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Q&A: Normal Stars, White Dwarf Stars, and Star
Clusters
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Q:
How are stars formed?
A:
Understanding how stars are formed has proved to be a difficult
task. One reason for this is that stars are born in the dark,
inside huge clouds of dust and gas. These clouds obscure the
view of optical wavelength telescopes until the new star’s
radiation can clear out a region around it. Infrared and radio
waves can pass through the dense clouds of dust and gas, so the
development of powerful infrared and radio telescopes has led to
greatly improved understanding of the star forming
process.
What we know is this:
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Stars form in huge clouds of molecules and dust, called
Giant Molecular Clouds (GMC). These clouds can range
from tens to hundreds of light years in diameter and
contain enough material to make thousands to millions of
stars.
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Stars don’t form alone but in clumps or clusters of
dozens to thousands of stars when a portion of the GMC is
compressed, increasing its gravity and causing it to
collapse.
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As it collapses, the large fragment breaks up into smaller
fragments which eventually become individual stars.
Observations show that the birth weight of stars can range
from a few percent to 50 times the mass of the Sun.
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It is not known for certain what causes the initial
compression of a GMC fragment. There is evidence that
shock waves play a role. These shocks could come from a
supernova explosion, or fierce winds blowing from a
cluster of newborn stars, or from a collision of the
entire galaxy with another galaxy. See
Starburst Galaxies
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