Dark matter could be gathering inside exoplanets over vast periods of time, potentially creating black holes that devour these worlds from within. This striking concept, proposed by researchers, suggests that extrasolar planets, or “exoplanets,” could be used to study the mystery of dark matter. In this new model, superheavy dark matter particles could become trapped by exoplanets, losing energy and drifting toward the planet’s core.
Once there, these particles accumulate until they collapse, forming a black hole. This black hole then ravenously eats its way out of its host planet. However, this dark matter black hole theory doesn’t work with all models of dark matter.
For instance, if the dark matter particles behave similarly to electrons meeting their antiparticles (positrons), then it wouldn’t be possible for them to gather in the quantities needed to collapse and form a black hole. The mass of the dark matter particles is another important factor. The particles need to have very large masses, which rules out one of the most highly favored dark matter candidates – a hypothetical particle with a very small mass.
“If the dark matter particles are heavy enough and don’t annihilate, they may eventually collapse into a tiny black hole,” says University of California, Riverside researcher Mehrdad Phoroutan-Mehr. The lightest black holes currently known are stellar mass black holes, which have masses between around three and one hundred times that of the sun.
Dark matter accumulation in exoplanets
These black holes are born when massive stars run out of nuclear fuel, leading to a supernova explosion that ejects the stars’ outer layers while their cores collapse. The Tolman–Oppenheimer–Volkoff (TOV) limit distinguishes between stellar cores that create black holes and those that form neutron stars. The TOV limit suggests that after ejecting most of its matter, a stellar core needs to have at least 2.2 to 2.9 times the mass of the sun to form a black hole.
The team proposes that this dark matter accumulation process could occur within planets that have masses similar to Jupiter, which has around 0.001 times the mass of the sun. “In gaseous exoplanets of various sizes, temperatures, and densities, black holes could form on observable timescales, potentially even generating multiple black holes in a single exoplanet’s lifetime,” Phoroutan-Mehr said. These results suggest that exoplanet surveys could be valuable for hunting superheavy dark matter particles, particularly in regions hypothesized to be rich in dark matter, like the core of the Milky Way.
Discovering a black hole with the mass of a planet would be a major breakthrough and offer strong evidence in favor of the superheavy non-annihilating dark matter model. This theory, combined with the growing catalog of over 5,000 worlds beyond our solar system, means these planets can be added to the celestial bodies suggested as dark matter probes. For instance, certain dark matter candidates could become trapped in neutron stars, gathering and gradually annihilating each other, thus heating these stellar remnants.
“As we continue to collect more data and examine individual planets in more detail, exoplanets may offer crucial insights into the nature of dark matter,” Phoroutan-Mehr concluded. The team’s research was published on Wednesday (August 20) in the journal Physical Review D.
