JWST data fuel new clues about the universe’s first stars
The James Webb Space Telescope (JWST) is helping astronomers push the boundaries of the early universe. A team led by Cosmin Ilie of Colgate University, with collaborators Shafaat Mahmud, Jillian Paulin, and Katherine Freese, reports four extremely distant objects whose spectra and shapes align with what researchers expect from supermassive dark stars. These objects, among the most remote ever observed, lie roughly 300 million years after the Big Bang and reach redshifts that place them among the earliest stellar structures known.
What are supermassive dark stars?
Supermassive dark stars are hypothetical, enormous, luminous clouds mostly made of hydrogen and helium. They differ from ordinary stars because their internal heat sources would include self-annihilating dark matter particles, a speculative form of matter that still eludes direct detection. In this framework, dark matter annihilation provides a steady heat source that counteracts gravitational collapse, allowing stars to grow to masses millions of times that of the Sun while remaining unusually puffy and bright. The idea, first proposed by Freese, Spolyar, and Gondolo, connects the birth of these stars to the dark matter halos that cradled the first galaxies and the seeds of supermassive black holes seen in the distant universe.
The four distant candidates and what the spectra show
The study analyzes four of the most distant objects ever observed by JWST: JADES-GS-z14-0, JADES-GS-z14-1, JADES-GS-z13-0, and JADES-GS-z11-0. In the new work, the team expanded their prior photometric assessments with JWST’s spectroscopy from the NIRSpec instrument. Three of the four targets are extremely compact, compatible with the glow of a dark star powering a surrounding nebula of ionized hydrogen and helium. One object, JADES-GS-z14-1, is unresolved and appears consistent with a point source—a hallmark often associated with a distant single star rather than a fully fledged galaxy.
Crucially, dark stars have a distinctive spectral fingerprint: an absorption feature at 1640 Angstroms caused by abundant singly ionized helium in their atmospheres. In the four objects analyzed, researchers report one clear hint of this 1640 Angstrom dip, a potential “smoking gun” signal for a dark star. Although the signal’s strength is modest (signal-to-noise around 2), its appearance in a candidate dark star makes it a notable, first-of-its-kind clue.
How ALMA observations fit into the picture
Complementary data from the Atacama Large Millimeter/submillimeter Array (ALMA) for JADES-GS-z14-0 reveal an oxygen emission line from surrounding nebular gas. If these spectral features are confirmed together, the object might not be a solitary dark star but rather a dark-star system embedded in a metal-rich environment. This could result from a merger between a dark-star-hosting halo and a nascent galaxy, or indicate that dark stars and ordinary stars could form in the same halo. Either scenario enriches our understanding of how the first luminous objects in the universe evolved and interacted with their surroundings.
Why this matters for dark matter and the dawn of galaxies
Confirming supermassive dark stars would open a direct observational avenue to probe the nature of dark matter, a major component of the cosmos whose particle properties remain unknown. Dark stars—powered by dark matter annihilation rather than nuclear fusion—could illuminate how the earliest massive structures formed and how supermassive black holes, powering the most distant quasars, came to be. The finding marks a potential turning point in the study of dark-matter-powered stars and their role as cosmic seeds in the first galaxies.
Limitations, caveats, and next steps
As with any nascent discovery, the authors emphasize caution. The four objects could also be interpreted as unusual galaxies or clusters of stars; their interpretations as dark stars remain consistent but not proven. Additional spectra, higher signal-to-noise observations, and broader statistical samples across JWST’s NIRSpec surveys will be essential to distinguish dark stars from other early-universe sources. Future work will aim to confirm the 1640 Angstrom absorption feature across multiple objects and to refine models of how dark matter heating would shape the spectra and morphology of these objects.
About the researchers and funding
The collaboration blends expertise from Colgate University, the University of Pennsylvania, UT Austin, and beyond, highlighting an international effort to test a bold idea about the universe’s first stars. The PNAS study builds on a 2023 analysis that identified initial dark-star candidates using JWST photometry and leverages new spectroscopic data to assess their nature. Funding for the research came from Colgate University, the Picker Institute, the U.S. Department of Energy, the Swedish Research Council, and several private foundations, underscoring broad support for exploring dark matter’s role in cosmic dawn.
Looking ahead
As JWST continues to deliver high-quality spectra of the earliest objects, the coming years could bring decisive tests of the supermassive dark star hypothesis. Whether these objects prove to be true dark stars, or galaxies with unusual properties, the work advances our quest to illuminate the dark—and to understand how the first luminous structures in the cosmos came to life.
