Webb’s Little Red Dots May Expose How Giant Black Holes Begin
Hundreds of small red dots captured by NASA’s James Webb Space Telescope might just show the beginning stages of supermassive black hole formation that astronomers failed to see over the past few decades. The latest discovery is no ordinary light either; it is an X-ray coming from a distant object named 3DHST-AEGIS-12014, located at 11.8 billion light years away from Earth and corresponding to one of the little red dots. This fact is crucial since little red dots have been puzzling scientists mostly due to what made them different from other black hole candidates. Namely, if they were typical black holes that feed, they should be emitting more X-rays, while little red dots appeared to be relatively compact, red and obscured by whatever was keeping their inner secrets hidden.
Now, the latter detail becomes crucial in the description of these mysterious dots as well. Scientists increasingly refer to little red dots as “black hole stars,” namely gas cocoons hiding black holes, that absorb most of ultraviolet and X-ray emissions that otherwise make a feeding black hole detectable. 3DHST-AEGIS-12014 seems like a brief transitional state, in which the black hole devoured most of its cocoon, creating a partial gap from which high-energy light can pass through. “This single X-ray object may be to use a phrase what lets us connect all of the dots.” noted Raphael Hviding.
The implications go far beyond finding out yet another peculiarity about the Universe. In fact, thanks to JWST, scientists know that the supermassive black holes existed even in the early Universe, in some cases as soon as within 500 million years after the Big Bang occurred. Naturally, that fact put pressure on conventional growth scenarios, since building up an incredibly massive black hole through feeding and mergers could take much more time. Thus, little red dots are seen as potentially critical in this process – being relatively small, gas-rich environments that help the black holes grow extremely fast while remaining concealed within the environment where they appeared. Consequently, little red dots cannot be viewed simply as some odd observations discovered by JWST. Rather, they represent an important process that connects the formation of supermassive black holes to their further evolution to the state of active galactic nuclei.
In turn, this discussion became quite intense because potential explanations for little red dots became less relevant over time. Originally, many astronomers assumed they were young compact galaxies and dusty systems with unusual stellar light signatures. However, subsequent research showed that dust-rich models were unable to explain why many of them were not detected in any of the multiple surveys aimed specifically at detecting dust emission. On the contrary, the gas flow accompanying many little red dots pointed directly to a compact central source that fits better into the scenario with black hole accretion rather than stellar activity alone.
One important implication of the newest interpretation concerns scale. If the red signature is not produced by dust, then black holes in those objects will likely appear less massive compared to earlier assessments, closer to seeds than giants. As a result, this assumption solves another problem: early Universe simply did not have enough resources to produce many gigantic black holes.
“If we confirm the X-ray dot as a little red dot in transition, not only would it be the first of its kind, but we may be seeing into the heart of a little red dot for the first time,” stated Hanpu Liu. For now, a single X-ray counterpart may be not enough to prove the theory behind the origin of little red dots. Still, it helps to move from questions regarding the existence of a black hole inside them to figuring out how exactly it happens and how often this process produces supermassive black holes.
