signatures in data from the NASA/ESA/CSA James Webb Space Telescope. The star TRAPPIST-1’s variability, with frequent flares, provides a challenging testing ground for these methods.
Credit: NASA, ESA, CSA, J. Olmsted (STScI)

Bibliographic information:

Caroline Piaulet-Ghorayeb et al.,  ApJ 989 181 2025, DOI: 10.3847/1538-4357/adf207

 

Press release from ESA Webb.

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WD 0525+526: Hubble uncovers rare white dwarf merger remnant

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WD 0525+526 This illustration depicts a white dwarf star siphoning material off of a red giant star. The white dwarf has a long tail behind it and an orange shockwave in front of it as it flies through the extended atmosphere of the red giant, shown as a red glow. A broad stream of red gas is being pulled up from the red giant’s surface to the white dwarf.

WD 0525+526: Hubble uncovers rare white dwarf merger remnant

An international team of astronomers using the NASA/ESA Hubble Space Telescope have discovered a stellar rarity: an ultra-massive white dwarf that formed when a white dwarf merged with another star, rather than through the evolution of a single star. This discovery, which was made possible by Hubble’s sensitive ultraviolet observations, suggests that these rare white dwarfs may be more common than previously suspected.

A white dwarf is the end state for a star that is not massive enough to explode as a core-collapse supernova. The transition to a white dwarf begins when a star exhausts the supply of hydrogen in its core. The changes in and around the star’s core cause the star to expel its outer layers in a massive stellar sigh, revealing the star’s dense, Earth-sized core, which evolves into a white dwarf. The cores of white dwarfs are mostly composed of either carbon and oxygen or oxygen and neon, depending on the mass of the progenitor star. The Sun will become a white dwarf in about 5 billion years.

White dwarfs can theoretically have masses up to about 1.4 times the mass of the Sun, but white dwarfs that are more massive than the Sun are rare. These objects, which astronomers call ultra-massive white dwarfs, can form either through the evolution of a single massive star or through the merger of a white dwarf with another star.

Recently, astronomers used Hubble’s Cosmic Origins Spectrograph to investigate one such ultra-massive white dwarf, WD 0525+526. WD 0525+526 is just 128 light-years away and is 20% more massive than the Sun.

In visible light, the spectrum of WD 0525+526’s atmosphere resembled that of a typical white dwarf. However, Hubble’s ultraviolet spectrum revealed something unusual: evidence of carbon in the white dwarf’s atmosphere.

White dwarfs that form through the evolution of a single star have atmospheres composed of hydrogen and helium. These thick atmospheres blanket the carbon–oxygen or oxygen–neon surface of the white dwarf, usually preventing these elements from appearing in its spectrum.

When carbon appears in the spectrum of a white dwarf, it can signal a more violent origin than the typical single-star scenario: the collision of two white dwarfs, or of a white dwarf and a subgiant star. Such a collision can burn away the hydrogen and helium atmospheres of the colliding stars, leaving behind a scant layer of hydrogen and helium around the merger remnant that allows carbon from the white dwarf’s core to float upward, where it can be detected.

“It’s a discovery that underlines that things may be different from what they appear to us at first glance,” said the principal investigator of the Hubble programme, Boris Gaensicke, of the University of Warwick in the United Kingdom. “Until now, this appeared as a normal white dwarf, but Hubble’s ultraviolet eyes revealed that it had a very different history from what we would have guessed. It’s like asking a person you think you know well a different kind of question.”

This discovery marks the first time that a white dwarf born from colliding stars has been identified by its ultraviolet spectrum. Prior to this study, six white dwarf merger products were discovered via carbon lines in their visible-light spectra. All seven of these are part of a larger group that were found to be bluer than expected for their masses and ages from a study with ESA’s Gaia mission in 2019, with the evidence of mergers providing new insights into their formation history.

WD 0525+526 is remarkable even within the small group of white dwarfs known to be the product of merging stars. With a temperature of almost 21 000 kelvins and a mass of 1.2 solar masses, WD 0525+526 is hotter and more massive than the other white dwarfs in this group.

WD 0525+526’s extreme temperature posed something of a mystery for the team. For cooler white dwarfs, such as the six previously discovered merger products, a process called convection can mix carbon into the thin hydrogen–helium atmosphere. WD 0525+526 is too hot for convection to take place, however. Instead, the team determined that a more subtle process called semi-convection brings a small amount of carbon up into WD 0525+526’s atmosphere. WD 0525+526 has the smallest amount of atmospheric carbon of any white dwarf known to result from a merger, about 100 000 times less than other merger remnants.

The high temperature and low carbon abundance mean that identifying this white dwarf as the product of a merger would have been impossible without Hubble’s sensitivity to ultraviolet light; spectral lines from elements heavier than helium, like carbon, become fainter at visible wavelengths for hotter white dwarfs, but these spectral signals remain bright in the ultraviolet, where Hubble is uniquely positioned to spot them.

“Hubble’s Cosmic Origins Spectrograph is the only instrument that can obtain the superb quality ultraviolet spectroscopy that was required to detect the carbon in the atmosphere of this white dwarf,” said study lead Snehalata Sahu from the University of Warwick.

Because WD 0525+526’s unusual origin was revealed only once astronomers glimpsed its ultraviolet spectrum, it’s likely that other seemingly ‘normal’ white dwarfs are actually the result of cosmic collisions — a possibility that the team is excited to explore in the future.

“We would like to extend our research on this topic by exploring how common carbon white dwarfs are, and how many stellar mergers are hiding among the normal white dwarf family,” said study co-lead Antoine Bedrad from the University of Warwick. “That will be an important contribution to our understanding of white dwarf binaries, and the pathways to supernova explosions.”

This illustration depicts a white dwarf star siphoning material off of a red giant star. The white dwarf has a long tail behind it and an orange shockwave in front of it as it flies through the extended atmosphere of the red giant, shown as a red glow. A broad stream of red gas is being pulled up from the red giant’s surface to the white dwarf.
This image is an illustration of a merging white dwarf remnant.
An international team of astronomers using the NASA/ESA Hubble Space Telescope have discovered a stellar rarity: an ultra-massive white dwarf that formed when a white dwarf merged with another star, rather than through the evolution of a single star. This discovery, which was made possible by Hubble’s sensitive ultraviolet observations, suggests that these rare white dwarfs may be more common than previously suspected.
Credit: NASA, ESA, R. Crawford (STScI)

Bibliographic information:

Sahu, S., Bédard, A., Gänsicke, B.T. et al. A hot white dwarf merger remnant revealed by an ultraviolet detection of carbon, Nat Astron (2025), DOI: https://doi.org/10.1038/s41550-025-02590-y

Press release from ESA Hubble.

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Webb finds new evidence for a gas giant orbiting Alpha Centauri A

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Illustration of a large spherical object that looks like a gas giant planet. The object appears to have bands of tan, orange, and dark red horizontal lines forming patterns similar to those in the atmosphere of Jupiter. The background is filled with thousands of distant stars that form a Milky Way-like band running from left to right. The host star, Alpha Centauri A, appears as a glowing white circle to the upper left of the planet. Further off in the distance above and to the right of the planet is a smaller glowing circle, nearby Alpha Centauri B. The words “Artist’s Concept” are in the lower left corner.

Webb finds new evidence for planet, a gas giant orbiting Alpha Centauri A, our closest solar twin

Astronomers using the NASA/ESA/CSA James Webb Space Telescope have found strong evidence of a giant planet orbiting a star in the stellar system closest to our own Sun. At just 4 light-years away from Earth, the Alpha Centauri triple star system has long been a compelling target in the search for worlds beyond our solar system.

Illustration of a large spherical object that looks like a gas giant planet. The object appears to have bands of tan, orange, and dark red horizontal lines forming patterns similar to those in the atmosphere of Jupiter. The background is filled with thousands of distant stars that form a Milky Way-like band running from left to right. The host star, Alpha Centauri A, appears as a glowing white circle to the upper left of the planet. Further off in the distance above and to the right of the planet is a smaller glowing circle, nearby Alpha Centauri B. The words “Artist’s Concept” are in the lower left corner.
This artist’s concept shows what the gas giant orbiting Alpha Centauri A could look like. Observations of the triple star system Alpha Centauri using the NASA/ESA/CSA James Webb Space Telescope indicate the potential gas giant, about the mass of Saturn, orbiting the star by about two times the distance between the Sun and Earth.
In this concept, Alpha Centauri A is depicted at the upper left of the planet, while the other Sun-like star in the system, Alpha Centauri B, is at the upper right. Our Sun is shown as a small dot of light between those two stars.
Credit: NASA, ESA, CSA, STScI, R. Hurt (Caltech/IPAC)

Visible only from Earth’s Southern hemisphere, it’s made up of the binary Alpha Centauri A and Alpha Centauri B, both Sun-like stars, and the faint red dwarf star Proxima Centauri. Alpha Centauri A is the third brightest star in the night sky. While there are three confirmed planets orbiting Proxima Centauri, the presence of other worlds surrounding Alpha Centauri A and Alpha Centauri B has proved challenging to confirm.

Now, Webb’s observations from its Mid-Infrared Instrument (MIRI) are providing the strongest evidence to date of a gas giant orbiting Alpha Centauri A. The results have been accepted in a series of two papers in The Astrophysical Journal Letters.

Three panels, each showing a different view of the binary star system Alpha Centauri. The panel on the left is a Digitized Sky Survey image showing a single bright blue point source at the center of a black image with small stars scattered throughout. The very center of this bright source is outlined with a vertical box, tilted slightly to the left, with two diagonal lines leading to the second panel. The second panel is a Hubble Space Telescope image that shows two white stars with 4 diffraction spikes each against a black background. The top star is labeled Alpha Cen B and the bottom Alpha Cen A. Alpha Cen A is outlined with a white square with two diagonal lines leading to the third panel at the furthest right, which shows a James Webb Space Telescope image of the star. An orange star icon and central black circle outlined in white marks the location of Alpha Cen A. A large white circle outlines a blurry red-toned field that surrounds the location of the star. A bright orange blob at 9 o’clock in relation to the star is labeled “S1” and circled
This image shows the Alpha Centauri star system from several different ground- and space-based observatories: the Digitized Sky Survey (DSS), the NASA/ESA Hubble Space Telescope, and the NASA/ESA/CSA James Webb Space Telescope. Alpha Centauri A is the third brightest star in the night sky, and the closest Sun-like star to Earth.
The ground-based image from DSS shows the triple system as a single source of light, while Hubble resolves the two Sun-like stars in the system, Alpha Centauri A and Alpha Centauri B.
The image from Webb’s MIRI (Mid-Infrared Instrument), which uses a coronagraphic mask to block the bright glare from Alpha Centauri A, reveals a potential planet orbiting the star.
Credit: NASA, ESA, CSA, STScI, DSS, A. Sanghi (Caltech), C. Beichman (JPL), D. Mawet (Caltech), J. DePasquale (STScI)

If confirmed, the planet would be the closest to Earth that orbits in the habitable zone of a Sun-like star. However, because the planet candidate is a gas giant, scientists say it would not support life as we know it.

“With this system being so close to us, any exoplanets found would offer our best opportunity to collect data on planetary systems other than our own. Yet, these are incredibly challenging observations to make, even with the world’s most powerful space telescope, because these stars are so bright, close, and move across the sky quickly,” said Charles Beichman, NASA’s Jet Propulsion Laboratory and the NASA Exoplanet Science Institute at Caltech’s IPAC astronomy center, co-first author on the new papers. “Webb was designed and optimized to find the most distant galaxies in the universe. The operations team at the Space Telescope Science Institute had to come up with a custom observing sequence just for this target, and their extra effort paid off spectacularly.”

Several rounds of meticulously planned observations by Webb, careful analysis by the research team, and extensive computer modeling helped determine that the source seen in Webb’s image is likely to be a planet, and not a background object (like a galaxy), foreground object (a passing asteroid), or other detector or image artifact.

The first observations of the system took place in August 2024, using the coronagraphic mask aboard MIRI to block Alpha Centauri A’s light. While extra brightness from the nearby companion star Alpha Centauri B complicated the analysis, the team was able to subtract out the light from both stars to reveal an object over 10,000 times fainter than Alpha Centauri A, separated from the star by about two times the distance between the Sun and Earth.

While the initial detection was exciting, the research team needed more data to come to a firm conclusion. However, additional observations of the system in February 2025 and April 2025 (using Director’s Discretionary Time) did not reveal any objects like the one identified in August 2024.

“We are faced with the case of a disappearing planet! To investigate this mystery, we used computer models to simulate millions of potential orbits, incorporating the knowledge gained when we saw the planet, as well as when we did not,” said PhD student Aniket Sanghi of the California Institute of Technology in Pasadena, California. Sanghi is a co-first author on the two papers covering the team’s research.

In these simulations, the team took into account both the 2019 sighting of a potential exoplanet candidate by the European Southern Observatory’s Very Large Telescope, the new data from Webb, and considered orbits that would be gravitationally stable in the presence of Alpha Centauri B, meaning the planet wouldn’t get flung out of the system.

Three panels, each showing a different view of the binary star system Alpha Centauri from the Webb. The left panel shows a rectangular image tilted at a 45 degree angle outlined in white on a grey background. The image is a blown-out bright source at the center, with 8, double columned reddish white diffraction spikes. The center of this bright source is outlined with a vertical box, tilted slightly to the left, with two diagonal lines leading to the second panel. This shows a view of both Alpha Centauri A at the bottom and Alpha Centauri B at the top, both with orange star icons over each star. The star icons are surrounded by mottled red and white blotches. The bottom star is outlined with a white square with two diagonal lines leading to the third panel. Within a large white circle there is a blurry red-toned field with an orange star icon and central black circle outlined in white marking the location of Alpha Cen A. A bright orange blob at 9 o’clock in relation to the star is labeled “S1” and circled.
This 3-panel image captures the NASA/ESA/CSA James Webb Space Telescope’s observational search for a planet around the nearest Sun-like star, Alpha Centauri A. The initial image shows the bright glare of Alpha Centauri A and Alpha Centauri B, then the middle panel shows the system with a coronagraphic mask placed over Alpha Centauri A to block its bright glare. However, the way the light bends around the edges of the coronagraph creates ripples of light in the surrounding space. The telescope’s optics (its mirrors and support structures) cause some light to interfere with itself, producing circular and spoke-like patterns. These complex light patterns, along with light from the nearby Alpha Centauri B, make it incredibly difficult to spot faint planets. In the panel at the right, astronomers have subtracted the known patterns (using reference images and algorithms) to clean up the image and reveal faint sources like the candidate planet.
Credit: NASA, ESA, CSA, STScI, A. Sanghi (Caltech), C. Beichman (JPL), D. Mawet (Caltech), J. DePasquale (STScI)

Researchers say a non-detection in the second and third round of observations with Webb isn’t surprising.

“We found that in half of the possible orbits simulated, the planet moved too close to the star and wouldn’t have been visible to Webb in both February and April 2025,” said Sanghi.

Based on the brightness of the planet in the mid-infrared observations and the orbit simulations, researchers say it could be a gas giant approximately the mass of Saturn orbiting Alpha Centauri A in an elliptical path varying between 1 to 2 times the distance between Sun and Earth.

“These are some of the most demanding observations we’ve done so far with MIRI’s coronagraph,” said Pierre-Olivier Lagage, of CEA, France, who is a co-author on the papers and was the French lead for the development of MIRI. “When we were developing the instrument we were eager to see what we might find around Alpha Centauri, and I’m looking forward to what it will reveal to us next!”

“If confirmed, the potential planet seen in the Webb image of Alpha Centauri A would mark a new milestone for exoplanet imaging efforts,” Sanghi says. “Of all the directly imaged planets, this would be the closest to its star seen so far. It’s also the most similar in temperature and age to the giant planets in our solar system, and nearest to our home, Earth,” he says. “Its very existence in a system of two closely separated stars would challenge our understanding of how planets form, survive, and evolve in chaotic environments.”

If confirmed by additional observations, the team’s results could transform the future of exoplanet science.

“This would become a touchstone object for exoplanet science, with multiple opportunities for detailed characterization by Webb and other observatories,” said Beichman.

 

Press release from ESA Webb.

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Hubble makes size estimate of interstellar comet 3I/ATLAS

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At the center of the image is a comet that appears as a teardrop-shaped bluish cocoon of dust coming off the comet’s solid, icy nucleus and seen against a black background. The comet appears to be heading to the bottom left corner of the image. About a dozen short, light blue diagonal streaks are seen scattered across the image, which are from background stars that appeared to move during the exposure because the telescope was tracking the moving comet.

Hubble makes size estimate of interstellar comet 3I/ATLAS

A team of astronomers has taken the sharpest-ever picture of the unexpected interstellar comet 3I/ATLAS, using the crisp vision of the NASA/ESA Hubble Space Telescope.

This image of interstellar comet 3I/ATLAS was captured by the Hubble Space Telescope’s Wide Field Camera on 21 July 2025.The scale bar is labeled in arcseconds, which is a measure of angular distance on the sky. One arcsecond is equal to an angular measurement of 1/3600 of one degree. There are 60 arcminutes in a degree and 60 arcseconds in an arcminute (the full Moon has an angular diameter of about 30 arcminutes). The actual size of an object that covers one arcsecond on the sky depends on its distance from the telescope. The north and east compass arrows show the orientation of the image on the sky. Note that the relationship between north and east on the sky (as seen from below) is flipped relative to direction arrows on a map of the ground (as seen from above). This image shows visible wavelengths of light. Credit: NASA, ESA, D. Jewitt (UCLA); Image Processing: J. DePasquale (STScI)
This image of interstellar comet 3I/ATLAS was captured by the Hubble Space Telescope’s Wide Field Camera on 21 July 2025.
The scale bar is labeled in arcseconds, which is a measure of angular distance on the sky. One arcsecond is equal to an angular measurement of 1/3600 of one degree. There are 60 arcminutes in a degree and 60 arcseconds in an arcminute (the full Moon has an angular diameter of about 30 arcminutes). The actual size of an object that covers one arcsecond on the sky depends on its distance from the telescope.
The north and east compass arrows show the orientation of the image on the sky. Note that the relationship between north and east on the sky (as seen from below) is flipped relative to direction arrows on a map of the ground (as seen from above).
This image shows visible wavelengths of light.
Credit: NASA, ESA, D. Jewitt (UCLA); Image Processing: J. DePasquale (STScI)

Hubble’s observations are allowing astronomers to more accurately estimate the size of the comet’s solid icy nucleus. The upper limit on the diameter of the nucleus is 5.6 kilometers, though it could be as small as 320 metres across, researchers report. Though the Hubble images put tighter constraints on the nucleus size compared to previous ground-based estimates, the solid heart of the comet presently cannot be directly seen, even by Hubble. Observations from other observatories, including the NASA/ESA/CSA James Webb Space Telescope, will help refine our knowledge about the comet, including its chemical makeup.

Hubble also captured a dust plume ejected from the Sun-warmed side of the comet, and the hint of a dust tail streaming away from the nucleus. Hubble’s data yields a dust-loss rate consistent with comets that are first detected around 480 million kilometres from the Sun. This behaviour is much like the signature of previously seen Sun-bound comets originating within our Solar System.

The big difference is that this interstellar visitor originated in some other Solar System elsewhere in our Milky Way galaxy.

3I/ATLAS is traveling through our Solar System at roughly 210,000 kilometres per hour, the highest velocity ever recorded for a Solar System visitor. This breathtaking sprint is evidence that the comet has been drifting through interstellar space for many billions of years. The gravitational slingshot effect from innumerable stars and nebulae the comet passed added momentum, ratcheting up its speed. The longer 3I/ATLAS was out in space, the higher its speed grew.

This comet was discovered by the Asteroid Terrestrial-impact Last Alert System (ATLAS) on 1 July 2025 at a distance of 675 million kilometres from the Sun. 3I/ATLAS should remain visible to ground-based telescopes through September, after which it will pass too close to the Sun to observe and is expected to reappear on the other side of the Sun by early December.

The paper will be published in The Astrophysical Journal Letters. It is already available here.

At the center of the image is a comet that appears as a teardrop-shaped bluish cocoon of dust coming off the comet’s solid, icy nucleus and seen against a black background. The comet appears to be heading to the bottom left corner of the image. About a dozen short, light blue diagonal streaks are seen scattered across the image, which are from background stars that appeared to move during the exposure because the telescope was tracking the moving comet.
This is a Hubble Space telescope image of the interstellar comet 3I/ATLAS. Hubble photographed the comet on 21 July 21 2025, when the comet was 365 million kilometres from Earth. Hubble shows that the comet has a teardrop-shaped cocoon of dust coming off its solid, icy nucleus. Because Hubble was tracking the comet moving along a hyperbolic trajectory, the stationary background stars are streaked in the exposure.
Credit: NASA, ESA, D. Jewitt (UCLA); Image Processing: J. DePasquale (STScI)

Press release from ESA Hubble.

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Astronomy

NGC 6072: Webb traces details of complex planetary nebula

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colourful mostly red image of near-infrared light from a glowing cloud with a distorted, asymmetrical shape, illuminated from within by a bright central star. The asymmetrical shape resembles paint splattered on the ground. In the centre of this image, a light blue glow casts over areas of dark pockets that appear dark blue and are traced with orange material. It has a clumpy appearance. The shells become a deeper red with distance from the centre. The shells appear as lobes that push gas toward the equatorial plane, forming a disc. The background of the image is black and speckled with tiny bright stars and distant galaxies.

Webb traces details of complex planetary nebula – More than one star contributes to the irregular shape of NGC 6072

Webb’s newest look at planetary nebula NGC 6072 in the near- and mid-infrared shows what may appear as a very messy scene resembling splattered paint. However, the unusual, asymmetrical scene hints at more complicated mechanisms underway, as the star central to the scene approaches the very final stages of its life and expels shells of material, losing up to 80 percent of its mass.

Since their discovery in the late 1700s, astronomers have learned that planetary nebulae, or the expanding shell of glowing gas expelled by a low-intermediate mass star late in its life, can come in all shapes and sizes. Most planetary nebulae present as circular, elliptical, or bi-polar, but some stray from the norm, as seen in new high-resolution images of the planetary nebula NGC 6072 by the NASA/ESA/CSA James Webb Space Telescope.

colourful mostly red image of near-infrared light from a glowing cloud with a distorted, asymmetrical shape, illuminated from within by a bright central star. The asymmetrical shape resembles paint splattered on the ground. In the centre of this image, a light blue glow casts over areas of dark pockets that appear dark blue and are traced with orange material. It has a clumpy appearance. The shells become a deeper red with distance from the centre. The shells appear as lobes that push gas toward the equatorial plane, forming a disc. The background of the image is black and speckled with tiny bright stars and distant galaxies.
The NASA/ESA/CSA James Webb Space Telescope’s view of planetary nebula NGC 6072 in the near-infrared shows a complex scene of multiple outflows expanding out at different angles from a dying star at the centre of the scene. These outflows push gas toward the equatorial plane, forming a disc.
Astronomers suspect there is at least one other star interacting with the material cast off by the central dying star, creating the abnormal appearance of this planetary nebula.
In this image, the red areas represent cool molecular gas, for example, molecular hydrogen.
Credit: NASA, ESA, CSA, STScI

In Webb’s NIRCam (Near-Infrared Camera) view of the object, it’s readily apparent that this nebula is multi-polar. This means there are several different elliptical outflows jetting out either way from the centre. These outflows compress gas towards the equatorial plane and create a disc. Astronomers say this is evidence that there are likely at least two stars at the centre of this scene. Specifically, a companion star is interacting with an aging star that had already begun to shed some of its outer layers of gas and dust.

The central region of the planetary nebula glows from the hot stellar core, seen as a light blue hue in near-infrared light. The dark orange material, which is made up of gas and dust, follows pockets or open areas that appear dark blue. This clumpiness could be created when dense molecules formed while being shielded from hot radiation from the central star. There could also be a time element at play. Over thousands of years, inner fast winds could be ploughing through the halo cast off from the main star when it first started to lose mass.

colourful, mostly blue, image of mid-infrared light from a glowing cloud with a distorted, asymmetrical shape. A star at the centre of the image is a small point of pinkish-white light. The asymmetrical shape of the expanding cloud of gas and dust resembles paint splattered on the ground. The filaments of the expanding shells are wispy, and mostly white and blue. The shells appear as lobes that push gas toward the equatorial plane, forming a disc. A perfect circle of white-ish blue dust traces the outer edges of the shells. The background of the image is black and speckled with tiny bright stars and distant galaxies.
The mid-infrared view of planetary nebula NGC 6072 from the NASA/ESA/CSA James Webb Space Telescope shows expanding circular shells around the outflows from the dying central star, which astronomers suspect is that pinkish white dot at the centre of the image. The longer wavelengths captured by Webb’s MIRI (Mid-Infrared Instrument) highlight the dust being cast off by the central dying star.
In this image, the blue represents cool molecular gas seen in red in the image from Webb’s NIRCam (Near-Infrared Camera) due to colour mapping.
Credit: NASA, ESA, CSA, STScI

The longer wavelengths captured by Webb’s MIRI (Mid-Infrared Instrument) are highlighting dust, revealing the star researchers suspect could be central to this scene. It appears as a small pink-white dot in this image. Webb’s look in the mid-infrared wavelength also reveals concentric rings expanding from the central region, the most obvious circling just past the edges of the lobes.

This may be additional evidence of a secondary star at the centre of the scene hidden from our view. The secondary star, as it circles repeatedly around the original star, could have carved out rings of material in a spiral pattern as the main star was expelling mass during an earlier stage of its life.

The red areas in NIRCam and blue areas in MIRI both trace cool molecular gas (likely molecular hydrogen) while central regions trace hot ionized gas.

Planetary nebulae will remain a topic of study for astronomers using Webb who hope to learn more about the full life cycle of stars and how they impact their surrounding environments. As the star at the centre of a planetary nebula cools and fades, the nebula will gradually dissipate into the interstellar medium — contributing enriched material that helps form new stars and planetary systems, now containing those heavier elements.

Webb’s imaging of NGC 6072 opens the door to studying how the planetary nebulae with more complex shapes contribute to this process.

Webb image of NGC 6072 with compass arrows, scale bar, and colour key. It has a mostly red image of near-infrared light from a glowing cloud with a distorted, asymmetrical shape, illuminated from within by a bright central star. In the centre of this image, a light blue glow casts over areas of dark pockets that appear dark blue and are traced with orange material. It has a clumpy appearance. The shells become a deeper red with distance from the center. At the bottom right is a scale bar labeled .5 light-years. The length of the scale bar is about one fifth of the total image. At the bottom right are compass arrows indicating the orientation of the image on the sky. Below the image is a colour key showing which NIRCam filters were used to create the image and which visible-light colour is assigned to each filter.
This image of NGC 6072, captured by the James Webb Space Telescope’s NIRCam (Near-Infrared Camera), shows compass arrows, scale bar, and colour key for reference.
The north and east compass arrows show the orientation of the image on the sky. Note that the relationship between north and east on the sky (as seen from below) is flipped to the direction arrows on a map of the ground (as seen from above). The scale bar is labeled in light-years, which is the distance that light travels in one Earth-year (it takes 0.5 years for light to travel a distance equal to the length of the scale bar). One light-year is equal to about 9.46 trillion kilometers. This image shows invisible near-infrared wavelengths of light that have been translated into visible-light colours. The colour key shows which NIRCam filters were used when collecting the light. The colour of each filter name is the visible light colour used to represent the infrared light that passes through that filter.
Credit: NASA, ESA, CSA, STScI

Press release from ESA Webb.

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