H II region
NGC 604, a giant H II region in the Triangulum Galaxy.
An H II region is a cloud of glowing gas and plasma, sometimes several hundred light years across, in which star formation is taking place.
H II region
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An H II region is a cloud of glowing gas and plasma, sometimes several hundred light-years across, in which star formation is taking place.
H II Region
(a) 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.
H II regions. By necessity these require active star formation and OB stars. They are luminous and measurable to very large distances.
H II Region: A region in space around one or more very hot, bright stars where most of the hydrogen gas is ionized.
Halo: The spherical region of a spiral galaxy composed of diffuse gas an$containing few stars and star clusters.
H II Region
A region of ionized hydrogen around a hot star.
H-R Diagram ...
H II region
a region of hot gas surrounding a young star or stars that is mostly ionized. The energetic light from these young stars ionizes the existing gas.
H II region
Ionized hydrogen regions located in interstellar space. H II regions are visible as a part of nebulae, where hot young stars ionize their nearby hydrogen womb.
H II region cloud of ionized hydrogen around a hot, luminous star (usually O or B-type).
H II region - (n.)
An interstellar region of ionized hydrogen.
Ha - (n.) ...
H II region
An H II region is a cloud of glowing gas and Plasma , sometimes several hundred light-years across, in which star formation is taking place....
List of diffuse nebulae ...
An H II region, a supernova remnant, or a planetary nebula. H II regions have an emission-line optical spectrum, ...
NGC 2997 showing H II regions in the spiral arms.
Credit: 2dF Quasar Survey
Quasar Spectra ...
Largest H II Region Diameters
Hot luminous stars ionize the hydrogen gas around them, producing an H II region like the Orion nebula.
The Orion nebula has been mentioned as a good example of an H II region, and it is also one of the most studied ones out there.
The interstellar gas is electrically neutral at points far removed from any star (H I regions) but is highly ionized (the electrons are detached from their atoms) in the immediate vicinity of the most massive and hottest stars (H II regions).
H II regions: assuming that the diameters of H II regions are constant, the distance to nearby galaxies can be inferred.Hubble method: measure the Doppler shift of an astronomical body and compute the radial velocity.
Do all these newly discovered H II regions cause this figure to increase? Based on the density of the detected nebulae, the answer is not significantly. However, there is an important footnote to this.
(Added 08/23/04) This Hubble Space Telescope (HST) image shows an H II region in the Large Magellanic Cloud (LMC), named N44F.
As the more massive stars appear, they transform the cloud into an H II region of glowing gas and plasma.
Thermal radio emission is observed from clouds of ionized hydrogen (termed H II regions) located along the spiral arms of the Galaxy.
IC5070 and IC5067 or the Pelican Nebula is located in an H II region, a cloud of glowing gas and plasma in which stars are formed. Lying close to [3967] Deneb, the nebula resembles the pelican in shape.
1. What spectral class of star is needed to ionize an H II region?
O stars and only the hottest of the B stars (B0 and B1).
2. Why does a reflection nebula appear blue?
A generic term for a fuzzy, diffuse astronomical object. Astronomers have observed four different types of nebulae: H II regions, reflection nebulae, planetary nebulae, and supernova remnants.
Radio Programs
Featured Images ...
(spectral types 0 and B) in a region from a few to a few hundred parsecs across. The stars are generally not gravitationally bound together and so the associations are dispersing. They are the remnant of recent star formation in a large H II region.
 See also: Light, Star, Galaxies, Galaxy, Solar
  
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