Hypothetical celestial bodies dubbed “dark dwarfs,” theorized to be powered by dark matter, could have originated from the cooling processes of brown dwarfs, according to a collaborative research endeavor by astronomers from Durham University, the University of Hawai’i, and the University of Liverpool.
An AI impression of a dark dwarf. Image credit: Gemini AI.
Our current comprehension of dark matter acknowledges its existence and behavioral patterns, yet its fundamental composition remains elusive.
Over the preceding half-century, numerous theoretical frameworks have been put forth, but none have yet garnered sufficient empirical validation to achieve widespread acceptance.
Among the most prominent contenders for the identity of dark matter are Weakly Interacting Massive Particles (WIMPs). These are exceptionally massive particles that exhibit minimal interaction with baryonic matter; they traverse substances undetected, emit no discernible radiation, and are unaffected by electromagnetic forces, revealing their presence solely through their gravitational influence.
The existence of dark dwarfs is predicated on this particular classification of dark matter.
Professor Jeremy Sakstein of the University of Hawai’i posited, “Given that dark matter exerts gravitational forces, it is plausible for it to be captured by stellar bodies and accumulate within them.”
“Should this phenomenon occur, it might also engage in self-interaction, leading to annihilation events that generate heat within the star.”
The luminosity of conventional stars is a direct consequence of nuclear fusion processes occurring within their central regions, which yield substantial quantities of thermal energy and power.
Fusion is initiated when a star possesses sufficient mass, causing gravitational forces to compress matter towards its core with such immense pressure that it triggers reactions among atomic nuclei.
This intricate process liberates an prodigious amount of energy, which we perceive as light. Dark dwarfs, too, radiate light, but their luminescence is not attributed to nuclear fusion.
Professor Sakstein elaborated, “Dark dwarfs represent objects of exceedingly low mass, approximately 8% of the Sun’s mass.”
“Such a diminutive mass is insufficient to instigate nuclear fusion reactions.”
“Consequently, these entities—despite being remarkably prevalent throughout the cosmos—typically emit only a faint glow and are recognized by the scientific community as brown dwarfs.
However, if brown dwarfs are situated in environments with a high concentration of dark matter, such as the galactic center of the Milky Way, they can undergo a metamorphosis.
Professor Sakstein further explained, “These celestial bodies assimilate dark matter, facilitating their transformation into dark dwarfs.”
“An increased abundance of ambient dark matter allows for greater capture rates.”
“Furthermore, as more dark matter accumulates internally, the energy output from its annihilation escalates.”
“For dark dwarfs to materialize, dark matter must consist of WIMPs or any other heavy particle exhibiting self-interaction with sufficient intensity to produce detectable matter.”
“Alternative dark matter candidates that have been proposed, such as axions—which are ultra-light particles with wave-like properties—or sterile neutrinos, are all too insubstantial to generate the anticipated effects within these objects.”
“Only massive particles, capable of mutual interaction and subsequent annihilation into observable energy, could serve as the power source for a dark dwarf.”
Nevertheless, the theoretical framework supporting this hypothesis would hold limited consequence without a tangible method for identifying a dark dwarf.
To address this, Professor Sakstein and his associates have put forward a distinctive diagnostic signature.
Professor Sakstein remarked, “While several potential indicators were considered, we propose lithium-7, as it presents a truly unique characteristic.”
“Lithium-7 is exceptionally volatile and is rapidly depleted in conventional stellar bodies.”
“Therefore, if one were to discover an object resembling a dark dwarf, detecting the presence of this lithium would be crucial, given its absence would be expected in a brown dwarf or an analogous celestial object.”
The scientific discourse authored by the research team is published in the Journal of Cosmology and Astroparticle Physics.
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Djuna Croon et al. 2025. Dark dwarfs: dark matter-powered sub-stellar objects awaiting discovery at the Galactic center. JCAP 07: 019; doi: 10.1088/1475-7516/2025/07/019
