How can gamma rays exist without mass?

"There's really nothing out there that can produce gamma rays."

Scientists have that University of California, Riverside, Clemson University and University of Chicago announced. According to Dave Dixon, a physicist at UCR, this new, unexpected distribution of gamma rays associated with the Compton Gamma Ray Observatory taken by NASA, an aurora many thousands of light years thick and possibly surrounding the entire Milky Way. The discovery was made on November 4th at the conference of High Energy Astrophysics Division the Astronomical Society announced.

“In other wavelength ranges there is actually nothing out there that could produce gamma rays. These gamma rays provide the first evidence that a high energy process is taking place out there, ”said Dixon, who made the discovery together with Dieter Hartmann, astrophysicist at the Clemson University, and Eric Kolaczyk, statistician at the University of Chicago made.

The three scientists analyzed data showing that Energetic Gamma-Ray Experiment Telescope (EGRET). The EGRET is one of four instruments on board the Compton Gamma Ray Observatorythat orbits the earth and measures and records invisible gamma rays that cannot be detected on earth because they are absorbed by the earth's atmosphere.

The visible light from stars and galaxies, which is perceived with light telescopes, represents only a fraction of the energy that is given off by celestial bodies and other phenomena in space. Of all types of radiation, gamma rays have the highest energy, even more than X-rays. For example, a single gamma-ray photon from the newly discovered halo has about a billion times as much energy as a photon from normal, visible light. Gamma rays are of great interest to astrophysicists because they may provide clues about some of the most daunting events in the universe, such as the death of a star that becomes a supernova or the birth of a galaxy.

According to Dixon, the strange thing about the newly discovered gamma-ray cloud is that the photons do not seem to come from compact sources such as other galaxies or black holes. "This is interesting because there is no obvious source of these gamma rays that would be seen in astronomical observations at other wavelengths," he said. "As far as we can tell with the help of other telescopes, the space around our galaxy is pretty empty, i.e. it contains nothing that in our opinion could generate gamma rays in the observed brightness distribution."

So far, based on the current data, there is no clear explanation for the phenomenon. Dixon and Hartmann offer three options:

  1. Gamma rays are generated when high energy cosmic rays collide with low energy photons such as visible or infrared light;
  2. they are given off by neutron stars that spin or spin at breakneck speed
  3. the distribution of gamma rays provides evidence of dark matter - the missing mass in the universe that scientists have not been able to directly observe before.

The observed high-energy gamma rays could be the result of the so-called inverse Compton effect be: High-energy electrons, which fly through space almost at the speed of light, collide with low-energy photons. The electrons transfer part of their energy to the photons and thereby increase their energy so that they reach the level of gamma rays.
Recently it was reported that several other spiral galaxies similar to the Milky Way are surrounded by a faint halo of infrared photons. The interaction of these photons with energetic electrons could result in gamma radiation.
In the centers of some galaxies, so-called starbursts observed, i.e. the rapid formation and destruction of huge stars. These star giants are short-lived; they die in gigantic explosions, so-called supernovas. The shock wave of energy from these supernovas leads to the formation of more stars. This turns the center of such galaxies into a great cauldron of tremendous activity. A starburst would generate huge amounts of cosmic rays and thus provide the energetic electrons that are needed to generate the gamma rays.
The discovered gamma-ray cloud could provide evidence that the Milky Way once also did starburst-Galaxy, said Dixon. “This question is still open at the moment,” he said. "There seems to be an as yet unexplained reference to previous such activities in the center of the Milky Way." Viewed from Earth, the center of the Milky Way is approximately 25,000 light years away in the direction of the constellation Sagittarius.