Intergalactic dust is cosmic dust in between galaxies in intergalactic space. Evidence for intergalactic dust has been suggested as early as 1949, and study of it grew throughout the late 20th century. There are large variations in the distribution of intergalactic dust. The dust may affect intergalactic distance measurements, such as to supernovae and quasars in other galaxies.
Intergalactic dust can form intergalactic dust clouds, known since the 1960s to exist around some galaxies. By the 1980s, at least four intergalactic dust clouds had been discovered within several megaparsecs (Mpc) of the Milky Way galaxy, exemplified by the Okroy cloud.
In February 2014, NASA announced a greatly upgraded database for tracking polycyclic aromatic hydrocarbons (PAHs) in the universe. According to scientists, more than 20% of the carbon in the universe may be associated with PAHs, possible starting materials for the formation of life. PAHs seem to have been formed as early as two billion years after the Big Bang, are widespread throughout the universe, and are associated with new stars and exoplanets.