University of California, Berkeley | 2018 Oct 02
For one brief shining moment after the 2015 detection of gravitational waves from colliding black holes, astronomers held out hope that the universe’s mysterious dark matter might consist of a plenitude of black holes sprinkled throughout the universe.
- A supernova (bright spot at lower left) and its host galaxy (upper center), as they would appear if gravitationally lensed by an intervening black hole (center). The gravitational field of the black hole distorts and magnifies the image and makes both the galaxy and the supernova shine brighter. Gravitationally magnified supernovas would occur rather frequently if black holes were the dominant form of matter in the universe. The lack of such findings can be used to set limits on the mass and abundance of black holes. (Credit: Miguel Zumalacárregui)
UC Berkeley physicists have dashed those hopes
Based on a statistical analysis of 740 of the brightest supernovas discovered as of 2014, and the fact that none of them appear to be magnified or brightened by hidden black hole “gravitational lenses,” the researchers concluded that primordial black holes can make up no more than about 40 percent of the dark matter in the universe. Primordial black holes could only have been created within the first milliseconds of the Big Bang as regions of the universe with a concentrated mass tens or hundreds of times that of the sun collapsed into objects a hundred kilometers across.
The results suggest that none of the universe’s dark matter consists of heavy black holes, or any similar object, including massive compact halo objects, so-called MACHOs.
Dark matter is one of astronomy’s most embarrassing conundrums: despite comprising 84.5 percent of the matter in the universe, no one can find it. Proposed dark matter candidates span nearly 90 orders of magnitude in mass, from ultralight particles like axions to MACHOs.
Several theorists have proposed scenarios in which there are multiple types of dark matter. But if dark matter consists of several unrelated components, each would require a different explanation for its origin, which makes the models very complex. ...
Supernova Study Dampens Dark Matter Theory
Physics Viewpoint | American Physical Society | 2018 Oct 01
Limits on Stellar-Mass Compact Objects as Dark Matter
from Gravitational Lensing of Type Ia Supernovae ~ Miguel Zumalacarregui, Uros Seljak