Answer Key for
Cosmic Abundances Activity
This activity provides practice for reading and interpreting the log plot of solar system elemental abundances.
Refer to the chart of the solar system abundances ...
Cosmic Abundances
The relative proportions of chemical elements in the Sun, the solar system, and the local region of the Milky Way galaxy.
cosmic abundances A standard listing of the relative numbers of the various elements, determined by studies of the spectral lines in astronomical objects and averaged for many stars in our cosmic neighborhood.
TABLE 21.1 Cosmic Abundances of the Elements
ELEMENTAL GROUP OF PARTICLES PERCENT ABUNDANCE BY NUMBER*
Hydrogen (1 nuclear particle)
90 ...
A peak in the cosmic abundance of elements near to iron. It arises from the high stability of the iron nucleus which makes it the end point for normal nucleosynthesis reactions.
IRREGULAR GALAXY ...
Second, and most importantly, the observed abundances of elements other than nitrogen in the atmosphere do not match the cosmic abundances expected from simple accretion from the nebula. One example mentioned by Owen (1982) is the abundance of neon.
Cosmic Abundance of Helium and Hydrogen
The Big Bang theory provides a natural way to explain the present abundance of the elements.
Figure: Relative cosmic abundances for the different elements. There are peaks at carbon, oxygen, neon and iron corresponding to important elements in nucleosynthesis.
These are amongst the oldest stellar systems known within our own Galaxy and they have very low abundances of the heavy elements relative to the average cosmic abundances.
GeH4, PH3, and As3 are also consistent. SiH4 is predicted to be unobservable if it has an internal origin. Its lack of detection despite its much higher cosmic abundance therefore argues against an external origin.
alpha process leads inevitably to the buildup of iron in the stellar core. Because helium-capture reactions are so much more common, elements with nuclear masses of 4 units (4He, 12C, 16O,20Ne, 24Mg, and 28Si) have markedly higher cosmic abundances ...
One is that nucleosynthesis in an early hot universe correctly accounts for the cosmic abundance of the light nuclear isotopes such as hydrogen, deuterium, helium-3, helium-4, and lithium-7.
For some elements the abundance of a particular nuclide depends on the source. [DC99]
(c) The relative amounts of chemical elements. For example, hydrogen makes up about 75 of the mass of the Universe, so its "cosmic abundance" is 75%. [LB90] ...
 See also: Element, Elements, Earth, Hydrogen, Solar
  
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