“These primordial black holes may make up a large part—or even all—of dark matter.”
“Little Red Dots,” mysterious objects discovered by the James Webb Space Telescope (JWST), may be early nurseries of massive black holes that formed not from collapsing stars, but directly from vast clouds of gas.
If confirmed, this idea could help explain both the nature of these enigmatic objects and another major JWST discovery since its launch in 2022—the presence of numerous supermassive black holes just 500 million years after the Big Bang.
This poses a challenge to existing theory, which suggests that supermassive black holes—millions to billions of times the mass of the Sun—form through mergers and gradual growth over time, a process previously thought to take at least a billion years to produce such cosmic giants at the centers of galaxies.
This challenge could be resolved if the formation of supermassive black hole mergers begins with a “heavy seed”—a direct-collapse black hole formed when extremely dense regions inside primordial gas clouds collapse under their own gravity. This is different from a “light seed,” which arises when massive stars die in supernova explosions, leaving behind stellar-mass black holes.
Unlike light seeds, heavy seeds would remove strict mass limitations at the start of the growth process and could allow black holes to begin forming and merging even before the first generation of massive stars had completed their life cycles.
“As a result, all galaxies likely host a supermassive black hole at their centre, and its origin remains one of the major open questions in modern astrophysics,” said study lead Elia Cenci of the University of Geneva. “One possible pathway is direct collapse, where a short-lived supermassive star forms from pristine gas at the centre of dark matter haloes that meet specific conditions. These conditions mainly prevent molecular hydrogen from forming, since it would cool the gas and favor the creation of smaller stars.”
Cenci added that the so-called “Little Red Dots” are unusual, compact sources of light that appeared when the universe was less than a billion years old. First identified in deep extragalactic surveys with the James Webb Space Telescope (JWST), they appear extremely red and tightly packed, which is how they got their name.
Little Red Dots are unusual for several reasons, including the pattern of light they emit, their spectra, their physical characteristics, and the fact that they appear to vanish early in the history of the 13.8-billion-year-old universe.
“A leading explanation is that we are observing a large population of faint, massive black holes in the early universe, surrounded by extremely dense gas and stars that earlier instruments would not have been able to detect,” Cenci said.
Cenci and his team linked Little Red Dots to direct-collapse black holes through high-resolution simulations of early cosmic evolution.
Little Red Dots are unusual for several reasons, including the pattern of light they emit, their spectra, their physical characteristics, and the fact that they appear to vanish early in the history of the 13.8-billion-year-old universe.
“A leading explanation is that we are observing a large population of faint, massive black holes in the early universe, surrounded by extremely dense gas and stars that earlier instruments would not have been able to detect,” Cenci said.
Cenci and his team linked Little Red Dots to direct-collapse black holes through high-resolution simulations of early cosmic evolution.
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