James Webb reveals small red dots are compact galaxies with black holes

A new study published in Nature Astronomy proposes an explanation for the mysterious "little red dots" observed by the James Webb Space Telescope (JWST) in the early universe. The research, which analyzed 217 such objects, suggests they are not isolated objects but bright nuclei within compact, star-forming galaxies, likely powered by supermassive black holes at their centers Source: infobae. By combining multiple JWST images, the team detected a faint extended glow around the bright centers, indicating the presence of surrounding galaxies with total masses near a billion solar masses Source: infobae. These galaxies are extremely compact, with an average radius of about 210 parsecs (685 light-years), making them roughly 2.5 times more compact than similar star-forming galaxies at comparable cosmic epochs Source: infobae.

The debate

The little red dots, first seen in JWST deep-field images in 2022, have puzzled astronomers because they appeared too massive and too early in cosmic history (600 million to 1.5 billion years after the Big Bang). Some researchers even claimed they "broke cosmology" due to their apparent black hole-to-galaxy mass ratios of up to 30%, far exceeding the 0.1%–0.5% seen in local galaxies Source: ABC. Earlier hypotheses included Population III stars or optical illusions, but the new findings point to a more mundane explanation Source: ABC.

A separate discovery

In a related but distinct study, also published in Nature Astronomy, a team led by the University of Leiden used JWST and the Very Large Telescope to study nine early galaxies and found a hidden population of small, faint stars. This suggests these galaxies may contain up to four times more stellar mass than previously estimated, challenging assumptions about star formation in the early universe Source: elconfidencial. While both studies involve early galaxies, they address different phenomena: the red dots' nature versus the stellar mass budget of early galaxies.