The Star Cycle

-All stars start out as a nebula, which is a cloud of matter usually made up of hydrogen and dust floating in open space.

-There are different types of Nebulas.  An Emission Nebula glows has its bright glow because of previously formed Nebulas.  Reflection Nebulas reflects light onto the dust of the nebulas (Pleides cluster).  Dark Nebulas are dense clouds of hydrogen that completely absorb surrounding light.

The Horsehead Nebula

- A planetary nebula surrounds an already formed star.

-Surface temperatures of stars range from 2000 degrees celcius to over 30000 degrees clecius.  Stars that are red in color and stars that are blue in color are the hottest.

-The smallest size a star can be is 8% the size of the sun, smaller than that and nuclear reactions cant take place.

- Our sun is a red giant-very bright because of its size, not surface temperature.  Compared to other stars, the surface temperature of our sun is quite "cool".

- When a star becomes a Red Dwarf, it is very cool and small, usually one tenth the diameter of the sun.  They burn very slowly and last for 100 billion years.  An example is the star Proxima Centauri.

- A White Dwarf is very small and hot and is the last stage in the star cycle.  Eventually, the sun will become a White Dwarf.  The surface temperature will rise and so will the density.

 A white dwarf star.