This Little Red Dot Might Be Hiding a Black Hole From the Beginning of Time

3 min readHere’s what you’ll learn when you read this story:NASA’s James Webb Space Telescope has revealed a black hole star that dates back to just 660 million years after the Big Bang.The JWST has also revealed many similar “red dots” that puzzle scientists.This most recently discovered red dot is likely gas and not a galaxy, as evidenced by its specific red color and wavelengths.A team of scientists believes they’ve identified the true nature of the small red dots that are popping up on many images of the farthest reaches of the universe. The red dot studied in the new research—which appears in the journal Nature—may be a black hole “100,000 times as massive as the Sun,” with a surrounding gaseous body the size of our Solar System.Working with data from NASA’s James Webb Space Telescope (JWST), the team picked a patch of sky to survey, wrote an algorithm to single out one red dot, and then built and interpreted a model to explain it.The Webb telescope can see fainter, more distant objects than any telescope before it, and in sharper detail. Because light travels at a finite speed, the farther away it looks, the further back in time it sees, which makes its images a window onto the primordial universe. These images show small red dots whose identities have so far eluded scientists—as far as we know, there’s nothing analogous in our images of the more modern universe. That suggests that the red dots are old and distant objects that disappeared billions of years ago, within about one billion years after the Big Bang.“What exactly these objects are has been one of the most debated topics of the JWST era,” lead author Rohan Naidu, an astronomer and cosmologist who studies young universe objects at the University of Hawaii, said in an MIT statement. His team framed the puzzle as a choice: miracle or mirage? Is this a genuine galaxy that somehow assembled itself just after the Big Bang, or merely something dressed up to look like one? The answer, it turned out, was written in the object’s color.“Here we present a source 660 million years after the Big Bang that exhibits singular properties: among the largest hydrogen Balmer breaks reported at any redshift [...] and Balmer line absorption in several transitions. We model this source as an enshrouded black hole in which the Balmer break and absorption features are a result of extremely dense, turbulent gas forming a dust-free envelope around a supermassive black hole.”The Balmer break helps explain why the dot is red. Dust is one common reason that astronomical bodies are red, since dust scatters blue light and lets red through. But dust dims light smoothly, across a broad range of wavelengths. This red dot instead showed an abrupt break at one exact wavelength, where hydrogen atoms get absorbed very strongly. It’s one of the largest Balmer breaks ever recorded. So the red dot’s color wasn’t coming from dust—it was coming from a huge amount of tightly-packed hydrogen.The type of lines in the Webb telescope’s readings suggested that this object, whatever it is, had far denser gas than almost anything else we can observe in the universe. That narrows down the options for what type of object it could be, as well as the basic physical chemistry it can enable, because particles behave differently under such great levels of density. By modeling different versions of their theory, the scientists arrived at the best explanation for what this thing really is—a black hole star surrounded by an enormous gas cloud from billions of years ago.The results are intriguing, but they’re only the very beginning, the scientists explain. Due to the unusually dense and obscuring red color, “black hole masses [...] may therefore be overestimated by orders of magnitude.” That means the next step is likely either a more complex model or new observations to try to deepen our knowledge. They conclude: “We emphasize that this modeling exercise is highly simplistic and only serves to provide broad physical intuition that dense gas enveloping a central engine may account for the singular observed features.”Indeed, another recently published study shows how a different red dot with a different spectral reading could be parsed as a galaxy instead of a black hole star, meaning that it’s full of exactly the kind of dust and debris that scientists didn’t find in the more recently studied object. The more we can learn, the better we can categorize these extremely ancient and faraway objects.Caroline Delbert is a writer, avid reader, and contributing editor at Pop Mech. She's also an enthusiast of just about everything. Her favorite topics include nuclear energy, cosmology, math of everyday things, and the philosophy of it all.