Sunday, November 18, 2012
Unknown
In astronomy, the metallicity of an object is the proportion
of its matter made up of chemical elements other than hydrogen and helium. Majority
of visible matter in the universe is hydrogen and helium; hence elements other
than this are together termed as ‘metals’. (Do not confuse metals in astronomy
with the definition of metals in chemistry).
As we know, older stars have lesser metallicities. Based on
this, stars are divided into 3 categories namely population I, II and III. The oldest
and the newest stars are populations III and I respectively.
According to current stellar models, population III stars
would have exploded to form supernovae; dispersing metals all over the
universe. Since these stars exploded a long time ago, their existence is
believed to be restricted only in distant galaxies. But proving their
non-existence still remains a debatable issue.
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