Supernova from the dawn of the universe captured by James Webb Space Telescope
Luminous Fast Blue Optical Transient (Artist's Concept) Caption: This is an artist's concept of one of brightest explosions ever seen in space. Credits: Artwork - NASA, ESA, NSF's NOIRLab, Mark Garlick , Mahdi Zamani
An international team of astronomers has achieved a first in probing the early universe, using the James Webb Space Telescope (JWST), detecting a supernova – the explosive death of a massive star – at an unprecedented cosmic distance.
The explosion, designatedSN in GRB 250314A, occurred when the universe was only about730 million years old, placing it deep in the era of reionisation. This remarkable discovery provides a direct look at the final moments of a massive star from a time when the first stars and galaxies were just beginning to form.
The event, which has been reported on in the recently published academic paper ‘(opens in a new window)JWST reveals a supernova following a gamma-ray burst at z≃7.3,’ (Astronomy & Astrophysics,704, December 2025),was initially flagged by a bright burst of high-energy radiation, known as a long-duration Gamma-Ray Burst (GRB), detected by the space-based multi-band astronomical Variable Objects Monitor (SVOM) on March 14, 2025. Follow-up observations with the European Southern Observatory’s Very Large Telescope (ESO/VLT) confirmed the extreme distance.
The key finding came from targeted observations with JWST's Near-Infrared Camera (NIRCAM) approximately 110 days after the burst. Scientists were able to separate the light of the explosion from its faint, underlying host galaxy.
Co-author, and astrophysicist at UCD School of Physics,(opens in a new window)Dr Antonio Martin-Carrillosaid: “The key observation, or smoking gun, that connects the death of massive stars with gamma-ray bursts is the discovery of a supernova emerging at the same sky location. Almost every supernova ever studied has been relatively nearby to us,with just a handful of exceptions to date.When we confirmed the age of this one,we saw a unique opportunity to probe how the Universe was there and what type of stars existed and died back then.
“Using models based on the population of supernovae associated with GRBs in our local universe, we made some predictions of what the emission should be and used it to proposed a new observation with the James Webb Space Telescope. To our surprise, our model worked remarkably well and the observed supernova seems to match really well the death of stars that we see regularly. We were also able to get a glimpse of the galaxy that hosted this dying star.”
The data indicate that the distant supernova is surprisingly similar in brightness and spectral properties to the prototype GRB-associated supernova,SN 1998bw, which exploded in the local universe.
This similarity suggests that the massive star that collapsed to create GRB 250314A was not significantly different from the progenitors of GRBs observed locally, despite the vastly different physical conditions (such as lower metallicity) in the early universe. The observations also ruled out a much more luminous event, such as a Superluminous Supernova (SLSN).
The findings challenge the assumption that the stars of the early universe, formed under extremely low-metallicity conditions, would lead to markedly different, perhaps brighter or bluer, stellar explosions than those seen today.
While this discovery provides a powerful anchor point for understanding stellar evolution in the early universe, it also opens new questions about the observed uniformity.
The research team plans to secure a second epoch of JWST observations in the next one to two years. By that time, the supernova light is expected to have faded significantly (by over two magnitudes), allowing the team to completely characterise the properties of the faint host galaxy and confirm the supernova's contribution.
Quelle: University College Dublin
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NASA’s Webb telescope finds bizarre atmosphere on a lemon-shaped exoplanet
Faraway planet defies our understanding of planet formation, say UChicago scientists
A strange planet (left) orbits a rapidly spinning neutron star called a pulsar (right). This artist's illustration shows that gravitational forces from the much heavier pulsar are pulling the world into the shape of a lemon. This planet, studied with NASA’s James Webb Space Telescope, appears to have an exotic atmosphere unlike any ever seen before.Image courtesy of NASA, ESA, CSA, Ralf Crawford (STScI)
Scientists using NASA’s James Webb Space Telescope have observed an entirely new type of exoplanet whose atmospheric composition challenges our understanding of how this type of planet forms.
This bizarre, lemon-shaped body, possibly containing diamonds at its core, blurs the line between planets and stars.
Officially named PSR J2322-2650b, this object has an exotic helium-and-carbon-dominated atmosphere unlike any ever seen before. It has a mass about the same as Jupiter, but soot clouds float through the air—and deep within the planet, these carbon clouds can condense and form diamonds. It orbits a rapidly spinning neutron star.
How the planet came to be is a mystery.
This animation shows an exoplanet orbiting a distant pulsar - a rapidly rotating neutron star that sends off strong radio pulses every few milliseconds. The planet, which orbits about 1 million miles away from the pulsar, is stretched into a lemon shape by the pulsar’s strong gravitational tides.Animation courtesy of NASA, ESA, CSA, Ralf Crawford (STScI)
“The planet orbits a star that's completely bizarre — the mass of the Sun, but the size of a city,” explained the University of Chicago’s Michael Zhang, the principal investigator on this study, which is accepted for publication in The Astrophysical Journal Letters. “This is a new type of planet atmosphere that nobody has ever seen before.”
“This was an absolute surprise,” said team member Peter Gao of the Carnegie Earth and Planets Laboratory in Washington, D.C. “I remember after we got the data down, our collective reaction was ‘What the heck is this?’”
A bizarre pair
The new planet, PSR J2322-2650b, is orbiting a rapidly spinning neutron star, also known as a pulsar.
This star emits beams of electromagnetic radiation from its magnetic poles at regular intervals just milliseconds apart. But the star is emitting mostly gamma rays and other high-energy particles, which are invisible to the Webb telescope’s infrared vision.
This means scientists can study the planet in intricate detail across its whole orbit—normally an extremely difficult task, because stars usually far outshine their planets.
“This system is unique because we are able to view the planet illuminated by its host star, but not see the host star at all,” explained Maya Beleznay, a graduate student at Stanford University who worked on modelling the shape of the planet and the geometry of its orbit. “So we get a really pristine spectrum. And we can better study this system in more detail than normal exoplanets.”
Taking stock of the planet, the team was surprised.
“Instead of finding the normal molecules we expect to see on an exoplanet—like water, methane and carbon dioxide—we saw molecular carbon, specifically C3 and C2,” said Zhang.
At the core of the planet, subjected to intense pressure, it’s possible this carbon could be squeezed into diamonds.
But to the scientists, the larger question is how such a planet could have formed at all.
“It's very hard to imagine how you get this extremely carbon-enriched composition,” said Zhang. “It seems to rule out every known formation mechanism.”
How the planet came to be is a mystery.
‘A puzzle to go after’
PSR J2322-2650b is extraordinary close to its star, just 1 million miles away. In contrast, the Earth’s distance from the Sun is about 100 million miles.
Because of its extremely tight orbit, the exoplanet’s entire year—the time it takes to go around its star—is just 7.8 hours.
Applying models to the planet’s brightness variations over its orbit, the team finds that immense gravitational forces from the much heavier pulsar are pulling the Jupiter-mass planet into a lemon shape.
Together, the star and exoplanet may be considered a “black widow” system. Black widows are a rare type of system where a rapidly spinning pulsar is paired with a small, low-mass companion. In the past, material from the companion would have streamed onto the pulsar, causing it to spin faster over time, which powers a strong wind. That wind and radiation then bombard and evaporate the smaller and less massive star.
Like the spider for which it is named, the pulsar slowly consumes its unfortunate partner.
But in this case, the tiny companion is officially considered an exoplanet by the International Astronomical Union, not a star.
An artist's illustration of what exoplanet PSR J2322-2650b might look like. Because of its extremely tight orbit, the planet’s entire year—the time it takes to go around the pulsar—is just 7.8 hours.Illustration courtesy of NASA, ESA, CSA, Ralf Crawford (STScI)
“Did this thing form like a normal planet? No, because the composition is entirely different,” said Zhang. “Did it form by stripping the outside of a star, like ‘normal’ black widow systems are formed? Probably not, because nuclear physics does not make pure carbon.”
Team member Roger Romani, of Stanford and the Kavli Institute for Particle Astrophysics and Cosmology Institute, is one of the world’s preeminent experts on black widow systems. He proposes one evocative phenomenon that could occur in the unique atmosphere.
“As the companion cools down, the mixture of carbon and oxygen in the interior starts to crystallize,” Romani theorized. “Pure carbon crystals float to the top and get mixed into the helium, and that's what we see. But then something has to happen to keep the oxygen and nitrogen away. And that's where there's controversy.”
“But it's nice to not know everything,” said Romani. “I'm looking forward to learning more about the weirdness of this atmosphere. It's great to have a puzzle to go after.”
With its infrared vision and exquisite sensitivity, this is a discovery only the Webb telescopecould make. Its perch a million miles from Earth and its huge sunshield keeps the instruments very cold, which is necessary for conducting these observations.
“It's very hard to imagine how you get this extremely carbon-enriched composition. It seems to rule out every known formation mechanism.”
—Michael Zhang
“On the Earth, lots of things are hot, and that heat really interferes with the observations because it's another source of photons that you have to deal with,” explained Zhang. “It's absolutely not feasible from the ground.”
Other UChicago scientists on the study included Prof. Jacob Bean, graduate student Brandon Park Coy and Rafael Luque, who was then a postdoctoral researcher at UChicago and is now with the Instituto de Astrofísica de Andalucía in Spain.
