H II regions
E459029
H II regions are vast, glowing clouds of ionized hydrogen gas surrounding young, hot stars, marking active sites of recent star formation in galaxies.
Observed surface forms (2)
| Surface form | Occurrences |
|---|---|
| H II region | 0 |
| Sharpless catalog of H II regions | 1 |
Statements (57)
| Predicate | Object |
|---|---|
| instanceOf |
astronomical object
ⓘ
emission nebula ⓘ ionized gas region ⓘ |
| associatedWith |
B-type stars
ⓘ
O-type stars ⓘ |
| boundedBy | ionization front ⓘ |
| canTrigger |
compression of nearby molecular gas
ⓘ
sequential star formation ⓘ |
| composedOf |
electrons
ⓘ
helium ⓘ ionized hydrogen gas ⓘ protons ⓘ trace heavier elements ⓘ |
| emits |
H-alpha line
ⓘ
forbidden lines of nitrogen ⓘ forbidden lines of oxygen ⓘ forbidden lines of sulfur ⓘ hydrogen recombination lines ⓘ radio free-free continuum ⓘ |
| example |
30 Doradus
NERFINISHED
ⓘ
Carina Nebula NERFINISHED ⓘ Eagle Nebula NERFINISHED ⓘ Lagoon Nebula NERFINISHED ⓘ NGC 604 NERFINISHED ⓘ Orion Nebula NERFINISHED ⓘ |
| foundIn |
Milky Way
NERFINISHED
ⓘ
external galaxies ⓘ |
| hasCause | ultraviolet radiation from hot young stars ⓘ |
| hasPhysicalProperty |
high electron density compared to diffuse interstellar medium
ⓘ
low overall density ⓘ often clumpy structure ⓘ often filamentary structure ⓘ often irregular morphology ⓘ strong emission lines ⓘ temperature around 7000–10000 K ⓘ |
| hasSubtype |
compact H II region
ⓘ
giant H II region ⓘ ultra-compact H II region ⓘ |
| ionizedBy | Lyman continuum photons ⓘ |
| locatedIn |
galactic disks
ⓘ
irregular galaxies ⓘ spiral arms of galaxies ⓘ |
| marks | sites of recent star formation ⓘ |
| namedAfter | singly ionized hydrogen (H II) notation ⓘ |
| observedWith |
infrared telescopes
ⓘ
optical telescopes ⓘ radio telescopes ⓘ |
| partOf | interstellar medium ⓘ |
| relatedTo | Strömgren sphere NERFINISHED ⓘ |
| surroundedBy |
molecular clouds
ⓘ
neutral hydrogen gas ⓘ |
| surrounds | young massive stars ⓘ |
| typicalAge | less than a few million years ⓘ |
| typicalSize | a few to hundreds of light-years across ⓘ |
| usedFor |
measuring chemical abundances in galaxies
ⓘ
studying massive star formation ⓘ tracing spiral structure of galaxies ⓘ |
Referenced by (6)
Full triples — surface form annotated when it differs from this entity's canonical label.
subject surface form:
NGC 281
this entity surface form:
Sharpless catalog of H II regions