Scientists have suggested that dark matter, potentially consisting of axions, could cause vibrations in space-time by borrowing energy from black holes. Axions, proposed decades ago to explain certain features of strong interactions, have yet to be experimentally found. Nevertheless, their elusive nature makes them promising candidates for dark matter, given their minimal interaction with ordinary matter.
If dark matter does indeed comprise axions or particles related to them, it possesses peculiar attributes. These particles could be incredibly lightweight – billions of times less massive than an electron. Such a minuscule mass implies that they may exhibit more wave-like behavior than particle-like characteristics, particularly on a cosmic scale.
One potential manifestation of this wave nature could be observed in the vicinity of spinning black holes. Through a process called super-radiance, dark matter can acquire angular momentum from the black hole, preventing it from crossing the event horizon. Instead, axions may form an imperceptible shell around the black hole.
As the black hole depletes all available energy, the dark matter starts to dissipate, leading to the vibration of space-time. These fluctuations generate robust gravitational waves distinct from those generated during black hole mergers. Despite their lower intensity, modern and planned gravitational-wave observatories could detect these waves due to their unique frequency.
A recent study by a group of scientists posits that black holes could serve as an ideal testing ground for one of the dark matter candidates – axions. The findings of their research are outlined in an article published in October on the arXiv preprint database.
The researchers suggest meticulously analyzing existing data for signs of such phenomena and adjusting future experiments to more precisely hunt for these signals. Even in the absence of confirmation, this approach can enhance our understanding of dark matter and refine our methodologies for studying it.