https://www.vice.com/en_us/article/akvabe/a-vast-faint-universe-of-rogue-stars-is-revealing-dark-matter > Astronomers are learning to decipher clues imprinted in the ultra-faint light of free-floating stars that have been kicked out of their galaxies and left to wander the vast interstitial realms of space.  > This ambient glow, known as intracluster light because it shines between galaxies in clusters, is a powerful new way to probe longstanding mysteries, such as the nature of dark matter, an unidentified substance that is abundant in the universe.