cold dark matter

A Dictionary of Astronomy | 1997 | 700+ words | Copyright

cold dark matter (CDM) A particular type of non-baryonic matter that, according to some theories, is created in the early stages of the Big Bang and survives to the present time in sufficient numbers to contribute significantly to the present density of the Universe. The term ‘cold’ signifies that these particles move at speeds much less than that of light, usually because they are heavy. There are many possible candidates for cold dark matter, such as axions, photinos, and primordial (low-mass) black holes. Evidence for the existence of cold dark matter has come from recent observations that show the overall amount of dark matter in the Universe is roughly 50 times greater than the amount of matter contained in stars. Other observations show that roughly 80% of this dark matter is non‐baryonic.

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