Why are gamma rays emanating from Milky Way's core?
What's the story
A new study has left the door open for self-annihilating dark matter to explain the gamma-ray emissions from the center of our galaxy. The Galactic Center Excess is a spherical glow of gamma rays that extends thousands of light-years from the core of the Milky Way. This high-energy light has puzzled researchers for over a decade, with various theories proposed to explain its origin.
Dark matter debate
Dark matter under
One of the leading theories for the Galactic Center Excess involves a specific type of dark matter particle. Dark matter, which makes up 85% of the universe's matter, is invisible as it doesn't interact with light or ordinary atomic matter. This has led to several proposed candidate particles for dark matter, including some that are their own antiparticles and self-annihilate when they meet, releasing energy in the process.
Annihilation process
Self-annihilating dark matter
Self-annihilating dark matter particles would be their own antiparticles, meaning when they interact, they would annihilate and release energy as gamma rays. Despite dark matter outnumbering ordinary matter by a factor of five, this annihilation is rare because it rarely interacts with itself. This phenomenon only occurs in regions where dark matter is densely clustered, such as the heart of a galaxy.
Research hurdles
Study uses machine learning to analyze gamma rays
Studying the heart of the Milky Way is no easy task. "Interpreting the signal is particularly difficult because the Galactic Center is an exceptionally bright and crowded region of the gamma-ray sky," said team member and University of Vienna researcher Florian List. To explore if annihilating dark matter could explain this phenomenon, List and his team used machine learning trained on over a million simulated gamma-ray observations.
Study results
Research shows that dark matter is still in the game
The new research found that previously proposed bright, unresolved light sources as a potential cause of the Galactic Center Excess would be extremely faint. This suggests that the pulsar population at the heart of the Milky Way would have to be over 35,000 to explain these gamma rays. "Our new analysis shows that the sources would have to be so faint that they would be almost indistinguishable from the emission expected from annihilating dark matter," said team member Nick Rodd.
Dark matter possibility
Research doesn't confirm dark matter as source of gamma rays
While this research keeps dark matter in the game as a plausible explanation, it doesn't confirm the annihilation of this mysterious stuff as the source of the Galactic Center Excess. "The origin of the Galactic Center Excess is one of the longest-running debates in astrophysics," List said. "Our work does not show that dark matter is responsible for the signal. However, it suggests that it is still too early to rule out this possibility," he added.