Jul 29 2015

Where is the Sun on the H-R diagram?

In one of my earlier posts I described a Hertzsprung Russell diagram which shows the relationship between a stars temperature and its luminosity. But where does our Sun sit on this diagram? Our sun sits squarely in the main sequence line. The main sequence makes up the majority of a stars life when it is burning hydrogen at the core, steadily and consistently, and it makes up the main diagonal line from bottom right to top left on the diagram. Our Sun has been on the main sequence for about 4.5 billion years and will continue there for another 4.5 billion years. Stars that are larger, brighter and burn hotter than our Sun are further up the H-R diagram towards the blue end of the main sequence while stars that are smaller, dimmer and cooler than our Sun are towards the red end of the main sequence.

Once our Sun starts to use up its hydrogen reserves it will start to burn helium which will make the it expand and dim in brightness, moving it off to the red giant area of the H-R diagram. It will no longer sit on the main sequence and will begin its final journey around the H-R diagram, but where it ends up is for another blog post.


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