Our planet is constantly bombarded by high-energy particles that scientists say make up cosmic radiation.
It is actually quite impossible to directly identify the sources responsible for the production of cosmic rays, and so it has remained one of the greatest scientific mysteries for more than a century.
Now, astronomers running the High Energy Stereoscopic System or H.E.S.S. observatory in Namibia believe they may have identified the source of the cosmic rays for the first time ever. In fact, the source can accelerate cosmic rays to energies that are 100 times bigger than those achieved at the Large Hadron Collider or CERN. So where is the source?
"The most plausible 'engine' for this cosmic ray acceleration is the super-massive black hole right at the heart of our galaxy," said Gavin Rowell of University of Adelaide, one of the study researchers.
Indeed, the center of the Milky Way is home to objects capable of creating high-energy cosmic rays, including a pulsar wind nebula, a supernova remnant and a compact cluster of massive stars. Out of all these objects, the super-massive black hole called Sgr A* is the most possible source.
Cosmic rays interact with gas and light, producing gamma rays that travel in straight lines, get un-deflected by magnetic fields and act as "tracers." The H.E.S.S. telescopes have provided direct indications over the past decade of a very powerful point source of gamma rays in the center of the galaxy.
H.E.S.S. measured the gamma ray emission in the cosmic region. From there scientists were able to infer the spectrum of protons that have been accelerated by the super-massive black hole. Sgr A*, which has a mass of 4 to 5 million suns, is very likely accelerating cosmic rays that consequently get "blasted" to Earth.
All this violent activity makes this cosmic region one of the brightest objects in the sky for astronomers to study, from radio waves up to high-energy gamma rays.
Lastly, the scientists argue that if Sgr A* was more active in the past, then it could truly be the source of the bulk of cosmic rays that are observed today from our planet.
The findings of the study are featured in the journal Nature.