The First Stage To A Star - Nebula A stars life is like a human, it begins almost as a fetus, then infant, adult, middle-aged, and then death. The first stage to a star is called the nebula. A nebula is a cloud of gas and dust. The element hydrogen makes up 97% of the nebula, and the other element helium takes up 3% of it. The rest of the other elements are less than 1%. Gravity will begin pulling all of the particles together. Then the cloud of the particles in the nebula begin to collapse because of the gravity. After that, the temperature and density increase. The outcome of this is that the nebula becomes a proto star.

PROTO STAR A proto star is a dense area of gasses in the nebula that might become a star. If it doesn’t get larger that one-tenth of mass of the sun, then is becomes a Brown Dwarf. The Brown Dwarf does not get hot enough to start a fusion, which is It is the reaction in which two atoms of hydrogen combine together, or fuse, to form an atom of helium. They shine dimly, but in time they cool off. If the proto star gains enough mass, or weight, then it becomes a star called the Main Sequence. MAIN SEQUENCE  The lifecycle of the main sequence depends on the amount of mass it has. Larger stars fuse hydrogen very fast. These stars may run out of hydrogen in 20 million years. Medium sized stars (like the sun) fuse hydrogen more slowly. The sun will burn for a total of 10 billion years! Small main sequence stars fuse hydrogen very slowly. They may last one trillion years.

Red Giants and the Planetary Nebula bula.gif A Red Giant star is small to medium sized, and it runs on the element hydrogen. It begins to fuse the element helium. When this happens, it becomes a planetary nebula star. This is when the red giant star t totally and completely stops fusing and the outer layers of the star are driven away.

 Only the hot core of the star remains from the planetary nebula. This core becomes a very hot young white dwarf, which cools down over the course of about billion years. Then when the billion years are over, it turns into a black dwarf. This is when it has cooled down enough that it no longer emits light.light

Massive Main Sequence Instead of fusing the hydrogen much slower that the small and medium stars, it begins to fuse even faster for the high mass stars. This means that they live less longer than the smaller ones because it doesn’t fuse as slow in order to make more time to live. The massive sequence stars eventually turns into a Red Supergiant. g

The Supernova and the Neutron Star!! When the fusion entirely stops, the star collapses and creates a huge explosion. When viewed from the earth, a person can see the explosion as a huge ray of light. The burst of radiation, or light, can shine out an entire galaxy. The supernovas are known as the most powerful explosion on the whole universe. Smaller supernovas leave the super giant star’s core behind in the form of a neutron star. A neutron star spins rapidly, at about 600 times per second, and is exceptionally dense, packing about 1.4 times the mass of the sun into an area not much bigger than the city of Chicago in the United States. As a neutron star spins, it creates radio waves which have been detected on Earth. These rapidly spinning stars are often called pulsars.

Last Stage: The Black Hole The black hole is 25 to 50 times more then the sun’s mass left over from a black hole. They are so dense that nothing entering its gravitational field ever escapes, not even light! The edge of a black hole is referred to as event horizon. Once event horizon has reached a body, it cannot escape; it is drawn to the center of mass of the hole, where there is presumed to exist a singularity. Obviously, scientists do not know precisely what can be found at the singularity, as nothing can escape the gravitational field of a black hole. So there is no possible way to see what is beyond a black hole. So for now, it is all just a mystery.

This was a presentation of The Lifecycle of Stars by: