These clusters will have those pristine, first stars.
In the ancient light of a distant galaxy, Canadian astronomers have found what may be the universe's oldest known stars—stellar fires that ignited a mere 500 million years after the Big Bang, preserved within dense globular clusters orbiting a galaxy they have named the Sparkler. Using the James Webb Space Telescope and the magnifying grace of an intervening galaxy cluster, a team from Toronto and the National Research Council peered further back into cosmic time than any instrument before them could manage. The discovery does not merely add a date to a catalog; it suggests that globular clusters may be the universe's first architecture, the earliest structures to emerge from primordial darkness—and that within them, the seeds of everything that followed were quietly burning.
- A decades-long debate in cosmology—whether globular clusters predate, follow, or form alongside their host galaxies—has been sharpened into a near-answer by a single set of Webb images.
- The Sparkler galaxy, so faint and distant it would have been invisible to any prior telescope, was only accessible because a massive foreground galaxy cluster bent and amplified its light up to a hundredfold.
- Five of the twelve objects surrounding the Sparkler were confirmed as globular clusters whose stars formed just 500 million years after the Big Bang, placing them among the oldest known stellar structures in existence.
- The remaining seven objects carry unresolved ages, leaving the full picture incomplete and the team already planning deeper observations to refine their models of cosmic magnification.
- If these clusters truly harbored the universe's first metal-free stars, Webb's ongoing analysis could rewrite the foundational chapter of how light, matter, and structure first organized themselves in the early cosmos.
When the James Webb Space Telescope returned its first images last July, a group of Canadian astronomers gathered in Halifax and found themselves transfixed by a single elongated smear of orange light surrounded by a dozen yellowish dots. They called it the Sparkler. The dots, they suspected, were globular clusters—those ancient, gravity-bound spheres of millions of stars that orbit galaxies like our own Milky Way. But a fundamental question had long haunted the field: when, exactly, did these structures form? Before their host galaxies? After? How close to the very beginning?
The team, led by Chris Willott of the National Research Council Canada and Bob Abraham of the University of Toronto, set to work. Co-investigators Kartheik Iyer and Lamiya Mowla guided the analysis while Abraham distributed candy to colleagues as each task was completed—a small ritual that kept spirits high. The Sparkler itself was only visible because a massive galaxy cluster called SMACS 0723 sat between it and Earth, its gravity bending the distant galaxy's light like a lens and magnifying it by a factor of ten to a hundred. What would otherwise have been invisible became, suddenly, a subject of study.
The results were unambiguous: five of the twelve surrounding objects were confirmed globular clusters, their stars formed just 500 million years after the Big Bang—among the oldest known in the universe. Abraham had wagered on age and won, though the ambiguity surrounding the remaining seven objects meant the whole team claimed candy in the end.
The significance runs deeper than a single data point. Mowla noted that while the Milky Way's globular clusters have always been known to be old, their precise origins remained blurry. This discovery suggests these structures may have been the universe's first, sheltering the pristine, metal-free stars that seeded all subsequent cosmic evolution. Michel Fich of the University of Waterloo, an outside expert, called it compelling evidence that settles a long-running debate. The team is already planning further observations, refining their magnification models and pressing Webb toward its central purpose: finding the very first stars, and understanding what the universe looked like when light itself was new.
When the James Webb Space Telescope sent back its first images last July, a room full of Canadian astronomers in Halifax gathered around a table to see what the universe's most powerful eye had found. What they saw stopped them cold: thousands of galaxies scattered across the darkness like embers, their light traveling billions of years to reach the camera. One image in particular caught their attention—an elongated orange smear near the center, surrounded by a dozen yellowish dots. Someone called it the Sparkler.
The dots were likely globular clusters, those dense spheres of tens of thousands to millions of stars bound together by gravity. Our own Milky Way carries about 150 of them, ancient and mysterious. But no one really knew when these clusters formed—whether they came before their host galaxies, after them, or how close to the Big Bang itself they had emerged. The question had nagged at astronomers for decades. As the team began analyzing the Sparkler's data, the debate turned playful. Some researchers bet that the clusters were old; others insisted they were young. The stakes were exotic candy from a Halifax shop. Bob Abraham, a professor at the University of Toronto, wagered on age.
Over the following weeks, the team worked through the analysis methodically. Chris Willott, leading the research from the National Research Council Canada, and Abraham handed out candy to team members as they completed each task—a small ritual that kept the mood light as the data accumulated. Kartheik Iyer and Lamiya Mowla, both Dunlap Fellows at Toronto, co-led the investigation. They were looking at something no one had been able to see clearly before: the Sparkler galaxy itself was so distant and faint that it would have been invisible to any other telescope. But the James Webb had a secret weapon. A massive galaxy cluster called SMACS 0723 sat between Earth and the Sparkler, and its gravity bent the light of the distant galaxy like a lens, magnifying it by a factor of ten to a hundred times. What would have been too faint to detect suddenly became bright enough to study in detail.
When the analysis was complete, the answer was clear and stunning: five of the twelve objects surrounding the Sparkler were not just globular clusters—they were among the oldest known stars in the universe. They had formed only 500 million years after the Big Bang. The universe itself is 13.8 billion years old. These stars had ignited when the cosmos was still in its infancy, when the first galaxies were just beginning to take shape. Abraham had won his bet, but the real victory belonged to everyone. The remaining seven objects' ages remained uncertain, which meant the wager was ambiguous enough that the entire team claimed candy.
The discovery matters because it answers a question that has haunted cosmology: Are globular clusters relics of the ancient universe, the very first structures to coalesce from the primordial darkness? The evidence now suggests yes. Mowla explained the significance with clarity: the Milky Way's 150 globular clusters are known to be old, but their exact age has always been fuzzy. If the Sparkler's clusters truly formed so soon after the Big Bang, it means these structures may have harbored the universe's first stars—the pristine, metal-free giants that seeded everything that came after. Michel Fich, a star formation specialist at the University of Waterloo who was not part of the study, called the paper "great evidence" that globular clusters formed very early, settling a long-running debate.
The team is already planning to refine their work, gathering more data from the James Webb and building more precise models of how much the Sparkler's light was magnified. But the larger mission is clear: Webb was designed to find the first stars, and if globular clusters were born in that pristine early environment, studying them more deeply will reveal what was happening in the universe when light itself was young. The candy wager in Halifax was just the beginning.
Notable Quotes
These clusters will have those pristine or first stars. If globular clusters are born from that pristine environment, when first stars were getting born, studying these globular clusters more will get us to the answer of what was happening in the universe.— Lamiya Mowla, Dunlap Fellow at the University of Toronto
A great bit of evidence in support of globular clusters—significant numbers of globular clusters—forming very, very early after the Big Bang.— Michel Fich, University of Waterloo
The Hearth Conversation Another angle on the story
Why does it matter whether these stars formed 500 million years after the Big Bang versus, say, a billion years after?
Because the difference is the difference between witnessing the universe's first breath and watching it a few moments later. Those first 500 million years are when the very first stars ignited. If we can study clusters from that era, we're studying the seeds of everything.
But you said the age of the other seven objects in the Sparkler is still unknown. Doesn't that undermine the finding?
Not really. It actually made the whole team happy—because it meant nobody could definitively lose the bet. But more importantly, it shows us there's still so much to learn. The five confirmed clusters are the breakthrough. The others are the next question.
The gravitational lensing—that's the galaxy cluster bending light like a lens. How does that help you see something so far away?
It magnifies the light by ten to a hundred times and stretches it out. Without that magnification, the Sparkler would be too faint for any telescope to resolve. The universe is doing the magnifying for us.
So you're saying the James Webb couldn't have found these stars without luck—without that galaxy cluster sitting in the right place?
Exactly. It's not just the telescope's power. It's the telescope's power combined with the universe's own geometry. That's what makes this discovery possible.
What happens next? Do you just keep looking for more ancient clusters?
We refine the models, gather more data, study these clusters in deeper detail. If globular clusters really were born from the universe's first stars, then studying them is like reading the earliest chapters of cosmic history. That's what we're after.