Dark matter does not emit or reflect light, nor does it interact with electromagnetic forces, making it difficult to detect, but it has been indirectly identified around black holes.
A research team from EdUHK (The Education University of Hong Kong) selected two nearby black holes (A0620-00 and XTE J1118+480) as research subjects, both considered to be binary systems. That is, each of the black holes has a companion star that orbits it. Based on the orbits of the companion stars, observations indicate that their orbital decay rates are about one millisecond (1 ms) per year, which is about 50 times greater than the theoretical estimate of about 0.02 ms per year. anus.
A research team from EdUHK (The Education University of Hong Kong) selected two nearby black holes (A0620-00 and XTE J1118+480) as research subjects, both considered to be binary systems. That is, each of the black holes has a companion star that orbits it. Based on the orbits of the companion stars, observations indicate that their orbital decay rates are about one millisecond (1 ms) per year, which is about 50 times greater than the theoretical estimate of about 0.02 ms per year. anus.
To examine whether dark matter exists around black holes, the EdUHK team applied the “dynamic friction model of dark matter”, a widely accepted theory in academia, to the two chosen binary systems, through simulations by computer. The team found that the rapid orbital decay of the companion stars precisely matches the observed data.
In particular, this is indirect evidence that dark matter around black holes can generate significant dynamic drag, which slows down the orbital velocity of companion stars.
The findings, which verified a theoretical hypothesis formulated at the end of the 20th century, represent for the authors a great advance in the investigation of dark matter. Dark matter close enough to black holes is hypothesized to be swallowed, leaving the debris to redistribute. The process ends up forming a “density peak” around the black holes.
Dr. Chan Man-ho, Associate Professor in the Department of Science and Environmental Studies and Principal Investigator, explained that such a high density of dark matter would create dynamic friction with the companion star, similar to the drag force.
“This is the first study to apply the ‘dynamic friction model’ in an effort to validate and prove the existence of dark matter surrounding black holes,” he said. “The study provides an important new direction for future dark matter research.”
Dr. Chan further mentioned that previous studies, which relied mainly on gamma ray and gravitational wave detection to examine the presence of dark matter, relied on the occurrence of rare events, such as the merging of two black holes. According to him, that could require a long wait time for astronomers.
However, the novel approach taken by the EdUHK team will no longer be constrained by these limitations. He added: “In the Milky Way galaxy alone, there are at least 18 binary systems similar to our research subjects, which may provide valuable information to help unravel the mystery of dark matter.”
The results of the study are published in The Astrophysical Journal Letters.
https://iopscience.iop.org/article/10.3847/2041-8213/acaafa
.