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A
STAR IS BORN
The scientists who study the universe and its
origins have evidence that the universe began between 13 and 15
billion years ago. Scientists theorize that within tens of minutes
after the beginning of the universe, space contained hydrogen widely
spread out. After a few million years clumps of hydrogen began to
develop. Gravitational attraction continued to work to pull the
hydrogen even closer together. Eventually the hydrogen began to
clump into clouds of gas. As large masses of hydrogen got closer
together, gravitational attraction compressed the hydrogen more
and more. If the mass was at least half as much as our Sun, then
the hydrogen became so compressed and hot that nuclear fusion began,
and the new star gave off heat, light, and charged particles. This
is a simple story of star birth. A more complete story is contained
in the article "We
are All Star Stuff" by Neil F. Comins and in History
of the Universe.
About 5 billion years ago the Sun also formed
out of clumps of material in space. In the case of our Sun this
material came from the remains of older stars that lived out their
life cycles, converting some of their hydrogen fuel into all of
the other elements of the Periodic Table.
The Hubble Space Telescope has provided us with clear images of stellar
nurseries, notably the Eagle
Nebula, in which stars are being born.
The material was made of gas and
dust at very low densities. Again, gravitational attraction caused
the matter to contract and rotate faster. Shock waves from the explosion
of a nearby star may have accelerated the process. Increased density
resulted in increased contraction and more matter was attracted
to the location of our developing star. The rate of rotation also
increased due to conservation
of angular momentum. The roughly spherical cloud flattened into
a disk with a fat center. The center contained most of the gas and
dust. The outer regions of the disk clumped together forming the
planets. At some point the contraction of the center developed such
intense pressure that nuclear fusion reactions were started and "A
Star Is Born". The concept of the Sun as a spinning nuclear
fusion furnace seems to be a reliable foundation for our research.
However, other details of The
Amazing Structure of the Sun are important to understanding
our closest star and how it affects Earth.
+ Website Link for a simple explanation of the
birth of a solar system
+ Website Link to a tutorial on star formation with
discussion of evidence at a college level
+ Back to Sun &
Earth Background | +
Top | + Next Adventures
in Geospace
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