News release

From: Springer Nature

Astronomy: Little red dots may be black holes in disguise

A family of ‘mysterious’ objects known as little red dots in distant galaxies may be young supermassive black holes hidden by clouds of neutral gas and electrons, according to an analysis of data from the James Webb Space Telescope published in Nature. This finding suggests a previously unknown phase of black hole growth in the early Universe.

Astronomers have been debating the identity of a collection of little red dots, detected during early experiments using the James Webb Space Telescope. The dots have been thought to be supermassive black holes or signs of star formation, but their behaviour does not fit neatly into either category.

Vadim Rusakov and colleagues analysed data from 12 individually studied galaxies, combined with data from another 18 to get a better sense of the little red dots’ behaviour over time. After studying the emission spectra from the centre of these galaxies, they found that the spectra were caused by photons scattering off electrons in dense clouds of gas at the galactic centre, surrounding the black holes. The authors calculated that the black holes are likely one hundred times smaller than previous estimates suggested. They also suggest that these smaller black holes are enveloped in a cocoon of high-density gas, which could be responsible for the majority of their radiation.

The authors suggest that these black holes are in an early stage of development, when they are buried in dense material that blocks X-rays and radio waves and reshapes their light into specific patterns. Some details, such as why X-rays are so weak, still need further investigation. Future observations could explore whether this “cocoon phase” is common and how it influences the growth of black holes and galaxies.