1 / 29

Using Known Long-Period Comets to Constrain the Inner Oort Cloud and Comet Shower Bombardment

Using Known Long-Period Comets to Constrain the Inner Oort Cloud and Comet Shower Bombardment. Nathan Kaib & Tom Quinn University of Washington. Outline. Long-Period Comet Production Inner Oort Cloud Comet Production Constraints from Known LPCs Comet Shower Significance. Long-Period Comets.

aman
Télécharger la présentation

Using Known Long-Period Comets to Constrain the Inner Oort Cloud and Comet Shower Bombardment

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. Using Known Long-Period Comets to Constrain the Inner Oort Cloud and Comet Shower Bombardment Nathan Kaib & Tom Quinn University of Washington

  2. Outline Long-Period Comet Production Inner Oort Cloud Comet Production Constraints from Known LPCs Comet Shower Significance

  3. Long-Period Comets

  4. X

  5. 25000 AU Jupiter-Saturn Barrier • Comets must have large perihelion shift to make it past Jupiter/Saturn in one orbital period • Only weakly bound comets will have large perihelion changes • Jupiter/Saturn shield inner solar system from inner 20,000 AU of Oort Cloud

  6. Simulations • Initial cloud orbits (~106) drawn from recent OC formation simulation results (Kaib & Quinn, 2008) • Oort Cloud model has 1.5:1 inner-to-outer population ratio • Modify SWIFT (Levison & Duncan, 1994) with time-reversible adaptive timestepping routine (Kaib & Quinn, 2008) • Evolved under influence of Sun, 4 giant planets, Milky Way tide and passing stars for 1.2 Gyrs • Analyze LPCs from last 200 Myrs

  7. Start OC Objects Fates a = 500,000 AU Start Constrained a (AU) x Unconstrained NOC

  8. Inner OC LPCs q = 1 AU a = 28,000 AU Start Similar evolution in SDO simulations (Levison et al., 2006)

  9. Inner OC LPCs Constrained a (AU) Unconstrained NOC

  10. Original Orbits qLPC < 5 AU

  11. Incoming Orbits qLPC < 5 AU

  12. Inner OC LPCs a (AU) Start NOC

  13. Population Constraints • Predicted LPC rate: 1/116,000 per Myr • Max Observed rate: 10 per yr (everhart, 1967) • Predicted population: ~1012 km-sized bodies between 3,000 and 20,000 AU (assuming nOC ~ r -3.2) • Not much larger than current outer Oort Cloud population estimates (3-5 x 1011) • Modest inner Oort Cloud can produce observed LPC flux

  14. 25000 AU Comet Showers • Rare close stellar encounters (< 5000 AU) are able to perturb more tightly bound orbits • The Earth is temporarily exposed to the entire Oort Cloud • Possible source of mass extinctions seen in fossil record (Hut et al., 1987; Farley et al., 1998)

  15. Comet Shower LPCs a (AU) NOC

  16. 25,000 AU 4 AU M* = MSun v = 20 km/s, Dmin = 3000 AU Dt = 105 yrs

  17. Relative Shower Strength DvSun = (2GM*)/(bv)

  18. 1.5:1 3:1 10:1 Relative Shower Strength 1/t ~ (DvSun)-2(Rickman, 2008)

  19. Constrained Shower Curve (Weissman, 2007) most powerful showeryields 2-3 km-sized impactors

  20. 3 impacts 2 Myr He3 spike (Farley et al., 1998) Rohde & Muller (2005)

  21. Conclusions • Inner Oort Cloud is a significant and perhaps dominant source of LPCs • Current LPC flux gives an estimate of the total Oort Cloud population, not just outer • Implies comet showers are not responsible for more than ~1 extinction event

  22. Oort Cloud Mass Problem • Outer Oort Cloud traps 1-2% of planetesimals during formation • Previous outer Oort Cloud mass estimates implied > 200 MEarth planetesimal disk between 4 and 40 AU (Dones et al., 2004) • Inner Oort Cloud can trap more efficiently (5-15%) and still produce observed LPCs (Brasser et al., 2006; Kaib & Quinn, 2008)

  23. Disk Mass Requirements Minimum mass solar nebula  40 MEarth(Dones et al., 2004)

  24. LPC Inclinations 55% Retrograde

  25. LPC semimajor axes Inner amed = 26,000 AU; Outer amed = 35,000 AU Observed amed = 27,000 AU

  26. Compact Inner Clouds (Brasser et al., 2006) ~103 MSun/pc3 produces Sedna and LPCs

  27. Showers from Alternative Clouds A < 3,000 AU case requires 1200 MEarth disk

  28. Quantifying Shower Strength M* = 0.8 MSun v = 20 km/s Dmin = 1300 AU LPC defined as q < 5 AU

  29. Jupiter-Saturn Barrier Edge log D(1/a) q (AU) Duncan et al. (1987)

More Related