Study: Tiny black holes fed by dark matter could grow instead of evaporating inside stars

By the Everything Space news desk · 05 Sep 2026 · written from the sources below

Image: Phys.org

New calculations suggest dark matter-fed black holes as light as 40 tons could survive and grow inside compact stars, offering a new way to constrain dark matter properties.

A new theoretical study explores how extremely small black holes could form inside neutron stars and white dwarfs if these stars capture a hypothetical type of heavy dark matter particle. Over time, such particles could build up in a star's core, collapse under their own gravity, and form a tiny black hole embedded within the host star.

Normally, black holes this small would be expected to evaporate almost immediately through Hawking radiation, the quantum process by which black holes lose mass over time. But the researchers calculated that if the black hole continues absorbing ordinary stellar matter and fresh dark matter from its surroundings, it can gain mass faster than it loses it, allowing it to survive and grow rather than vanish.

The team identified a critical starting mass above which growth wins out over evaporation. Without factoring in ongoing dark matter feeding, this threshold works out to roughly 10 billion kilograms in typical compact stars. But when continuous dark matter accretion is included, the required starting mass falls dramatically depending on environment: about 10,000 metric tons for a white dwarf in a typical galactic region, dropping to just 40 metric tons in the dark matter-dense galactic bulge, and around 600 metric tons for a neutron star in that same crowded region.

Importantly, the researchers stress this does not mean a 40-ton black hole has actually been detected. It means that under the right conditions, a black hole starting at that tiny mass could theoretically avoid evaporating and instead grow steadily, eventually consuming its host star and turning it into a full black hole.

The findings also work as a constraint in reverse. Because millisecond pulsars and white dwarfs are known to survive for billions of years, their continued existence limits how massive and interactive this hypothetical dark matter could realistically be. In effect, long-lived stars act as natural experiments testing dark matter properties over cosmic timescales.

The research, accounting for both quantum and classical descriptions of matter falling into these minuscule black holes, appears in Physical Review D.

Written in Everything Space’s own words by our news-desk model from the sources above, and checked against them in code: every number in this report appears in its sources, and no sentence is copied from them.