What is dark matter?Why is it so important?And what does it have to do with black holes?These questions may bother many people who are interested in the universe. This article will uncover the answers to these questions and introduce you to a new scientific discovery that may be the first to uncover circumstantial evidence that there is a large amount of invisible dark matter around a black hole. This discovery, if confirmed, could represent a major breakthrough in dark matter research.
Dark matter is a mysterious substance that accounts for about 85% of all matter in the universe. However, astronomers are almost completely blind to it. This is because, unlike matter, which includes stars, planets, and everything else around us, dark matter does not interact with light and is invisible. Dark matter is like the best person in the universe, and its existence can only be perceived through its influence.
Fortunately, dark matter does have a gravitational effect, allowing researchers to infer the existence of dark matter by looking at its gravitational effect on ordinary matter. For example, dark matter can affect the rotational speed and shape of galaxies, as well as gravitational lensing effects between galaxy clusters. The gravitational effect of dark matter can also contribute to the formation and evolution of the structure of the universe.
The study of dark matter is essential to understanding the nature and origin of the universe. Dark matter not only makes up the main component of the universe, but is also closely related to another mysterious substance, dark energy. Dark energy is a force that accelerates the expansion of the universe, and it accounts for 95% of the remaining energy in the universe. Dark matter and dark energy together make up the dark side of the universe, and they are the greatest unsolved mystery in cosmology.
A black hole is an extreme celestial body that has a very large mass but is so small that its gravitational field is so strong that even light cannot escape. Black holes are created by star collapse or other high-energy events, and they can exist everywhere in the universe, from the center of the Milky Way, to distant clusters of galaxies. The study of black holes is of great significance for exploring the nature of gravity and the limits of physics.
What is the relationship between black holes and dark matter?One possible answer is that black holes can devour dark matter close enough to them. In this way, a "ring" of dark matter, or a "density peak", is formed around the black hole. This ring of dark matter creates an additional gravitational effect on the objects around the black hole, affecting their motion.
In the new study, a team of scientists from the Education University of Hong Kong used stars orbiting black holes in a binary star system as the objects. A binary star system is a system of celestial bodies consisting of two stars orbiting each other, which can be two ordinary stars or a star and a black hole. These binary star systems can be observed in different ways, such as through the light, rays, or gravitational waves they emit.
The team observed a binary star system called XTE J1118+480, which is located about 6,000 light-years from Earth in the constellation Cygnus. This binary star system consists of a black hole and a star, and their orbital period is about 41 hour. The team used the Kepler Space Telescope of the National Aeronautics and Space Administration (NASA) to make continuous observations of the binary star system for four years.
The team found that the orbits of the two stars decay or slow slightly by about 1 millisecond per year while moving around their associated black holes. The team concluded that the deceleration is the result of the dark matter surrounding the black hole, which creates significant friction and drag on the star as it whips around their high-quality partners. It's like a black hole with an invisible "slime" around it that slows down the star.
Using computer simulations of black hole systems, the team applied a widely adopted model in cosmology called the Dark Matter Dynamics Friction Model, which measures the specific momentum loss of an object interacting with dark matter. The simulation results show that the observed orbital decay rate is consistent with the friction model. The observed rate of orbital decay is about 50 per year compared to binary systems lacking dark matterThe theoretical estimate of orbital decay of 0 milliseconds is about 02 times higher.
This is the first-ever study to apply a 'dynamic friction model' to verify and prove the existence of dark matter around a black hole," said Chan Man-ho, team leader and Associate Professor of the Department of Science and Environmental Studies at EdUHK, in a statement. Chen Wenhao is a well-known cosmologist who worked on China's "Wukong" dark matter particle detection satellite project, the world's first satellite dedicated to dark matter.