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physical object > natural object > particle > hypothetical particle > dark matter > hot dark matter

hot dark matter comparison table

Subject	is a kind of	has definition
dark matter	hypothetical particle	Matter whose presence is inferred from dynamical measurements but which has no optical counterpart. The luminous regions of galaxies have mass-luminosity ratios of about 10. However, the mass-luminosity ratio in the outer halos of many spiral galaxies is 100 or more; one sees the brightness fall off with distance from the center of the galaxy but considerable mass is present. A similar situation prevails in galaxy clusters, where nonluminous matter must provide most of the self-gravitational attraction that holds the clusters together. The missing mass is not really missing; it is present but invisible (at least to current detectors). It is generally believed to consist either of the remnants of massive stars or of planetary-sized objects comparable in mass to Jupiter.
hot dark matter	dark matter	Any form of dark matter which was relativistic at its point of decoupling.

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