Strange events seen at the very heart of the Milky Way could be smoking gun evidence of a new dark matter suspect. If that is the case, scientists may have been missing the subtle impact of dark matter , the universe's most mysterious "stuff," on cosmic chemistry.
This newly proposed dark matter candidate not only would this new form of dark matter be lighter compared to previously theorized candidates, but it would also have the property of self-annihilation. In essence, when two such dark matter particles encounter one another, they obliterate each other and generate a negative charge. electron and its positively charged equivalent, a positron.
This process and the flood of electrons and positrons would provide the energy needed to strip electrons away from neutral atoms, a process called ionization, in dense gas in the center of the Milky Way. That could explain why there is so much ionized gas in the central region called the Central Molecular Zone (CMZ).
Even if the annihilation of dark matter is rare, it stands to reason it would occur more frequently at the heart of galaxies where it is thought to conglomerate.
"We propose that dark matter lighter than a proton [the particles found in the nuclei of atoms] could be responsible for an unusual effect seen in the center of the Milky Way Team Leader and Postdoctoral Research Fellow at King’s College London, Shyam Balaji, stated to Pawonation.com. 'In contrast to many dark matter candidates that are typically investigated via their gravitational impacts, this particular type of dark matter could potentially be identified through its ability to ionize gases, effectively removing electrons from atoms within the Central Molecular Zone,' he explained.
This scenario could occur if dark matter particles destroy each other. electron-positron pairs , which subsequently interacts with the surrounding gas."
Dark matter chemistry
It is believed that dark matter makes up about 85% of the material in the universe; however, even though it is widespread, scientists cannot “observe” it like much of normal matter. This is due to the fact that dark matter does not engage with light, or if it does, these interactions are extremely feeble and infrequent to detect.
This indicates that scientists have determined that dark matter cannot consist of baryonic particles such as electrons, protons, and neutrons, which make up the atoms that constitute ordinary matter. stars, Planets, moons, as well as all the things we encounter regularly every day.
The sole rationale for scientists hypothesizing the existence of dark matter is due to its interaction with other entities. gravity, and this influence impacts light and "ordinary" matter.
This has led scientists to explore past what is referred to as the " standard model of particle physics to look for particles that might explain dark matter.
These particles differ in terms of their mass, measured in electronvolts (eV), as well as in properties. There is a suggestion that certain ones, akin to this newly identified candidate, might annihilate themselves.
The current "leading suspects" for dark matter are axions And axion-like particles, which span a broad spectrum of masses. Nonetheless, Balaji and his team have largely excluded axions and similar particles as potential candidates for dark matter associated with the ionization of gas in the CMZ.
"Most axion models do not predict significant annihilation into electron-positron pairs in the way our proposed dark matter does," Balaji said. "Our proposed dark matter subject is sub-GeV (one billion eV) in mass and self-annihilates into electrons and positrons."
"This sets it apart because it directly affects the interstellar medium , generating a distinctive signature through additional ionization, which is not usually anticipated from axions."
Dark matter: Its Own Worst Enemy
Within the tightly clustered CMZ, produced positrons cannot move far or escape before interacting with surrounding hydrogen molecules, which strip off their electrons. This renders the process highly effective in this core area.
"The primary issue this model addresses is an overabundance of ionization in the CMZ," Balaji stated. Cosmic rays ,, the typical agents responsible for ionizing gas appear insufficient to account for the high degree of ionization we are observing."
Cosmic rays are charged particles that move close to the speed of light. speed of light However, based on the findings of this research group, the ionization signal originating from the Central Molecular Zone (CMZ) appears to suggest a less massive source moving at a slower velocity compared to numerous alternative dark matter possibilities.
Additionally, if cosmic rays were causing ionization in the Central Molecular Zone, we would expect to observe corresponding emissions. gamma rays These are extremely energetic photons. Nonetheless, such emissions are absent from research focusing on the CMZ.
"Should dark matter be behind the ionization of the CMZ, this could imply that we’re identifying dark matter through its faint chemical influence on the gases within our galaxy rather than directly observing it," explained Balaji.
Nevertheless, there is an enigmatic weak gamma-ray emission coming from the center of our galaxy that could potentially be connected to positrons and ionization as well.
Establishing a clear link between ionization and this gamma-ray emission might bolster the argument for dark matter," Balaji stated. "While there appears to be an association between the two phenomena, we require additional evidence at present to make a firmer assertion.
Furthermore, this annihilation model of dark matter might also account for an observable light emission from the Central Molecular Zone caused by collisions between positively charged positrons and negatively charged electrons merging into a state referred to as positronium , which subsequently breaks down quickly into X-rays, Light possessing marginally lower energy compared to gamma rays.
The figures align far more closely than anticipated. Typically, theories involving dark matter encounter problems as they forecast signals that ought to have already been detected by observatories," explained Balaji. "However, with this scenario, the ionization rate generated by sub-GeV dark matter sits comfortably inside recognized limits and does not conflict with current gamma-ray observations. cosmic microwave background (CMB) observations."
The researcher noted that the initial convergence with the X-ray emissions is equally fascinating.
"That's a rare and exciting situation in dark matter research," Balaji added.
The investigation into this potential dark matter candidate is still in its initial stages.
Certainly, this fresh contender for dark matter is still in the early stages of its theoretical existence; it hasn’t been bestowed with a catchy moniker such as WIMP (Weakly Interacting Massive Particle) or MACHO (MAssive Compact Halo Object)!
For comparison, axions have existed since their initial proposal by theoretical physicists. Frank Wilczek and Steven Weinberg in 1978.
This indicates that extensive theoretical work needs to be carried out before this candidate can join others like axions, WIMPs, MACHOs, primordial black holes, and so forth in the realm. dark matter suspect line-up.
More accurate measurements of ionization within the Central Molecular Zone are essential; mapping this with precision would help us determine if it aligns with the anticipated dark matter distribution," Balaji explained. "By eliminating alternative explanations for the observed ionization, the case for dark matter grows stronger.
Additional proof linking annihilating dark matter to peculiar emanations from the CMZ might come from NASA’s forthcoming mission. COSI (The Compton Spectrometer and Imager) gamma-ray telescope, scheduled for launch in 2027.
COSI needs to offer improved data concerning astrophysical phenomena at the MeV (1 million electron-volt) level, as this could assist in validating or dismissing this particular theory about dark matter.
In any event, this study has yielded results. a fresh perspective on the impact of dark matter .
Dark matter continues to be one of the greatest enigmas in physics, and this research suggests that we might have missed its slight yet significant chemical impacts on the universe," Balaji stated. "Should this hypothesis prove correct, it could introduce an altogether different approach for investigating dark matter—not only via its gravitational influence but also through how it molds the structure of our Milky Way.
The team's research was published on Monday (March 10) in the journal Physical Review Letters.
Post a Comment