1. Hubble Space Telescope imaging of Ceres and Vesta L. McFadden and J.Y. Li (University of Maryland, College Park), J. Parker and E. Young (Southwest Research Institute), M. Sykes (University of Arizona), P. Thomas (Cornell University), C. Russell and B. Schmidt (University of California, Los Angeles), M. Mutchler and Z. Levay (Space Telescope Science Institute) Version 22 June 2007

2. The planet vote of 2006

3. The IAU therefore resolves that planets and other bodies in our Solar System, except satellites, be defined into three distinct categories in the following way: (1) A “planet” is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit. (2) A “dwarf planet” is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite. (3) All other objects, except satellites, orbiting the Sun shall be referred to collectively as “Small Solar System Bodies”. http://www.iau2006.org Final Resolution 5 for GA-XXVI: Definition of a Planet 24 August 2006

4. Historical perspective: how many planets are there? Antiquity -- 7 planets; geocentric model (Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn) 1550 – 6 planets; heliocentric model (add Earth, remove Moon & Sun) 1781 – 7 planets (add Uranus) 1807 – 11 planets (add Ceres, Pallas, Juno, Vesta) 1845 – 12 planets (add Astraea) 1846 – 13 planets (add Neptune) 1851 – 8 planets (exclude objects in Asteroid Belt – any déjà vu?) 1930 – 9 planets (add Pluto) 1992 – Discovery of 1992 QB 1 …the Kuiper Belt! 2005 – Discovery of Eris (UB 313 ) 2006 – 8 planets (remove Pluto; don’t add Ceres, Charon, Eris or other “dwarf planets”) 2009 – Another vote?

5. Ceres Asteroid Belt Kuiper Belt Discovered 1801-1851 Discovered in 1992…or 1930? Ceres and Pluto: The “ugly duckling” problem of being the first of an entire class

7. Hubble images of Ceres in January 2004 Advanced Camera for Surveys (ACS) High Resolution Channel (HRC) Filters: F220W, F330W, F555W Sub-sampled (dithered) images were drizzled to enhance resolution Color composite images: F330W+F555W Movies made from lower-resolution images (full phase coverage)

8. Hubble images of Ceres reveal roundness, surface features, and colors Three different faces of Ceres

9. Hubble images of Ceres reveal roundness, surface features, and colors Three different faces of Ceres

10. Why does roundness matter ?

11. Differentiation of the asteroid Ceres as revealed by its shape Thomas, Parker, McFadden, Russell, Stern, Sykes, Young, 2005, Nature Letters, Vol 437

12. Hubble images of Vesta in May 2007 Wide Field Planetary Camera 2 (WFPC2); Advanced Camera (ACS) failed in January 2007 Filters: F439W, F673N, F953N, F1042M No subsampling dithers: Vesta rotates too fast Preliminary image deconvolution via Maximum Entropy Method (MEM); MISTRAL next… Color composite images: F439W+F673N Movies and albedo maps

13. Hubble WFPC2 F439W image of asteroid Vesta in May 2007: raw

14. Hubble WFPC2 F439W images of asteroid Vesta in May 2007: deconvolved (MEM)

15. Hubble WFPC2 image of asteroid Vesta: artist’s impression

16. Hubble WFPC2 F439W images of asteroid Vesta in May 2007: raw

17. Hubble WFPC2 F439W images of asteroid Vesta in May 2007: deconvolved (MEM)

18. Hubble WFPC2 F673N images of asteroid Vesta in May 2007: raw

19. Hubble WFPC2 F673N images of asteroid Vesta in May 2007: deconvolved (MEM)

20. Hubble WFPC2 F953N images of asteroid Vesta in May 2007: raw

21. Hubble WFPC2 F953N images of asteroid Vesta in May 2007: deconvolved (MEM)

22. Hubble WFPC2 F1042M images of asteroid Vesta in May 2007: raw

23. Hubble WFPC2 F1042M images of asteroid Vesta in May 2007: deconvolved (MEM)

24. Hubble WFPC2 images of asteroid Vesta in May 2007: color composite

25. Hubble WFPC2 images of asteroid Vesta in May 2007: color composite movie

27. http://www.dawn-mission.org Dawn Vesta 2011 Ceres 2015 Launch July 7!