New dark matter theory links ionisation in Milky Way’s core to self-annihilating particles

A new hypothesis about the dark matter may provide insights into the mysterious ionisation occurring in the core of the Milky Way.

Scientists propose that a lightweight, self-annihilating form of dark matter could be playing a previously overlooked role in cosmic chemistry.

This theory suggests that when two of these dark matter particles collide, they annihilate each other, releasing electrons and positrons. These high-energy particles could be responsible for the unusually high levels of ionisation observed in the Central Molecular Zone (CMZ), a dense region of gas at the galaxy’s centre.

If confirmed, this would mark a significant shift in the way dark matter is studied, moving beyond its gravitational influence to its potential chemical effects on the interstellar medium.

A study published in Physical Review Letters and led by Shyam Balaji, a Postdoctoral Research Fellow at King's College London, introduces the idea that dark matter particles with masses lower than that of a proton could be influencing the ionisation levels in the CMZ.

Traditionally, dark matter candidates have been examined primarily through their gravitational interactions. However, Balaji and his team suggest that its presence might also be detectable through its impact on cosmic gas, offering a novel approach to its study.

Dark matter is estimated to make up 85% of the universe's mass, yet it remains elusive due to its inability to interact with light. The researchers argue that while dark matter annihilation is expected to be rare, it should occur more frequently in dense regions such as the Milky Way’s core, where dark matter is concentrated. The ionisation levels in the CMZ appear too high to be solely attributed to cosmic rays, making dark matter interactions a compelling alternative explanation.

Balaji emphasised that current astronomical data does not contradict this hypothesis, and future space missions could offer crucial evidence to support it.

In particular, the upcoming COSI gamma-ray telescope, set for launch in 2027, could help detect the telltale signs of dark matter annihilation. If proven, this discovery would not only reshape our understanding of dark matter but also open new possibilities for studying its role in shaping galaxies.