Massive stars are continually being created in our spiral arm galaxy. Plasmas of energetic protons and electrons combine and form hydrogen, the lowest element on the periodic table. [In many cases, the plasmas of elementary particles were ejected during past supernova explosions.] A new star is formed as this super heated hydrogen accumulated into a great spherical ball.
The process of fusion begins as the star gains sufficient mass. Two atoms of hydrogen are combined and transformed into an atom of helium releasing vast amount of fusion energy. O-type stars are very hot and luminous, and appear in the visible spectrum as bluish-white stars. These stars are commonly called giants, and supergiants. These stars have between 15 and 90 times the mass of our Sun and surface temperatures between 30,000 and 52,000° K.
They are between 30,000 times and several million times as luminous as our Sun. The massive O- and B-type stars that occupy the spiral arms have relatively short life spans in the order of 3-30 million years depending on their size. As these stars exhaust their nuclear fuel, they self-destruct in a massive explosion called a supernova leaving behind a dead carcass called a black hole.
The reason why these stellar remnants are referred to as black holes is because they are essential invisible. In general, light and matter that enters a black hole never comes out again. After a black hole has formed, it can continue to grow by absorbing mass from its surroundings. By absorbing and merging with other stars, black holes can grow in size. Some black holes are so large that they anchor entire galaxies together with its massive gravitational force. Generally these supermassive black holes exist in the centers of most galaxies. For example, Sagittarius A, at the core of our own Milky Way galaxy, contains a supermassive black hole with an estimated mass equivalent to approximately 4.3 million times the mass of our sun.......To Read More....