Two stars were observed to decelerate down in their paths around black
holes, and researchers came to the conclusion that this was due to the
"drag" produced by dark matter.
For the first time, researchers may have found indirect proof that black
holes are surrounded by significant quantities of unseen dark matter. If the
finding is verified, it could mark a significant advance in the study of
dark matter.
Nearly all of the dark matter in the cosmos, which makes up about 85% of
all matter, is undetectable to astronomers. This is due to the fact that
dark matter is invisible and does not interact with light like the matter
that makes up stars, planets, and everything else in our universe.
Fortunately, dark matter does interact gravitationally, allowing scientists
to deduce its existence by observing its gravitational effects on "proxies"
made of conventional matter. In the recent study, a group of researchers
from The Education University of Hong Kong (EdUHK) used these stars as
models for black holes in paired systems.
The team observed the paths of two stars, A0620-00 and XTE J1118+480, as
they rotated around their partner black holes, decaying, or slightly
slowing, by about 1 millisecond per year. The researchers came to the
conclusion that the black holes' surrounding dark matter caused the stars to
slow down as they whirled around their massive companions, creating
considerable drag and friction.
The researchers applied a widely accepted cosmological theory dubbed the
dark matter dynamical friction model to computer models of the black hole
systems. This theory forecasts a particular loss of momentum on objects
interacting gravitationally with dark matter. The results of the
calculations showed that the friction model's forecasts were in line with
the measured rates of orbital decay. In comparison to the theoretical
prediction of 0.02 milliseconds of orbital decay per year for paired systems
without dark matter, the measured rate of orbital decay is roughly 50 times
higher.
Chan Man Ho, the team leader and an associate professor in the Department
of Science and Environmental Studies at EdUHK, stated in a statement that
this is the first study to use the "dynamical friction model" in an effort
to validate and prove the existence of dark matter surrounding black
holes.
The team's findings, which were published Jan. 30 in The Astrophysical Journal Letters, support the long-held cosmological
hypothesis that black holes can consume dark matter if it approaches them
closely enough. This causes the dark matter to be redistributed in the area
encircling the black holes, resulting in a "density spike" there that can
slightly affect the trajectory of objects nearby.
Chan stated that prior studies of dark matter in the vicinity of black
holes have depended on gravitational waves or the release of high-energy
light in the form of gamma rays. These emissions come from the uncommon
cosmic occurrence of black holes colliding and merging, which can take a
long time for scientists to gather enough evidence for.
This work offers researchers a fresh perspective on the distribution of
dark matter around black holes, which may enable them to be more proactive
in their quest. The EdUHK team plans to look for comparable black hole
binary systems in the future to investigate.
According to Chan, "the study offers a crucial new direction for future
dark matter research." There are at least 18 binary systems that are similar
to our study subjects in the Milky Way Galaxy alone, and they can offer
valuable knowledge that can help solve the mystery of dark matter.
