lecture30
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- The document discusses the conditions needed for life to exist, namely liquid water, and the concept of the "habitable zone" where liquid water can exist on a planet based on its distance from its star. - It notes that over 4,000 exoplanets have been discovered so far, and finding exoplanets within the habitable zones of their stars is key to searching for life in the universe. Approximately 50 exoplanets located in habitable zones have been discovered. - The document also provides context on the timeline of life in the universe, noting that based on a "Cosmic Calendar" where the history of the universe is compressed into one year, life first emerged on September 21st, and human history only began in
lecture30
- 1. Introduction to modern astronomy 30 島袋隼⼠(Hayato Shimabukuro)（云南⼤学、 SWIFAR） ©GETTYIMAGES
- 2. Searching for Earths Are there any planets where life may exist? (Question) What are the conditions for life to exist?
- 3. Searching for Earths Are there any planets where life may exist? (Question) What are the conditions for life to exist? (Answer) Existence of water in the form of liquid
- 4. Searching for Earths •If the temperature of the planets is high…. Water evaporates（⽔蒸发） •If the temperature of the planets is low…. Water freezes（⽔结冰） For the existence of liquid water, the temperature of planets should be not too hot and not too cold. The region of the orbit of planets where life can exist is called the habitable zone（宜居带）
- 5. Habitable zone •In the case of our solar system, the habitable zone is between 0.97 AU and 1.4 AU from the sun. Cold Hot
- 6. Habitable zone •If the main stars are different, the habitable zone is also different (e.g., The sun's surface temperature (G type) is roughly 5700K). •The larger mass stars have a higher temperature. The habitable zone depends on the mass of the main stars. The region of the orbit of planets where liquid water can exist is called the habitable zone（宜居带）
- 7. Habitable zone •The larger mass stars have a higher temperature. The habitable zone of the exoplanets orbiting high-mass stars is far from main stars. High-mass main stars Far from main stars
- 8. For finding life in the universe •We have already discovered more than 4000 exoplanets. •~65-75 % of stellar stars have exoplanets whose periods are less than 10 years! Mayor et al (2009)
- 9. For finding life in the universe •We have discovered more than 4000 exoplanets in the Milky Way. (Question) How many exoplanets are located in the habitable? 1. ~50 2. ~100 3. ~1000 4. >1000 Discover exoplanets that are located in the habitable zone is the first step to finding life in the universe!
- 10. For finding life in the universe •We have discovered more than 4000 exoplanets in the Milky Way. (Question) How many exoplanets are located in the habitable? 1. ~50 2. ~100 3. ~1000 4. >1000 Discover exoplanets that are located in the habitable zone is the first step to finding life in the universe!
- 11. Summary • Our solar system is not the only planetary system. We have already discovered more than 4000 exoplanets. • Life may exist on the planets where water can keep the form of liquid. • Those planets are located in the habitable zone. • We have already discovered ~50 exoplanets which are located in the habitable zones.
- 13. Before I start the life in the universe, I would like to ask a question. If the history of the universe is 1 year, when do you think life and human being came into being? (如果宇宙的历史是⼀年，你认为⽣命和⼈类是何 时出现的？)
- 15. https://en.wikipedia.org/ wiki/Cosmic_Calendar 1/1: The universe was born (Big bang) 1/26: First galaxies form
- 17. https://en.wikipedia.org/ wiki/Cosmic_Calendar 3/16: The Milky Way Galaxy formed. 5/13:Milky way Galaxy disk formed.
- 20. https://en.wikipedia.org/ wiki/Cosmic_Calendar 9/2: Formation of solar system. 9/21: First life emerged.
- 22. https://en.wikipedia.org/ wiki/Cosmic_Calendar 12/5: First multicellular life(多细胞⽣命).
- 25. https://en.wikipedia.org/ wiki/Cosmic_Calendar 12/25:Dinosaurs（恐⻰🦕）. We focus on December.
- 26. https://en.wikipedia.org/ wiki/Cosmic_Calendar 12/25:Dinosaurs（恐⻰🦕）. 12/30:Dinosaurs extinct（恐⻰绝种🦕）. We focus on December.
- 29. https://en.wikipedia.org/ wiki/Cosmic_Calendar 12/31 6:05 :Apes（类⼈猿）. We focus on 12/31.
- 30. https://en.wikipedia.org/ wiki/Cosmic_Calendar 12/31 6:05 :Apes（类⼈猿）. We focus on 12/31. 12/31 20:00 : Humans and Chimpanzees split.
- 32. https://en.wikipedia.org/ wiki/Cosmic_Calendar 12/31 22:30:Human started to use stone tools. We focus on 12/31.
- 33. https://en.wikipedia.org/ wiki/Cosmic_Calendar 12/31 22:30:Human started to use stone tools. We focus on 12/31. 12/31 23:52: Modern humans evolve.
- 35. https://en.wikipedia.org/ wiki/Cosmic_Calendar Human history began last 1 minute on 12/31.
- 37. Before I start the life in the universe, I would like to ask a question. If the history of the universe is 1 year, when do you think life and human being came into being? (如果宇宙的历史是⼀年，你认为⽣命和⼈类是何 时出现的？) (Answer) 9/21: First life emerged. 12/5: First multicellular life(多细胞⽣命). 12/25:Dinosaurs（恐⻰🦕）. 12/31 6:05 :Apes（类⼈猿）. 12/31 23:52: Modern humans evolve. Human history began last 1 minute on 12/31. After the summer holidays, the solar system formed!