Some of the weaker sources in the James Webb Space Telescope images don’t quite fit into the existing categories. They appear as red dots embedded in deep views of the early universe, appearing at very early times and then largely disappearing after a few hundred million years.
A new study published in nature He now links these fleeting signals to a specific stage in the black hole’s growth. Rather than identifying massive early galaxies, the “little red dots” look like young black holes captured during a short but intense growth phase, embedded in dense clouds of gas that change how their light reaches us.
“We captured images of young black holes in the middle of their growth spurt at a stage we had never observed before,” said Darach Watson, one of the lead researchers involved in the study. “The dense gas cocoon surrounding them provides the fuel they need to grow very quickly.” press release.
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What are the “little red dots” in JWST really?
Small red dots captured by JWST
(Image credit: Oak Watson/JWST)
The red dots initially stood out because their brightness and color did not match expectations. Objects that form very early in cosmic history must be either faint or resemble starry galaxies that persist and evolve over time. Instead, these combined sources appeared briefly, then faded from view.
One early explanation was that the dots represented unusually massive galaxies forming much earlier than current models allow. But galaxies take time to form stars, dust, and structure, and the timing wasn’t right. The new analysis instead points to a much more compact energy source: black holes are smaller than initially assumed, but they are actively pulling in surrounding material.
As the gas rises inward, it heats up and emits intense radiation. In these early black holes, this radiation is filtered through a dense envelope of ionized gas. High-energy light is absorbed and re-emitted at longer, redder wavelengths, giving objects their distinctive appearance in infrared web images.
How do young black holes grow inside dense gas clouds?
Even when they grow quickly, black holes don’t eat efficiently. Most of the gas attracted to it never crosses the event horizon. Instead, the energy released near the black hole pushes much of that material out into space.
As the falling gas accelerates and compresses, it reaches extreme temperatures and glows intensely. Strong radiation and magnetic forces then produce outflows that remove surrounding material over time. This process fuels and limits the growth of the black hole.
Although these young black holes are modest by cosmic standards, weighing millions of times more than the Sun, they can briefly outpace entire galaxies during this phase. Once the surrounding gas is blown out, the nature of the black hole’s light changes, and the object no longer appears as a compact red source.
What red dots reveal about the first black holes in the universe
Astronomers have long struggled to explain how supermassive black holes, some of which weigh billions of times more than the Sun, formed so quickly after the Big Bang. The newly identified red dots likely represent a missing stage in that process, when black holes are still embedded in dense gas and growing at their fastest rate.
By capturing these objects in mid-growth, the James Webb Space Telescope revealed a stage that had previously been inferred but not directly observed. Rather than rare anomalies, the red dots may represent a common step in the early evolution of galaxies and the black holes at their centers.
If so, the smallest dots in the James Webb Space Telescope images shed light on one of the universe’s biggest mysteries: how its most extreme objects got their start.
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