The Universe is full of mysteries. Scientists and astronomers still cannot account for all of the high-energy light and particles in the Universe. While scientists can trace the origin of some of the gamma radiation and neutrinos, the origin of a majority of them is still a mystery.
Recently, a team of researchers led by astronomer Shigeo Kimura of Tohoku University in Japan have explained the source of some of these high-energy particles. They can trace the source of some of Gamma radiation and neutrinos to the supermassive black holes that are nearly dormant, and at the same time, not entirely active. These black holes account for the excess of soft gamma radiation in the kiloelectronvolt to Gigaelectronvolt range. Their research has been published in Nature Communications.
Gamma radiations are the most energetic form of light in the Universe, with the smallest wavelength in the electromagnetic spectrum. Their energies are in the teraelectronvolt range.
Also referred to as the ghost particles, the neutrinos are nearly massless objects and barely interact with anything in the Universe. Due to this nature, detecting neutrinos is very complex. They, too, have been detected with very high energies.
A cosmic accelerator, such as supernova remnants or active black holes, is required to generate such high energies as seen in gamma radiation and neutrinos. While such accelerators account for the high energy light and particles, they cannot account for the gamma-ray excess in lower ‘soft’ energies and neutrino excess.
Immense gravitation force acting on the materials in the accretion disk of a supermassive black hole generates a wide range of electromagnetic radiations, including gamma rays. Some of these materials are launched into space from the poles, almost close to the speed of light.
Every galaxy in the Universe is thought to have a supermassive black hole at its center. However, not every such black hole is active. According to Kimura and his team, such not-so-active black holes produce soft gamma-rays in the megaelectronvolt range. Based on the team’s calculations, even though these black holes are not so active, they can still have plasma up to billions of degrees, producing these soft gamma rays.
Protons accelerated by the plasma when interacts with radiation and matter can generate neutrinos. This explains the neutrino excess observed in the Universe.
The study is just a hypothesis for now. However, it takes us closer to solving the mystery of these high-energy radiations in the Universe. Astronomers can use this vital information for their future observations.