Dust in the universe

The possible existence of intergalactic dust with properties similar to interstellar dust is examined in some detail. If such dust does exist, it could result in a correction to the observed deceleration parameter. The relation of the dust to possible intergalactic gas is examined, including survival times in a hot gas. The possible origins of intergalactic dust are also discussed. It is shown that uniform filling of the universe with dust is exceedingly unlikely, whereas dust halos around galaxies and clusters of galaxies may be quite likely. The dust optical depth across a cluster halo is estimated to be approximately 0.1.