Has Dark Matter Altered the Universe Beyond Recognition?

0158_ir In the early Universe clumps of dark matter are thought to have attracted gas, which then coalesced into stars that eventually formed the galaxies we see today. In their efforts to understand galaxy formation and evolution, astronomers have spent a good deal of time attempting to simulate the build up of dark matter.

Two astronomers based at the National Autonomous University of Mexico (UNAM) have found a hint of the way dark matter behaves near black holes.

The UNAM astronomers, Dr. Xavier Hernandez and Dr. William Lee, calculated the way in which the black holes millions and billions of times the mass of the Sun found at the center of galaxies absorb dark matter.

The researchers modelled the way in which the dark matter is absorbed by black holes and found that the rate at which this happens is very sensitive to the amount of dark matter found in the black holes’ vicinity. If this concentration were larger than a critical density of seven Suns of matter spread over each cubic light year of space, the black hole mass would increase rapidly, hence engulfing such large amounts of dark matter, that soon the entire galaxy would be altered beyond recognition.

Dr. Hernandez explains, “Over the billions of years since galaxies formed, such runaway absorption of dark matter in black holes would have altered the population of galaxies away from what we actually observe.”

Their work therefore suggests that the density of dark matter in the centers of galaxies tends to a constant value. By comparing their observations to what current models of the evolution of the Universe predict, Hernandez and Lee conclude that it is probably necessary to change some of the assumptions that underpin these models – dark matter may not behave in the way scientists thought it did.

Casey Kazan via materials provided by Royal Astronomical Society.

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