2. The Solar System

3. The Sun’s Family - the Giants

4. The Sun’s Family - the Dwarfs Earth Venus Mars GanymedeTitanMercury Callisto Io Moon EuropaTriton Pluto

6. Planet Types  Terrestrial  Mercury  Venus  Earth  Mars  Jovian  Jupiter  Saturn  Uranus  Neptune

7. Overall System Properties  Orbits coplanar  Orbit in same direction  Most rotate in same direction  Moons tend to orbit parent body in the same direction  Lenticular “laws”  Diameter  Number of moons

8. Orbital Inclinations

9. Comparing the Planet Types  Distance from Sun  Diameter  Mass  Density  Composition  Rotation Rate TerrestrialJovian CloseFar SmallLarge Small Large Small Rocky Solar SlowRapid

10. Planetary Observations Mass  Follow the orbit of a moon.  Follow the trajectory of a spacecraft.  Perturbations in the orbit of a nearby planet.

11. Planetary Observations Radius  Angular Diameter and Distance

12. Angular Diameter and Distance Telescope Field of View Angular Diameter (seconds of arc)

13. Radius  Angular Diameter and Distance  Stellar Occultations Planetary Observations

14. Stellar Occultations Light Curve

15. Rings of Uranus

16. The Discovery of Uranus  William Hershel 1781  Perturbations in the orbit discovered  Must be due to another planet  F g  M/d 2  Mass from trends in the outer solar system iAssumed about the mass of Uranus  Distance from Bode’s Law

17. Bode-Titius Law 4 7 10 16 28 52 100 196 0 3 6 12 24 48 96 192 0.4 0.7 1.0 1.6 2.8 5.2 10.0 19.6 Mercury d Venus e Earth  Mars f Jupiter g Saturn h Uranus i Asteroids 384 388 38.8

18. Neptune Found  Position predicted by John Couch Adams and Urbain Jean Joseph Le Verrier  Observed by Johann Gottfried Galle and Heinrich Louis d’Arrest on Sept 23, 1846  Two moons found quickly  Mass 17.2 M   Distance 30 AU

19. The search for Planet IX  Soon became apparent that Neptune didn’t solve all the problems  New search conducted by Percival Lowell  Looking for a small Jovian planet Mass 6.6 M  Magnitude 10  Clyde Tombaugh succeeds in 1930 Named Pluto Fainter than expected

20. Pluto Found

21. The Mass of Pluto  Pre-discovery 6.6 M  1968 0.91 1976 0.11 1978 0.0002

22. More Planets?  Reanalysis of Voyager 2 data suggests that all perturbations are accounted for  In fact the hunt for Pluto need not have been conducted if more accurate data had been available

23. The Kuiper Belt

24. Radius  Angular Diameter and Distance  Stellar Occultations  Radar Planetary Observations

25. Radar

26. Radius by Radar  Send out very short pulse  One nanosecond is typical  Signal reflects off of different parts of the planet at different times  Returned signal spread out in time

27. Planetary Observations Rotational Period  Radar

28. Rotational Rate by Radar  Send out signal of only one wavelength  Signal is Doppler shifted by surface of a rotating planet  Signal received spread out in wavelength Blue Shift here Red Shift here

29. Rotation of Mercury

30. Rotation of Venus  Orbital Period=224.7 d  Rotational period=243 d retrograde  always presents the same face toward Earth when the two planets are at their closest approach.

31. Radar Map of Mercury

32. Comparing Twins

33. Venus

34. Other Radar Findings  Jupiter  No solid surface  Saturn  Nature of Rings

35. Rotational Period  Radar  Surface features Planetary Observations

37. Rotational Period  Radar  Surface features  Slant of spectral lines

38. Spectrum of Saturn Rings Planet Slit of Spectrograph

39. Planetary Observations Rotational Period  Radar  Surface features  Slant of spectral lines  Light variations

40. Asteroid Ida

41. Planetary Observations Albedo  Information required  Sun-Planet distance  Planet-Earth distance  Brightness of Sun  Brightness of Planet  Basic Information on surface, atmosphere, clouds, ice caps

42. Albedos  Mercury0.11  Venus0.65  Earth0.37  Mars0.15  Jupiter0.52  Saturn0.47  Uranus0.50  Neptune0.5  Pluto0.6

43. End of Section