Asteroid Occultations & Light-curve Inversion models

1. Asteroid Occultations&Light-curve Inversion models

2. This is based on a paper published in ICARUS this year, with the following authors: Josef Durech, MikkoKaasalainen, David Herald, David Dunham, Brad Timerson, Josef Hanus, Eric Frappa, John Talbot, Tsutomu Hayamizu, Brian D. Warner, Frederick Pilcher, Adrian Galad

3. Asteroidal occultations…. Give dimensions of an asteroid (at about 1-km accuracy) as oriented at the time of the occultation

4. (135) Hertha 2008 Dec 11

5. (234) Barbara 2009 Nov 21

6. However occultations only give a single snap-shot. Difficult to get a full 3-D picture of an asteroid

7. Light curve analysis

8. Irregular shape causes rotational light curve variation • When polar axis is inclined to the ecliptic, the parts of the asteroid that are ‘visible’ varies, depending on location in orbit • Can model the shape of the asteroid using the differing light curves – called ‘inversion models’

9. Requires accurate measurement of the rotation period, and determination of the direction of the axis of rotation • The model gives a shape for the asteroid, but not its size • Most models currently are limited to convex surfaces • Sometimes more than one model fits the available data

10. [break to demo 3-D model]

11. Combining Occultations with inversion models • If the 3-D model is generated for the orientation at the time of an occultation, it can be matched. • Matching: • Puts a definite scale to the 3-D model • Discriminates between different models

12. Very recent example :(516) Amherstia 2011 Apr 18

13. (516) Amherstia 2011 Apr 18 #1

14. (516) Amherstia 2011 Apr 18 #2

15. Hertha against shape model

18. (3) Juno

19. 5 Astraea

20. 17 Thetis

21. 88 Thisbe

22. 372 Palma

23. 925 Alphonsina