1. Life Cycle of Stars

3. 1st Step: Stars form from nebulas
Regions of concentrated dust and gas left from the BIG BANG (or other stars’ demise)
Gas and dust begin to collide, contract and heat up
All due to gravity, even the smallest particle has gravitational attraction!
[What 2 things affect gravity?]

4. Eagle Nebula
Orion Nebula

5. Horsehead Nebula

6. Triangulum Nebula

7. 2nd Step:
As nebula contracts, a small star is formed
Called a protostar
Eventually, the protostar will begin nuclear FUSION
Hydrogen protons attract to each other
Strong nuclear force (Nucleus particles stick)
Heat (15,000,000° C) + gravity and…..
\FUSION begins
Continued FUSION is necessary for stars to survive.
Can take 30,000,000 years for protostar to form

11. 3rd Step: The Hertzsprung-Russell Diagram
Star joins the main sequence
90% of stars spend life here
Nuclear fusion = Hydrogen into Helium
Mass of star determines location on main sequence
Ranges in size from ½ Sun to 20 times the Sun’s size
Color depends on the surface temperature

14. Beginning of the End: Stars begin to die when they run out of hydrogen
Gravity begins to take over

15. Really Low Mass Star Doesn’t burn Hydrogen (dud) 
Begins to cool and forms a Brown Dwarf

17. Low Mass Stars From ½ all the way down to 0.075% of the Sun’s mass
Burn cool, less than 3500 K. Dim light.
Can live a REALLY long time. 10,000,000,000,000 years?
Our nearest star neighbor is Proxima Centauri, a red dwarf.
Most numerous stars in the entire Universe!

18. Intermediate mass Stars (like the Sun up to 5x Sun)
Star core begins to shrink; outer core of hydrogen begins to fuse and expand
Star gets bigger

19. Red Giant!

20. Eventually the outer shell is blown off (planetary nebula) and the remaining core is a white, hot and small…
White Dwarf!

23. High Mass Stars—form supergiants!

24. Supergiant
Red Giant S S

26. Supernova! Life Cycle of Stars Core is no longer fusing (iron is it!)
The balance of pressure loses and the entire star collapses
Massive explosion
Creates heavier elements
Supernova!

28. Neutron Star
Star with a core from 1.4 to 3 times the size of the Sun becomes a neutron.
Electrons and neutrons combine into neutrons.
10 km (6 mi) in diameter with a mass more than our Sun!
A teaspoon of neutron star would be about 10 million tons
Acts like a huge magnet with magnetic poles, can be a pulsar

30. What is a Black Hole???
An object so massive and dense that not even light can escape its gravity
The end result from a supernova that leaves a core of 3+ times the Sun.
Collapses to a singularity
Black Holes Info Sheet

32. Life Cycle of Stars Recap: Death of Stars: Low and Medium Mass
Main Sequence Star
Red Dwarf
Red Giant
Planetary Nebula
White Dwarf
Black Dwarf

33. Death of Stars: High Mass
Life Cycle of Stars
Death of Stars: High Mass
Main Sequence Star
Red Super Giant
Supernova
Neutron Star
Black Hole

34. Life Cycle of Stars Recap: High Mass Stars:
Core size greater than 1.4x our sun
Create high mass elements such as iron
Neutron Star
Formed if remaining star is 1.4-3x sun’s mass.
Black Holes
Formed if remaining star > 3x sun’s mass
Recap Video

35. Death of Stars: What stars end up as depend on mass
Low and Medium mass stars
Planetary nebula white dwarf
High mass stars
Supernova neutron star or black hole

36. What about our Sun?
As fusion begins to slow down, the core of the sun will contract
Temperature in the core will rise
The outer layers of the sun will expand, consuming in the inner planets
Sun will become a Red Giant

37. Video Link

38. Continuing over the next 100 million years…
Core of the sun will begin to fuse helium into larger elements such as carbon and oxygen
Continuing over the next 100 million years…
Core will become entirely carbon and oxygen
Core will contract
Outer layers will expand
Outer layers will form a planetary nebula
Core of sun will become a white dwarf

39. What about our solar system?
How did it start?

40. Gravity, gas pressure, magnetic fields, and rotation cause disk to form around protostar.
Conservation of angular momentum! 