When a massive star dies, it explodes in a supernova. This explosion releases a tremendous amount of energy and matter into space. The matter from the supernova can then form new stars and planets.

The process of star formation begins with the collapse of a cloud of gas and dust. This cloud is called a nebula. The nebula is made up of hydrogen, helium, and other elements. As the nebula collapses, it heats up and begins to glow. This glowing nebula is called an emission nebula.

At the center of the emission nebula, a protostar forms. A protostar is a young star that is still forming. The protostar continues to grow as it accretes more and more matter from the nebula.

Eventually, the protostar becomes hot enough to ignite nuclear fusion. This is the process by which stars generate energy. Once nuclear fusion begins, the protostar becomes a main-sequence star.

The main-sequence stage is the longest stage in a star's life. During this stage, the star burns hydrogen into helium. The star will remain on the main sequence until it runs out of hydrogen.

When the star runs out of hydrogen, it begins to evolve off the main sequence. The star will become a red giant, then a white dwarf, and finally a black dwarf.

The death of a massive star can trigger the formation of new stars. The supernova explosion releases a tremendous amount of energy and matter into space. This matter can then form new stars and planets.