News release

From: Springer Nature

Little red dots may reside in small, dense galaxies with total masses equivalent to around one billion times that of the Sun, according to research published in Nature Astronomy. The findings offer new clues about how these mysterious objects developed within the first billion years after the Big Bang.

Little red dots are small, red objects seen at far distances from Earth. However, the nature of little red dots and the source of their light remains unclear. Previous research has found signs of material around some of these objects at ultraviolet wavelengths, possibly indicating the presence of galaxies. However, there has been little evidence of this material in optical light (light that human eyes can see), which gives a clearer view of stellar mass.

Xuheng Ding, Lilan Yang, and colleagues combined James Webb Space Telescope images of 217 little red dots to reveal faint optical emission, meaning light extending beyond the central objects, that could not be clearly detected in individual images. Modelling of the data indicates that this emission likely comes from star-forming galaxies, with little red dots residing in their centres as supermassive black holes. The galaxies have average radii of just 210 parsecs (about 685 light years), making them about 2.5 times more compact than other star-forming galaxies of a similar mass seen at a comparable period in the Universe’s history.

The findings suggest that little red dots are not simply single points of light but likely exist within compact star-forming galaxies, which helps to explain their origin. However, the authors note that the results describe the average properties of the full sample, as the extended emission is too faint to be detected around most individual objects. Further work is needed to confirm the sample spectroscopically, by analysing the objects’ light to verify their distances.