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Astronomy190 - Topics in Astronomy

Astronomy190 - Topics in Astronomy. Astronomy and Astrobiology Lecture 18 : Habitable Zone II Ty Robinson. Questions of the Day. How have we constrained the locations of the inner and outer edges of the Habitable Zone? How does the presence of clouds affect the limits of the Habitable Zone?

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Astronomy190 - Topics in Astronomy

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  1. Astronomy190 - Topics in Astronomy Astronomy and Astrobiology Lecture 18 : Habitable Zone II Ty Robinson

  2. Questions of the Day • How have we constrained the locations of the inner and outer edges of the Habitable Zone? • How does the presence of clouds affect the limits of the Habitable Zone? • What is the Continuously Habitable Zone and how do we determine its location?

  3. HZ Plot

  4. The HZ around the Sun

  5. Deuterium and Venus Hydrogen Venus then Hydrogen Deuterium Venus now

  6. Water on Venus

  7. Water on Venus 0.75 AU Limits of HZ around Sun Inner Edge Outer Edge

  8. Water on Mars Mars then Mars now

  9. Water on Venus 0.75 AU Water on Mars 1.77 AU Limits of HZ around Sun Inner Edge Outer Edge

  10. The HZ around the Sun I hot surface temperature cold small large separation = 1au separation

  11. The HZ around the Sun II hot surface temperature cold small large separation

  12. The HZ around the Sun III hot surface temperature cold small large separation

  13. The HZ around the Sun IV hot surface temperature cold small large separation

  14. CO2 Clouds Question Why would forming CO2 clouds spell the end of a world’s habitability? clouds increase a planet’s albedo, so less radiation is absorbed clouds decrease a planet’s albedo, so less radiation is absorbed clouds do not have a very strong greenhouse effect clouds emit thermal radiations to space

  15. } Cloud Uncertainty provide warming } provide cooling

  16. Water on Venus 0.75 AU Water on Mars 1.77 AU CO2 Clouds 1.37 AU Limits of HZ around Sun Inner Edge Outer Edge

  17. maximum greenhouse Maximum Greenhouse hot CO2 surface temperature cold small large Question CO2 Amount Why doesn’t Earth simply get warmer and warmer as you add CO2? Rayleigh scattering

  18. Water on Venus 0.75 AU Water on Mars 1.77 AU CO2 Clouds 1.37 AU Maximum greenhouse 1.67 AU Limits of HZ around Sun Inner Edge Outer Edge hot surface temperature cold small large CO2 Amount

  19. The HZ around the Sun V hot surface temperature cold small large separation = 1au separation

  20. The HZ around the Sun VI hot surface temperature cold small large separation

  21. The HZ around the Sun VII hot surface temperature cold small large separation

  22. The HZ around the Sun VIII hot surface temperature cold small large separation

  23. Water Critical Point bars 221

  24. Runaway Greenhouse more water evaporates surface temperature increases greenhouse effect strengthens

  25. Water on Venus 0.75 AU Critical point 0.84 AU Water on Mars 1.77 AU CO2 Clouds 1.37 AU Maximum greenhouse 1.67 AU Limits of HZ around Sun Inner Edge Outer Edge

  26. Moist Greenhouse cool warm ~1 Gyr

  27. Water on Venus 0.75 AU Critical point 0.84 AU Moist Greenhouse 0.95 AU Water on Mars 1.77 AU CO2 Clouds 1.37 AU Maximum greenhouse 1.67 AU Limits of HZ around Sun Inner Edge Outer Edge

  28. HZ Plot

  29. Solar Luminosity Changes with Time

  30. Continuously Habitable Zone = The range of distances around a star where an Earth-like planet could remain habitable for some large portion of the star’s lifetime Continuously Habitable Zone = HZ

  31. CHZ II = HZ

  32. CHZ III = HZ

  33. = HZ CHZ IV

  34. = HZ, start CHZ V

  35. = HZ, start = HZ = CHZ CHZ VI

  36. = HZ, start = HZ = CHZ CHZ VII

  37. The CHZ around the Sun = CHZ

  38. Questions of the Day • How have we constrained the locations of the inner and outer edges of the Habitable Zone? • How does the presence of clouds affect the limits of the Habitable Zone? • What is the Continuously Habitable Zone and how do we determine its location?

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