Astrophysicists solve the mystery of ’empty sky’ gamma rays

Star-forming galaxies are responsible for creating gamma rays so far not associated with a known origin, confirms a study by the ANU (Australian National University).

Lead author Dr Matt Roth of the ANU Research School of Astronomy and Astrophysics said it was not clear until now what created gamma rays, one of the most energetic forms of light in the Universe, which appear in patches. seemingly ’empty’ from heaven.

The discovery, which is published in Nature, could offer clues to help astronomers solve other mysteries of the Universe, such as what kinds of particles make up Dark Matter, one of the holy grails of astrophysics.

“It is a significant milestone to finally discover the origins of this gamma ray emission, solving a mystery of the Universe that astronomers have been trying to unravel since the 1960s,” Roth said in a statement.

“There are two obvious sources that produce large amounts of gamma rays that are seen in the Universe. One when gas falls into supermassive black holes at the center of all galaxies, called the active galactic nucleus (AGN), and the another associated with the formation of stars in the disks of galaxies.

“We modeled the gamma ray emission from all galaxies in the Universe and compared our results with predictions from other sources and found that it is the star-forming galaxies that produce most of this diffuse gamma ray radiation and not the AGN process. “.

The ANU researchers were able to identify what created these mysterious gamma rays after gaining a better understanding of how cosmic rays, particles that travel at speeds very close to the speed of light, move through gas between stars. Cosmic rays are important because they create large amounts of gamma ray emission in star-forming galaxies when they collide with interstellar gas.

Data from NASA’s Hubble Space Telescope and the Fermi Gamma-ray Space Telescope were a key resource used to discover the unknown origins of gamma rays. The researchers analyzed information about many galaxies, such as their star formation rates, total masses, physical size, and distances from Earth.

“Our model can also be used to make predictions of radio emission, electromagnetic radiation that has a frequency similar to that of a car radio, from star-forming galaxies, which could help researchers understand more about the structure. internal galaxies, “Roth said.

“We are currently looking to produce gamma-ray sky maps that can be used to inform upcoming gamma-ray observations from next-generation telescopes. This includes the Cherenkov telescope array, in which Australia is involved.