Life and Death of Stars

1. Life and Death of Stars Recapitulation of How Elements are Formed

2. Spectral Classes vs. H-R Diagram

3. HR Diagram • Describe the general trend between temperature and brightness. • What is the color and brightness of the most abundant stars? The rarest stars? • What are the characteristics of the stars that do not conform to the graph’s trend? • In terms of the graph’s trend, is our sun typical or exceptional? • If you replaced the temperature scale on the graph’s x-axis with a color scale, which color would be closest to the graph’s origin and which would farthest away?

4. HR Diagram • What is luminosity? • What 2 criteria are used to classify stars on the HR diagram? • Why might stars of one color be much more abundant than stars of another color? • Which type(s) of star should we consider first when looking for stars that might have life-supporting worlds around them? Why?

5. Apparent and Absolute Magnitude • Apparent magnitude is the brightness of a star as seen from Earth. • Absolute magnitude is brightness of a star as if it were 32.6 light years from Earth. • The brightness of the stars is compared to the brightness of our Sun. We call this luminosity.

6. The Big Bang and Soon After The “Cosmic Microwave Background Radiation” (CMB), Present Day "Ilc 9yr moll4096" by NASA / WMAP Science Team - http://map.gsfc.nasa.gov/media/121238/ilc_9yr_moll4096.png. Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Ilc_9yr_moll4096.png#mediaviewer/File:Ilc_9yr_moll4096.png

7. Life Cycle of a Star

8. The Big Bang and Soon After (ctd.)Temp Cools from 10 Billion K to 1 Billion K "Scheme of nuclear reaction chains for Big Bang nucleosynthesis" by Pamputt - Own work ; vectorisation de The main nuclear reaction chains for Big Bang nucleosynthesis.jpg. Licensed under CC BY-SA 4.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Scheme_of_nuclear_reaction_chains_for_Big_Bang_nucleosynthesis.svg#mediaviewer/File:Scheme_of_nuclear_reaction_chains_for_Big_Bang_nucleosynthesis.svg

9. Life of a Small Star Around the mass of 1 Sun up to ~5 Solar Masses

10. “Before she became a star…”Nebula – Cloud of Gas (mostly H) "Eagle nebula pillars" by Credit: NASA, Jeff Hester, and Paul Scowen (Arizona State University) - http://hubblesite.org/newscenter/newsdesk/archive/releases/2003/34/image/a. Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Eagle_nebula_pillars.jpg#mediaviewer/File:Eagle_nebula_pillars.jpg

11. “On her way to the audition…”Protostar (NOT A STAR YET) "Witness the Birth of a Star" by NASA/JPL-Caltech/R. Hurt (SSC) - Image of the day gallery. Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Witness_the_Birth_of_a_Star.jpg#mediaviewer/File:Witness_the_Birth_of_a_Star.jpg

12. Once it’s hot enough…NUCLEAR FUSION "FusionintheSun" by Borb. Licensed under CC BY-SA 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:FusionintheSun.svg#mediaviewer/File:FusionintheSun.svg

13. How Fusion Works(Yes, you can actually know this.) • Need very high temperatures, ~10-15 million K • Protons overcome repulsion • Stick due to “Strong Nuclear Force” • Mass of 4 p+ > Mass of 1 He • Where did the missing mass go?

14. How Fusion Works(ctd.) • E = mc2 • Lost mass is converted to energy! • Basis for all fusion processes that release (or absorb) energy

15. “A star is born!”Main Sequence – Doing H Fusion "Sirius A and B Hubble photo" by NASA, ESA, H. Bond (STScI), and M. Barstow (University of Leicester) - http://www.spacetelescope.org/images/html/heic0516a.html. Licensed under CC BY 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Sirius_A_and_B_Hubble_photo.jpg#mediaviewer/File:Sirius_A_and_B_Hubble_photo.jpg "The Sun in extreme ultraviolet" by NASA - [1]. Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:The_Sun_in_extreme_ultraviolet.jpg#mediaviewer/File:The_Sun_in_extreme_ultraviolet.jpg

16. After billions of years… • H fuel runs out in the middle, He accumulates • Not hot enough to fuse together He atoms • Gravity starts to take over!

17. “She suffered a partial collapse…”A Small Star Evolves • Outside comes in, REHEATING DUE TO GRAVITATIONAL POTENTIAL • It’s Red Giant time! • Hot enough to fuse He into C, N • (See next slide for size comparison)

18. Red Giant Stage –An Old “Small” Star "The life cycle of a Sun-like star (annotated)" by ESO/M. Kornmesser - http://www.eso.org/public/images/eso1337a/. Licensed under CC BY 4.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:The_life_cycle_of_a_Sun-like_star_(annotated).jpg#mediaviewer/File:The_life_cycle_of_a_Sun-like_star_(annotated).jpg

19. “So explosive!”Losing the Shell – Planetary Nebula • Fusion of He to C, N releases much more energy • Gravity can’t hold it together • Loses the outer gases – Planetary Nebula • NOTHING TO DO WITH PLANETS "Seeing into the Heart of Mira A and its Partner" by ESO/S. Ramstedt (Uppsala University, Sweden) & W. Vlemmings (Chalmers University of Technology, Sweden) - http://www.eso.org/public/images/potw1447a/. Licensed under CC BY 4.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Seeing_into_the_Heart_of_Mira_A_and_its_Partner.jpg#mediaviewer/File:Seeing_into_the_Heart_of_Mira_A_and_its_Partner.jpg

20. Another Planetary Nebula • Colors = different elements • helium (blue) • oxygen (green) • nitrogen (red) "M57 The Ring Nebula" by The Hubble Heritage Team (AURA/STScI/NASA) - http://hubblesite.org/newscenter/archive/releases/1999/01/image/a/ (direct link). Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:M57_The_Ring_Nebula.JPG#mediaviewer/File:M57_The_Ring_Nebula.JPG

21. “How do you feel inside?”The Leftover Core – White Dwarf • Core is white hot, but NOT hot enough to fuse C with C • Most white dwarfs simply fade out over a LONG time • Theoretical “black dwarf” is typical fate • But there may be another way to go out! "Sirius A and B Hubble photo.editted" by Bokus - http://upload.wikimedia.org/wikipedia/commons/f/f3/Sirius_A_and_B_Hubble_photo.jpg. Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Sirius_A_and_B_Hubble_photo.editted.PNG#mediaviewer/File:Sirius_A_and_B_Hubble_photo.editted.PNG

22. Type Ia Supernova“She got help from a friend…” Enough energy is released to fuse C into elements heavier than C. "Progenitor IA supernova" by NASA, ESA and A. Feild (STScI); vectorisation by chris 論 - http://hubblesite.org/newscenter/archive/releases/star/supernova/2004/34/image/d/. Licensed under CC BY 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Progenitor_IA_supernova.svg#mediaviewer/File:Progenitor_IA_supernova.svg

23. Type Ia Supernova – Example High-Z Supernova Search Team/HST/NASA

24. Life of a Large Star Around the mass of 8 Suns and up

25. Life Cycle of a Star

26. Large Stars on the Main Sequence More mass → More gravitational energy → Higher core temperature → Faster fusion rate → Shorter time on the main sequence "Hot and brilliant O stars in star-forming regions" by ESO - http://www.eso.org/public/images/eso1230b/. Licensed under CC BY 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Hot_and_brilliant_O_stars_in_star-forming_regions.jpg#mediaviewer/File:Hot_and_brilliant_O_stars_in_star-forming_regions.jpg

27. A Large Star Evolves – Red Supergiant Stage(s) • Akin to small mass star, fuel runs out, core reheats, fusing He to C • Enough mass to repeat the process, fusing heavier and heavier elements • Ne, Mg, Al, for example • All the way up to Fe • Resembles an onion Betelgeuse at upper left is a red supergiant "Orion Head to Toe" by Rogelio Bernal Andreo - http://deepskycolors.com/astro/JPEG/RBA_Orion_HeadToToes.jpg. Licensed under CC BY-SA 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Orion_Head_to_Toe.jpg#mediaviewer/File:Orion_Head_to_Toe.jpg

28. “A total collapse!”End of a Large Star • Fe builds up in the core • Not enough outward pressure • Gravity takes over • Outer layers rush in, and BOUNCE off the core • Enough energy released to fuse ANY naturally occurring element • Surplus of energy can form Au, Pb, I, etc. "HST SN 1987A 20th anniversary" by NASA, ESA, P. Challis, and R. Kirshner (Harvard-Smithsonian Center for Astrophysics) - http://hubblesite.org/newscenter/archive/releases/2007/10/image/a/ (direct link). Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:HST_SN_1987A_20th_anniversary.jpg#mediaviewer/File:HST_SN_1987A_20th_anniversary.jpg

29. The Aftermath – Neutron Stars and Black Holes "IsolatedNeutronStar" by Original uploader was Northgrove at en.wikipedia - Transferred from en.wikipedia. Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:IsolatedNeutronStar.jpg#mediaviewer/File:IsolatedNeutronStar.jpg "BH LMC" by User:Alain r - Own work. Licensed under CC BY-SA 2.5 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:BH_LMC.png#mediaviewer/File:BH_LMC.png

30. Other Element Formation – Cosmic Rays • High-energy particles either left over from the Big Bang or ejected from stars/supernovae • Slam into heavier elements occasionally and split them into smaller nuclei • E.g., Li, Be, B Earth’s Moon blocks muon cosmic rays "Moon's shadow in muons" by http://hepweb.rl.ac.uk/ppUKpics/POW/pr_990602.html. Licensed under Fair use via Wikipedia - http://en.wikipedia.org/wiki/File:Moon%27s_shadow_in_muons.gif#mediaviewer/File:Moon%27s_shadow_in_muons.gif

31. Life Cycle of a Star

32. Summary – Different Processes Make Elements • Big Bang – H, He, Li (a little) • Small Mass Stars • He (main sequence) • C, N (red giant) • Heavier than C (only type Ia supernova) • Large Mass Stars • He (main sequence) • C, N, etc., all the way up to Fe (red supergiant) • All natural elements (only type II supernova) • Cosmic Rays – Li, Be, B (split off from larger atoms)