High mass second phase

http://www.youtube.com/watch?v=A-83VlAqXf0

High mass second phase:

If the star is 10 times  bigger then our sun it will go through Supernova stage (picture above). This is a massive explosion.

Once massive stars reach the red giant phase, the core temperature increases as carbon atoms are formed from the fusion of helium atoms. Gravity continues to pull carbon atoms together as the temperature increases forming oxygen, nitrogen, and eventually iron. At this point, fusion stops and the iron atoms start to absorb energy.

Gravity gives the supernova its energy. Once the core has gained so much mass that it cannot withstand its own weight, the core collapses. This implosion can usually be brought to a halt by neutrons – the repulsive force between the nuclei overcomes the force of gravity. This is only thing in nature that can stop such a gravitational collapse. When the collapse is abruptly stopped, matter bounces off the hard iron core, producing shockwave and thus turning the implosion into an explosion: Ka-BOOM. A supernova can light up the sky for weeks. The temperature in a supernova can reach 1,000,000,000 °C.

After this there are two other paths that the star can take, based on the size of the remnant. It can either become either a Black Hole or a Neutron Star.

Both the Neutron star and the black hole have high density.  Just one teaspoon from the Neutron star would weigh 10 million kg!