Dark matter, the mysterious matter that scientists have yet to be able to observe, makes up most of the matter in our galaxy by a factor of 6 to 1. According to the author of a new study, it also governs the growth of super-massive black holes.

Every massive galaxy has a black hole at its center, and is surrounded on the exterior by a halo of dark matter that weighs as much as a trillion suns and extends for hundreds of thousands of light years.

The more massive the galaxy, the bigger the black hole at its center. Because the black hole is millions of times smaller than it’s galaxy it seems counter-intuitive that the size of the galaxy should determine the size of the black hole and according to a new study there is no relationship. Instead it is dark matter that determines the size of the black hole.

“There seems to be a mysterious link between the amount of dark matter a galaxy holds and the size of its central black hole, even though the two operate on vastly different scales,” said lead author Akos Bogdan of the Harvard-Smithsonian Center for Astrophysics (CfA) in a statement.

The research was designed to settle a dispute in astrophysics. It was originally thought that the total mass of stars in elliptical galaxies determined the mass of the black hole. More recent studies suggested that it was the dark matter halo surrounding the galaxy that determined the mass of black holes. Both of these theories still have their proponents.

If you look out the window of your house and see trees bending and swaying and leaves and bits of debris blowing by you know it is windy, even though you cannot see the wind. Dark matter works something like that. It cannot be seen but scientists know it is there because of the gravitational effect it has on objects.

To investigate the link the team used data from the Sloan Digital Sky Survey and the ROSAT X-ray satellite’s all-sky survey to study 3,000 football-shaped elliptical galaxies. Bogan, along with Andy Goulding of Princeton University, used the motion of stars to determine the weight of the galaxies’ central black holes. Next they used x-ray measurements of hot gas surrounding the galaxies to determine the weight of the dark matter halo.

Although scientists cannot determine the mass of the dark matter itself, they know that the hot gas it can hold onto.

The researchers found a clear and consistent relationship between the dark matter halo and the mass of the central black hole. The relationship was much more distinct than that between the galaxy’s stars and the black hole.

The team thinks it likely that this is related to how elliptical galaxies grow and form. When two small galaxies merge, the stars and dark matter they contain mix together. The dark matter which makes up the bulk of the mass of the two galaxies, molds the newly formed elliptical galaxy and the growth of the black hole at its core.

“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.

The paper based on Bogdan and Goulding has been accepted for publication in the Astrophysical Journal.