There we have it. The makings for a star are all laid out. The main ingredient: hydrogen. Although this does not sound like much of a tasty meal, the cooking process is worth the anticipation.

Although it may not be obvious to everyone hydrogen has weight. Because hydrogen floats some people are inclined to believe it has no weight. In reality it simply has less mass than the oxygen compound O2 we breath. So it just appears to be weightless.

Since hydrogen has weight, it has mass. Since it has mass, it has a gravitational pull. When a large enough mass of hydrogen builds up the gravitational pull of the mass begins to pull it to one center point. The process is slow, but so worth the wait.

Now the hydrogen's gravity has pulled it into a tight enough space the real fun can begin. There is an enormous amount of hydrogen producing an enormous amount of gravity. This gravity compresses the gas into a spherical form. That sphere is further crushed by the incredible gravity.

Since there is so much gravity pressing the hydrogen together they start to fuse together. Much the same way pieces of clay would if you pressed them together. However unlike clay, these hydrogen atoms become something completely different. The hydrogen becomes helium. The process of fusing into helium also emits a large amount of energy in the form of heat and radiation. This is what the star's light and heat come from. The resulting helium, being heavier than hydrogen, sinks into the center of the sun.

This process of fusing hydrogen into helium is called the star's Main Sequence. During the main sequence, the star is not actually burning hydrogen, it is turning it into something else.

The high level of energy being produces pushes out and away from the star. The only reason the star doesn't fly apart like a nuclear explosion is because the star's gravity is still crushing it. This balance between gravity and nuclear fusion forms an equilibrium maintaining the star from either flying apart or being crushed.

The main sequence cannot last forever. Eventually enough hydrogen is smooched into helium that there is not enough left to maintain the equilibrium. The gravity then begins to crush the star. Then the star gets a new lease on life. The gravity starts fusing the helium.

The star works in much the same way it did when it was in its main sequence. The fusing releases energy and that energy pushes against the gravitational pull of the star's mass. The fusing helium turns to carbon. That heavy carbon, now the heaviest element in the star, sinks to the center.

Now if this were any normal star, this would be the end of its life as a burning star. Once the helium is all gone the star would turn into nothing but a glowing clump of carbon called a White Dwarf.

However this is no normal star. This is a freakin huge star! It has a mass equivalent to thirty Suns (30 solar masses). So it has more phases to go through. It fuses that carbon. That carbon fuses into oxygen. After it finishes fusing the carbon, it fuses oxygen. That oxygen fuses into neon, which in turn fuses into silicon, then sulfur, then finally it fuses into iron.

Now the star has a problem. The sulfur is nearly finished fusing and the star is losing its nuclear power. The gravity gains the upper hand and begins to crush the star again. If the star has enough mass, it will start to fuse iron. However fusing iron does not produce the desired

effect of enormous nuclear power. The gravity finally has its way with the star, but the star has one more trick up its sleeve.

Keep in mind that this star has been fusing for a long time. Its surface is very hot. As the gravity compresses the star, that heat is also compressed, and the temperature rises. The collapse of the star is quick, and what results is even quicker. An explosion occurs resulting from the compression. This is called Supernova.

This supernova produces so much force that the elements cast away are fused together, forming the heavy elements we find in our world today.

The outer layers of the star explode into a flash of energy greater than everything the star has produced to this point. The explosion escapes the star's gravity at 1/100^th the speed of light. This shock wave of burning mass is called a super nova reminiant.

Only the outer layers of the star were flung off with the supernova. The remaining heavy elements such as iron in the center of the star remain. The gravity continues to crush these elements down to what is oddly called Infinite Density.

Once the star is at infinite density the gravitational pull is so great in such a small area that the star is no longer capable of expelling its energy. Any radiation, light or otherwise, cannot escape the relentless pull of gravity. This is called a Black Hole.

This Black Hole's mass, and therefore its gravitational power, is actually significantly lower than when it was a standard star, but it is so compressed that it takes on exaggerated properties. The gravity of the black hole can swallow planets, nebula, or even other stars.

It was the general belief of scientists for a long time that this was the end of the star. Black holes never forfeit any mass, so it could never lose any gravity. If it never lost gravity, it would always exist.

We might know better now. Taking into account the concept of Anti-particles, the end of a black hole seems like a real possibility, albeit a far off one. The black hole's gravity ensures that even right before its threshold, called the Event Horizon, is something. The space is not entirely empty because the gravity exists there. This gravity creates particles. These particles are created in pairs, positive and negative particles. They spread apart then crash into each other in normal space.

So in normal space these particles come into existence, exist for an instant, then cease to exist when they collide. However, if standing at an event horizon, you are not in normal space. The negative particle gets sucked into the black hole, while the positive particle might escape as radiation.

This negative particle needs to collide with something. Its brother positive particle is now out of reach, so it collides with the first particle it meets inside the black hole. Both disappear and the black hole just lost some mass.

Keep in mind that this is an mindbogglingly slow process. Even if a black hole was created at the theoretical start of the universe, it would not have reached this point by now. Also anytime the black hole eats any matter, it adds more particles to its mass, increasing the number needing to be destroyed.

When the black hole does eventually come to its end some believe that it explodes as its pent up mass overcomes the gravitational pull crushing it. This release of energy would be staggering.

Images courtesy of NASA.