Primordial Black Holes May Have Created Dark Matter
Astronomers have reportedly started to think that dark matter could be made up of primordial black holes. According to Alexander Kashlinsky, a researcher from the NASA Goddard Space Flight Center, primeval black holes that formed right after the Big Bang can be the explanation for the gravitational waves or ripples in space-time observed by the Laser Interferometer Gravitational-Wave Observatory (LIGO) in 2015. In fact, as per reports, previous observations of the early Universe also give such indications.
If Kashlinsky's theory is right then it would imply that dark matter is made up of primordial black holes, and thereby vast spheres of black holes may surround all galaxies. The theory suggests that a young Universe may have evolved in a manner different to what scientists currently believe. According to Kashlinsky's paper published in The Astrophysical Journal Letters, during the initial 500 million years of the Universe's evolution, dark matter disintegrated into clusters called halos. Subsequently, the halos provided the gravitational seeds that would in the future lead to the accumulation of matter that would create the first stars and galaxies.
However, if the dark matter was made up of primordial black holes then it would have led to the creation of numerous more halos. Such a phenomenon could explain the presence of the excess cosmic infrared background and cosmic X-ray background that Kashlinsky and his team observed several years ago with the help of the Spitzer Space Telescope in 2005 and NASA's Chandra X-ray Observatory in 2013 respectively. "And the only sources that would be able to produce this in both infrared and X-rays are black holes," Alexander Kashlinsky said. "It never crossed my mind at that time that these could be primordial black holes".
Incidentally, primordial black holes did not originate from the collapse of a dead star, the mechanism that generated the relatively later black holes in the Universe's history. Primordial black holes could have occasionally come nearer and started orbiting each other, like a binary system. Over the course of time, two black holes orbiting each other would spiral in conjunction and radiate gravitational waves in the process, such as the one discovered by LIGO. As per reports, more in depth analysis is needed at the moment to understand whether black holes are indeed primordial, or belong to the relatively later part of the Universe's history.