Context:
- A recent study published in the Journal of Cosmology and Astroparticle Physics claims a possible detection of dark matter, reigniting debate in the scientific community.
- The claim is based on observations from the Fermi Gamma-ray Space Telescope, but experts have urged caution and further verification.
- Dark matter remains one of the greatest unresolved mysteries in cosmology.
Key Highlights:
Scientific Background / Conceptual Framework:
- Dark matter is believed to constitute about 27% of the universe’s total mass-energy content, while ordinary matter accounts for only ~5%.
- First proposed in the 1930s by Fritz Zwicky after observing unusually high galaxy rotation speeds in the Coma Cluster.
- Dark matter does not emit, absorb, or reflect light, making it invisible to telescopes.
Hypothesis: WIMPs (Weakly Interacting Massive Particles):
- One leading theory suggests dark matter consists of WIMPs.
- Characteristics:
- Barely interact with normal matter
- Do not interact with electromagnetic radiation
- Detectable indirectly through high-energy gamma rays produced when WIMPs annihilate each other
New Claim / Observational Evidence:
- Tomonori Totani (University of Tokyo) claims detection of a gamma-ray halo near the centre of the Milky Way.
- Observed gamma rays have energies around 20 GeV.
- Energy spectrum reportedly matches predictions for annihilation of WIMPs with masses ~500 times that of a proton.
- Signal shape aligns with expectations from a dark matter halo surrounding the galaxy.
Expert Concerns and Counterviews:
- Scientists caution that:
- Similar “signals” in the past were later explained by other astrophysical sources.
- The signal size appears larger than expected from standard WIMP models.
- Possible alternative sources:
- Supernovae
- Neutron stars
- Black holes
- Lack of confirmation from other dark-matter-rich regions raises doubts.
Statistical and Model Uncertainty Issues:
- Particle physics discoveries usually require 5-sigma confidence.
- Experts note:
- Modelling uncertainties are not fully accounted for.
- “Error on the error bars” remains significant, weakening certainty of the claim.
UPSC Relevance (GS-wise):
- GS Paper III: Science & Technology – Space, Fundamental Research
- GS Paper I: Geography – Universe, Cosmology
- GS Paper II: Role of international scientific cooperation