Life Cycle of Stars

 

Birth:

Stars are born in nebulas – clouds of gas and dust that represents the raw materials that stars are made of. 

Nuclear fusion takes place inside stars; in this process, hydrogen atoms are fused together to form helium atoms.  Some mass is given off in the form of energy - heat and light - this is what makes stars shine.

 

Main Sequence:

This is the time in between birth and death, how long a star spends in the main sequence phase depends on its mass.  When a star is in the main sequence phase its temperature and luminosity are stable.  Most visible stars are in the main sequence phase; the sun will spend about 10 billion years in the phase.

 

Death:

After millions to billions of years, depending on the stars mass, stars run out of hydrogen atoms to fuse and the stars starts to die.  Without it’s main fuel supply, nuclear fusion stops and the stars outer layers begin to collapse in on itself.  This pressure of the stars collapsing causes the temperature to increase and the star expands – this is called a red giant, the stars first step towards death. 

 

Medium Sized Stars – (up to 1.5 times the mass of the sun)

Stars with solar masses of .4 – 3 will become go through this stage.  After red giant, they turn into a white dwarf.  This is the phase when the star begins to cool down and gives off a white glow.  After white dwarf comes black dwarf, this is when the star is cold and still.

 

Huge Stars – (from 1.5 to 3 times the mass of the sun)

Like medium sized stars, huge stars go into the red giant phase when nearing death.  After red giant comes supernova – this is the most powerful force in the universe, all the heavy elements were created in supernova explosions.  After the supernova explosion the star is a neutron star.  A neutron star is usually 10 miles in diameter and has 1.4 times the mass of the sun, they spin very rapidly and are the densest known objects in space.  If a neutron star emits radio waves, or “pulses”, it’s called a pulsar.

 

Giant Stars – (over 3 times the mass of the sun)

Like huge stars they go from red giant to supernova, but instead of producing a neutron star they end in a black hole.  Black holes are collapsed cores of giant stars, inside a black hole space and time stops.  Black holes have no volume and such a strong gravitational force that even light cannot escape.  Black holes can only be detected by the radiation emitted from objects that are sucked into them.

 

Hertzprung-Russell Diagram:

This is a diagram, which shows the relationship between the absolute magnitude, amount of light a star actually gives off, and the surface temperature of stars.