1. Lecture 11: The Discovery of the World of Exoplanets
What are exoplanets & where are they?
Indirect methods for planet detection

2. Planets Orbiting Other Stars
Number of planets discovered around
other stars:
540 planets
58 multiple planet systems
Reminder: gives minimum mass
F to G etc.
Compute this more exactly by updating excel spreadsheet on plane

6. Star-to-planet inequalities:
In light: (optical) to 107 (infrared)
In mass: to 103
In size: to 10.

7. Four main methods of discovery:
Direct
Radial velocity or Doppler ‘wobble’
Transits
Gravitational microlensing

8. 51 Peg b & HD 209458b: “Hot Jupiters”

9. Method of discovery: Radial velocity ‘wobble’ of the star
Radial velocities seen
in star HD
the variation is due
to a planet that is less
massive than Jupiter.
(Mazeh et al. 1999;
Marcy et al. 2000)

10. Ups And System vs. Solar System

11. Kepler-11 System vs. Solar System

12. HD b: a Hot Jupiter

13. Transits: A Method for Planet Discovery

14. Venus in Front of the Sun

15. Transit Measurements

16. Kepler discoveries

17. Evidence for Planet OGLE-TR-56b
Doppler Shift
Light Dimming
Konacki, Torres, Sasselov,
Jha, 2003, Nature

18. Method of discovery: Radial velocity ‘wobble’ of the star
Radial velocities seen
in star HD
the variation is due
to a planet that is less
massive than Jupiter.
(Mazeh et al. 1999;
Marcy et al. 2000)

19. Mass: For HD 209458b: Mp sin(i) = Ms vs P / 2 ap
= const. x (Ms /1.1MSun) Mjup
Transit light curve helps derive the orbit inclination: i = 86o
Both Mp and Rp determined to better than 5%!

20. What can we learn from transiting extrasolar planets
HD b: Dimming of light due to transit, observed with HST.
Tells us
DIRECTLY:
Planet radius,
INDIRECTLY:
Planet density
Planet composition
Just to remind you, that this transiting planet was first discovered by the standard spectroscopic “wobble” technique,
and only afterwards were transits detected.
Brown, Charbonneau, Gilliland, Noyes, Burrows (2001)

21. Radius Mass Kepler: New Planets on the Mass-Radius Diagram
after Latham et al.’10

22. Transiting Planets - the search is on!
Transits occur due to chance alignments,
therefore one has to observe millions of stars
in order to ‘catch’ a few transiting planets;
Here at Harvard we have 2 automated networks of small telescopes searching: HAT & MEarth.

23. The HAT Network: FLWO Mt.Hopkins AZ
(Bakos et al. 2004)

24. … and at Mauna Kea Obs., Hawaii

27. Main points to take home:
Four main methods of discovery: direct, Doppler wobble, transits, microlensing.
Doppler effect: deriving planet mass.
Transits: (1) detection probability; (2) deriving the radius.
NASA Kepler Mission