Cosmic data shows dark matter is not made of massive black holes
Researchers used early universe light to limit the mass of hypothetical dark matter black holes to 100 billion solar masses.
By Javier Cabrera ·
A team of physicists has determined that black holes larger than entire galaxies do not make up a large portion of the universe's missing mass. The study places a strict upper limit on the size of these hypothetical objects, ruling out any black hole with more than 100 billion times the mass of the sun as a primary component of dark matter.
The research focuses on a class of objects the authors describe as stupendously large. These theoretical black holes would outweigh whole galaxies if they exceeded roughly 1 million billion to 10 million billion solar masses. No such object has been detected to date, and the largest confirmed black hole currently weighs about 36 billion solar masses.
To test whether these massive objects exist in hidden quantities, the team analyzed the cosmic microwave background. This radiation is the light released from the early universe when the hot plasma that filled the cosmos cooled and atoms formed. The light provides a snapshot of the universe as it was 380,000 years after the Big Bang.
Christopher Gerlach, a theoretical physicist at the Mainz Institute for Theoretical Physics in Germany, explained that if dark matter were concentrated in a few gigantic objects, the universe would appear grainy on large scales. Instead, the data shows a smooth distribution. Antonio Iovino, a theoretical physicist at New York University Abu Dhabi, noted that the background's temperature varies by only about one part in 100,000 from place to place.
The lack of expected graininess in the data indicates that the massive black holes are not a major constituent of dark matter. Nicholas Leister, also of the Mainz Institute, stated that the results confirm these objects cannot account for a significant share of the mystery substance. Dark matter is estimated to make up about five-sixths of all matter in the cosmos and is believed to provide the gravitational pull that holds galaxies together.
The authors clarified that the findings do not prove these enormous black holes cannot exist, only that they are not a primary source of dark matter. The team is now examining whether smaller black holes, roughly the size of asteroids, could still be a major component.
The findings will be published in the journal Physical Review Letters on October 26.
Source: Space.com
