Stars, Life and Light

1. Stars, Life and Light

2. S1-4-06bExplain the life cycle of a star. KEY WORDS FusionCoreNebula 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 and25% 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 PowerPlants: splitting (fission) things to release energy

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

7. Layers of the Sun: • Inside • Core– centre (site of nuclearfusion) • Outside • Photosphere – cooler surface(5500 oC • sunspots, surface storms – the part we “see” • Chromosphere– inner atmosphere • small solar explosions (flares), large (prominences) • Corona– outeratmosphere(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 starthat begins to release energy as a main sequence (MS) star Scientists categorize MS stars accordingto mass: • Small- last longer(billions of years) • Large - brighter butshort-lived(fewmillion yrs)

9. Actually nebulae captured by NASA space telescopes

10. 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. 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. Birth: Nebulae main sequence (MS) star Largest Smallest 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) • Constantlyin motion • Many shapes: spiral, elliptical, and irregular

17. 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 FusionCoreNebula Main sequence Red dwarf Neutron Star Red giant White dwarf Supernova Red supergiant Black hole Galaxy