1. The birth, life, and death of stars By Nigel Sangster
Lifecycle of Stars
The birth, life, and death of stars
By Nigel Sangster

2. Contents What is a Star? Where do stars come from?
The evolution of stars
What happens to stars at the end of their lives?

3. What is a star?
A star is a massive, luminous sphere of gas held together by gravity.
For the majority of its life, a star shines due to thermonuclear fusion of hydrogen into helium in its core, releasing energy that traverses the star's interior and then radiates into outer space.
Almost all naturally occurring elements heavier than helium are created by stars, either via stellar nucleosynthesis during their lifetimes or by supernova nucleosynthesis when very massive stars explode.

4. The Sun
The Sun is the nearest star to the Earth and is a very average star.
Here you see the sun viewed through a Hydrogen Alpha filter and can clearly see a massive coronal loop.
These are caused by the Sun’s chaotic magnetic field.

5. The Sun’s magnetic field

7. Hertzsprung–Russell diagram

8. Where do stars come from?
After explaining the diagram, switch to the simulation.

9. Young star with protoplanetray disc

10. Pillars of Creation

11. Tarantula Nebula

12. Orion Nebula

13. Pleaides

14. Double Cluster in Perseus

15. As stars of at least 0.4 solar masses[2] exhaust their supply of hydrogen at their core, their outer layers expand greatly and cool to form a red giant.
For example, in about 5 billion years, when the Sun is a red giant, it will expand out to a maximum radius of roughly 1 astronomical unit (150 million kilometres), 250 times its present size.
As a giant, the Sun will lose roughly 30% of its current mass.[61][68]
In a red giant of up to 2.25 solar masses, hydrogen fusion proceeds in a shell-layer surrounding the core.[69] Eventually the core is compressed enough to start helium fusion, and the star now gradually shrinks in radius and increases its surface temperature. For larger stars, the core region transitions directly from fusing hydrogen to fusing helium.[4]
After the star has consumed the helium at the core, fusion continues in a shell around a hot core of carbon and oxygen. The star then follows an evolutionary path that parallels the original red giant phase, but at a higher surface temperature.

16. Supergiant Structure
During their helium-burning phase, very high mass stars with more than nine solar masses expand to form red supergiants. Once this fuel is exhausted at the core, they can continue to fuse elements heavier than helium.
The core contracts until the temperature and pressure are sufficient to fuse carbon (see carbon burning process). This process continues, with the successive stages being fueled by neon (seeneon burning process), oxygen (see oxygen burning process), and silicon (see silicon burning process). Near the end of the star's life, fusion can occur along a series of onion-layer shells within the star. Each shell fuses a different element, with the outermost shell fusing hydrogen; the next shell fusing helium, and so forth.[70]
The final stage is reached when the star begins producing iron. Since iron nuclei are more tightly bound than any heavier nuclei, if they are fused they do not release energy—the process would, on the contrary, consume energy. Likewise, since they are more tightly bound than all lighter nuclei, energy cannot be released by fission.[69] In relatively old, very massive stars, a large core of inert iron will accumulate in the center of the star. 

17. Comparative sizes

18. What happens to stars at the end of their lives?
Planetary Nebula
Supernovae
Neutron Stars
Black Holes

19. Planetary Nebula – Ring Nebula
An evolved, average-size star will now shed its outer layers as a planetary nebula. If what remains after the outer atmosphere has been shed is less than 1.4 solar masses, it shrinks to a relatively tiny object (about the size of Earth) that is not massive enough for further compression to take place, known as a white dwarf

20. Eskimo Nebula

21. Helix Nebula

22. Cats Eye Nebula

23. Supernova
In larger stars, fusion continues until the iron core has grown so large (more than 1.4 solar masses) that it can no longer support its own mass. This core will suddenly collapse as its electrons are driven into its protons, forming neutrons and neutrinos in a burst of inverse beta decay, or electron capture. The shockwave formed by this sudden collapse causes the rest of the star to explode in a supernova. Supernovae are so bright that they may briefly outshine the star's entire home galaxy. 
All natural occurring elements that have a heavier atomic mass than iron are formed in Supernova explosions.
Within a massive, evolved star
the onion-layered shells of elements undergo fusion, forming an iron core
that reaches Chandrasekhar-mass and starts to collapse. The inner part of the core is compressed into neutrons
causing infalling material to bounce
and form an outward-propagating shock front (red). The shock starts to stall
(e), but it is re-invigorated by a process that may include neutrino interaction. The surrounding material is blasted away
leaving only a degenerate remnant.

24. Supernova Remnant

25. Neutron Stars
Neutron stars contain 500,000 times the mass of the Earth in a sphere with a diameter no larger than that of  a small town.
This density is approximately equivalent to the mass of a Boeing 747 compressed to the size of a small grain of sand, or the human population condensed to the size of a sugar cube.

26. Pulsars

27. Black Hole
Formed when a stellar remnant is greater than about 4 solar masses.
The picture is an artists impression of a black hole in front of the Large Magellanic Cloud.