= Solution
Three physically distinct contributions are unseen <dark matter>, hot diffuse <intracluster gas> omitted from the summed stellar <mass>, and faint stars or <stellar remnants> missed by transferring the <Milky Way> <mass-to-light ratio> to the cluster. The first two are actual additional components; the third changes the inferred stellar budget. Departures from <virial equilibrium>, <velocity anisotropy> or extra nonthermal <pressure> can also bias the dynamical or <X-ray> estimates, although they need not remove the discrepancy.
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