1. Stars, Life and Light

2. S1-4-06b Explain the life cycle of a star.
KEY WORDS
Fusion Core Nebula
Main sequence Red dwarf Neutron Star
Red giant White dwarf Supernova
Red supergiant Black hole Galaxy

3. Our Sun
A small star
About 5 billion years old (should last 5 more)
Composed of 75% hydrogen and 25% helium
All elements in plasma phase
(hotter state than gas)
Energy comes from a Nuclear Fusion Reaction

4. Nuclear Fusion Reaction
Fusion = join/merge
Joining two hydrogen to create helium
Releases large amount of energy

5. Fusion = join Fission = split
Sun: joining (fusion) things to release energy
Power Plants: splitting (fission) things to release energy

6. There is obviously more to the Sun then “burning ball of gas”

7. Core – centre (site of nuclear fusion) Outside
Layers of the Sun:
Inside
Core – centre (site of nuclear fusion)
Outside
Photosphere – cooler surface (5500 oC
sunspots, surface storms – the part we “see”
Chromosphere – inner atmosphere
small solar explosions (flares), large (prominences)
Corona – outer atmosphere (1 million oC)
charged gas particles blow outward (solar winds)

8. “Life Cycle” of a Star:
Birth: Stars start out as Nebulae
Nebula – huge cloud of dust and gases
Youth – Middle Age:
Gravity collapses a nebula into star that begins to release energy as a main sequence (MS) star
Scientists categorize MS stars according to mass:
Small - last longer (billions of years)
Large - brighter but short-lived (few million yrs)

9. Actually nebulae captured by NASA space telescopes

10. We can’t see most Red Dwarf stars – their light is too weak
Small MS star – Red Dwarf
Very cool temperatures of their outer gases
Death:
Forms a cool, dim star called a White Dwarf
Fades out until it no longer emits light energy
We can’t see most Red Dwarf stars – their light is too weak

11. Medium MS star – like the Sun Separated into small-med and large-med
Death:
Runs out of elements for fusion reaction
Collapses then swells to produce a Red Giant
small-med eventually fades out as white dwarf
large-med explodes as a Supernova leaving
behind a Neutron star
“Pulsar” neutron star

12. Extreme energy produced for a short period
Large MS star
Extreme energy produced for a short period
Fuses heavier elements (iron) after lighter ones
Death:
Collapses then swells to a Red Supergiant
Gravity collapses the largest into a Black Hole
Stars are in balance: nuclear fusion explodes outwards, large gravitational force collapses inwards
When the reactor runs out of elements to fuse, gravity wins and the star collapses and (sometimes) explodes

13. Nothing can escape the gravitational pull of a black hole

14. There is still more to this puzzle, but…this is close enough
Birth:
Nebulae
Smallest
main sequence (MS) star
Largest
Medium
Red Dwarf
Red Giant
Red Supergiant
Supernova
Death:
White Dwarf
Neutron star
Black Hole
There is still more to this puzzle, but…this is close enough

15. What do you notice?

16. Galaxies
Huge collections of gas, dust and billions of stars and planets (collected by gravity)
Constantly in motion
Many shapes: spiral, elliptical, and irregular

17. Contains 400 billion stars
Milky Way Galaxy
Contains 400 billion stars
Disc-shaped, with spiral arms – spiral galaxy
We are on one of the arms
Has a thicker Central Bulge
Rotates around the bulge
New evidence suggests the “central bulge” is actually a SUPER-MASSIVE BLACK HOLE!

18. CAN YOU ANSWER THESE QUESTIONS? S1-4-06b:
How do stars like the Sun make energy?
How do stars form and how do small, med and large stars eventually “die?”
KEY WORDS
Fusion Core Nebula
Main sequence Red dwarf Neutron Star
Red giant White dwarf Supernova
Red supergiant Black hole Galaxy