It has been suggested for a long time that dark matter would form a density spike around a black hole. However, no promising evidence has been observed so far to verify this theoretical suggestion. In a new paper, astronomers from the Education University of Hong Kong report the existence of dark matter density spikes around two nearby stellar-mass black holes: A0620-00 and XTE J1118+480.
“We selected two nearby black holes (A0620-00 and XTE J1118+480) in binary systems,” said Education University of Hong Kong astronomers Man Ho Chan and Chak Man Lee.
“Based on the orbits of the companion stars, observations indicate that their rates of orbital decay are approximately one millisecond (1 ms) per year, which is about 50 times greater than the theoretical estimation of about 0.02 ms annually.”
“To examine whether dark matter exists around black holes, we applied the ‘dark matter dynamical friction model’ to A0620-00 and XTE J1118+480 systems through computer simulations.”
The authors found that the fast orbital decay of the companion stars precisely matched the observational data.
Notably, this is indirect evidence that dark matter around black holes can generate significant dynamical friction, slowing down the orbital speed of the companion stars.
The findings, which verified a theoretical hypothesis formulated in the late 20th century, represent a breakthrough in dark matter research.
According to the hypothesis, dark matter close enough to black holes would be swallowed, leaving the remnants to be redistributed.
The process ends up forming a density spike around the black holes.
“Such a high density of dark matter would create dynamical friction to the companion star, in a way similar to drag force,” Dr. Chan said.
“This is the first-ever study to apply the ‘dynamical friction model’ in an effort to validate and prove the existence of dark matter surrounding black holes.”
“The study provides an important new direction for future…
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