What is dark matter made of?
In plain words
Galaxies, clusters and the cosmic microwave background all require extra unseen mass, about five times the ordinary matter. The task is to find out what that mass physically is.
Precise statement
Determine the microscopic identity (mass, spin, non-gravitational couplings, production mechanism) of the non-baryonic component with $\Omega_c h^{2} = 0.120 \pm 0.001$ inferred from the CMB in LCDM. An answer is a candidate confirmed by a reproducible non-gravitational signal (direct, indirect or collider detection, or a compact-object census) whose abundance accounts for $\Omega_c$.
What would settle it
A reproducible non-gravitational detection of a candidate whose inferred cosmic abundance matches $\Omega_{c}$.
Status in the literature
Unverified note: it names recent work and was partly written without a live literature search; it awaits a check by an editor.
No candidate has been detected as of 2026; the leading searches (xenon detectors, axion haloscopes, gamma-ray telescopes, microlensing) report null or contested results.
Problems built on this one
Special cases
- Scalar ultralight dark matter coupled to photons: detect or exclude · open
- Is dark matter the QCD axion? · open
- Is dark matter self-interacting with a velocity-dependent cross section? · open
- Is dark matter a thermal-relic weakly interacting massive particle? · open
- Can asteroid-mass primordial black holes be all the dark matter? · open
Results
No results have been posted on this problem yet.
Post a result · how results are checked
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