Giant worlds beyond the Solar System could be the probe we need to figure out how dark matter manifests in the Universe.
According to a new study, one particular dark matter model could see the mysterious mass accumulating in the cores of giant planets, collapsing into tiny black holes destined to consume the surrounding material over time.
If we can find evidence of the resulting planet-mass object, it might validate the existence of a hefty form of dark matter that doesn’t destroy itself.
“If the dark matter particles are heavy enough and don’t annihilate, they may eventually collapse into a tiny black hole,” says astrophysicist Mehrdad Phoroutan-Mehr of the University of California, Riverside.
“This black hole could then grow and consume the entire planet, turning it into a black hole with the same mass as the original planet. This outcome is only possible under the superheavy non-annihilating dark matter model.”
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Dark matter appears to permeate the Universe, accounting for some 85 percent of the matter throughout. We know that it is there because there is far more gravity than can be accounted for based on normal matter; however, we have, as yet, been able to detect dark matter directly.
That means we don’t know what dark matter is… but scientists can try to narrow it down. There are a number of leading candidates, and they all behave in slightly different ways.
Figuring out what these behaviors are and how they would appear in the Universe could help scientists devise experiments to better identify dark matter’s more obscure features.
This brings us to dark matter accumulating in the cores of giant exoplanets. According to a paper by Phoroutan-Mehr and his colleague, astrophysicist Tara Fetherolf of UC Riverside, heavy dark matter that doesn’t self-annihilate – that is, dark matter particles that are not also their own antiparticles – could be captured by giant worlds, lose energy, and sink towards the core where they concentrate.
Eventually, these accumulations could grow dense enough to collapse under gravity, forming tiny black holes.
“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,” he explains.
“These results show how exoplanet surveys could be used to hunt for superheavy dark matter particles, especially in regions hypothesized to be rich in dark matter like our Milky Way’s galactic center.”
There are a few challenges to finding evidence of this process, however. The biggest is that we simply don’t have technology sensitive enough for the job. A black hole with the mass of Jupiter, for example, would be just 5.6 meters (18.4 feet) across.
Humanity is, however, refining space observation technology all the time. It’s not entirely unfeasible that one day, instruments will emerge that are powerful enough to detect a planet-mass black hole.
“If astronomers were to discover a population of planet-sized black holes, it could offer strong evidence in favor of the superheavy non-annihilating dark matter model,” Phoroutan-Mehr says. “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.”
The findings have been published in Physical Review D.
