Stellar Evolution

In the Beginning A star begins as a cloud of gas and dust called a nebula According to Newton, the gravitational force increases as the distance between molecules decreases Particles come together to start to form a sphere of gas and dust As the nebula shrinks it spins more rapidly The nebula’s shrinking and spinning causes it to flatten into a disk shape.

Protostar Stage 1 of stellar evolution is the formation of a protostar. The center of the rotating disk is called a protostar The temperature increases from more and more collisions of particles as they get closer. The pressure also increases. When the temperature get to about 10,000,000º C nuclear fusion begins and a star is born.

Main-Sequence Stars Stage 2 of stellar evolution is a main sequence star. Stars remain main sequence stars for 90% of their life. It is the longest stage in stellar evolution. In the core, nuclear fusion is taking place. The first fusion to take place is hydrogen atoms fusing to become helium atoms. The star stays about the same size because the gravity is pulling together even though energy from nuclear fusion is pushing outward. The star is stable as long as there is enough energy to continue nuclear fusion.

Giants and Supergiants Stage 3 of stellar evolution are red giants and supergiants. Begins when almost all of the gases are used up by nuclear fusion and the star does not have enough energy to continue nuclear fusion. The core of the star becomes unstable. The star expands and changes temperature and luminosity (brightness).

White & Black Dwarfs This is the 4th and 5th stages of small mass stars. Small mass stars will collapse into white dwarfs after being red giants. The outer gases are lost, which allows us to see the core of the star. The white dwarf is very dense and hot. The emit (release) less light than they did when they were stars. As these white dwarfs cool they become fainter. When there is no more energy being emitted (released), they are called black dwarfs.

Supernovas This is the 4th stage of large mass stars. Some red giants and red supergiants explode in a supernova. Supernovas can result in one of three things: neutron star, black hole, or nebula

Black Holes Some stars are so massive that they cannot form neutron stars. Instead they form black holes The force of gravity is so strong that everything, including the core, is crushed inward. The gravity is so great that light cannot escape it.

Poster Requirements Title – Stellar Evolution or something appropriate. All steps in stellar evolution included Three facts for each step A picture for each step Needs to show order (arrows to next step) Has to have color and labels for each step Be creative!!!