Astrophys. J. 681, 1035–1045 (2008)

Astronomers have found that vast stores of hot gas in the areas between clusters of gravitationally bound galaxies do form stars, though not many. The gas falls into one of the cluster's bright central galaxies, where it cools and condenses enough for star formation. This process was thought to be negligible in the present-day Universe.

Christopher O'Dea from the Rochester Institute of Technology in New York and his colleagues considered data from 62 of these central galaxies, from which they estimate that 1–10% of the gas contributes to star birth. X-ray emissions served as a proxy for the amount of hot gas falling in, and infrared emissions as a proxy for new stars being formed. Some mechanism, the authors suggest, keeps the gas from cooling completely — perhaps a supermassive black hole in the galactic core, or the new stars themselves.