Deep-sky object class · e.g. The Orion Nebula (M42)
HII Region
A large cloud of ionised atomic hydrogen (H II) surrounding one or more hot O- and B-type stars, whose ultraviolet light strips the electrons from the surrounding gas. HII regions are the glowing signposts of massive-star formation, and their sizes and spectra are used to trace star formation across galaxies.
Highlights
- ›Ionised hydrogen around newborn massive stars
Examples & related concepts
Across the encyclopedia
Knowledge connections
- Associated withEmission Nebula
- Associated withOrion Nebula
- Associated withEmission Nebula
- Associated withSharpless Catalogue
- Associated withStar-Forming Regions
- Associated withThe Cone Nebula
- Associated withNarrowband Imaging
Sources
The primary and reference sources this topic draws on.
- NASANational Aeronautics and Space Administration
Mission data, planetary science, space telescopes, and public-domain imagery.
Most NASA-produced imagery is in the public domain; individual items are checked for usage terms before publication.