Nickel solar abundance

Natural isotopes of nickel and their solar abundances... 

Figure 3 Observations of the star BD+75°325 (thick solid line) obtained by the Goddard high-resolution spectrometer on board the Hubble space telescope, showing numerous iron and nickel lines in various ionization stages. These data are compared with model atmosphere spectra. The thin solid line is the best fit model for an iron abundance of 4 x 10- and the dotted line is for solar abundances (4 X 10-5). A solar iron-to-nickel ratio has been assumed in both models. Reproduced with permission from Lanz T, Hubeny I and Heap SR (1997) Astrophysical Journal 485 843.

We present here the results of abundance measurements of iron, calcium and nickel in four open clusters, from UVES spectra of solar type stars. A code developed by one of the authors (Francois) performs line recognization, equivalent width measurements and finally obtains the abundances by means of OSMARCS LTE model atmosphere [4]. Temperature, gravity and microturbulence velocity have to be input to the program. This is made in an automatic way for a grid of values chosen on photometric basis. Those that best reproduce excitation and ionization equilibria are selected and used, namely when no significant trend of the computed abundances is seen, neither versus the excitation potential of the line nor versus its equivalent width, and for which the abundances obtained with lines of different ionization stages of the same specie give equal results within the errors. This check is made with iron lines, we have in fact at least thirty Fe I lines in each star, and six Fell lines. 

Among the elements that make up rocks and minerals, silicon, magnesium, and iron are of almost equal abundance followed by sulfur, aluminum, calcium, sodium, nickel, and chromium. Two of the most common minerals in meteorites and in the terrestrial planets are olivine ((Mg,Fe)2Si04) and pyroxene ((Mg,Fe,Ca)Si03). The composition obtained by averaging these two minerals is very similar to the bulk solar system composition, so it is really no surprise that they are so abundant. 

Murer, Ch. A., Baur, H., Signer, P., Wider, R. (1997) Helium, neon, and argon abundances in the solar wind In vacuo etching of meteoritic iron-nickel. Geochim. Cosmochim. Acta, 61, 1303-14. 

From the isotopic decomposition of normal nickel one finds that the mass-58 isotope, 58Ni, is the most abundant of all nickel isotopes 68.3% of all Ni. Using the total abundance of elemental Ni = 4.93 x 104 per million silicon atoms in solar-system matter, this isotope has... 

Iron is the second most abundant metal after A1 and the fourth most abundant element in the earth s crust. The earth s core is believed to consist mainly of iron and nickel, and the occurrence of iron meteorites suggests that it is abundant throughout the solar system. The major iron ores are hematite (Fe203), magnetite (Fe304), limonite [FeO(OH)], and siderite (FeC03). 

Based on the bulk chemistry, IDPs are divided into two groups (i) micrometer-sized chondritic particles and (ii) micrometer-sized nonchondritic particles. A particle is defined as chondritic when magnesium, aluminum, silicon, sulfur, calcium, titanium, chromium, manganese, iron, and nickel occur in relative proportions similar (within a factor of 2) to their solar element abundances, as represented by the Cl carbonaceous chondrite composition (Brownlee et al., 1976). Chondritic IDPs differ significantly in form and texture from the components of known carbonaceous chondrite groups and are highly enriched in carbon relative to the most carbon-rich Cl carbonaceous chondrites (Rietmeijer, 1992 Thomas et al., 1996 Rietmeijer, 1998, 2002). 

Harkins (1917) showed that 99% of the material in ordinary meteorites consists of seven, even-numbered elements - iron (Fe), oxygen (O), nickel (Ni), silicon (Si), magnesium (Mg), sulfur (S) and calcium (Ca). However, Payne (1925) and Russell (1929) showed in the 1920s that the solar atmosphere is mostly hydrogen (H) and helium (He). Today there are theories (e. g. Manual et al. 1998) that the sun s chemical composition (at least in the core) is similar to that of meteorites, i.e., Fe is the most abundant element. 

The study of the comet particles returned by the Stardust Mission could have been made easier and more comprehensive if aerogels other than silicon dioxide had been used. This is due to the fact that since silicon was the major element in the capture medium and most of the Wild 2 particles fragmented and mixed at the microscopic scale with the aerogel, it was not possible to determine elemental ratios using silicon as the standard, for example, iron to silicon ratio and nickel to silicon ratio. Silicon is typically used as the standard for the determination of elemental abundances in geochemistry and cosmochemis-try, since it is found throughout our planet and the solar system. Since silicon could not be used and iron was used as the standard element for the Stardust geochemical analyses. 

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