The Life Cycle of Stars

Imagine you were an alien from a planet where beings were very different to us. Could you put these photos in the right order?

pics   Barrysclipart.com

Astronomers have observed thousands of stars and have figured out that what they are seeing is a life cycle, just like that above. Stars are born, they grow old and then die.

A good starting point is to plot a graph of the luminosity of different classes (essentially temperatures) of star.

This is called a Hertzsprung Russell diagram.

You should be able to sketch the main features of this very important diagram including labelling the axes. (notice they are logarithmic, not linear)

Clearly there are several patterns here. Different types of star fall into different groups. Most stars, like our Sun at the moment, fall into the group called the Main Sequence. Though in the future it will probably become a red giant and then a white dwarf. The evolution of a star depends greatly on its mass.

Important - Our Sun is in The Main Sequence at this time. At other points in its life it will not be.

By examining the light coming from a star (its spectra) we can determine what class of star it is and where it fits on the diagram above.

Here is the cycle for a heavy star ( greater than 8 solar masses)

pics NASA

A neutron star is incredibly dense, made entirely of nuclear matter. Neutron stars often spin emitting jets of matter and radiation into space. The first pulsars detected were thought possibly to be signals from an alien intelligence until it was figured out that they were spinning neutron stars emitting radio waves.