Glossary term: Nebula

Description: A nebula is a diffuse cloud, usually of gas or dust or both. Historically, nebulae included any extended fuzzy-looking object, including what we today recognize as galaxies. Today, the term nebula is restricted to cold and dark molecular clouds (such as those where stars are formed), cool and diffuse "cirrus" clouds, and hot and ionized HII regions, Herbig-Haro objects, planetary nebulae, and supernova remnants.

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Term and definition status: This term and its definition is still awaiting approval

The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".