Gas and dust particles are pulled together by gravitational force.
Clumps of gas and dust will from within a nebula and continue to become more massive. A center core forms and begins to rotate.
When the core reaches a temperature of approximately 15 million °C, nuclear fusion begins and a star is born. Nuclear fusion is a process that produces energy caused by two nuclei joining to form one large nucleus.
Massive stars consume hydrogen very rapidly; the core gets so hot that the helium can fuse into heavier elements. So much energy is released that the star swells into a super giant.
Silicon in the core is transformed into iron, which results in a huge explosion called a supernova. Once the core has become iron, no more fusion can occur an the core collapses.
If the remaining core is about 1.4 to 3 solar masses, gravity causes it to collapse down to an extremely dense object known as a neutron star.