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There is disagreement in the literature for some line designations; for example, the Fraunhofer d line may refer to the cyan iron line at 466.814 nm, or alternatively to the yellow helium line (also labeled D 3) at 587.5618 nm. Similarly, there is ambiguity regarding the e line, since it can refer to the spectral lines of both iron (Fe) and ...
The globular cluster M80. Stars in globular clusters are mainly older metal-poor members of population II. In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal currently detectable (i.e. non- dark) matter in the universe is either hydrogen or helium, and ...
Chlorine, sulfur and carbon (as coal) are cheapest by mass. Hydrogen, nitrogen, oxygen and chlorine are cheapest by volume at atmospheric pressure. When there is no public data on the element in its pure form, price of a compound is used, per mass of element contained.
They have strong hydrogen lines, at a maximum by A0, and also lines of ionized metals (Fe II, Mg II, Si II) at a maximum at A5. The presence of Ca II lines is notably strengthening by this point. About 1 in 160 (0.625%) of the main-sequence stars in the solar neighborhood are A-type stars, [ c ] [ 10 ] which includes 9 stars within 15 parsecs.
On Thursday, the U.S. government sold the Federal Helium Reserve, a massive underground stockpile based in Amarillo, Texas, that supplies up to 30% of the country’s helium.
A spectral line is a weaker or stronger region in an otherwise uniform and continuous spectrum. It may result from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to identify atoms and molecules. These "fingerprints" can be compared to the previously collected ones ...
Helium storage and conservation is a process of maintaining supplies of helium and preventing wasteful loss. Helium is commercially produced as a byproduct of natural gas extraction. Until the mid-1990s, the United States Bureau of Mines operated a large scale helium storage facility to support government requirements for helium.
Helium-rich B stars, such as σ Orionis E, are chemically unusual spectral B or OB main sequence stars that show strong neutral helium lines. Hydrogen-deficient binaries , such as υ Sgr, have helium lines on a metallic spectrum and show large radial velocities that are thought to result from Population I stars orbiting the Galactic Center .