Mysterious Gamma Ray Found Outside the Milky Way Linked to Ultra-High-Energy Cosmic Rays

Astronomers made a surprising find as they searched for the cosmic fossil. They found a mysterious gamma-ray feature.

Bizarre Gamma-Ray Feature Found During Cosmic Fossil Hunt

Astronomers have found an unusual and mysterious object outside of our Milky Way galaxy that emits gamma rays, a high-energy light.

The team that made the finding discovered the gamma-ray signal, which included NASA and University of Maryland cosmologist Alexander Kashlinsky. The team searched through 13 years of data from NASA's Fermi Telescope.

Kashlinsky said in a statement that it was a "serendipitous discovery." They reportedly found a stronger signal in a different part of the sky than where they were looking.

The fact that this gamma-ray signal is directed toward another mysterious space feature origin of some of the most potent cosmic particles ever discovered is even more bizarre.

Scientists believe the new signal is associated with these high-energy particles, also known as cosmic rays, mostly composed of atomic nuclei, protons, and neutrons.

The origin of these ultra-high-energy cosmic rays (UHECRs) is still one of the greatest mysteries in astronomy, and the discovery of this gamma-ray source has further complicated it. UHECRs have more energy than a billion times that of gamma rays.

The scientists turned to Fermi and its Large Area Telescope (LAT), which scans the sky over Earth multiple times daily to capture and consolidate many years of data. The researchers hoped that a dipole emission pattern detectable in gamma rays was hidden within the LAT data.

Due to the high-energy nature of gamma rays and the effects of special relativity, this dipole should be five times more conspicuous in this data than in the CMB's low-energy microwave radiation. Though not where they anticipated, the crew discovered something that resembled this pattern.

"We found a gamma-ray dipole, but its peak is located in the southern sky, far from the CMB's [peak], and its magnitude is 10 times greater than what we would expect from our motion," said team member Chris Shrader, an astrophysicist at the Catholic University of America. "While it is not what we were looking for, we suspect it may be related to a similar feature reported for the highest-energy cosmic rays."

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New Gammay-Ray Linked to UHECRs

First seen by the Pierre Auger Observatory in Argentina in 2017, there is a similar dipole in the showers of high-energy charged particles that make up UHECRs as they arrive at Earth.

They observed that despite the deflection of the charged particles from the magnetic field of the Milky Way and other magnetic fields as they traverse toward Earth, the deflection's strength depends on the particle's energy and its charge—the UHECR dipole peaks in the exact location where Kashlinsky and colleagues spotted the gamma-ray source.

Since unknown sources are producing both the mysterious gamma rays and the UHECRs, the team theorizes that a connection between the two occurrences is likely due to their similar location.

To find the source, or sources, of this ultra-high energy light and these ultra-high energy particles, astronomers now wish to look into the locations of these emissions. Only then will they be able to identify whether or not these sources are related and whether they represent one or more cosmic mysteries that need to be solved?

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