Comparing Stars

Stars are very mysterious. They are composed of only gases, yet they are able to hold their own gravity. Most bodies need to have more mass to accomplish this. But by this gravity, the star pulls itself inward, and attempts to condense or collapse. This would occur, but due to the pressure that the gases exert, the star is unable to collapse, which forms a star. During most of the stars life, or the "Main Sequence", the main reactions occur near the center and create nuclear energy. The phase that occurs before the "Main Sequence" is the "Contraction" phase, where the center of the star is unable to create enough heat to form reactions, but due to the gravity, the star begins to collapse, and forms pressure, which builds up heat to get to the "Main Sequence." Through the "Main Sequence" the star uses up the energy in the center, and there is no more reactions occur. But because of the lack of reactions, there is no longer pressure in the star, and then it collapses. This is the basic life cycle of a star. This is good to know because there are many different types of stars.

Red Giant: A red giant is a star near the ending of its Main Sequence. It does not have reactions occurring in the center of the star, and they mainly occur in the outer regions of the star, but these are not powerful enough to fuse and create the necessary energy to survive too long. The star begins to contract in upon itself, and the outer shell moves into the center of the star and begins to use up the outer gases and begins to swell. This is what makes it a "giant". The reactions become even hotter that it was previously due to the new energy source, which makes it red due to the immense heat.

The Sun: Our sun is obviously one of the main attractions of our solar system. It has been active for what scientists believe to be about 4.6 billion years. This allows the sun to be active for several years. About 5 million to be exact. So this means that it is about 3/4 of the way through its Main Sequence. After that, the sun will grow to become a Red Giant. But after the Red Giant stage, there is one other stage that follows.

White Dwarf: After a star has used up all of its energy, it collapses and becomes a white dwarf. It starts by removing all of the material from within itself and forms a nebula. Then it begins to cool down, which can take thousands upon billions of years. These are the result of a medium to low energy stars. They are very common in our own galaxy, the Milky Way. The mass of a White Dwarf can be over the Chandrasekhar limit, which is the limit of the weight of a White Dwarf. But this equals about one and a half of our own sun. Most of the White Dwarf are about half of the Chandreadekhar limit though.

Black Holes: Black Holes are supposedly collapsed massive stars. Stephen Hawking is one of the great idealist about Black Holes. He came up with the Paradox Theory. This is based on where there are several different dimensions that if matter is thrown into a black hole, it will be expunged into an alternate dimension. This new dimension does not have a black hole at that location. There was a lot of scepticism about this Theory, and he knew it. So he came up with another theory, and is still working on maintaining that theory.

The stars that form Black Holes are about 10-15 times more massive than our own sun. They are relatively small, and are hard to locate. But there is some research being done and they believe that there is a black hole in the center of each Galaxy. This is what causes the galaxies to rotate all of the matter surrounding it. So it's similar to the our solar system, but on a much larger scale. There is still a lot to learn about Black Holes and there are several different theories and beliefs about them. Which do you believe?