Visualisation of the simulation by ATERUI III showing a rapidly growing black hole surrounded by gas. Red indicates areas of higher temperature. Credit: Sunmyon Chon, Takaaki Takeda, 4D2U Project, NAOJ.

The Japanese supercomputer ATERUI III has explained the James Webb Space Telescope’s ‘Little Red Dots’ as fast-growing ancient black holes.

Of all the discoveries from the James Webb Space Telescope, the multitude of Little Red Dots it has observed is one of the most enigmatic.

Now, simulations using the Japanese Supercomputer ATERUI III have explained the nature of the Little Red Dots without requiring any exotic assumptions.

The simulations show that the Little Red Dots are black holes growing at a rate that would be impossible today thanks to the conditions in the early Universe.

In this study, a research team led by Sunmyon Chon at the Max Planck Institute for Astrophysics used the ATERUI III supercomputer at the National Astronomical Observatory of Japan to conduct the most detailed cosmological simulations to date of conditions in the early Universe.

The team’s simulation started with the conditions surrounding a galaxy in the early Universe, then zoomed in to individual gas clouds.

These computationally intense simulations were made possible by ATERUI III’s high-resolution computing power.

These mysterious red objects that appear small on the sky emerge in large numbers around 600 million years after the Big Bang and undergo a rapid decline in quantity around 1.5 billion years after the Big Bang. Credit: Image: NASA, ESA, CSA, STScI, Dale Kocevski (Colby College), Public domain, via Wikimedia Commons.

Supermassive stars

The simulations show that in the early Universe, intense far-ultraviolet (FUV) radiation from nearby galaxies suppresses star formation in gas clouds, so that rather than forming many little stars, the gas can form a single, supermassive star, which then collapses into a black hole seed.

The simulations show that, once formed, these black hole seeds are surrounded by dense gas disks.

This environment traps radiation, enabling the black holes to grow at rates dozens of times faster than would be possible in the modern Universe.

The simulated properties of these rapidly growing black holes provide a good match to the Little Red Dots (LRDs) observed by the James Webb Space Telescope (JWST).

A long-standing mystery in Astronomy has been how the super-massive black holes, with masses millions or even billions of times that of the Sun, observed in the early Universe appeared so quickly, in less than 600 million years after the Big Bang.

JWST was expected to answer this question by allowing us to see fainter, more distant galaxies.

Because light travels at a finite speed, looking at more distant objects is like looking back in time.

When we observe a galaxy 11 billion light-years away, that light has had to travel 11 billion years to reach us.

That light shows us what the galaxy looked like when the light left 11 billion years ago. Likewise, the light from a galaxy 12 billion light-years away is 12 billion years old.

Deceptively simple

JWST allows us to look back further in time than ever before, but instead of finding the answer to the rapid growth of black holes, it revealed a population of small, enigmatic, extremely red objects which were dubbed Little Red Dots (LRDs).

These new simulations show that the LRDs are the answer to the black hole growth mystery, and a deceptively simple answer at that.

In the simulation, these results happened as a natural consequence of the conditions in the early Universe, without requiring any exotic assumptions or chance accidents. This is important for explaining the ubiquity of LRDs.

As JWST continues to reveal more LRDs and future telescopes probe deeper into the early Universe, this new model provides a powerful roadmap for understanding how the cosmos evolved.

The study is published in Nature.