2. You will learn how stars are made. You will also learn how stars are your great – – – – – – –great – great – – – – –great – great - grandparents! Hi, kids! The Sun Song (rock version) The Sun Song (classic version)

3. All stars are “born” in nebulae. A nebula is an enormous cloud of hydrogen and helium gas in space. nebula

4. One of the “stars” in Orion is actually a nebula click to zoom in

5. Another famous nebula: The “Horsehead” nebula

6. Over time, the nebula’s own gravity makes the nebula come together into a ball, called a protostar nebula protostar

7. When hydrogen fuses into helium, it gives off light (photons). This is why stars shine! The pressure inside a protostar is so strong that hydrogen (H) fuses together to become helium (He) HH HH He

8. Fusion happens billions of times every second inside a star HH HH He HH HH HH HH HH HH

9. Stars shine because of nuclear fusion! HH HH He HH HH HH HH HH HH HH HH HH HH HH HH HH HH

10. Protostars look like this:

11. Eventually, protostars give off enough light to be officially called stars Don’t forget – a star is just a big ball of gas! Our sun is just a big ball of gas

12. This imaginary center is called the “Barycenter” Most stars have a “buddy star” – pairs of stars are called binary star systems X However, you wouldn’t be here without stars...

13. Every atom in your body was made by a star! “The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, and the carbon in our apple pies were all made in the interior of collapsing stars. We are made of starstuff” – Carl Sagan The atoms of everything in this room, this town, and this planet were created inside a star!

14. Stars make all the different elements: 3 helium atoms fuse into 1 carbon atom He C

15. 4 helium atoms fuse into 1 oxygen atom He O

16. Eventually stars run out of their hydrogen fuel, from the center out This star has no more hydrogen in its center – only in its outer edge. This causes the star’s exterior to expand and cool. This star is now a called a “Red Giant” – “cool” stars are red

17. Our sun will become a red giant in about 5 billion years

18. Oh no, the sun will blow up in 157, 787, 999, 999, 999,seconds ! (2,629,800,000,000,000 minutes) (43,830,000,000,000 hours) (1,826,250,000,000 days) (5,000,000,000 years) Assume 365.25 days per year Debug: in presentation mode, start countdown. Then escape from presentation mode. Then return to presentation mode. It will work

19. M V Mercury and Venus will be destroyed Our sun is currently a “Main Sequence” star – but will grow into a Red Giant! Help! Is it getting hot in here or is it just me? E

20. After all the fusion stops inside a red giant, the gases float away and only the core remains This core is called a “White Dwarf” This leftover gas is called a “Planetary Nebula”

21. Example of a planetary nebula

25. The White Dwarf is the burned out core of the star – like a burnt piece of charcoal

26. Eventually, white dwarfs fade to black as they cool off

27. Stars smaller than our sun never become red giants – they just fizzle out into white dwarfs Which eventually burns out completely into a Black Dwarf

28. Stars much larger than our sun become enormous red giants Betelgeuse click to zoom in

29. A super red giant has intense fusion in its core – and explodes into a supernova A supernova can be brighter than a million stars!

30. Example of a Supernova The last Supernova we observed without a telescope was in 1604. It was so bright you could see it in the day time!

31. The white dwarf inside a supernova collapses into a neutron star neutron star

32. A neutron star inside the Puppis Supernova You’ll learn more about neutron stars soon…

33. Really big neutron stars collapse into black holes You’ll learn more about black holes soon too…