H II region
The Orion Nebula was observed in 1610 by Nicolas-Claude Fabri de Peiresc by telescope, the first such object discovered. Study of extragalactic H-II regions is important in determining the distance and chemical composition of galaxies. The term H is pronounced “H two” by astronomers, and is the chemical symbol for hydrogen. “II” is the Roman numeral for 2.
About H II region in brief
An H II region or HII region is a region of interstellar atomic hydrogen that is ionized. It is typically a cloud of partially ionized gas in which star formation has recently taken place. The Orion Nebula was observed in 1610 by Nicolas-Claude Fabri de Peiresc by telescope, the first such object discovered. Study of extragalactic H-II regions is important in determining the distance and chemical composition of galaxies. Some galaxies contain huge H II regions, which may contain tens of thousands of stars. Examples include the 30 Doradus region in the Large Magellanic Cloud and NGC 604 in the Triangulum Galaxy. The term H is pronounced “H two” by astronomers, and is the chemical symbol for hydrogen, and “II” is the Roman numeral for 2. In spoken discussion with non-astronomers there is sometimes confusion between the identical spoken forms of “H II” and “H2” The term “nebulium” was first used in the early 20th century to refer to an unknown element, rather than a new element, due to a familiar astronomical context. Interstellar nebulae were not considered an astronomical matter in the unfamiliar context of matter in which they were found. However, helium was isolated on earth soon after its discovery in the spectrum of the sun, and soon became the most abundant element in the universe. The discovery of nebulium led to the discovery of helium through analysis of the Sun’s spectrum in 1868, which was at a line of 500 nanometres.
In the early 21st century Henry Norris proposed that rather than being a new Element, the line at 7nm was due to the unfamiliar conditions in which interstellar matter, such as the nebula, was being formed. This idea led to a similar idea being put forward for the element nebula, but it was not considered to be familiar in the astronomical context, and was not discovered until the 1970s. The first nebulas were discovered by William Huggins and his wife Mary in the 1800s. They were found to have spectra quite similar to those of stars, but turned out to be galaxies consisting of hundreds of millions of individual stars. Others looked very different, with absorption lines superimposed on a strong continuum with superimposed, the Orion Nebula and other similar objects showed only a small number of emission lines, which did not correspond with any known chemical element. In planetary nebulAE, the brightest line of these objects was a line at a 7 nanometres wavelength of 500 nm, and it was hypothesized that the line might be due to any unknown element. This was not the case, and instead the line of the line was thought to be a familiar element, the nebulusium, which had been discovered by Henry Norris in the 1950s and 1960s. A few of the brightest H II regions are visible to the naked eye, but none seem to have been noticed before the advent of the telescope in theearly 17th century.
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This page is based on the article H II region published in Wikipedia (as of Dec. 06, 2020) and was automatically summarized using artificial intelligence.
