EntityQ1209551· pop 15· linked from 31 articlesdensity wave theorySign in to savetheory to explain the spiral arm structure of spiral galaxiesConnectionsluminous infrared galaxyEntitystarburst galaxyEntityinteracting galaxyEntitygalaxyEntitysupermassive black holeEntityradio galaxyEntitylenticular galaxyEntitygalaxy groupEntitygalactic discEntityunbarred spiral galaxyEntityLindblad resonanceEntityInternational Standard Book NumberEntityHubble Space TelescopeEntitydigital object identifierEntityInternational Standard Serial NumberEntitydark matterEntityquasarEntityCassini−HuygensEntitymoon of SaturnEntityinterstellar mediumEntityCategoriesExtragalactic astronomyGalactic astronomy