Chapter 5: Formation of Stars and Planets (and more) Part 3 - exoplanets

1. Chapter 5: Formation of Stars and Planets (and more) Part 3 - exoplanets

2. Planets Beyond the Solar System Extrasolar Planets --> planets orbiting around other starsExtrasolar planets can not be imaged directly.Like being in San Francisco and trying to see a pinhead 15 meters from a grapefruit in Washington, D. C. exoplanet.eu/catalog.php (3/7/12) 760 planets about 100 systems

3. The first planet observed around a Sun-like star (1995)

5. The Doppler Effect

6. Noisey yellow object standing still concentric circles represent sound waves

7. Doppler shift: the wavelength of light changes due to the motion of the source. Speed is CONSTANT!! Always = speed of light “redshifted” “blueshifted”

8. Doppler shift tells us ONLY about the part of an object’s motion toward or away from us:

9. The Doppler Effect The Doppler effect allows us to measure the source’s radial velocity. vr

12. Measuring the Shift Stationary Away Away Faster Moving Toward Toward Faster

13. Methods to Detect Exoplanets Radial velocity (Doppler Method, Wobble Method) Pulsar timing Transit method Gravitational microlensing Direct imaging http://rml3.com/a10p/detecting.htm

14. The motion of a light source toward or away from us changes the wavelength of the waves reaching us. • This Doppler effect is one way to find other planets. • Redshift = away. • Blueshift = toward.

15. Radial velocity (Doppler Method, Wobble Method) Sun’s motion around solar system’s center of mass depends on tugs from all the planets

16. Indirect Detection of Extrasolar PlanetsObserving periodic Doppler shifts of stars with no visible companion Over 100 extrasolar planets detected so far.

17. Doppler Measurements Yield Planet Mass Mass = 4.6 M

18. 51 Pegasi Other Extrasolar Planets Large planet mass Highly eccentric orbit

19. 3. Transit method lookforsmalldimmingasplanet moves across the face of the star.

20. Transit method: a planet passing in front of a star can decrease the total brightness of the star. • Gravitational lensing makes a star temporarily brighter through a planet’s gravity focusing its light.

21. catalogue (OGLE) name of object being observed magnified from top graph

22. 5. Direct Detection • Direct imaging: It is very difficult to directly see a faint planet in the bright glow of its star, but it can be done.

23. Special techniques can eliminate light from brighter objects • These techniques are enabling direct planet detection

25. So far … • Why is it so difficult to detect planets around other stars? • Direct starlight is billions of times brighter than starlight reflected from planets • How do we detect planets around other stars? • A star’s periodic motion (detected through Doppler shifts) tells us about its planets • Transiting planets periodically reduce a star’s brightness • Direct detection is possible if we can block the star’s bright light

26. The Formation of Other Solar Systems What have we learned about extrasolar planets?Exoplanets seem to have highly eccentric orbitsMost of the detected planets have orbits smaller than Jupiter’s Can we explain the surprising orbits of many extrasolar planets? Do we need to modify our theory of solar system formation?

27. Revisiting the Nebular Theory • Nebular theory predicts that massive Jupiter-like planets should not form inside the frost line (at << 5 AU) • Discovery of “hot Jupiters” has forced reexamination of nebular theory • “Planetary migration” or gravitational encounters may explain “hot Jupiters” Modifying the Nebular Theory • Observations of extrasolar planets have shown that nebular theory was incomplete • Effects like planet migration and gravitational encounters might be more important than previously thought

28. Planets: Common or Rare? • One in ten stars examined so far have turned out to have planets • The others may still have smaller (Earth-sized) planets that current techniques cannot detect • The physical processes that led to the Solar System should be commonplace. • We can see young stars with disks.

29. Disks in the Orion Nebula Irradiated by the Trapezium stars (left) & in silhouette against bright nebular emission (bottom). Bally, O’Dell, McCaughrean 2000 Translucent edge in disk: Measured opacity at 3 wavelengths  large grains (cm sized – protoplanetary?) (Bally et al. 2002)

31. Kepler’s First Rocky Planet Kepler 22b (first “water world”)

32. Kepler 16b http://www.nasa.gov/mission_pages/kepler/news/kepler-16b.html

33. Kepler 11 solar system

34. AstroTourStar Formation Click here to launch this AstroTour (Requires an active Internet connection.)

35. AstroTourSolar System Formation Click here to launch this AstroTour (Requires an active Internet connection.)

36. AstroTourDoppler Effect Click here to launch this AstroTour (Requires an active Internet connection.)