Yttrium solar abundance

Cowley has done much to dissipate the belief that the Sr, Cr, Eu stars constitute a fairly homogeneous class (with the exception of the three maverick stars discussed above). The number of detectable spectral lines, and their intensities, of yttrium, barium and lanthanides [40] in 29 Ap and A , stars were carefully compared. In most of these stars, yttrium and lanthanum are unexpectedly scarce. The relative solar abundances of 12 lanthanides (altogether... 

Yttrium is a moderately abundant element in Earth s crust. Its abundance is estimated to be about 28 to 70 parts per million. That makes yttrium about as abundant as cobalt, copper, and zinc. As with other elements, the abundance of yttrium is quite different in other parts of the solar system. Rocks brought back from the Moon, for example, have a high yttrium content. 

By the time our sun had formed, countless stars had already completed their life cycles. The clot of gas that produced the sun was a mixture of primordial hydrogen and heavier elements. These heavier elements were essential to producing the inner planets, satellites, asteroids, and other objects in the solar system which cannot be constructed from hydrogen and helium. The bulk of the heavy elements in the solar system is in the outer portions of the sun itself, which contains more than 99.87 percent of all the mass of the solar system. (The outer portions of the sun do not mix with the core, where nuclear reactions destroy heavy elements.) The abundances of yttrium and the lanthanides in the sun s atmosphere have been determined spectroscopically and are believed known with medium accuracy (Ross and Aller, 1976). Pieces of the Earth, the Moon, and meteorites, all of which condensed from the same batch of material as the sun, have been analyzed chemically to determine their abundances. 

Of all the materials sampled in the laboratory, the class of meteorites called chondrites is believed to come the closest to retaining the nonvolatile elements of the solar system in their primitive relative abundances. If the processes that formed those meteorites did not appreciably fractionate the nonvolatile elements, then surely they did not separate yttrium and the members of the lanthanide series from each other. Thus, from analyses of chondritic meteorites, the relative elemental abundances of Y and the lanthanides in the solar system are known to a high degree of confidence. 

Fig. 21.1. Concentrations of lanthanides and yttrium in a composite sample of 9 chondritic meteorites (Haskin et al., 1%8) are plotted against lanthanide atomic number in the lowest part of the figure. Relative lanthanide abundances for the solar atmosphere (Ross and Aller, 1976) and lanthanide concentrations for a composite of 40 North American shales (Haskin et al., 1968) are compared with the chondritic abundances in the middle and upper parts of the figure by plotting ratios of their lanthanide concentrations to those of the chondrites. Such comparison diagrams are used throughout this chapter.

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