1. Lecture 14: Searching for planets orbiting other stars III: Using Spectra 1.The Spectra of Stars and Planets 2.The Doppler Effect and its uses 3.Using spectroscopy to measure orbits and masses of exoplanets

2. NASA Messenger space probe enters into orbit around Mercury

3. NASA Messenger around Mercury: First Image

5. Using Spectra for Remote Sensing Measuring spectral lines in the spectrum

6. Using Spectra for Remote Sensing Forming spectral lines in the spectrum

7. Venus in Front of the Sun

8. The Sun in One Spectral Line

9. Using Spectra for Remote Sensing Forming spectral lines in the spectrum

10. Direct Detection of Planets The best case to-date of a planet-like system detected in infrared light:

11. Indirect methods of planet detection Newton’s law of universal gravitation

12. The Astrometric method Binary stars - Sirius A & B.

13. The Astrometric method Not successful in planet discovery yet.

14. The Doppler shift method Doppler shift is measured from the spectral lines of two stars in a binary system:

15. Using Spectra for Remote Sensing Measuring spectral lines in the spectrum

16. The Doppler shift What is a Doppler shift ? - true for all waves.

17. The Doppler shift Doppler shift is measured from the spectral lines:

19. Mass: Radial velocities seen in star HD 209458 - the variation is due to a planet that is less massive than Jupiter. (Mazeh et al. 1999; Marcy et al. 2000)

20. Mass: For HD 209458b: M p sin(i) = M s v s P / 2  a p = const. x ( M s / 1.1M Sun ) M jup + 0.018 + 0.1 Transit light curve helps derive the orbit inclination: i = 86 o.7 + 0.2 Both M p and R p determined to better than 5%!

21. Mass: Radial velocities seen in star HD 168443 - they are due to 2 planets, each larger than our Jupiter. (Marcy & Butler 2002; Mayor et al. 2002)

22. The Spectra of Planets Mars

23. Main points to take home: 1) Visible light: form of electromagnetic energy (radiation) to which our eyes are sensitive. 2) Spectrum: the amount of light of any given wavelength, emitted or reflected by an object. 3) Thermal spectrum: a simple spectrum that depends only on the object’s temperature. 4) Spectral lines: in emission or absorption; every atom and molecule has a specific set.