1. Exoplanets Worlds Without End
Copyright Lynette Cook, used with permission

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

3. Copyright – Tyler Nordgren
Are there other Earths?

4. How do we Know? Two methods: Radial Velocity. Transit
Copyright Lynette Cook, used with permission

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

6. Emission Lines
Every element has a DIFFERENT finger print.

7. Doppler Shift
The greater the velocity the greater the shift.

8. Concept Test
I spin an object emitting a constant tone over my head. What do you hear?
A constant tone.
A tone that goes back and forth between high and low frequency.
A constant tone of lower intensity.
Two constant tones, one of higher frequency and one of lower frequency.
One tone going smoothly from low to high intensity.

9. Concept Test
I spin an object emitting a constant tone over my head. What do I hear?
A constant tone.
A tone that goes back and forth between high and low frequency.
A constant tone of lower intensity.
Two constant tones, one of higher frequency and one of lower frequency.
One tone going from smoothly from low to high intensity.

10. So Now… From the presence and position of Spectral Lines we can know:
Composition (H, He, H2O, etc.)
Movement through space (towards or away)
How fast?

11. 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

12. The “Wobble”

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

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

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

16. Result: 51 Pegasi Mayor and Queloz a = 0.052 AU
Copyright Lynette Cook, used with permission
Result: 51 Pegasi
a = AU
Mayor and Queloz

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

19. Worlds without End? Known Planets: Known Planetary Systems:
In our Solar System: 8
Outside our Solar System:
680
Known Planetary Systems:
Prior Sept. 1995: 1 (ours)
As of Feb 2012: 92
Copyright Lynette Cook, used with permission

20. Concept Question
What is the biggest surprise about extrasolar planetary systems?
Most of the systems only have one planet.
Many systems have several planets larger than Jupiter.
Many systems have very large planets orbiting close to the star.
Most of the planets do not fit into the categories of terrestrial or jovian planets.
C. Many systems have very large planets orbiting close to the star.

21. Upsilon Andromedae
Copyright Lynette Cook, used with permission

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

23. Planet Shadows

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

25. Concept Question
From the Radial Velocity Method we learn a planet’s mass. If we see that planet transit then we can also learn its:
Size
Density
Composition
All of the above
None of the above

26. Kepler Mission

27. Kepler Systems

29. Smallest Kepler planets

31. Copyright Lynette Cook, used with permission

32. Hubble Space Telescope
Savage et al. 2001
Hubble Space Telescope

33. Homework for Friday
Find a favorite exoplanet (or exoplanetary system). Go to one of the following:
Search the catalog and find your favorite.
Write down the following and bring to class:
Name of the Star
Mass or Radius of the planet (number of planets and their masses/radii if it is a system)
Period of the planet (periods of the planets)
Orbital radius of the planet (radii of their orbits)
Why you picked it.