James Webb Telescope data may reveal ultra-massive early stars behind mysterious 'Little Red Dots'

More than 300 compact infrared sources, dubbed Little Red Dots (LRDs), have been detected in James Webb Space Telescope observations of the early universe, appearing around 600 million years after the Big Bang and fading by about 1.5 billion years. The objects are unusually bright, emit a mix of red and ultraviolet light, and lack the strong X-ray or radio signatures typical of active galactic nuclei.

Initial hypotheses suggested that LRDs might be heavily dust-enshrouded supermassive black holes, but recent theoretical work proposes they could instead be supermassive stars with masses up to 100,000 solar masses. Such stars are predicted to develop thick gas envelopes that would produce the observed spectral features, including nitrogen-rich ejecta.

Astrophysicist Devesh Nandal of the Harvard-Smithsonian Center for Astrophysics, co-author of a new paper in The Astrophysical Journal Letters, said the model “is the first capable of simultaneously explaining so many observed features—from the spectra to the morphology and chemical signatures.” He added that the LRDs “combine clues that normally don’t go together, showing something very bright hidden inside dense gas.”

If the supermassive-star scenario is correct, these objects would represent some of the first generation of stars, eventually collapsing directly into black-hole seeds that could later grow into the supermassive black holes powering quasars. The new models also reproduce the thick gas cocoons that make LRDs appear compact in JWST images, supporting the idea that they are transient, unstable stars undergoing violent pulsations before collapse.