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Astronomy

Hubble traces hidden history of the Andromeda Galaxy

By ScientifiCult 16 January 2025

Hubble traces hidden history of the Andromeda Galaxy

Panorama of nearest galaxy unveils hundreds of millions of stars

The largest photomosaic of the Andromeda galaxy, assembled from NASA/ESA Hubble Space Telescope observations, has been unveiled. It took more than 10 years to collect data for this colorful portrait of our neighboring galaxy and was created from more than 600 snapshots. This stunning, colorful mosaic captures the glow of 200 million stars, and is spread across roughly 2.5 billion pixels.

In the years following the launch of the NASA/ESA Hubble Space Telescope, astronomers have tallied over 1 trillion galaxies in the universe. But only one galaxy stands out as the most important nearby stellar island to our Milky Way: the magnificent Andromeda galaxy (Messier 31). It can be seen with the naked eye on a very clear autumn night as a faint cigar-shaped object roughly the apparent angular diameter of our Moon.

A century ago, Edwin Hubble first established that this so-called “spiral nebula” was actually far outside our own Milky Way galaxy — at a distance of approximately 2.5 million light-years, or roughly 25 Milky Way diameters. Prior to that, astronomers had long thought that the Milky Way encompassed the entire universe. Overnight, Hubble’s discovery turned cosmology upside down by unveiling an infinitely grander universe.

Now, a century later, the space telescope named for Hubble has accomplished the most comprehensive survey of this enticing empire of stars. The Hubble telescope is yielding new clues to the evolutionary history of Andromeda, and it looks markedly different from the Milky Way’s history.

Without Andromeda as a proxy for spiral galaxies in the universe at large, astronomers would know much less about the structure and evolution of our own Milky Way. That’s because we are embedded inside the Milky Way.

Hubble’s sharp imaging capabilities can resolve more than 200 million stars in the Andromeda galaxy, detecting only stars brighter than our Sun. They look like grains of sand across the beach. But that’s just the tip of the iceberg. Andromeda’s total population is estimated to be 1 trillion stars, with many less massive stars falling below Hubble’s sensitivity limit.

Photographing Andromeda was a herculean task because the galaxy is a much bigger target on the sky than the galaxies Hubble routinely observes, which are often billions of light-years away. The full mosaic was carried out under two Hubble observing programs. In total it required over 1,000 Hubble orbits, spanning more than a decade.

The Andromeda galaxy is shown at the top of the visual. It is a spiral galaxy that spreads across the image. It is tilted nearly edge-on to our line of sight so that it appears very oval. The borders of the galaxy are jagged because the image is a mosaic of smaller, square images against a black background. The outer edges of the galaxy are blue, while the inner two-thirds is yellowish with a bright, central core. Five callout squares highlight interesting features of the galaxy — This is the largest photomosaic ever made by the Hubble Space Telescope. The target is the vast Andromeda galaxy that is only 2.5 million light-years from Earth, making it the nearest galaxy to our own Milky Way. Andromeda is seen almost edge-on, tilted by 77 degrees relative to Earth’s view. The galaxy is so large that the mosaic is assembled from approximately 600 separate fields of view taken over 10 years of Hubble observing. The mosaic image is made up of at least 2.5 billion pixels. Hubble resolves an estimated 200 million stars that are hotter than our sun, but still a fraction of the galaxy’s total estimated stellar population.
Interesting regions include:
Clusters of bright blue stars embedded within the galaxy, background galaxies seen much farther away, and photo-bombing by a couple bright foreground stars that are actually inside our Milky Way;
NGC 206 the most conspicuous star cloud in Andromeda;
A young cluster of blue newborn stars;
The satellite galaxy M32, that may be the residual core of a galaxy that once collided with Andromeda;
Dark dust lanes across myriad stars.
Credit: NASA, ESA, B. Williams (U. of Washington)

This panorama started with the Panchromatic Hubble Andromeda Treasury (PHAT) program about a decade ago. Images were obtained at near-ultraviolet, visible, and near-infrared wavelengths using the Advanced Camera for Surveys and the Wide Field Camera aboard Hubble to photograph the northern half of Andromeda.

This program was followed up by the Panchromatic Hubble Andromeda Southern Treasury (PHAST), which added images of approximately 100 million stars in the southern half of Andromeda. This region is structurally unique and more sensitive to the galaxy’s merger history than the northern disk mapped by the PHAT survey.

The combined programs collectively cover the entire disk of Andromeda, which is seen almost edge-on — tilted by 77 degrees relative to Earth’s view. The galaxy is so large that the mosaic is assembled from approximately 600 separate fields of view. The mosaic image is made up of at least 2.5 billion pixels.

The complementary Hubble survey programs provide information about the age, heavy-element abundance and stellar masses inside Andromeda. This will allow astronomers to distinguish between competing scenarios where Andromeda merged with one or more galaxies. Hubble’s detailed measurements constrain models of Andromeda’s merger history and disk evolution.

Though the Milky Way and Andromeda formed presumably around the same time many billions of years ago, observational evidence shows that they have very different evolutionary histories, despite growing up in the same cosmological neighborhood. Andromeda seems to be more highly populated with younger stars and unusual features like coherent streams of stars, say researchers. This implies it has a more active recent star-formation and interaction history than the Milky Way.

A possible culprit is the compact satellite galaxy Messier 32, which resembles the stripped-down core of a once-spiral galaxy that may have interacted with Andromeda in the past. Computer simulations suggest that when a close encounter with another galaxy uses up all the available interstellar gas, star formation subsides.

Hubble’s new findings will support future observations by the NASA/ESA/CSA James Webb Space Telescope.

The Andromeda galaxy, a spiral galaxy, spreads across the image. It is tilted nearly edge-on to our line of sight so that it appears very oval. The borders of the galaxy are jagged because the image is a mosaic of smaller, square images against a black background. The outer edges of the galaxy are blue, while the inner two-thirds is yellowish with a bright, central core. Dark, dusty filamentary clouds wrap around the outer half of the galaxy’s disk. At 10 o’clock, a smaller dwarf elliptical galaxy forms a fuzzy, yellow blob. Hubble’s sharp vision distinguishes about 200 million stars within the image. — This the largest photomosaic ever assembled from NASA/ESA Hubble Space Telescope observations: it is a panoramic view of the neighboring Andromeda galaxy, located 2.5 million light-years away. It took over 10 years to make this vast and colorful portrait of the galaxy, requiring over 600 Hubble snapshots. The galaxy is so close to us, that in angular size it is six times the apparent diameter of the full Moon, and can be seen with the unaided eye. For Hubble’s pinpoint view, that’s a lot of celestial real estate to cover. This stunning, colorful mosaic captures the glow of 200 million stars. That’s still a fraction of Andromeda’s population. And the stars are spread across about 2.5 billion pixels. The detailed look at the resolved stars will help astronomers piece together the galaxy’s past history that includes mergers with smaller satellite galaxies.
Credit: NASA, ESA, B. Williams (University of Washington)

Press release from ESA Hubble

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Astronomy

Webb watches Wolf-Rayet 140: carbon-rich dust shells form, expand in star system

By ScientifiCult 13 January 2025

Webb watches Wolf-Rayet 140: carbon-rich dust shells form, expand in star system

Astronomers using the NASA/ESA/CSA James Webb Space Telescope have identified two stars responsible for generating carbon-rich dust a mere 5000 light-years away in our own Milky Way galaxy. As the massive stars in Wolf-Rayet 140 swing past one another on their elongated orbits, their winds collide and produce the carbon-rich dust. For a few months every eight years, the stars form a new shell of dust that expands outward — and may eventually go on to become part of stars that form elsewhere in our galaxy.

The image shows a bright white point of light surrounded by 17 regularly spaced, hazy dust shells at the bottom, right, and upper right, which look like tree rings. There is noticeably less colour in the upper left. The central point, where the two stars are located, has a roughly hexagonal shape. — Astronomers using the NASA/ESA/CSA James Webb Space Telescope have identified two stars responsible for generating carbon-rich dust a mere 5000 light-years away in our own Milky Way galaxy. As the massive stars in Wolf-Rayet 140 swing past one another on their elongated orbits, their winds collide and produce the carbon-rich dust. For a few months every eight years, the stars form a new shell of dust that expands outward — and may eventually go on to become part of stars that form elsewhere in our galaxy. Every shell is racing away from the stars at more than 2600 kilometers per second, almost 1% the speed of light. Wolf-Rayet 140 lies just over 5000 light-years away in our Milky Way galaxy. Credit: NASA, ESA, CSA, STScI, E. Lieb (University of Denver), R. Lau (NSF NOIRLab), J. Hoffman (University of Denver)

A three-part graphic showing observations of Wolf-Rayet 140, two massive stars with 17 dust shells around them. An inset appears at right, showing a portion of the two observations matched up to show that the arced dust has moved. — Compare the two mid-infrared images taken by the James Webb Space Telescope of Wolf-Rayet 140, a system of dust shells ejected by two massive stars that are in an elongated orbit. Look to the top right of the first two images. Two triangles are matched up to show how much difference 14 months makes: the dust is racing away from the central stars at almost 1% the speed of light and no longer lines up in the third image. When the winds of the massive stars, which are buried within the white central region in the first and second images, collide and that material compresses, it forms carbon-rich dust that moves away from the stars. This occurs for a few months during each eight-year orbit, which is one reason why the dust isn’t ‘sprayed’ equally around the stars to form complete shells. Wolf-Rayet 140 lies just over 5000 light-years away in our Milky Way galaxy. Credit: NASA, ESA, CSA, STScI, E. Lieb (University of Denver), R. Lau (NSF NOIRLab), J. Hoffman (University of Denver)

Astronomers have long tried to track down how elements like carbon, which is essential for life, become widely distributed across the Universe. Now, the James Webb Space Telescope has examined one ongoing source of carbon-rich dust in our own Milky Way galaxy in greater detail: Wolf-Rayet 140 [1], a system of two massive stars that follow a tight, elongated orbit.

As they swing past one another (within the central white dot in the Webb images), the stellar winds from each star slam together, the material compresses, and carbon-rich dust forms. Webb’s latest observations show 17 dust shells shining in mid-infrared light that are expanding at regular intervals into the surrounding space.

“The telescope confirmed that these dust shells are real, and its data also showed that the dust shells are moving outward at consistent velocities, revealing visible changes over incredibly short periods of time,”

said Emma Lieb, the lead author of the new paper and a doctoral student at the University of Denver in Colorado.

Every shell is racing away from the stars at more than 2600 kilometres per second, almost 1% the speed of light.

“We are used to thinking about events in space taking place slowly, over millions or billions of years,” added Jennifer Hoffman, a co-author and a professor at the University of Denver. “In this system, the observatory is showing that the dust shells are expanding from one year to the next.”

“Seeing the real-time movement of these shells between Webb’s observations that were taken only 13 months apart is truly remarkable,” said Olivia Jones, a co-author at the UK Astronomy Technology Centre, Edinburgh. “These new results are giving us a first glimpse of the potential role of such massive binaries as factories of dust in the Universe.”

Like clockwork, the stars’ winds generate dust for several months every eight years, as the pair make their closest approach during a wide, elongated orbit. Webb also shows where dust formation stops — look for the darker region at top left in both images.

The telescope’s mid-infrared images detected shells that have persisted for more than 130 years (older shells have dissipated enough that they are now too dim to detect). The researchers speculate that the stars will ultimately generate tens of thousands of dust shells over hundreds of thousands of years.

“Mid-infrared observations are absolutely crucial for this analysis, since the dust in this system is fairly cool. Near-infrared and visible-light observations would only show the shells that are closest to the star,” explained Ryan Lau, a co-author and astronomer at NSF NOIRLab in Tucson, Arizona, who led the initial research about this system. “With these incredible new details, the telescope is also allowing us to study exactly when the stars are forming dust — almost to the day.”

The distribution of the dust isn’t uniform. Though these differences aren’t obvious in Webb’s images, the team found that some of the dust has ‘piled up’, forming amorphous, delicate clouds that are as large as our entire Solar System. Many other individual dust particles float freely. Every speck is as small as one-hundredth the width of a human hair. Clumpy or not, all of the dust moves at the same speed and is carbon rich.

The future of this system

What will happen to these stars over millions or billions of years, after they have finished ‘spraying’ their surroundings with dust? The Wolf-Rayet star in this system is 10 times more massive than the Sun and nearing the end of its life. In its final ‘act’, this star will either explode as a supernova — possibly blasting away some or all of the dust shells — or collapse into a black hole, which would leave the dust shells intact.

Though no one can predict with any certainty what will happen, researchers are rooting for the black hole scenario.

“A major question in astronomy is, where does all the dust in the universe come from?” Lau said. “If carbon-rich dust like this survives, it could help us begin to answer that question.”

“We know carbon is necessary for the formation of rocky planets and solar systems like ours,” Hoffman added. “It’s exciting to get a glimpse into how binary star systems not only create carbon-rich dust, but also propel it into our galactic neighborhood.”

These results have been published in the Astrophysical Journal Letters and were presented in a press conference at the 245th meeting of the American Astronomical Society in National Harbor, Maryland.

Notes

[1] A Wolf-Rayet star is born with at least 25 times more mass than our Sun and is nearing the end of its life, when it will likely collapse directly to black hole, or explode as a supernova. Burning hotter than in its youth, a Wolf-Rayet star generates powerful winds that push huge amounts of gas into space. The Wolf-Rayet star in this particular pair may have shed more than half its original mass via this process.

Press release from ESA Webb.

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Astronomy

Massive black hole in the early universe is lying dormant in its host galaxy, GN-1001830

By ScientifiCult 18 December 2024

Massive black hole in the early universe spotted taking a ‘nap’ after overeating, and lying dormant in its host galaxy, GN-1001830

JWST buco nero dormiente GN-1001830 Illustrazione artistica che rappresenta l'aspetto potenziale del buco nero supermassiccio scoperto dal team di ricerca durante la sua fase di intensa attività super-Eddington. Crediti: Jiarong Gu — A study in *Nature* finds that black holes in the early Universe go through short periods of ultra-fast growth, followed by long periods of dormancy. Picture credits: Jiarong Gu

Scientists have spotted a massive black hole in the early universe that is ‘napping’ after stuffing itself with too much food.

Like a bear gorging itself on salmon before hibernating for the winter, or a much-needed nap after Christmas dinner, this black hole has overeaten to the point that it is lying dormant in its host galaxy, GN-1001830.

An international team of astronomers, led by the University of Cambridge, used the NASA/ESA/CSA James Webb Space Telescope to detect this black hole in the early universe, just 800 million years after the Big Bang.

The black hole is huge – 400 million times the mass of our Sun – making it one of the most massive black holes discovered by Webb at this point in the universe’s development. The black hole is so enormous that it makes up roughly 40% of the total mass of its host galaxy: in comparison, most black holes in the local universe are roughly 0.1% of their host galaxy mass.

However, despite its gigantic size, this black hole is eating, or accreting, the gas it needs to grow at a very low rate – about 100 times below its theoretical maximum limit – making it essentially dormant.

Such an over-massive black hole so early in the universe, but one that isn’t growing, challenges existing models of how black holes develop. However, the researchers say that the most likely scenario is that black holes go through short periods of ultra-fast growth, followed by long periods of dormancy. Their results are reported in the journal Nature.

When black holes are ‘napping’, they are far less luminous, making them more difficult to spot, even with highly-sensitive telescopes such as Webb. Black holes cannot be directly observed, but instead they are detected by the tell-tale glow of a swirling accretion disc, which forms near the black hole’s edges. The gas in the accretion disc becomes extremely hot and starts to glow and radiate energy in the ultraviolet range.

“Even though this black hole is dormant, its enormous size made it possible for us to detect,” said lead author Ignas Juodžbalis from Cambridge’s Kavli Institute for Cosmology. “Its dormant state allowed us to learn about the mass of the host galaxy as well. The early universe managed to produce some absolute monsters, even in relatively tiny galaxies.”

According to standard models, black holes form from the collapsed remnants of dead stars and accrete matter up to a predicted limit, known as the Eddington limit, where the pressure of radiation on matter overcomes the gravitational pull of the black hole. However, the sheer size of this black hole suggests that standard models may not adequately explain how these monsters form and grow.

“It’s possible that black holes are ‘born big’, which could explain why Webb has spotted huge black holes in the early universe,” said co-author Professor Roberto Maiolino, from the Kavli Institute and Cambridge’s Cavendish Laboratory. “But another possibility is they go through periods of hyperactivity, followed by long periods of dormancy.”

Working with colleagues from Italy, the Cambridge researchers conducted a range of computer simulations to model how this dormant black hole could have grown to such a massive size so early in the universe. They found that the most likely scenario is that black holes can exceed the Eddington limit for short periods, during which they grow very rapidly, followed by long periods of inactivity: the researchers say that black holes such as this one likely eat for five to ten million years, and sleep for about 100 million years.

“It sounds counterintuitive to explain a dormant black hole with periods of hyperactivity, but these short bursts allow it to grow quickly while spending most of its time napping,” said Maiolino.

Because the periods of dormancy are much longer than the periods of ultra-fast growth, it is in these periods that astronomers are most likely to detect black holes.

“This was the first result I had as part of my PhD, and it took me a little while to appreciate just how remarkable it was,” said Juodžbalis. “It wasn’t until I started speaking with my colleagues on the theoretical side of astronomy that I was able to see the true significance of this black hole.”

Due to their low luminosities, dormant black holes are more challenging for astronomers to detect, but the researchers say this black hole is almost certainly the tip of a much larger iceberg, if black holes in the early universe spend most of their time in a dormant state.

“It’s likely that the vast majority of black holes out there are in this dormant state – I’m surprised we found this one, but I’m excited to think that there are so many more we could find,” said Maiolino.

The observations were obtained as part of the JWST Advanced Deep Extragalactic Survey (JADES). The research was supported in part by the European Research Council and the Science and Technology Facilities Council (STFC), part of UK Research and Innovation (UKRI).

Bibliographic Information:

“A dormant, overmassive black hole in the early Universe”, by Ignas Juodžbalis, Roberto Maiolino, William M. Baker, Sandro Tacchella, Jan Scholtz, Francesco D’Eugenio, Raffaella Schneider, Alessandro Trinca, Rosa Valiante, Christa DeCoursey, Mirko Curti, Stefano Carniani, Jacopo Chevallard, Anna de Graaff, Santiago Arribas, Jake S. Bennett, Martin A. Bourne, Andrew J. Bunker, Stephane Charlot, Brian Jiang, Sophie Koudmani, Michele Perna, Brant Robertson, Debora Sijacki, Hannah Ubler, Christina C. Williams, Chris Willott, Joris Witstok, has been published on Nature (18-Dec-2024).

Press release from the University of Cambridge

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Astronomy

By observing NGC 346, Webb finds planet-forming discs lived longer in early Universe

By ScientifiCult 16 December 2024

By observing NGC 346, Webb finds planet-forming discs lived longer in early Universe: new data refutes current theories of planet formation in Universe’s early days

The NASA/ESA/CSA James Webb Space Telescope just solved a conundrum by proving a controversial finding made with the NASA/ESA Hubble Space Telescope more than 20 years ago.

This image features NGC 346, one of the most dynamic star-forming regions in nearby galaxies, as seen by the NASA/ESA/CSA James Webb Space Telescope.
NCG 346 is located in the Small Magellanic Cloud (SMC), a dwarf galaxy close to our Milky Way.
Credit: NASA, ESA, CSA, STScI, A. Pagan (STScI)

In 2003, Hubble provided evidence of a massive planet around a very old star, almost as old as the Universe. Such stars possess only small amounts of heavier elements that are the building blocks of planets. This implied that some planet formation happened when our Universe was very young, and those planets had time to form and grow big inside their primordial discs, even bigger than Jupiter. But how? This was puzzling.

A side-by-side comparison of a Hubble image of the massive star cluster NGC 346 (left) versus a Webb image of the same cluster (right). The Hubble image shows the cluster in shades of blue against a black background punctuated by white stars of various sizes. Ethereal nebulosity, looking much like draped chiffon, dominates the image. The Webb view, in shades of pink and orange against a black background, is speckled with fewer stars than in the Hubble version. These stars are white and pink. Webb pierces through the cluster’s clouds to reveal more of its structure, which looks like twisted fibers. — This side-by-side comparison shows a Hubble image of the massive star cluster NGC 346 (left) versus a Webb image of the same cluster (right). While the Hubble image shows more nebulosity, the Webb image pierces through those clouds to reveal more of the cluster’s structure. NGC 346 has a relative lack of elements heavier than helium and hydrogen, making it a good proxy for stellar environments in the early, distant universe.
Credit: NASA, ESA, CSA, STScI, O. C. Jones (UK ATC), G. De Marchi (ESTEC), M. Meixner (USRA), A. Nota (ESA)

To answer this question, researchers used Webb to study stars in a nearby galaxy that, much like the early Universe, lacks large amounts of heavy elements. They found that not only do some stars there have planet-forming discs, but that those discs are longer-lived than those seen around young stars in our Milky Way galaxy.

“With Webb, we have a really strong confirmation of what we saw with Hubble, and we must rethink how we model planet formation and early evolution in the young Universe,” said study leader Guido De Marchi of ESA’s European Space Research and Technology Centre in Noordwijk, Netherlands.

A different environment in early times

In the early Universe, stars formed from mostly hydrogen and helium, and very few heavier elements such as carbon and iron, which came later through supernova explosions.

“Current models predict that with so few heavier elements, the discs around stars have a short lifetime, so short in fact that planets cannot grow big,” said the Webb study’s co-investigator Elena Sabbi, chief scientist for Gemini Observatory at the National Science Foundation’s NOIRLab in Tucson. “But Hubble did see those planets, so what if the models were not correct and discs could live longer?”

To test this idea, scientists trained Webb on the Small Magellanic Cloud, a dwarf galaxy that is one of the Milky Way’s nearest neighbors. In particular, they examined the massive, star-forming cluster NGC 346, which also has a relative lack of heavier elements. The cluster served as a nearby proxy for studying stellar environments with similar conditions in the early, distant Universe.

The center of the image contains arcs of orange and pink that form a boat-like shape. One end of these arcs points to the top right of the image, while the other end point toward the bottom left. Another plume of orange and pink expands from the center to the top left of the image. To the right of this plume is a large cluster of white stars. There are various other white stars and a few galaxies of different sizes spread throughout the image. Ten, small, yellow circles overlaid at various points across the image indicate the positions of the ten stars surveyed in this study. — This is a NASA/ESA/CSA James Webb Space Telescope image of NGC 346, a massive star cluster in the Small Magellanic Cloud, a dwarf galaxy that is one of the Milky Way’s nearest neighbors. With its relative lack of elements heavier than helium and hydrogen, the NGC 346 cluster serves as a nearby proxy for studying stellar environments with similar conditions in the early, distant Universe. Ten, small, yellow circles overlaid on the image indicate the positions of the ten stars surveyed in this study.
Credit: NASA, ESA, CSA, STScI, O. C. Jones (UK ATC), G. De Marchi (ESTEC), M. Meixner (USRA)

Hubble observations of NGC 346 from the mid 2000s revealed many stars about 20 to 30 million years old that seemed to still have planet-forming discs around them. This went against the conventional belief that such discs would dissipate after 2 or 3 million years.

“The Hubble findings were controversial, going against not only empirical evidence in our galaxy but also against the current models,” said De Marchi. “This was intriguing, but without a way to obtain spectra of those stars, we could not really establish whether we were witnessing genuine accretion and the presence of discs, or just some artificial effects.”

Now, thanks to Webb’s sensitivity and resolution, scientists have the first-ever spectra of forming, Sun-like stars and their immediate environments in a nearby galaxy.

“We see that these stars are indeed surrounded by discs and are still in the process of gobbling material, even at the relatively old age of 20 or 30 million years,” said De Marchi. “This also implies that planets have more time to form and grow around these stars than in nearby star-forming regions in our own galaxy.”

By observing NGC 346, Webb finds planet-forming discs lived longer in early Universe: new data refutes current theories of planet formation in Universe’s early days. This image features NGC 346, one of the most dynamic star-forming regions in nearby galaxies, as seen by the NASA/ESA/CSA James Webb Space Telescope.
NCG 346 is located in the Small Magellanic Cloud (SMC), a dwarf galaxy close to our Milky Way.
Credit: NASA, ESA, CSA, STScI, A Pagan (STScI)

A New Way of Thinking

This finding refutes previous theoretical predictions that when there are very few heavier elements in the gas around the disc, the star would very quickly blow away the disc. So the disc’s life would be very short, even less than a million years. But if a disc doesn’t stay around the star long enough for the dust grains to stick together and pebbles to form and become the core of a planet, how can planets form?

The researchers explained that there could be two distinct mechanisms, or even a combination, for planet-forming discs to persist in environments scarce in heavier elements.

First, to be able to blow away the disc, the star applies radiation pressure. For this pressure to be effective, elements heavier than hydrogen and helium would have to reside in the gas. But the massive star cluster NGC 346 only has about ten percent of the heavier elements that are present in the chemical composition of our Sun. Perhaps it simply takes longer for a star in this cluster to disperse its disc.

The second possibility is that, for a Sun-like star to form when there are few heavier elements, it would have to start from a larger cloud of gas. A bigger gas cloud will produce a bigger disc. So there is more mass in the disc and therefore it would take longer to blow the disc away, even if the radiation pressure were working in the same way.

“With more matter around the stars, the accretion lasts for a longer time,” said Sabbi. “The discs take ten times longer to disappear. This has implications for how you form a planet, and the type of system architecture that you can have in these different environments. This is so exciting.”

The science team’s paper appears in the 16 December 2024 issue of The Astrophysical Journal.

planet-forming discs Graphic titled Star in NGC 346, Molecular Hydrogen in Protoplanetary Disk, NIRSpec Microshutter Array Spectroscopy showing brightness of 2.02- to 2.37-micron light of a star and its environment (plotted in yellow) and a star’s environment only (plotted in pink) on an xy graph of brightness versus wavelength in microns. Two wavelength bands, ranging from 2.05 to 2.07 and 2.16 to 2.18, are highlighted in red and labeled Hot Atomic Helium, He. A band from 2.11 to 2.13 in blue is labeled Cold Molecular Hydrogen, H 2. The spectrum of the star plus environment (yellow) has prominent peaks at 2.06 and 2.17 microns (He), and at 2.12 microns (H). The spectrum of the star’s environment only (pink) also has peaks at 2.06 and 2.17 microns (He), but not at 2.12 (H). The two spectra are offset vertically for readability. An inset shows them plotted with the same vertical alignment: the helium peaks on the star plus environment spectrum are slightly taller than those of the environment only. — This graph shows, on the bottom left in yellow, a spectrum of one of the 10 target stars in this study (as well as accompanying light from the immediate background environment). Spectral fingerprints of hot atomic helium, cold molecular hydrogen, and hot atomic hydrogen are highlighted. On the top left in magenta is a spectrum slightly offset from the star that includes only light from the background environment. This second spectrum lacks a spectral line of cold molecular hydrogen.
On the right is the comparison of the top and bottom lines. This comparison shows a large peak in the cold molecular hydrogen coming from the star but not its nebular environment. Also, atomic hydrogen shows a larger peak from the star. This indicates the presence of a protoplanetary disc immediately surrounding the star. The data was taken with the microshutter array on the James Webb Space Telescope’s NIRSpec (Near-Infrared Spectrometer) instrument.
Credit: NASA, ESA, CSA, J. Olmsted (STScI)

Press release from ESA Webb

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Astronomy

Firefly Sparkle Found: first actively forming galaxy as lightweight as young Milky Way

By ScientifiCult 11 December 2024

Firefly Sparkle Found: first actively forming galaxy as lightweight as young Milky Way

For the first time, the NASA/ESA/CSA James Webb Space Telescope has detected and ‘weighed’ a galaxy that not only existed around 600 million years after the Big Bang, but also has a mass that is similar to what our Milky Way galaxy’s mass might have been at the same stage of development. Other galaxies Webb has detected at this period in the history of the Universe are significantly more massive. Nicknamed the Firefly Sparkle, this galaxy is gleaming with star clusters — 10 in all — each of which researchers examined in great detail.

“I didn’t think it would be possible to resolve a galaxy that existed so early in the Universe into so many distinct components, let alone find that its mass is similar to our own galaxy’s when it was in the process of forming,” said Lamiya Mowla, co-lead author of the paper and an assistant professor at Wellesley College in Massachusetts. “There is so much going on inside this tiny galaxy, including so many different phases of star formation.”

Thousands of overlapping objects at various distances are spread across this field, including galaxies in a massive galaxy cluster, and distorted background galaxies behind the galaxy cluster. The background of space is black. — Thousands of glimmering galaxies are bound together by their own gravity, making up a massive cluster formally classified as MACS J1423.
The largest bright white oval is a supergiant elliptical galaxy that is the dominant member of this galaxy cluster. The galaxy cluster acts like a lens, magnifying and distorting the light from objects that lie well behind it, an effect known as gravitational lensing that has big research benefits. Astronomers can study lensed galaxies in detail, like the Firefly Sparkle galaxy.
This 2023 image is from the James Webb Space Telescope’s NIRCam (Near-InfraRed Camera). Researchers used Webb to survey the same field that the Hubble Space Telescope imaged in 2010. Thanks to its specialisation in high-resolution near-infrared imagery, Webb was able to show researchers many more galaxies in far more detail.
Credit: NASA, ESA, CSA, STScI, C. Willott (NRC-Canada), L. Mowla (Wellesley College), K. Iyer (Columbia)

Webb was able to image the galaxy in sufficient detail for two reasons. One is a benefit of the cosmos: a massive foreground galaxy cluster radically enhanced the distant galaxy’s appearance through a natural effect known as gravitational lensing. And when combined with the telescope’s specialisation in high-resolution imaging of infrared light, Webb delivered unprecedented new data about the galaxy’s contents.

“Without the benefit of this gravitational lens, we would not be able to resolve this galaxy,” said Kartheik Iyer, co-lead author and NASA Hubble Fellow at Columbia University in New York. “We knew to expect it based on current physics, but it’s surprising that we actually saw it.”

Mowla, who spotted the galaxy in Webb’s image, was drawn to its gleaming star clusters, because objects that sparkle typically indicate they are extremely clumpy and complicated. Since the galaxy looks like a ‘sparkle’ or swarm of fireflies on a warm summer night, they named it the Firefly Sparkle galaxy.

Reconstructing the galaxy’s appearance

The research team modelled what the galaxy might have looked like if its image weren’t stretched by gravitational lensing and discovered that it resembled an elongated raindrop. Suspended within it are two star clusters toward the top and eight toward the bottom.

“Our reconstruction shows that clumps of actively forming stars are surrounded by diffuse light from other unresolved stars,” said Iyer. “This galaxy is literally in the process of assembling.”

Webb’s data show the Firefly Sparkle galaxy is on the smaller side, falling into the category of a low-mass galaxy. Billions of years will pass before it builds its full heft and a distinct shape. “Most of the other galaxies Webb has shown us aren’t magnified or stretched, and we are not able to see their ‘building blocks’ separately. With Firefly Sparkle, we are witnessing a galaxy being assembled brick by brick,” Mowla said.

Stretched out and shining, ready for close analysis

Since the image of the galaxy is warped into a long arc, the researchers easily picked out 10 distinct star clusters, which are emitting the bulk of the galaxy’s light. They are represented here in shades of pink, purple, and blue. Those colours in Webb’s images and its supporting spectra confirmed that star formation didn’t happen all at once in this galaxy, but was staggered in time.

“This galaxy has a diverse population of star clusters, and it is remarkable that we can see them separately at such an early age of the Universe,” said Chris Willott of the National Research Council Canada, a co-author and the observation programme’s principal investigator. “Each clump of stars is undergoing a different phase of formation or evolution.”

The galaxy’s projected shape shows that its stars haven’t settled into a central bulge or a thin, flattened disc, another piece of evidence that the galaxy is still forming.

Horizontal split down the middle. At left, thousands of overlapping objects at various distances are spread across this galaxy cluster. A box at bottom right is enlarged on the right half. A central oval identifies the Firefly Sparkle galaxy, a line with 10 dots in various colours. — For the first time, astronomers have identified a still-forming galaxy that weighs about the same as our Milky Way if we could wind back the clock to see our galaxy as it developed. The newly identified galaxy, the Firefly Sparkle, is in the process of assembling and forming stars, and existed about 600 million years after the Big Bang.
The image of the galaxy is stretched and warped by a natural effect known as gravitational lensing, which allowed researchers to glean far more information about its contents. (In some areas of Webb’s image, the galaxy is magnified over 40 times.)
While it took shape, the galaxy gleamed with star clusters in a range of infrared colours, which are scientifically meaningful. They indicate that the stars formed at different periods, not all at once.
Since the galaxy image is stretched into a long line in Webb’s observations, researchers were able to identify 10 distinct star clusters and study them individually, along with the cocoon of diffuse light from the additional, unresolved stars surrounding them. That’s not always possible for distant galaxies that aren’t lensed. Instead, in many cases researchers can only draw conclusions that apply to an entire galaxy. “Most of the other galaxies Webb has shown us aren’t magnified or stretched and we are not able to see the ‘building blocks’ separately. With Firefly Sparkle, we are witnessing a galaxy being assembled brick by brick,” explains astronomer Lamiya Mowla.
There are two companion galaxies ‘hovering’ close by, which may ultimately affect how this galaxy forms and builds mass over billions of years. Firefly Sparkle is only about 6500 light-years away from its first companion, and 42 000 light-years from its second companion. Let’s compare these figures to objects that are closer to home: the Sun is about 26 000 light-years from the centre of our Milky Way galaxy, and the Milky Way is about 100 000 light-years across. Not only are Firefly Sparkle’s companions very close, the researchers also suspect that they are orbiting one another.
Credit: NASA, ESA, CSA, STScI, C. Willott (NRC-Canada), L. Mowla (Wellesley College), K. Iyer (Columbia)

‘Glowing’ companions

Researchers can’t predict how this disorganised galaxy will build up and take shape over billions of years, but there are two galaxies that the team confirmed are ‘hanging out’ within a tight perimeter and may influence how it builds mass over billions of years.

Firefly Sparkle is only 6500 light-years away from its first companion, and its second companion is separated by 42 000 light-years. For context, the fully formed Milky Way is about 100 000 light-years across — all three would fit inside it. Not only are its companions very close, the researchers also think that they are orbiting one another.

Each time one galaxy passes another, gas condenses and cools, allowing new stars to form in clumps, adding to the galaxies’ masses.

“It has long been predicted that galaxies in the early Universe form through successive interactions and mergers with other tinier galaxies,” said Yoshihisa Asada, a co-author and doctoral student at Kyoto University in Japan. “We might be witnessing this process in action.”

“This is just the first of many such galaxies JWST will discover, as we are only starting to use these cosmic microscopes”, added team member Maruša Bradač of the University of Ljubljana in Slovenia. “Just like microscopes let us see pollen grains from plants, the incredible resolution of Webb and the magnifying power of gravitational lensing let us see the small pieces inside galaxies. Our team is now analysing all early galaxies, and the results are all pointing in the same direction: we have yet to learn much more about how those early galaxies formed.”

The team’s research relied on data from Webb’s CAnadian NIRISS Unbiased Cluster Survey, which include near-infrared images from NIRCam (Near-InfraRed Camera) and spectra from the microshutter array aboard NIRSpec (Near-Infrared Spectrograph). The CANUCS data intentionally covered a field that NASA’s Hubble Space Telescope imaged as part of its Cluster Lensing And Supernova survey with Hubble programme.

This work was published on 12 December 2024 in the journal Nature.

A graphic labelled “James Webb Space Telescope; MACS J1423.8+2404.” A rectangular image shows thousands of galaxies of various shapes and colours on the black background of space. — Thousands of glimmering galaxies are bound together by their own gravity, making up a massive cluster formally classified as MACS J1423.
The largest bright white oval is a supergiant elliptical galaxy that is the dominant member of this galaxy cluster. The galaxy cluster acts like a lens, magnifying and distorting the light from objects that lie well behind it, an effect known as gravitational lensing that has big research benefits. Astronomers can study lensed galaxies in detail, like the Firefly Sparkle galaxy.
This 2023 image is from the James Webb Space Telescope’s NIRCam (Near-Infrared Camera). Researchers used Webb to survey the same field the Hubble Space Telescope imaged in 2010. Thanks to its specialisation in high-resolution near-infrared imagery, Webb was able to show researchers many more galaxies in far more detail.
The north and east compass arrows show the orientation of the image on the sky.
The scale bar is labelled 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.
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.
NIRCam filters from left to right: F115W and F150W are blue; F200W and F277W are green; F356W and F444W are red.
Credit: NASA, ESA, CSA, STScI, C. Willott (NRC-Canada), L. Mowla (Wellesley College), K. Iyer (Columbia)

Press release from ESA Webb

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Webb finds surprises in Spiderweb protocluster field

By ScientifiCult 4 December 2024

$JWST Webb Spiderweb protocluster Hundreds of galaxies appear in this view, which is set against the black background of space. There are many overlapping objects at various distances. They include large, blue foreground stars, some with eight diffraction spikes, and white and pink spiral and elliptical galaxies. Numerous tiny orange dots appear throughout the scene.$

Webb finds surprises in Spiderweb protocluster field

Using the NASA/ESA/CSA James Webb Space Telescope, an international team of astronomers have found new galaxies in the Spiderweb protocluster. Their characteristics shed light on the growth of galaxies in these large cosmic cities, with the finding that gravitational interactions in these dense regions are not as important as previously thought.

Hundreds of galaxies appear in this view, which is set against the black background of space. There are many overlapping objects at various distances. They include large, blue foreground stars, some with eight diffraction spikes, and white and pink spiral and elliptical galaxies. Numerous tiny orange dots appear throughout the scene. — Using the NASA/ESA/CSA James Webb Space Telescope, an international team of astronomers have found new galaxies in the Spiderweb protocluster. Their characteristics shed light on the growth of galaxies in these large cosmic cities, with the finding that gravitational interactions in these dense regions are not as important as previously thought.
With the use of Webb’s capabilities, astronomers have now sought to better understand this protocluster and to reveal new galaxies within it. Infrared radiation passes more freely through cosmic dust than visible light, which is scattered by the dust. Because Webb can see infrared light very well, scientists used it to observe regions of the Spiderweb that were previously hidden to us by cosmic dust, and to find out to what degree this dust obscures them.
This image shows the Spiderweb protocluster as seen by Webb’s NIRCam (Near-InfraRed Camera).
Credit: ESA/Webb, NASA & CSA, H. Dannerbauer

Astronomers explore galaxy populations and uncover their physical characteristics across large-scale structures to better understand the build-up of galaxies and how their environments shape their assembly. The Spiderweb protocluster is a well-studied object in the early Universe. Its light has travelled over 10 billion years to reach us, and it shows us a galaxy cluster in formation, composed of more than a hundred known galaxies.

With the use of Webb’s capabilities, astronomers have now sought to better understand this protocluster and to reveal new galaxies inside it. Infrared light passes more freely through cosmic dust than visible light, which is scattered by the dust. Because Webb can see infrared light very well, scientists used it to observe regions of the Spiderweb that were previously hidden to us by cosmic dust, and to find out to what degree this dust obscures them.

“We are observing the build-up of one the largest structures in the Universe, a city of galaxies in construction,” explained Jose M. Pérez-Martínez of the Institute of Astrophysics of the Canary Islands (Instituto de Astrofísica de Canarias) and the University of La Laguna (Universidad de La Laguna in Spain). “We know that most galaxies in local galaxy clusters (the biggest metropolises of the Universe) are old and not very active, whereas in this work we are looking at these objects during their adolescence. As this city in construction grows, their physical properties will also be affected. Now, Webb is giving us new insights into the build-up of such structures for the first time.”

This annotated image shows hundreds of galaxies appearing in this view, which is set against the black background of space. There are many overlapping objects at various distances. Dozens of galaxies are individually identified with white circles, and a large white circle in the centre of the image highlights the collection of gravitationally-bound galaxies in the field. The bottom of the image shows a close-up of seven of these central galaxies. The objects visible in the image include large, blue foreground stars, some with eight diffraction spikes, and white and pink spiral and elliptical galaxies, as well as numerous tiny orange dots that appear throughout the scene. — Using the NASA/ESA/CSA James Webb Space Telescope, an international team of astronomers have found new galaxies in the Spiderweb protocluster. Their characteristics shed light on the growth of galaxies in these large cosmic cities, with the finding that gravitational interactions in these dense regions are not as important as previously thought.
With the use of Webb’s capabilities, astronomers have now sought to better understand this protocluster and to reveal new galaxies within it. Infrared radiation passes more freely through cosmic dust than visible light, which is scattered by the dust. Because Webb can see infrared light very well, scientists used it to observe regions of the Spiderweb that were previously hidden to us by cosmic dust, and to find out to what degree this dust obscures them.
This annotated image shows the galaxy distribution in the Spiderweb protocluster as seen by Webb’s NIRCam (Near-InfraRed Camera). The galaxies are annotated by white circles, and the collection of gravitationally-bound galaxies is identified in the centre of the image. A selection of these galaxies are featured as individual close-ups at the bottom of the image.
Credit: ESA/Webb, NASA & CSA, H. Dannerbauer

Webb enabled the team to study the hydrogen gas using a powerful diagnostic tracer that cannot be studied from ground-based observations. That allowed the team to reveal new, strongly obscured galaxies belonging to the cluster and to study how much they were obscured. This was accomplished using only about 3.5 hours of Webb’s observing time.

“As expected, we found new galaxy cluster members, but we were surprised to find more than expected,” explained Rhythm Shimakawa of Waseda University in Japan. “We found that previously-known galaxy members (similar to the typical star-forming galaxies like our Milky Way galaxy) are not as obscured or dust-filled as previously expected, which also came as a surprise.”

“This can be explained by the fact that the growth of these typical galaxies is not triggered primarily by galaxy interactions or mergers that induce star-formation,” added Helmut Dannerbauer of the Institute of Astrophysics of the Canary Islands (Instituto de Astrofísica de Canarias in Spain). “We now figure this can instead be explained by star formation that is fueled through gas accumulating at different locations all across the object’s large-scale structure.”

The new results used Webb’s NIRCam observations (Cycle 1 programme #1572, PIs: H. Dannerbauer and Y. Koyama) and are featured in two papers that have been published today in the Astrophysical Journal. The team is planning to study the (new) galaxy cluster members in more detail and confirm their existence with spectroscopic observations using Webb.

Press release from ESA Webb.

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The Sombrero Galaxy, or Messier 104, dazzles in new mid-infrared image from Webb

By ScientifiCult 25 November 2024

The Sombrero Galaxy, also known as Messier 104 (M104), dazzles in new mid-infrared image from Webb

A new mid-infrared image from the NASA/ESA/CSA James Webb Space Telescope features the Sombrero galaxy, also known as Messier 104 (M104). The signature, glowing core seen in visible-light images does not shine, and instead a smooth inner disk is revealed. The sharp resolution of Webb’s MIRI (Mid-Infrared Instrument) also brings into focus details of the galaxy’s outer ring, providing insights into how the dust, an essential building block for astronomical objects in the Universe, is distributed. The galaxy’s outer ring shows intricate clumps in the infrared for the first time.

Image of a galaxy on the black background of space. The galaxy is a very oblong, blue disk that extends from left to right at an angle (from about 10 o’clock to 5 o’clock). The galaxy has a small bright core at the centre. There is an inner disk that is clearer, with speckles of stars scattered throughout. The outer disk of the galaxy is whiteish-blue, and clumpy, like clouds in the sky. There are different coloured dots, distant galaxies, speckled among the black background of space surrounding the galaxy. — The NASA/ESA/CSA James Webb Space Telescope recently imaged the Sombrero galaxy with its MIRI (Mid-Infrared Instrument), resolving the clumpy nature of the dust along the galaxy’s outer ring.
The mid-infrared light highlights the gas and dust that are part of star formation taking place among the Sombrero galaxy’s outer disk. The rings of the Sombrero galaxy produce less than one solar mass of stars per year, in comparison to the Milky Way’s roughly two solar masses a year. It’s not a particular hotbed of star formation.
The Sombrero galaxy is around 30 million light-years from Earth in the constellation Virgo.
Credit: NASA, ESA, CSA, STScI

Researchers say the clumpy nature of the dust, where MIRI detects carbon-containing molecules called polycyclic aromatic hydrocarbons, can indicate the presence of young star-forming regions. However, unlike some galaxies studied with Webb, including Messier 82, where 10 times as many stars are born as in the Milky Way galaxy, the Sombrero galaxy is not a particular hotbed of star formation. The rings of the Sombrero galaxy produce less than one solar mass of stars per year, in comparison to the Milky Way’s roughly two solar masses a year.

The supermassive black hole at the centre of the Sombrero galaxy, also known as an active galactic nucleus (AGN), is rather docile, even at a hefty 9-billion-solar masses. It’s classified as a low luminosity AGN, slowly snacking on infalling material from the galaxy, while sending off a bright, relatively small, jet.

Also within the Sombrero galaxy dwell some 2000 globular clusters, a collection of hundreds of thousands of old stars held together by gravity. This type of system serves as a pseudo laboratory for astronomers to study stars – thousands of stars within one system with the same age, but varying masses and other properties is an intriguing opportunity for comparison studies.

In the MIRI image, galaxies of varying shapes and colours litter the background of space. The different colours of these background galaxies can tell astronomers about their properties, including how far away they are.

The Sombrero galaxy is around 30 million light-years from Earth in the constellation Virgo.

Stunning images like this, and an array of discoveries in the study of exoplanets, galaxies through time, star formation, and our own Solar System, are still just the beginning. Recently, scientists from all over the world converged—virtually—to apply for observation time with Webb during its fourth year of science operations, which begins in July 2025.

A two panel image. The top image is Webb’s view of the Sombrero galaxy, the bottom image is Hubble’s view. In the Webb view, the galaxy is a very oblong, blue disk that extends from left to right at an angle (from about 10 o’clock to 5 o’clock). The galaxy has a small bright core at the centre. There is a clear inner disk that has speckles of stars scattered throughout. The outer disk of the galaxy is whiteish-blue, and clumpy, like clouds in the sky. In the Hubble view, the galaxy is an oblong, pale white disk with a glowing core over the inner disk. The outer disk is darker and clumpy. — This image compares the view of the famous Sombrero Galaxy in mid-infrared light (top) and visible light (bottom). The James Webb Space Telescope’s MIRI (Mid-Infrared Instrument) reveals the smooth inner disk of the galaxy, while the Hubble Space Telescope’s visible light image shows the large and extended glow of the central bulge of stars.
Both the Webb and Hubble images resolve the clumpy nature of the dust that makes up the Sombrero galaxy’s outer ring.
Credit: NASA, ESA, CSA, STScI, Hubble Heritage Team (STScI/AURA)

General Observer time with Webb is more competitive than ever. A record-breaking 2377 proposals were submitted by the 15 October 2024 deadline, requesting about 78,000 hours of observation time. This is an oversubscription rate, the ratio defining the observation hours requested versus the actual time available in one year of Webb’s operations, of around 9 to 1.

The proposals cover a wide array of science topics, with distant galaxies being among the most requested observation time, followed by exoplanet atmospheres, stars and stellar population, then exoplanet systems.

Press release from ESA Webb

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Webb and Hubble examine spooky spiral galaxies: IC 2163 and NGC 2207

By ScientifiCult 31 October 2024

Webb and Hubble examine spooky spiral galaxies: IC 2163 and NGC 2207

Stare deeply at these galaxies. They appear as if blood is pumping through the top of a flesh-free face. The long, ghastly ‘stare’ of their searing eye-like cores shines out into the supreme cosmic darkness.

Two spiral galaxies take up almost the entire view and appear to be overlapping. The galaxy at left, IC 2163, is smaller and more compact than the galaxy at right, NGC 2207. The black background of space is dotted with foreground stars and extremely distant galaxies. — The gruesome palette of these galaxies is owed to a mix of mid-infrared light from the NASA/ESA/CSA James Webb Space Telescope, and visible and ultraviolet light from the NASA/ESA Hubble Space Telescope. The pair grazed one another millions of years ago. The smaller spiral on the left, catalogued as IC 2163, passed behind NGC 2207, the larger spiral galaxy at right.
Both have increased star formation rates. Combined, they are estimated to form the equivalent of two dozen new stars that are the size of the Sun annually. Our Milky Way galaxy forms the equivalent of two or three new Sun-like stars per year.
Both galaxies have hosted seven known supernovae, each of which may have cleared space in their arms, rearranging gas and dust that later cooled, and allowed many new stars to form. (Find these areas by looking for the bluest regions).
Credit: NASA, ESA, CSA, STScI

These galaxies have only grazed one another so far, with the smaller spiral on the left, catalogued as IC 2163, ever so slowly ‘creeping’ behind NGC 2207, the spiral galaxy on the right, millions of years ago.

The pair’s macabre colours represent a combination of mid-infrared light from the NASA/ESA/CSA James Webb Space Telescope and visible and ultraviolet light from the NASA/ESA Hubble Space Telescope.

Look for potential evidence of their ‘light scrape’ in the shock fronts, where material from the galaxies may have slammed together. These lines represented in brighter red, including the ‘eyelids’, may cause the appearance of the galaxies’ bulging, vein-like arms.

The galaxies’ first pass may have also distorted their delicately curved arms, pulling out tidal extensions in several places. The diffuse, tiny spiral arms between IC 2163’s core and its far left arm may be an example of this activity. Even more tendrils look like they’re hanging between the galaxies’ cores. Another extension ‘drifts’ off the top of the larger galaxy, forming a thin, semi-transparent arm that practically runs off screen.

Both galaxies have high star formation rates, like innumerable individual hearts fluttering all across their arms. Each year, the galaxies produce the equivalent of two dozen new stars that are the size of the Sun. Our Milky Way galaxy only forms the equivalent of two or three new Sun-like stars per year. Both galaxies have also hosted seven known supernovae in recent decades, a high number compared to an average of one every 50 years in the Milky Way. Each supernova may have cleared space in the galaxies’ arms, rearranging gas and dust that later cooled, and allowed many new stars to form.

To spot the star-forming ‘action sequences,’ look for the bright blue areas captured by Hubble in ultraviolet light, and the pink and white regions detailed mainly by Webb’s mid-infrared data. Larger areas of stars are known as super star clusters. Look for examples of these in the top-most spiral arm that wraps above the larger galaxy and points left. Other bright regions in the galaxies are mini starbursts — locations where many stars form in quick succession. Additionally, the top and bottom ‘eyelid’ of IC 2163, the smaller galaxy on the left, is filled with newer star formation and burns brightly.

A graphic labelled “Hubble and Webb Space Telescopes; Spiral Galaxies IC 2163 and NGC 2207.” At the centre are two overlapping spiral galaxies set against the black background of space. — This image of galaxies IC 2163 and NGC 2207, captured by the Hubble and James Webb space telescopes. Hubble’s data are from its Wide Field Planetary Camera 2 (WFPC2). Webb’s data are from its Mid-InfraRed Instrument (MIRI).
The image shows a scale bar, compass arrows, and colour key for reference.
The scale bar is labelled in light-years along the top, which is the distance that light travels in one Earth-year. (It takes three 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 kilometres.
The scale bar is also labelled in arcminutes, 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 invisible ultraviolet, visible, and mid-infrared wavelengths of light that have been translated into visible-light colours. The colour key shows which WFPC2 and MIRI 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

What’s next for these spirals? Over many millions of years, the galaxies may swing by one another repeatedly. It’s possible that their cores and arms will meld, leaving behind completely reshaped arms, and an even brighter, cyclops-like ‘eye’ at the core. Star formation will also slow down once their stores of gas and dust deplete, and the scene will calm.

Two spiral galaxies take up almost the entire view and appear to be overlapping. They are angled from top left to bottom right. The galaxy at left, IC 2163, is smaller and more compact than the galaxy at right, NGC 2207. The background of space is black, dotted with tiny foreground stars and extremely distant galaxies. — The James Webb Space Telescope’s mid-infrared image of galaxies IC 2163 and NGC 2207 recalls the iciness of long-dead bones mixed with eerie vapours. Two large luminous ‘eyes’ lie at the galaxies’ cores, and gauzy spiral arms reach out into the vast distances of space.
Webb’s mid-infrared image excels at showing where the cold dust glows throughout these galaxies — and helps pinpoint where stars and star clusters are buried within the dust. Find these regions by looking for the pink dots along the spiral arms. Many of these areas are home to actively forming stars that are still encased in the gas and dust that feeds their growth. Other pink dots may be objects that lie well behind these galaxies, including extremely distant active supermassive black holes known as quasars.
The largest, brightest pink region that glimmers with eight prominent diffraction spikes at the bottom right is a mini starburst — a location where many stars are forming in quick succession. Find the lace-like holes in the spiral arms. These areas are brimming with star formation.
Finally, scan the black background of space, where objects shine brightly in a rainbow of colours. Blue circles with tiny diffraction spikes are foreground stars. Objects without spikes are very distant galaxies.
Credit: NASA, ESA, CSA, STScI

Want to ‘pull apart’ these images? Examine the galaxies’ skeleton-like appearance in Webb’s mid-infrared image, and compare the Hubble and Webb images side by side.

Two views of the same object are shown side by side, split evenly. The Hubble observation is at left, and the Webb observation is at right. Both show an angled pair of spiral galaxies, IC 2163 at top left, and NGC 2207, at bottom right. — These are two views of the same scene, each showing two overlapping spiral galaxies, IC 2163 at left and NGC 2207 at right. The NASA/ESA Hubble Space Telescope’s ultraviolet- and visible-light observation is at left, and the NASA/ESA/CSA James Webb Space Telescope’s mid-infrared light observation is at right.
In Hubble’s image, the star-filled spiral arms glow brightly in blue, and the galaxies’ cores in orange. Both galaxies are covered in dark brown dust lanes, which obscure the view of IC 2163’s core at left.
In Webb’s image, cold dust takes centre stage, casting the galaxies’ arms in white. Areas where stars are still deeply embedded in the dust appear pink. Other pink dots may be objects that lie well behind these galaxies, including active supermassive black holes known as quasars.
Turn your eye toward the bottom right of the Webb image. The largest, brightest pink region that glimmers with eight prominent diffraction spikes is a mini starburst — a location where many stars are forming in quick succession. The same region in the Hubble image appears as a bright blue cluster of stars.
The lace-like holes in the white spiral arms of Webb’s images are often where supernovae exploded long ago. In the same regions, Hubble shows these areas are now populated with newer stars.
The black areas to the upper right and lower left of the Hubble image do not contain any data.
Credit: NASA, ESA, CSA, STScI

Press release from ESA Webb.

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Webb finds candidates for first young brown dwarfs outside the Milky Way, in the star cluster NGC 602

By ScientifiCult 23 October 2024

Webb finds candidates for first young brown dwarfs outside the Milky Way, in the star cluster NGC 602

An international team of astronomers has used the NASA/ESA/CSA James Webb Space Telescope to detect the first rich population of brown dwarf candidates outside the Milky Way in the star cluster NGC 602.

Near the outskirts of the Small Magellanic Cloud, a satellite galaxy roughly 200 000 light-years from Earth, lies the young star cluster NGC 602. The local environment of this cluster is a close analogue of what existed in the early Universe, with very low abundances of elements heavier than hydrogen and helium. The existence of dark clouds of dense dust and the fact that the cluster is rich in ionised gas also suggest the presence of ongoing star formation processes. Together with its associated HII [1] region N90, which contains clouds of ionised atomic hydrogen, this cluster provides a valuable opportunity to examine star formation scenarios under dramatically different conditions from those in the solar neighbourhood.

An international team of astronomers, including Peter Zeidler, Elena Sabbi, Elena Manjavacas and Antonella Nota, used Webb to observe NGC 602 and they detected candidates for the first young brown dwarfs outside our Milky Way.

“Only with the incredible sensitivity and spatial resolution in the correct wavelength regime is it possible to detect these objects at such great distances,” shared lead author Peter Zeidler of AURA/STScI for the European Space Agency. “This has never been possible before and also will remain impossible from the ground for the foreseeable future.”

Brown dwarfs are the more massive cousins of giant gas planets (typically ranging from roughly 13 to 75 Jupiter masses, and sometimes lower). They are free-floating, meaning that they are not gravitationally bound to a star as exoplanets are. However, some of them share characteristics with exoplanets, like their atmospheric composition and storm patterns.

“Until now, we’ve known of about 3000 brown dwarfs, but they all live inside our own galaxy,” added team member Elena Manjavacas of AURA/STScI for the European Space Agency.

“This discovery highlights the power of using both Hubble and Webb to study young stellar clusters,” explained team member Antonella Nota, executive director of the International Space Science Institute in Switzerland and the previous Webb Project Scientist for ESA. “Hubble showed that NGC602 harbors very young low mass stars, but only with Webb we can finally see the extent and the significance of the substellar mass formation in this cluster. Hubble and Webb are an amazingly powerful telescope duo!”

“Our results fit very well with the theory that the mass distribution of bodies below the hydrogen burning limit is simply a continuation of the stellar distribution,” shared Zeidler. “It seems they form in the same way, they just don’t accrete enough mass to become a fully fledged star.”

The team’s data include a new image from Webb’s Near-InfraRed Camera (NIRCam) of NGC 602, which highlights the cluster stars, the young stellar objects, and the surrounding gas and dust ridges, as well as the gas and dust itself, while also showing the significant contamination by background galaxies and other stars in the Small Magellanic Cloud. These observations were made in April 2023.

“By studying the young metal-poor brown dwarfs newly discovered in NGC602, we are getting closer to unlocking the secrets of how stars and planets formed in the harsh conditions of the early Universe,“ added team member Elena Sabbi of NSF’s NOIRLab, the University of Arizona, and the Space Telescope Science Institute.

“These are the first substellar objects outside the Milky Way” added Manjavacas. “We need to be ready for new ground-breaking discoveries in these new objects!”

These observations were made as part of the JWST GO programme #2662 (PI: P. Zeidler). The results have been published in The Astrophysical Journal.

A star cluster is shown inside a large nebula of many-coloured gas and dust. The material forms dark ridges and peaks of gas and dust surrounding the cluster, lit on the inner side, while layers of diffuse, translucent clouds blanket over them. Around and within the gas, a huge number of distant galaxies can be seen, some quite large, as well as a few stars nearer to us which are very large and bright. — Near the outskirts of the Small Magellanic Cloud, a satellite galaxy roughly 200 000 light-years from Earth, lies the young star cluster NGC 602, which is featured in this new image from the NASA/ESA/CSA James Webb Space Telescope. This image includes data from Webb’s NIRCam (Near-InfraRed Camera) and MIRI (Mid-InfraRed Instrument).
The local environment of this cluster is a close analogue of what existed in the early Universe, with very low abundances of elements heavier than hydrogen and helium. The existence of dark clouds of dense dust and the fact that the cluster is rich in ionised gas also suggest the presence of ongoing star formation processes. This cluster provides a valuable opportunity to examine star formation scenarios under dramatically different conditions from those in the solar neighbourhood.
An international team of astronomers, including Peter Zeidler, Elena Sabbi, and Antonella Nota, used Webb to observe NGC 602 and detected candidates for the first young brown dwarfs outside our Milky Way.
Credit: ESA/Webb, NASA & CSA, P. Zeidler, E. Sabbi, A. Nota, M. Zamani (ESA/Webb)

Notes

[1] Some of the most beautiful extended objects that we can see are known as HII regions, also called diffuse or emission nebulae. They contain mostly ionised hydrogen and are found throughout the interstellar medium in the Milky Way and in other galaxies.

Press release from ESA Webb.

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Galaxy GS-NDG-9422 (9422): Webb finds potential missing link to first stars

By ScientifiCult 25 September 2024

Galaxy GS-NDG-9422 (9422): Webb finds potential missing link to first stars

Looking deep into the early universe with the NASA/ESA/CSA James Webb Space Telescope, astronomers have found something unprecedented: a galaxy with an odd light signature, which they attribute to its gas outshining its stars.

A black background sprinkled with small, colourful galaxies in orange, blue, and white. On the left, a third of the way down from the top of the image, a very faint dot of a galaxy is outlined with a white square and pulled out in a graphic to be shown magnified. In the pullout square to the right, the galaxy is a hazy white dot edged in orange, with faint blue projections opposite each other at the 11 o’clock and 5 o’clock positions. — The galaxy GS-NDG-9422 may easily have gone unnoticed. However, what appears as a faint blur in this James Webb Space Telescope image may actually be a groundbreaking discovery that points astronomers on a new path of understanding galaxy evolution in the early universe.
Detailed information on the galaxy’s chemical makeup, captured by Webb’s NIRSpec (Near-Infrared Spectrograph) instrument, indicates that the light we see in this image is coming from the galaxy’s hot gas, rather than its stars. That is the best explanation astronomers have discovered so far to explain the unexpected features in the light spectrum. They think that the galaxy’s stars are so extremely hot and massive that they are heating up the nebular gas in the galaxy to more than 80,000 degrees Celsius, allowing it to shine even brighter in near-infrared light than the stars themselves.
The authors of a new study on Webb’s observations of the galaxy think GS-NDG-9422 may represent a never-before-seen phase of galaxy evolution in the early universe, within the first billion years after the big bang. Their task now is to see if they can find more galaxies displaying the same features.
Credit: NASA, ESA, CSA, STScI, A. Cameron (University of Oxford)

Found approximately one billion years after the big bang, galaxy GS-NDG-9422 (9422) may be a missing-link phase of galactic evolution between the universe’s first stars and familiar, well-established galaxies.

“My first thought in looking at the galaxy’s spectrum was, ‘that’s weird,’ which is exactly what the Webb telescope was designed to reveal: totally new phenomena in the early universe that will help us understand how the cosmic story began,” said lead researcher Alex Cameron of the University of Oxford in the United Kingdom.

Cameron reached out to colleague Harley Katz, a theorist, to discuss the strange data. Working together, their team found that computer models of cosmic gas clouds heated by very hot, massive stars, to an extent that the gas shone brighter than the stars, was nearly a perfect match to Webb’s observations.

“It looks like these stars must be much hotter and more massive than what we see in the local universe, which makes sense because the early universe was a very different environment,” said Katz, of Oxford and the University of Chicago, U.S.A.

In the local universe, typical hot, massive stars have a temperature ranging between 40,000 to 50,000 degrees Celsius. According to the team, galaxy 9422 has stars hotter than 80,000 degrees Celsius.

The research team suspects that the galaxy is in the midst of a brief phase of intense star formation inside a cloud of dense gas that is producing a large number of massive, hot stars. The gas cloud is being hit with so many photons of light from the stars that it is shining extremely brightly.

In addition to its novelty, nebular gas outshining stars is intriguing because it is something predicted in the environments of the universe’s first generation of stars, which astronomers classify as Population III stars.

“We know that this galaxy does not have Population III stars, because the Webb data shows too much chemical complexity. However, its stars are different from what we are familiar with – the exotic stars in this galaxy could be a guide for understanding how galaxies transitioned from primordial stars to the types of galaxies we already know,” said Katz.

At this point, galaxy 9422 is one example of this phase of galaxy development, so there are still many questions to be answered. Are these conditions common in galaxies at this time period, or a rare occurrence? What more can they tell us about even earlier phases of galaxy evolution? Cameron, Katz, and their research colleagues are actively identifying more galaxies to add to this population to better understand what was happening in the universe within the first billion years after the big bang.

“It’s a very exciting time, to be able to use the Webb telescope to explore this time in the universe that was once inaccessible,” Cameron said. “We are just at the beginning of new discoveries and understanding.”

The research paper is published in the Monthly Notices of the Royal Astronomical Society.

Press release from ESA Webb.

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