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Agenda

Agenda. Planet formation The search for life in the universe. What is this picture?. A distant star Neptune Earth A galaxy. The “pale blue dot”: Earth viewed from the edge of our solar system (taken by Voyager 1). How hard would it be to learn about Earth from a long way away?.

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Agenda

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  1. Agenda • Planet formation • The search for life in the universe

  2. What is this picture? • A distant star • Neptune • Earth • A galaxy The “pale blue dot”: Earth viewed from the edge of our solar system (taken by Voyager 1). How hard would it be to learn about Earth from a long way away?

  3. Aside:Disks in astronomy • Accretion disks around black holes • Planetary rings • Spiral galaxies astronomy.com HST Cassini

  4. When a star is born… • There is a disk of material left over. • Rotates in the same direction as the protostar.

  5. Notice the scale!

  6. Planet formation • Dust and gas is left over from star formation (1-100 AU in diameter) • Gravitational attraction brings particles together – creates a disk of material • Happens quickly - 3 to 30 million years

  7. Similar to Shepherd moons

  8. Disks around protostars

  9. The hunt for new planets • Seeing them directly is nearly impossible. • Star wobbles because of the tug from its planet. • The wobble causes a Doppler shift that we can observe!

  10. (motion of the star is greatly exaggerated!)

  11. The most easily found exo-planets are ____. A. Light and far from their star B. Light and close to their star C. Massive and far from their star D. Massive and close to their star

  12. To date… • Way over 200 extra-solar planets have been found • 276 as of March, 2008 • Most are: • Massive • Close to their star

  13. Kepler mission • NASA's first mission capable of finding Earth-size and smaller planets around other stars. • Works by transit method. • Launch scheduled for February, 2009.

  14. Can life exist anywhere? What is required for life to exist?

  15. What is required for life? • Water • Oxygen? • Energy input (usually sunlight) • Carbon?

  16. Location matters! Sun from Mercury

  17. Location matters! Sun from Saturn

  18. On the other hand… • Extremophiles live in very harsh conditions • Bacteria in Yellowstone • Bacteria under ice in the Arctic

  19. Star type matters • Remember OBAFGKM? • Sun is G2. • Is type B hotter or cooler than the Sun? • Hotter • Cooler • Same temperature • Cannot tell

  20. UV Radiation • Which has more UV in its spectrum: Sun or a B-type star? • Sun • B star • Same • Can’t tell • B is hotter, so it has more UV. • UV breaks down organic chemicals • Not conducive to life.

  21. How should we go about looking for life elsewhere? • Go there! • Send out signals • Look for others sending signals • Look for chemical signatures of life • We should not look for life

  22. Go there? • Example: NASA New Horizons mission • Going to pluto and outer solar system • Travels 47,000 mph • To get to the nearest star (4 ly away) • 57,000 years • OR, 2855 generations of people! • What would be required to make this work? (discuss)

  23. Send out a signal? • Radio technology on Earth is about 100 years old. • Only stars within 50 ly could have gotten a signal and responded so far • (About 1400 stellar systems) • No return signal yet! Marconi company, England, 1906 (wikipedia)

  24. Listen? — SETI • Project Phoenix • Observing since February, 1995 • Looking at nearby, Sun-like stars only • Nothing yet! SETI Institute

  25. Would we know life if we saw it?

  26. How do we know these are alive? coral lichen

  27. Look for chemical signature • Water vapor • CO2 (carbon dioxide) • Methane • Oxygen

  28. Clicker registration! • If you don’t see your number, it means that your clicker is already registered.

  29. Summary • Planets form quickly! • Looking for life: • Location matters • Look for byproducts of life • Exam 2 is Thursday at 6 pm!

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