Unraveling the Mystery of Gamma Rays in the Milky Way

For a long time, the faint gamma rays scattered near the center of the Milky Way galaxy have intrigued scientists, with their mysterious source remaining uncertain. This has led researchers to consider two main possibilities: either these rays result from the collision of dark matter particles or from rapidly spinning neutron stars known as millisecond pulsars.

Possible Explanations

According to a new study published in the journal Physical Review Letters, both explanations seem equally plausible at present. If the excess radiation is not emitted by ancient stars, it could represent the first concrete evidence that dark matter is real.

Joseph Silk, a professor at Johns Hopkins University and a researcher at the Institute of Astrophysics in Paris, stated, “Dark matter dominates the universe and binds galaxies together. It is of great significance, and we are constantly thinking of ways to detect it. Gamma rays, especially the excess light we observe at the center of our galaxy, might be our first clue.”

The Role of Advanced Computational Models

To explore this enigma, Joseph Silk and an international team of scientists used advanced computational models to map the distribution of dark matter in the Milky Way, incorporating the galaxy’s history and evolution for the first time.

Today, the Milky Way is largely self-sufficient, with little new material entering or leaving it. However, in the first billion years of its existence, it absorbed many smaller galaxies rich in dark matter that merged to form its structure. As dark matter particles gathered and concentrated towards the galactic center, the likelihood of their collisions increased.

Simulation Results and Real Observations

When the team included these more realistic interactions in their models, the simulation results closely matched real gamma-ray observations made by NASA’s gamma-ray telescope.

These consistent maps complete a trilogy of evidence suggesting that the excess radiation at the center of the Milky Way may originate from dark matter. Gamma rays produced by dark matter particle collisions would generate the same signal and possess the same characteristics observed in the real world, though this is not definitive proof.

The Alternative Theory: Millisecond Pulsars

Light emitted by rapidly rotating ancient neutron stars—known as millisecond pulsars—could also explain the existing gamma-ray map, measurements, and signature. However, this theory is incomplete, researchers say. To make these calculations work, scientists must assume a greater number of millisecond pulsars than have been observed.

Conclusion

As scientists continue their research, attention turns to a new telescope being built to observe gamma rays, known as the Cherenkov Telescope Array. Researchers believe that data from this high-resolution telescope, which has the ability to measure high-energy signals, will help solve this mystery. Meanwhile, the team is working on predictions about the locations of dark matter in the dwarf galaxies orbiting the Milky Way. By comparing these predictions with high-resolution data, scientists may be able to confirm one of the theories or perhaps encounter an even greater puzzle.