The gravitational center of most objects and clusters in the universe are the place where the most massive and high energy interactions take place. For the solar system, the Sun’s core is hot and energetic. For star clusters, central regions host the most massive and brightest stars. For galaxy clusters, the most massive galaxies in the universe are seen in the center. And for individual galaxies, the Milky Way included, the core is where the fun happens.
In the core of our galaxy, there are many massive and powerful objects, not limited to a supermassive star cluster, pulsars, supernova remnants, and of course, our supermassive black hole Sag A*. With so much matter and energy in one place, it has to radiate away somehow, as energy moves from higher to lower densities, by the second law of thermodynamics. This generally happens through the release of high energy gamma rays and cosmic rays. Cosmic rays are protons, neutrons, and electrons that are accelerated to near the speed of light. They are everywhere in the universe, constantly bombarding the Earth. You can see their effect in any RAW astrophysical image, as they brightly dot the field of view.
We know that there are sources in the galaxy that produce cosmic rays with energies of 100 Tev, or 100,000,000,000,000 electron volts. That’s pretty powerful, but theoretical calculations suggest we should have sources in our galaxy that can produce up to 10 times that, around 1 Pev (peta-electron-volt). By observing the energies of cosmic rays coming from the galactic center over the last decade, astronomers have confirmed that such a source exists.
We know it’s there, deep within the galactic core, but we don’t know what the specific source is, as the shroud of gas and dust obscures the region from view.
The cool part of this is that a 1 Pev cosmic ray is over 100 times as energetic as particles accelerated in the Large Hadron Collider at CERN. It’s pretty impressive that we can create a small collider on a tiny planet and experiment with energies that are somewhat close to what is seen in the most intense environments in nature. However, nature still wins, at least for now. It will take a new generation of terrestrial colliders to reach that threshold. And until we can probe the highest energies in the universe, we may never truly understand how everything works.
But we’re getting there!