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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
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Website Link to a tutorial on star formation with
discussion of evidence at a college level
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