Page 20 - Curriculum Visions Dynamic Book

Globular clusters are the oldest star clusters, averaging about 15 billion years. So these clusters are some of the oldest objects in the Universe.
The life and death of stars
Stars do not last for the entire existence of the Universe. Since the Universe began, many generations of
stars have been formed
and eventually have 3 faded away. As a
result, it is helpful
to think of stars as
having a life cycle.
The life of a star
can be divided
into birth (rapid
change), adulthood
(period of stability),
and decay or death.
The birth
of a star
The Universe contains
a vast amount of gas and
dust in the form of interstellar
matter, which can be made
into stars. It is simply a matter of enough of it coming together to begin a chain reaction.
It is thought that waves of radiation passing through the Universe stir up the interstellar gas and dust clouds, making them swirl around and so become more concentrated.
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Star begins to grow
1—The space between stars contains gas and dust. It can gather into clouds known as nebulae. When enough gas and dust collect in a nebula, it quickly collapses into one or more stars. The gas and dust are drawn ever more closely into a tight ball by the effects of gravity. The fusion that takes place releases enormous amounts of heat. Eventually, the star becomes hot enough to shine.
2, 3—During much of its life a star burns hydrogen gas by fusion and shines brightly, and little change appears to happen.
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