Labels:text | screenshot OCR: INTERSTELLAR MATTER THE REGIONS between stars in a galaxy are filled by the interstellar medium, or ISM. It consists mainly of hydrogen and helium gases, with traces of other gases, and a tiny amount of dust. This material is uneven in distribution and temperature, and its density is many billions of times less than that of air. Much of the ISM consists of clouds, some of which we can detect as nebulas if they emit or reflect light from stars in or around the cloud, or if they block light from more distant objects. The ISM is enriched by particles from stellar winds and by matter ejected from dying stars. THE ISM IN THE GALAXY In this false-color infrared image, stars appear as blue dots while SEE COSMIC-RAY FACT interstellar gas and dust warmed by stellar radiation appear reddish. NEXT AL ...
