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Exploring Stellar Life Cycles and Planetary Habitability

Delve into the evolution of stars, carbon origins, and implications for life, with a focus on older stars and planetary systems. Examining iron fractions, organic matter, and potential habitable planets in different star classes like F, G, K, and M. Consider the challenges and opportunities presented by M dwarf stars, binary systems, and exoplanet transits. Explore the significance of long-term stability, liquid water worlds, and atmospheric effects on planet habitability. Uncover the complexities of M dwarf stars, flares, synchronous rotations, and potential impacts on life. Discover the latest advancements in planet detection methods, including the James Webb Space Telescope and SPECULOOS for observing Ultra Cool Dwarfs.

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Exploring Stellar Life Cycles and Planetary Habitability

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  1. ASTR/GEOL-2040: Search for life in the Universe: Lecture 35 • Revisit star life • Kepler • Tidally locked, binaries Axel Brandenburg (Office hours: Mondays 2:30 – 3:30 in X590 and Wednesdays 11-12 in D230)

  2. Life cycle of stars • Carbon comes from nuclear fusion in stars • Late stages of evolution

  3. Older stars: iron fraction? • More than younger stars • The same • Less

  4. Analogy: who has more high tech? • You • Your father/mother • Your grandfather/grandmother

  5. Organic matter in the Universe • Carbon comes from nuclear fusion in stars • Late stages of evolution

  6. Periodic table: look at masses • 4 x 1.008 = 4.032; excess mass: 0.029 • 0.029 x 1.66x10-27 kg * c2 = 4.33 x 10-12 J

  7. Periodic table: look at masses • 55.933/56 = 0.9988, and 238.029/238 = 1.0001 • Uranium has more mass per nucleus than Fe

  8. Kepler, the spacecraft • More than younger stars • The same • Less

  9. Older stars: iron fraction? • Trailing the Earth

  10. 115 square degree • Small fraction of sky • (115*p/180)1/2=0.04 • 0.04/4p=0.003=0.3% • 156,000 stars • 2740 exoplanets

  11. Planet in transit • Actually 5 planets • ~ 10-4(=area fraction) • r/R = 0.01 • r/R = 10-4 • r/R = 10-8

  12. Planet in transit • Actually 5 planets • ~ 10-4

  13. Planet in transit • Actually 5 planets • ~ 10-4(=area fraction) • r/R = 0.01 • r/R = 10-4 • r/R = 10-8

  14. Older stars: iron fraction? • More than younger stars • The same • Less Kepler-444 1.33 RE 1.64 RE 1.75 RE 1.80 RE 2.45 RE

  15. How low can we go? • Kepler goal 10-5 • Instrumental difficulties • Other problems?

  16. Older stars, less Fe • Fe produced over stellar generations • Old stars: less

  17. Stellar surface variable • Starspots (random, but modulated) • Flares (random, much stronger) • Stellar activity cycles • What’s one astronomer’s noise is anothers one’s signal

  18. Again which stars? • Need long-term stability? • Fraction of heavy elements?

  19. Based on life span & abundance:which class of star is most likely to habor life? • A star • F star • G star • K star • M star

  20. Enough time for life? • Life might not emerge on O, B, and A stars • But they make up small percentage

  21. Based on life span & abundance:which class of star is most likely to habor life? • A star • F star • G star • K star • M star

  22. Worlds with liquid surface water What if star is dimer than the Sun? • Need to be closer (<< 1 AU) • Farther • Brightness doesn’t matter

  23. Worlds with liquid surface water What if star is dimer than the Sun? • Need to be closer (<< 1 AU) • Farther • Brightness doesn’t matter

  24. Problems with M dwarfs (Dwarf = main sequence stars) • M dwarfs have frequent flares • At least in their first 1 Gyr • Closer planet: synchronous rotation • What does this mean for life? • Discuss? • (and what about effect of atmosphere)

  25. Other problems with M dwarfs (Dwarf = main sequence stars) • M dwarfs have frequent flares • At least in their first 1 Gyr • Closer planet: synchronous rotation • What does this mean for life? • Discuss? • (and what about effect of atmosphere)

  26. Other problems with M dwarfs (Dwarf = main sequence stars) • M dwarfs have frequent flares • At least in their first 1 Gyr • Closer planet: synchronous rotation • What does this mean for life? • Discuss? • (and what about effect of atmosphere)

  27. Most stars are binaries • Triple system (2 stars + planet) often not stable • a: wide separation, each star with planet • b: Stars close together: planet orbits 2 stars

  28. Other problems with M dwarfs (Dwarf = main sequence stars) • M dwarfs have frequent flares • At least in their first 1 Gyr • Closer planet: synchronous rotation • What does this mean for life? • Discuss? • (and what about effect of atmosphere)

  29. Other problems with M dwarfs (Dwarf = main sequence stars) • M dwarfs have frequent flares • At least in their first 1 Gyr • Closer planet: synchronous rotation • What does this mean for life? • Discuss? • (and what about effect of atmosphere)

  30. Other problems with M dwarfs (Dwarf = main sequence stars) • M dwarfs have frequent flares • At least in their first 1 Gyr • Closer planet: synchronous rotation • What does this mean for life? • Discuss? • (and what about effect of atmosphere)

  31. Where to go from here • James Webb (JWST)  atmosph. • Search for Planets EClipsing ULtracOOL stars  SPECULOOS • Target for many planetary studes • And certainly SciFi

  32. Next time • Other planet detection methods • TRAPPIST-1 • http://www.trappist.one/ • Starshade • Longstaff: 339 – 341

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