Ever since the James Webb Space Telescope began sending back its first breathtaking images in late 2021, astronomers have been fascinated—and confused—by strange red dots scattered among distant stars and galaxies.
These tiny objects, now known as “little red dots,” appeared in images of the very early universe and then seemed to vanish a billion years later.
For more than two years, no one could agree on what they really were.
Now, researchers from the University of Copenhagen say they have solved the mystery.
Their findings, published in the journal Nature, reveal that the red dots are not ancient galaxies, as some scientists once thought, but young black holes hidden inside thick clouds of gas.
When the James Webb Space Telescope began observing the universe, it was looking billions of years back in time, to an era just a few hundred million years after the Big Bang.
That is when these red dots appeared. Some researchers suggested they were massive galaxies that formed surprisingly early, but that idea clashed with what scientists know about how galaxies grow over time.
After carefully studying the data, scientists at the Niels Bohr Institute’s Cosmic Dawn Center reached a different conclusion.
According to Professor Darach Watson, one of the lead researchers, the little red dots are young black holes surrounded by dense cocoons of gas.
These black holes are much smaller than previously assumed—about a hundred times less massive than early estimates—but they are growing rapidly.
As the black holes pull in surrounding gas, the material heats up to extreme temperatures. This produces intense radiation that shines through the gas cloud.
The thick cocoon absorbs much of the light and re-emits it at red wavelengths, giving the objects their distinctive appearance.
Although these black holes are considered “small” by cosmic standards, they are still enormous. Each one can weigh up to 10 million times more than the Sun and span tens of millions of kilometers. Yet they are tiny compared with the supermassive black holes found at the centers of galaxies today.
Black holes are also surprisingly inefficient eaters. As gas spirals toward them, only a small fraction actually crosses the event horizon.
Most of the material is blasted back into space by powerful radiation and jets, especially along the black hole’s poles. This chaotic process is why astronomers sometimes describe black holes as “messy eaters.”
The discovery helps answer a long-standing question in astronomy: how supermassive black holes grew so quickly in the early universe. By catching these black holes in the middle of a rapid growth phase, scientists now have evidence that dense gas cocoons allowed them to gain mass at extraordinary speeds.
At the center of our own galaxy, the Milky Way, sits a black hole four million times the mass of the Sun. Understanding how such giants formed begins with discoveries like these—tiny red dots that turn out to be the seeds of the universe’s most powerful objects.
Source: KSR.
