gcsescience.com                                                                       32                                                                       gcsescience.com

The Earth and Beyond

Stars  -  Life Cycle - Main Sequence.

After nuclear fusion reactions have begun, there are two opposing forces.
Gravity is the force causing the star to contract.
The heat released from fusion causes the star to expand.
These opposing forces balance each other
and the size of the star stays almost constant (the same).
The star has entered a stable phase (meaning it stays the same)
and it is now called a main sequence star.

The length of time that a star lasts as a main sequence star
depends on how big it is.
Big stars use up their hydrogen at a much faster rate than small ones.
The Sun has been a main sequence star for five billion years.
It is expected to last for another five billion years.
The Sun is about half way through its main sequence phase.

   Headings   The Earth and Beyond    Stars   Search   Questions  

gcsescience.com              Contents             Index              Quizzes             gcsescience.com

Copyright © 2008 Dr. Colin France. All Rights Reserved.