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

2. What is this picture? A. A distant star B. Neptune C. Earth D. 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? A. Hotter B. Cooler C. Same temperature D. Cannot tell

20. UV Radiation Which has more UV in its spectrum: Sun or a B-type star? A. Sun B. B star C. Same D. 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? A. Go there! B. Send out signals C. Look for others sending signals D. Look for chemical signatures of life E. 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? lichen coral

27. Look for chemical signature Water vapor CO 2 (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!