Download Red Giants: Giants, Dwarfs And Black Holes

Red Giants: Giants, Dwarfs And Black Holes
Depending on the size of a star, and what it is made of, a red giant can burn for millions of years. Eventually it collapses,
throwing pieces of white material everywhere. The pieces are lost in space, each becoming a tiny white dwarf· Although
white dwarfs are small compared to red giants, they have a lot of mass in a small volume (that is, they are very dense). In
the same way that shearers can pack enormous amounts of wool into fairly small bundles, so does a red giant ‘pack a lot
of star’ into a white dwarf. If a white dwarf were the size of an apple, it would weigh more than a large herd of elephants!
If the red giant star is heavier than usual, at least three times heavier than our Sun, it reaches an enormous supergiant
stage. Like any red giant, the heavy star expands to an incredible size in a final search for more fuel. Eventually it
undergoes a massive explosion called a supernova. Supernovae are so intense that they can be one billion times brighter
than our Sun and can create the mysterious black holes and neutron stars. It is at the point just before the supernova
explosion occurs that the awesome supergiant is created. From this point, one of the following two paths can be
followed.
i
If the star was twelve times heavier than the Sun (or more) and the supernova explosion did not destroy it, a super-compressed neutron star can result.
ii
If the star was destroyed, a black hole (‘collapsar’) is created.
1
Below is an illustration of the birth and death of a star. Copy the diagram and label the steps.
f _______________
c _______________
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b _______________
g _______________
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a ________________
d _______________
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e _______________
h _______________
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2 What does this define: ‘A hypothetical invisible area having a small volume but an immense gravitational field’?
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3 What does this define: ‘The explosion of a very large star releasing large amounts of energy’
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4
What does this define: ‘A bright star, much larger than the Sun, with a relatively low
surface temperature?’
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