8 Exoplanets Worlds Without End Copyright Lynette Cook, used with permission

8 Goals Are there planets around other stars? How do we know? Are they systems like ours? Copyright Lynette Cook, used with permission

8 Copyright – Tyler Nordgren Are there other Earths?

8 Putting it all together Copyright Lynette Cook, used with permission

8 1. Thermal Emission and Spectral lines A star like our Sun has absorption lines. HOT COOL You

8 2. Reflex Motion The Moon doesn’t orbit the Earth. The Earth doesn’t orbit the Sun. What do they do? They each orbit their combined center of mass. X

8 Center of Mass

8 The “Wobble”

8 3. Doppler Shifts Movement towards or away yields Doppler shifts. You X

8 4. Doppler Velocity From Doppler shifts we get a velocity and period.

8 5. Kepler Kepler’s Second Law: Kepler’s Third Law:

8 Result: 51 Pegasi Mayor and Queloz a = AU Copyright Lynette Cook, used with permission

8 How? P V

8

8

8 Concept Test We know of planets around other stars because: a.We have seen the changing velocity of a star caused by the pull of a small unseen planet. b.We have seen the motion of the planet caused by the wobble of the star. c.We have seen the changing position of the star caused by the pull of the small unseen planet. d.We have seen the changing velocity of the planet caused by the motion of the star. e.We have seen the planet reflecting the star’s light.

8 Worlds without End? Known Planets: –In our Solar System: 9 –Outside our Solar System: 206 Known Planetary Systems: –Prior Sept. 1995: 1 (ours) –As of Sept. 2004: 21 Copyright Lynette Cook, used with permission

8 Upsilon Andromedae

8 But Are They Real? Copyright Lynette Cook, used with permission

8 Planet Shadows

8 HD Based on Doppler curve, knew when planet might pass in front of its star. Greg Henry (Tennessee State Univ.)

8 Copyright Lynette Cook, used with permission

8 Savage et al Hubble Space Telescope

8 Hot Jupiters Atmosphere evaporation

8 51 Peg

8 Homework #10 For Friday 26-Sept: Read B Do: Problems 20, 25, 34, 52,57 Don’t forget Topic of Confusion