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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 ...
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 ...
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 helium star is a class O or B star (blue), which has extraordinarily strong helium lines and weaker than normal hydrogen lines, indicating strong stellar winds and a mass loss of the outer envelope. Extreme helium stars (EHe) entirely lack hydrogen in their spectra. Pure helium stars lie on or near a helium main sequence, analogous to the ...
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 .
U.S. Steel shares plunged Wednesday as Wall Street questioned whether its $14.1 billion deal with Japan's Nippon Steel is at risk of unraveling. U.S. Steel's stock price plunged as much as 25% in ...