Category: James Webb Space Telescope

Using the James Webb Space Telescope (JWST), astronomers have discovered the secrets of early galaxies that pumped the infant cosmos full of dust, which would become vital for the birth of new stars and the growth of galaxies.

However, while the JWST is powerful enough to see many of these early galaxies, it is still limited when it comes to delving into them in great detail. So, the team at the heart of this research worked around this by studying a much closer and more modern galaxy with many characteristics that resemble the universe's first galaxies.

In lieu of being able to study the processes that occurred in the early universe that allowed galaxies to be seeded with "metals, (the term astronomers use to describe elements heavier than hydrogen and helium), the researchers turned their attention to a dwarf galaxy just 4.6 million light-years away.

"Directly studying the galaxies that populated the early universe is still very difficult, which is why observing a nearby galaxy like Sextans A, which presents similar chemical conditions, offers us a precious opportunity to understand how the first generations of stars evolved and what role they played in transforming the interstellar medium," team leader Claudio Gavetti of the National Institute for Astrophysics (INAF) said in a statement.

How does Sextans A impersonate ancient galaxies?

The early universe was a pretty dull place in terms of chemistry. That is because it was dominated by the lightest element, hydrogen, with some helium and a tiny smattering of heavy elements, or metals. That means that the first generation of stars, so-called POP III stars, were correspondingly metal-poor.

During their lives, however, POP III stars fused hydrogen and helium in their cores to forge heavier elements. When these original stars reached the ends of their lives, they exploded in supernova explosions that dispersed these metals into the interstellar medium, the vast clouds of dust and gas between stars.

Eventually, dense and cool patches in these vast clouds collapsed under their own gravity, birthing the next generation of stars, POP II stars, which, thanks to the supernova deaths of their predecessors, were richer in metals.

Our own star, the sun, is classed as a POP I star, meaning it is even richer in metals than these second-generation stars. However, not all modern galaxies are so metal-rich; this is especially true for dwarf galaxies like Sextans A, even though it lies at the outer edge of our cosmic backyard, known as the "local group."

Sextans A is so metal-poor that it is estimated to contain only between 1% and 7% of the heavy elements found in the sun. That makes it a great proxy for the study of metal-poor early galaxies.

Using the JWST's NIRCam (Near-InfraRed Camera) and MIRI (Mid-Infrared Instrument) instruments, Gavetti and colleagues obtained high-resolution observations of Sextans A that allowed them to map the dwarf galaxy's entire population of stars during an evolutionary phase known as the "asymptotic red giant branch."

This phase occurs when stars larger than the sun exhaust helium in their cores, creating an inert carbon heart, but nuclear fusion continues in outer alternating helium- and hydrogen-burning layers. These stars "puff out" as a result of this and can undergo thousandfold increases in brightness.

The team's findings revealed that around 90% of the asymptotic red giant branch stars they studied were not surrounded by envelopes of dust. However, around 20 or so of these stars were embedded in thick dust shells. They also found that these "dust factories" formed between 2 billion and 3 billion years ago from stars with an initial mass about 1.5 times the mass of the sun.

This research is a leap forward in understanding which stars in the early universe were most likely to create the metal dust that would have enriched the next generations of stars. That means it helps paint a complete picture of how the universe as we see it today took shape.

The scientists behind this study say that this type of research would have been impossible before the launch of Webb.

"The JWST allows us to observe in unprecedented detail environments that until a few years ago were beyond our reach," team member Flavia Dell'Agli of the INAF. "The value of these data lies not only in the images, but in the ability to compare them with theoretical models and verify how correctly they describe the evolution of stars."

The team's research was published on Monday (July 20) in The Astrophysical Journal.

Separated by billions of miles and shaped by very different environments, Saturn's smoggy moon Titan and the dwarf planet Pluto have, on paper, little in common.

Titan is a geologically active world cloaked in an atmosphere denser than Earth's, its landscape shaped by seas of liquid methane and vast dunes built from organic particles that rain out of its skies. Pluto, by contrast, is a frigid outpost with a tenuous atmosphere hovering above an icy, frozen surface.

Yet, observations from the James Webb Space Telescope (JWST) have revealed these two disparate worlds share an identical, unexplained infrared signature on their surfaces — a sign that similar chemistry may be unfolding on both worlds despite their stark differences, scientists say.

Detailed in a new study, the feature appears at precisely the same infrared wavelength on both Titan and Pluto, indicating that it absorbs light identically on both worlds. The signal points to the presence of an unknown compound, or a family of related compounds, that scientists have yet to identify.

"It's rather mysterious," Bruno Bézard, a planetary scientist at the Paris Observatory who led the discovery, told Space.com. "We cannot say what it is."

Chasing the signal

Bézard first spotted the unexplained feature while analyzing Titan observations from November 2022, when JWST gathered infrared light leaking through the haze in very specific, narrow wavelength bands, allowing scientists to peer directly through the otherwise opaque atmosphere.

To make sense of this light, researchers rely on spectroscopy, a technique used to identify compounds by the specific wavelengths of light they absorb. Because every molecule leaves behind a unique spectral fingerprint that telescopes can detect, astronomers can routinely identify substances across the solar system and beyond, ranging from simple water ice to complex molecules.

But the newly detected feature neither matches any of the standard library spectra cataloged so far, nor does it appear to be a fluke of the hardware, the study notes. The exact same absorption feature was detected by two different JWST instruments — the Near-Infrared Spectrograph (NIRSpec) and the Mid-Infrared Instrument (MIRI) — ruling out the possibility of an instrumental artifact.

After failing to find a match with the cataloged spectral fingerprints of the simplest and most common planetary ices, Bézard wondered whether another world with similar atmospheric chemistry might hold a clue. He turned to his colleague Emmanuel Lellouch of the Paris Observatory, who had led a JWST program that had observed Pluto in May 2023.

"I asked him, 'Do you also have a signature [on Pluto] at this exact wavelength?'" Bézard recalled in the interview with Space.com. "So we looked, and we found that it is present there."

The ground truth

There is no evidence that the mystery molecule is a biosignature, Bézard said. Instead, it likely reflects the kind of prebiotic chemistry that has been operating in Titan's oxygen-free environment for more than 4 billion years.

One compelling possibility is that it belongs to a family of hydrocarbons known as allenes, which the study notes are essentially the only organic compounds known to exhibit strong absorption bands within the same 5-micron infrared range as the mystery signal.

But the allene family contains many complex variations for which complete spectra do not yet exist, Bézard said. Alternatively, the signature could belong to a known molecule whose spectral fingerprint has shifted, potentially because it is mixed with other planetary ices that have not yet been fully cataloged.

"We only have spectra for the simplest of them," Bézard said. "But it is possible that within this family you could find one or several compounds which are present together and make such an absorption feature."

Whatever the compound ultimately proves to be, he and his team believe it forms in the atmosphere through photochemical reactions before eventually "snowing" down onto the surface.

Despite their stark differences, both Titan and Pluto possess atmospheres dominated by nitrogen and methane. Scientists know from spacecraft observations and lab simulations that in the upper reaches of the planets' atmospheres, ultraviolet sunlight breaks these molecules apart, triggering a cascade of highly reactive chemical fragments. These fragments then reassemble into complex organic compounds, some of which condense and snow back down onto the surface below, which is where the JWST detected them.

A couple of different lines of evidence support this atmosphere-to-surface pipeline. First, the team analyzed how the signal behaved across Titan's disk. As the JWST scanned Titan from the center of its circular face toward its outer edge, or limb, the mysterious signal steadily weakened, the study notes.

"This is what you expect if it comes from the surface," said Bézard.

Because of the three-dimensional geometry of looking at a sphere, a signal coming from a flat surface will appear strongest at the center and grow fainter near the edge, where the angle of view through the atmosphere becomes longer and more obscured. This specific dimming trait was not shared by atmospheric carbon monoxide the team checked, which remained essentially unchanged from center to limb, Bézard said, which helped the team infer that this mystery molecule likely resides on the ground.

Pluto offered an independent line of evidence to back up this surface theory. Its near-vacuum atmosphere is physically too thin and sparse to generate an absorption feature of the observed depth, Bézard said, leaving the dwarf planet's solid surface as the only plausible source for the deep signature.

To further test their atmospheric-origin hypothesis, the team studied JWST observations of Jupiter's moon Ganymede. Because Ganymede lacks a nitrogen-methane atmosphere, it cannot run the same photochemical engine like Titan and Pluto do. Sure enough, the researchers found no trace of the mysterious feature, lending additional support to the theory that the compound is uniquely tied to the chemistry of nitrogen and methane skies.

Mapping Titan's surface

More clarity may arrive in the coming months. Researchers are currently analyzing newer JWST observations that provide a more complete view of Titan as it rotates. The data will allow the team to map the mysterious infrared signature across the moon's surface and determine whether it is associated with specific geologic features, such as Titan's vast organic-rich dune fields, which are continually replenished by a slow drizzle of complex particles produced in the atmosphere, Bézard said.

Further clues may have to wait for NASA's Dragonfly mission, a car-sized rotorcraft expected to launch in 2028 and arrive at Titan in the mid-2030s.

Although Dragonfly does not carry an infrared spectrometer to replicate JWST's light measurements, its onboard mass spectrometer will allow it to "taste" organic molecules across the various geologically interesting areas the spacecraft will fly to. By revealing which compounds are actually present on Titan's surface, the mission could give scientists a shortlist of candidates to replicate in laboratories back on Earth to see if they match the traits of the mystery molecule, Bézard said.

"It's always exciting when you discover something that was not seen before," Bézard said. "It's really the nicest part of our job."

The new study was accepted for publication in the journal Astronomy & Astrophysics.

July 2026 marks four years since NASA's James Webb Space Telescope (JWST) images were first revealed to the general public, marking a new era for astronomy. To celebrate this anniversary of the most powerful space telescope ever launched, NASA has released a stunning image of the strangely shaped galaxy called Centaurus A.

Located around 11 million light-years away, Centaurus A owes its unusual structure to a collision between two galaxies around 2 billion years ago. This merger provided the galaxy with an abundance of gas and dust, the raw material for intense star formation. It also supplied the supermassive black hole at the heart of this galaxy with an abundant supply of the same matter to feed upon and power a bright and violent central region, or active galactic nucleus (AGN), as that central area blasts out powerful, high-speed jets of plasma.

Though this galaxy is much closer to us than many of the early galaxies that the JWST has studied in its four years of operations, that doesn't mean it's any less useful. In fact, with its ultra-sensitive infrared vision, the JWST has been able to peer into the heart and inner workings of Centaurus A like no telescope that has gone before.

"No single telescope tells the whole story," Shawn Domagal-Goldman, division director of Astrophysics at NASA Headquarters in Washington, said in a statement. "Discoveries build over time, and new observatories expand on the foundations laid by earlier missions. The JWST represents the most powerful step forward yet, opening a window into wavelengths and details never before accessible.

"This allows astronomers to examine structures and processes that other telescopes could not see."

Building upon the legacy of Spitzer and Hubble

The key to the new view of Centaurus A that the JWST has been able to provide is the space telescope's powerful infrared vision. The thick dust that crowds the heart of this galaxy blocks visible light the Hubble Space Telescope previously relied on to study it. Infrared light is able to slip through these dense sheets of gas and dust.

The now-retired Spitzer Space Telescope had previously studied Centaurus A in infrared, but while it could resolve larger structures in the galaxy, it lacked the observational power to resolve individual stars and finer details.

However, even though the JWST has been able to use its MIRI (Mid-Infrared Instrument) and NIRCam (Near-Infrared Camera) to study Centaurus A like never before, there are still mysteries to be solved about this structure.

For example, in the MIRI image of Centaurus A, alongside the glowing stellar nurseries where new stars are born and spit gas and dust into their surroundings, there is a curious S-shaped feature. Scientists still don't know how this structure was formed and if the active black hole at the heart of Centaurus A played a role in its creation.

The JWST images of Centaurus A do reveal plenty about the role this galaxy's central black hole plays in carving out its morphology. For example, the JWST was able to see fast-moving ionized gas being shunted outwards by the black hole’s activity. The JWST data also revealed warmer molecular hydrogen in a warped and rotating disk near the heart of Centaurus A.

This data seems to show how a galaxy's central black hole can trigger bouts of intense star formation by condensing gas and dust, but also how these cosmic titans can stunt star birth and "kill" their host galaxies by purging the raw material needed for the star-formation process.

That means that thanks to the JWST, scientists are now building a more comprehensive cosmic history of Centaurus A, promising discoveries that can be applied to other galaxies to build a better picture of how the universe has evolved.

Here's to another four years of cosmic discoveries.

An intense demolition derby of at least six galaxies smashing into one another has been found lurking in the early universe by the James Webb Space Telescope. This merger is also expected to fuel the growth of a supermassive black hole and trigger the formation of what will eventually become one of the most massive galaxies in the cosmos.

"What makes this special is that we can follow both the build-up of a giant galaxy and the growth of the black hole at its center," Huub Röttgering, an astronomer at the Netherlands' Leiden Observatory, said in a statement.

The discovery came after a tip-off from radio astronomers who had noticed emissions that seemed to be coming from an undiscovered active black hole. When the James Webb Space Telescope (JWST) looked closer, it found a surprise.

"We didn't find a single galaxy, but an entire complex of at least six galaxies," said Aayush Saxena of the University of Oxford.

These six galaxies sit at a redshift of 4.0, which equates to a time about 12 billion years ago, just 1.8 billion years after the Big Bang.

Through the vision of the JWST's Near-Infrared Camera the six galaxies appear fuzzy, reminiscent of a faraway version of Stephan's Quintet, which is a collection of five galaxies, four of which form a compact group that are on course to merge to become a giant elliptical galaxy.

Similarly, the six galaxies spotted by the JWST, and collectively termed TGSSJ1530+1049, will undergo a series of rapid mergers to become what is known as a 'brightest cluster galaxy,' which is an enormous elliptical galaxy of the kind found at the center of galaxy clusters.

"We call structures like this protoclusters: the precursors of the vast collections of galaxies we see today," said Leiden's Roderik Overzier. "These are places where matter came together very early on. We think we are seeing a rare moment when several massive galaxies still exist separately, but are already in the process of forming one much larger galaxy."

Already a supermassive black hole has formed at the heart of this galactic maelstrom, and radio observations with the European VLBI (very long Baseline Interferometer) Network and the U.K.'s e-MERLIN (enhanced Multi-Element Remotely Linked Interferometer Network) at a resolution on the scale of a 100 milliarcseconds have identified radio lobes and hotspots typical of an active black hole's jet interacting with the gas surrounding it.

"Using a network of connected radio telescopes, we were able to produce a very sharp image of TGSSJ1530+1049," said Krisztina Gabányi of Eötvös Loránd University in Budapest, Hungary. "The radio emission is produced as material falls into the black hole, while some of it is expelled again at high speed."

The jet doesn't seem to extend as far as all the galaxies in TGSSJ1530+1049 yet, implying that the black hole is still fairly young.

The six galaxies of TGSSJ1530+1049 span a volume only a few tens of thousands of light-years across, which is smaller than our Milky Way galaxy — and yet, they pack in a humungous amount of stars, equivalent to hundreds of billions of solar masses and a star-formation rate somewhere between 70–163 solar masses per year. That's a frenetic pace compared to the Milky Way, which produces much less than ten solar masses per year.

TGSSJ1530+1049 is one of the densest collections of heavyweight galaxies found in the early universe so far, and is giving exciting clues as to how the most massive galaxies, clusters and black holes in the universe formed.

The JWST observations are reported in The Open Journal of Astrophysics, while the radio measurements are described in a paper in Astronomy & Astrophysics.

The image of the day for Monday (June 22) shows the star-forming clouds of Orion A in stunning detail.

Released as the James Webb Space Telescope (JWST) Picture of the Month, the image further demonstrates the impact the $10 billion space telescope has had on our view of the cosmos since it began operations in July 2022.

What is Orion A?

Located around 1,300 light-years from Earth and situated to the south of Orion's Belt in the night sky, Orion A is one of the largest and closest molecular clouds to our planet. Shaped like a filament, this structure of gas and dust is around 290 light-years long.

Part of the Orion molecular cloud complex, Orion A is a packed stellar nursery. Over the last few million years alone, it is estimated that Orion A has given birth to around 3,000 stellar objects.

The molecular cloud is also host to many young protostars surrounded by platters of gas and dust called protoplanetary disks, which, as the name suggests, will form planets. Thus, studying regions like Orion A could be key to understanding how the solar system came to be around 4.6 billion years ago.