Astronomers Propose 'Black Hole Stars' to Explain Webb's Little Red Dots

Astronomers using the James Webb Space Telescope have identified a candidate for a previously unknown type of celestial object: a black hole star. The finding, published August 12 in Nature, centers on an extremely bright source designated MoM-BH*-1, observed as it existed 660 million years after the Big Bang.

Since JWST began operations in 2022, it has detected hundreds of compact, red sources nicknamed "little red dots." Their nature has remained uncertain. MoM-BH*-1 stood out in the Mirage survey as the reddest and brightest of these objects, prompting detailed follow-up observations.

The object's light shows a strong Balmer break, a spectral feature typically associated with dense hydrogen gas around stars. However, the break is stronger than any seen in a normal star, and the overall luminosity exceeds what nuclear fusion can produce. The spectrum also indicates very little dust, ruling out a standard dust-reddened galaxy or quasar.

Researchers led by Rohan Naidu of the University of Hawaii ran computer simulations to match these properties. The models suggest MoM-BH*-1 is a black hole roughly 100,000 times the mass of the Sun, surrounded by a massive, solar-system-sized envelope of hot hydrogen gas that glows like a stellar surface.

In this configuration, the black hole's accretion powers the brilliant emission, while the dense gas envelope produces the star-like spectral signatures and red color. Independent astronomers Dominik Schleicher and Rodrigo Herrera-Camus noted in an accompanying commentary that the gas-dominated explanation for the red color is a significant clue for the whole little-red-dot population.

Naidu estimates that as of 2025, JWST has found 341 little red dots, each potentially consistent with a black hole star embedded in an early galaxy. MoM-BH*-1 is unusual because its central engine outshines its host galaxy almost completely, providing a relatively clean view of the proposed object.

The study does not confirm that all little red dots are black hole stars, nor does it establish how such objects form or evolve. Further observations and theoretical work are needed to test the hypothesis across the full population.