H II region concept from the Astronomy knowledge base

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H II region

subject fact

H II region has composition ionized hydrogen 2001-09-27 09:30:11.0
has definition Hydrogen gets ionized by hot O and B stars in H II regions. The most famous H II region is the Orion Nebula. has source: Croswell, K. 1995 The Alchemy of the Heavens, Anchor Books, 2001-09-27 09:30:11.0
has definition An area of ionized hydrogen. Most H II regions are red and arise from hot blue O and B stars, whose ultraviolet light can ionize all the hydrogen for dozens or even hundreds of light-years in every direction. The most famous H II region is the Orion Nebula. has source: Croswell, K. 1995 The Alchemy of the Heavens, Anchor Books, 2001-09-27 09:30:11.0
has definition Region of ionized hydrogen in interstellar space. H II regions occur near stars with high luminosities and high surface temperatures. The kinetic temperature of H II regions is about 10,000-20,000 K, and the density is about 10 atoms per cm³. Ionized hydrogen, of course, having no electron, does not produce spectral lines; however, occasionally a free electron will be captured by a free proton and the resulting radiation can be studied optically (see also radio recombination lines). has source: Hopkins, J. 1976 Glossary of Astronomy and Astrophysics, University of Chicago Press, 2001-09-27 09:30:11.0
is a kind of nebula

nebula is a part of gas 2001-09-27 09:32:19.0
has catalog nebula catalog 2001-09-27 09:30:10.0

celestial body has spectra 2001-09-27 09:30:09.0

physical object has location or center of gravity 2001-09-27 09:27:27.0
has angular momentum
has mass
has velocity
has momentum
has temperature
has volume
has extent
has material

Kinds of H II region :

compact H II region (1 kind, 9 facts) - A dense (n_e ≥ 10³ cm^-3) H II region of small linear dimensions (≤ 1 pc).
gaseous nebula (51 kinds, 288 facts) (emission nebula) - An H II region, a supernova remnant, or a planetary nebula. H II regions have an emission-line optical spectrum, and a thermal continuous spectrum declining in intensity as the wavelength increases (from maximum in the ultraviolet) through infrared and radio. Supernova remnants have an emission-line optical spectrum and a nonthermal radio spectrum. Temperatures of planetary nebulae are much higher than those of H II regions.
H II condensation (2 facts) - A high-density H II region.

Next nebula: reflection nebula Up: nebula Previous nebula: dark nebula

H II region	has composition ionized hydrogen
	has definition Hydrogen gets ionized by hot O and B stars in H II regions. The most famous H II region is the Orion Nebula.
	has definition An area of ionized hydrogen. Most H II regions are red and arise from hot blue O and B stars, whose ultraviolet light can ionize all the hydrogen for dozens or even hundreds of light-years in every direction. The most famous H II region is the Orion Nebula.
	has definition Region of ionized hydrogen in interstellar space. H II regions occur near stars with high luminosities and high surface temperatures. The kinetic temperature of H II regions is about 10,000-20,000 K, and the density is about 10 atoms per cm³. Ionized hydrogen, of course, having no electron, does not produce spectral lines; however, occasionally a free electron will be captured by a free proton and the resulting radiation can be studied optically (see also radio recombination lines).
	is a kind of nebula
nebula	is a part of gas
nebula	has catalog nebula catalog
celestial body	has spectra
physical object	has location or center of gravity
	has angular momentum
	has mass
	has velocity
	has momentum
	has temperature
	has volume
	has extent
	has material