1 / 32

Angular Momentum in the Kuiper Belt

Angular Momentum in the Kuiper Belt. Scott S. Sheppard Carnegie Institution of Washington Department of Terrestrial Magnetism. Main Asteroid Belt 24 > 200 km. Trojan Asteroids 2 ~ 200 km. Kuiper Belt 10,000 > 200 km. Size Comparison of Rocky/Icy Bodies in the Solar System.

rene
Download Presentation

Angular Momentum in the Kuiper Belt

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Angular Momentum in the Kuiper Belt Scott S. Sheppard Carnegie Institution of Washington Department of Terrestrial Magnetism

  2. Main Asteroid Belt 24 > 200 km Trojan Asteroids 2 ~ 200 km Kuiper Belt 10,000 > 200 km

  3. Size Comparison of Rocky/Icy Bodies in the Solar System For Diameters > 200 km: Gravitational Self Compression > Material Strength Primordial Distribution of Angular Momentum - Early Collisional environment

  4. Dynamical Classes in the Outer Solar System Dynamically Disturbed and Collisionally Processed.

  5. Sedna

  6. Plan View of the Kuiper Belt Brightest KBO is 19th magnitude Diameter > 200 km Mag < 22.5

  7. Overview of Data Sample of over 40 large KBOs Short and Long Term Variations 1) Light curves 2) Phase curves UH 2.2m -> Shapes -> Surface Characteristics -> Densities -> Binaries -> Angular Momenta -> Outgassing du Pont 2.5m

  8. Short-term Variability 2000 GN171 2000 GN171 period = 7.9 hours • Albedo • Elongation • 3. Binary

  9. KBOs (40 in sample) 29% > 0.15 mags 18% > 0.40 mags 12% > 0.60 mags

  10. 1. Albedo effects are usually only 10 to 20%(Degewij et al. 1979)

  11. 1/2 crit 2. Elongation For large objects (> 200 km) Spherical Gravitational Compression > Material Strength As angular momentum increases an object will go from being a sphere to biaxial to Triaxial elongation from rotational angular momentum P = (3 Pi / G rho) Centripetal acceleration = gravitational acceleration Rotational Triaxial Ellipsoids (Jacobi Ellipsoids) Fast Rotations < 7 hours (Leone et al. 1984)

  12. Axis Ratio from rotational light curve: Period and amplitude can be related to an objects density 0.4 x delta mag a/b = 10 Varuna

  13. Varuna Density ~ 1100 kg/m 3 Assume Rotationally distorted Strengthless Rubble Pile Chandrasekhar 1987 Leone et al. 1984 Cosmochemically Plausible Rock Fraction ~ 0.5 Porosity ~ 10 to 20% Jewitt and Sheppard 2002

  14. 3. Eclipsing Binaries • Probability of eclipse events to our line of sight decreases as the separation increases • Tidal interactions distort close components Photometric Range Max ~ 0.75 mags Photometric Range Max ~ 1.2 mags (Leone et al. 1984) 1999 TC36 (Trujillo and Brown 2002)

  15. Period = 13.7744 hours 2001 QG298 Diameter ~ 250 km Range = 1.1 mags

  16. 2001 QG298 is only the 3rd known minor planet with diameter > 50 km and a photometric range > 1 magnitude Kleopatra 2001 QG298 Hektor

  17. KBO 2001 QG298 Trojan Asteroid 624 Hektor Main Belt Asteroid 216 Kleopatra

  18. CFHT Adaptive Optics images of Kleopatra Merline, Dumas and Menard 1999

  19. Comparison of Large Main Belt Asteroids and Kuiper Belt Objects Sheppard and Jewitt 2004

  20. 100 km 20,000 km 100 km 1000 km 1 km 2.5 km Margot 2002 Comparison of typical binary systems within the Solar System.

  21. KBO Binary Formation Mechanisms: Three Body Interactions Tidal Disruption Direct Collisions Funato et al. 2004

  22. Known Binaries of Large Minor Planets in the Solar System Does a large angular momentum of the primary correspond to satellite formation? Current angular Momentum of Large objects hints At an earlier denser Kuiper Belt. Maybe 100 times more dense.

  23. We find 5 of 34 KBOs are in the close, similar component, eclipsing binary region (15%) (Because of projection effects, the fraction may be much larger) Noll et al. (2002) found about 4% of KBOs were binary with separations > 0.15” Consistent with Goldreich et al. (2002) model of binary formation but not with the Weidenschilling model (2002) Collisionless interactions In a denser Kuiper Belt During the formation epoch. - Dynamical Friction would create more close in binaries

  24. Conclusions - Many Kuiper Belt Objects have large amplitude light curves - Some may be rotationally deformed rubble piles - Many are probably contact or nearly contact binaries • Kuiper Belt must have been about 100 times more dense in the distant • past to explain current amount of angular momentum we see. • Binary formation is still unclear, but direct collisions may have be an • important factor.

  25. Short and Long Term Variability Consecutive Nights Multiple Months Absolute Photometry 2 2 2 Mag = Msun – 2.5 log(albedo x radius x phase / heliocentric x geocentric )

  26. Double-peak Period = 8.08 hours 1995 SM55 V-R=0.38 Binary or Cometary or Complex Rotation? Single-peak Period = 4.04 hours Damping time scale 2 3 t = u Q / p K r w u is rigidity Q is ratio energy in oscillation to that lost p is the density K is irregularity of body r is the radius w is angular frequency

  27. 1. Nonuniform Surface Markings Photometric Range ~ 2 mags B – V ~ 0.1 mags (Millis 1977) -synchronous rotation Iapetus Photometric Range ~ 0.3 mags -atmosphere

  28. 20000 Varuna Rotational Lightcurve(diameter ~ 900 km) Period = 6.3442 hours

  29. 20000 Varuna: Found No Color Variation with Rotation

  30. Asteroid and KBO Limiting Densities Sheppard and Jewitt 2002

  31. 5 KBOs can not be easily explained from albedo or rotational elongation

More Related