1. The Life Cycle of a Star

3. What is a Star? A star is ball of plasma undergoing nuclear fusion.
Stars give off large amounts of energy in the form of electromagnetic radiation.

4. Nebula – Birth of Star Stars are formed in a Nebula.
A Nebula is a very large cloud of gas and dust in space.

5. Protostars Gravity makes dense region of gas more compact
Soon take on a definite shape and are called protostars.

6. A new star!!
Once the core of a protostar reaches 10,000,000o C, nuclear fusion begins and the protostar ignites.
The protostar now becomes a star.
The bright spot is a new star igniting

7. Nuclear
Fusion
Nuclear Fusion is the process by which two nuclei combine to form a heavier element.
New stars initially will fuse hydrogen nuclei together to form helium.

8. Sort the stars by color, putting the blue stars on the left and the red stars on the right.
ω Centauri

10. Patterns among the stars?
Graph of color (temperature or spectral type) vs. magnitude (luminosity)
Stars don’t just fall anywhere, they tend to lie along a few well-defined sequences.
A star’s color and brightness tell us where a star lies in this diagram.
The unmistakable order in diagrams like this led astronomers to develop theories to explain stellar evolution.

11. Brightness vs Temperature
On the H-R Diagram, stars with similar physical properties fall into groups together.
HR DIAGRAM
Brightness vs Temperature
Main Sequence
Giants
Super giants
White Dwarfs