Dark matter and black holes are some of the most mysterious things in the Universe, so a connection between the two is absolutely thrilling. In a new study of elliptical galaxies led by Dr Akos Bogdan of the Harvard-Smithsonian Center for Astrophysics has revealed a surprising link between galaxies’ dark matter halos and their central black holes.
There is a massive black hole on the center of most galaxies, weighing millions or billions of times heavier than our Sun. Even though many scientists offered theories about the origins of black holes, we still don’t know for sure why and how they appear. One thing that we know for sure is that the larger the galaxy, the bigger its black hole… but the why was never answered. What is their connection?
In the recent study of a cluster of stars (elliptical galaxies), astronomers suggest that the missing piece of the explanation might be dark matter – the key ingredient which comprises most of the Universe’s mass. Akos Bogdan explains that they found a peculiar connection between the measure of dark matter in a galaxy and the size of its black hole, even if the two factors are measured based on two different scales.
The universe shows a ratio of dark matter to ordinary matter that is 6:1. Dark matter, which cannot be seen unlike ordinary matter, is only detectable via its suction force. It is the very glue that keeps galaxies from exploding into chaotic smithereens.
On the edges of each galaxy is present this mysterious dark matter which weighs as much as gazillions of stars put together and spreads out for many light years till the farthest recesses of the universe.
Scientists know this much, after the study of 3000 elliptical galaxies, that via the motion of these galaxies the weight of the black holes was discovered. The weight of the surrounding dark matter halo and the central black hole were correlated. And this link was stronger than the previous one between the galaxy and the black hole.
This connection is likely to be related to how elliptical galaxies grow. An elliptical galaxy is formed when smaller galaxies merge, their stars and dark matter mingling and mixing together. Because the dark matter outweighs everything else, it molds the newly formed elliptical galaxy and guides the growth of the central black hole.
“In effect, the act of merging creates a gravitational blueprint that the galaxy, the stars and the black hole will follow in order to build themselves,” explains Bogdan.
This study, which was conducted on the Teacup Glaaxy, might also provide information about black hole formation and development in galaxies – something on which we have very little information.