The Solar System

1. The Solar System

2. The Sun’s Family - the Giants

3. Mars Venus Earth Ganymede Titan Mercury Callisto Europa Triton Moon Pluto Io The Sun’s Family - the Dwarfs

5. Terrestrial Mercury Venus Earth Mars Jovian Jupiter Saturn Uranus Neptune Planet Types

6. 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

7. Orbital Inclinations

8. Terrestrial Jovian Comparing the Planet Types • Distance from Sun • Diameter • Mass • Density • Composition • Rotation Rate Close Far Small Large Large Small Small Large Solar Rocky Slow Rapid

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

10. Planetary Observations Radius Angular Diameter and Distance

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

12. Planetary Observations Radius • Angular Diameter and Distance • Stellar Occultations

13. Light Curve Stellar Occultations

14. Rings of Uranus

15. The Discovery of Uranus • William Hershel 1781 • Perturbations in the orbit discovered • Must be due to another planet • Fg M/d2 • Mass from trends in the outer solar system • Assumed about the mass of Uranus • Distance from Bode’s Law

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

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

18. 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

19. Pluto Found

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

21. 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

22. The Kuiper Belt

23. Planetary Observations Radius • Angular Diameter and Distance • Stellar Occultations • Radar

24. Radar

25. 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

26. Planetary Observations Rotational Period Radar

27. 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

28. Rotation of Mercury

29. Rotation of Venus • Orbital Period=224.7d • Rotational period=243dretrograde • always presents the same face toward Earth when the two planets are at their closest approach.

30. Radar Map of Mercury

31. Comparing Twins

32. Venus

33. Other Radar Findings • Jupiter • No solid surface • Saturn • Nature of Rings

34. Planetary Observations Rotational Period • Radar • Surface features

36. Planetary Observations Rotational Period • Radar • Surface features • Slant of spectral lines

37. Rings Planet Rings Spectrum of Saturn Slit of Spectrograph

38. Planetary Observations Rotational Period • Radar • Surface features • Slant of spectral lines • Light variations

39. Asteroid Ida

40. 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

41. Albedos • Mercury 0.11 • Venus 0.65 • Earth 0.37 • Mars 0.15 • Jupiter 0.52 • Saturn 0.47 • Uranus 0.50 • Neptune 0.5 • Pluto 0.6

42. End of Section