The Enigma of the Little Red DotsThe stars we know today rarely exceed about a hundred times the mass of our Sun.
The researchers produced an illustration showing distinct layers that represent the “envelope” created by massive stars—a likely source of the light we detect as these Little Red Dots.
Specifically, the LRDs do not produce the strong X-ray or radio emissions we’d expect from a rapidly growing supermassive black hole.
The latest research finally seems able to recreate the existence of thick gas “cocoons” that make the Little Red Dots appear so compact in JWST images.
The new models suggest these supermassive stars eject matter rich in nitrogen—precisely what’s observed in the LRD spectra.
The Enigma of the Little Red Dots
The stars we know today rarely exceed about a hundred times the mass of our Sun. But a few hundred million years after the Big Bang, things were a little different in the universe. Under those early physical and chemical conditions, scientists suspect that much more massive stars could have formed—some with masses around 100,000, or even a million times that of the Sun. Now, thanks to the James Webb Space Telescope (JWST), these cosmic giants may have finally stepped into the spotlight. But how?
The discovery of the now-famous Little Red Dots (LRD) through JWST is reminiscent of the quasar detection back in the early 1960s—a time when radio astronomy was booming with huge instruments, complemented by the advent of large optical telescopes earlier in the 20th century.
So what are these LRDs? For now, they are more than 300 infrared objects spotted in JWST’s data. They begin to emerge about 600 million years after the Big Bang and seem to fade away 1.5 billion years later. We know they are compact, dazzlingly bright, and emit a curious, never-seen-before combination of red and ultraviolet light.
Not Just Dusty Black Holes?
Early theories suggested two things: first, that these mysterious objects were wrapped in clouds of gas and dust (hence their unusually red color); second, that they could be supermassive black holes feeding on matter at the heart of galaxies—just like quasars.
Since then, a stream of scientific papers has explored variations on this hypothesis. Others have revisited a long-standing idea in relativistic astrophysics: the possibility of supermassive stars, as described in general relativity by pioneers like the renowned Indian astrophysicist Subrahmanyan Chandrasekhar and Nobel laureate Richard Feynman.
Could the James Webb Space Telescope Have Found the Legendary Million-Sun Stars?
Relativistic astrophysicists have been pondering the existence of incredibly massive stars for almost 60 years, as such objects provide solutions to several cosmic puzzles. In particular, it’s long been thought these behemoths might have been among the very first stars to appear after the Big Bang, even though no telescope had found evidence—until now, perhaps. Remarkably, that may be changing before our very eyes.
Astrophysicist Devesh Nandal at the Harvard College Observatory, part of the Center for Astrophysics (a collaborative effort between Harvard and the Smithsonian), has been working with colleagues on this question for some time. Recently, they’ve published a new article, freely available on arXiv and featured in The Astrophysical Journal Letters.
The researchers produced an illustration showing distinct layers that represent the “envelope” created by massive stars—a likely source of the light we detect as these Little Red Dots. The image also shows the scale of a supermassive star compared to more ordinary ones. (For scale: take our Sun, multiply by 100,000, and you’re still not done!)
In a statement from the Center for Astrophysics | Harvard & Smithsonian, Nandal explains:
“To my knowledge, this is the first model capable of simultaneously explaining so many observed features—from the spectra to the morphology and chemical signatures… Even competing scenarios are now starting to invoke supermassive stars as a central driving force.”
He adds:
“The Little Red Dots are mysterious because they combine clues that normally don’t go together. They seem to show us that something very bright is hidden inside dense gas.”
From Fantastical Stars to the Seeds of Quasars
The spectrum of these LRDs reveals clues not explained by current models of young galaxies or typical active galactic nuclei. Specifically, the LRDs do not produce the strong X-ray or radio emissions we’d expect from a rapidly growing supermassive black hole. Instead, the case is building for the involvement of truly fantastic stars—about 100,000 times more massive than the Sun.
But where do supermassive black holes, like those powering quasars at galactic centers, come from? According to current thinking, they formed from giant stars that later collapsed into huge black holes—the seeds of today’s supermassive ones.
The latest research finally seems able to recreate the existence of thick gas “cocoons” that make the Little Red Dots appear so compact in JWST images.
Supermassive stars are, by nature, unstable. Toward the end of their lives, they would undergo wild pulsations—what researchers now call “strange modes”—leading to the ejection of vast amounts of gas in shells around the star.
The new models suggest these supermassive stars eject matter rich in nitrogen—precisely what’s observed in the LRD spectra. After their final outburst, these stars would continue evolving until they undergo direct collapse, forming the seed of a supermassive black hole—just as long-proposed theories predicted.
