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Evaluating the Effects of Oort Cloud Comet Showers on the Earth

Evaluating the Effects of Oort Cloud Comet Showers on the Earth. Nathan Kaib University of Washington. Background. Halo of km-size bodies surrounding solar system Comprised of icy planetesimals leftover from planet formation Scattered out by encounters with giant planets

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Evaluating the Effects of Oort Cloud Comet Showers on the Earth

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  1. Evaluating the Effects of Oort Cloud Comet Showers on the Earth Nathan Kaib University of Washington

  2. Background • Halo of km-size bodies surrounding solar system • Comprised of icy planetesimals leftover from planet formation • Scattered out by encounters with giant planets • Reservoir of Long-Period Comets

  3. Oort Cloud extends out to ~200,000 AU

  4. Long-Period Comets

  5. X

  6. 25000 AU Jupiter Barrier • Comets must have large perihelion shift to make it past Jupiter in one orbital period • Only weakly bound comets will have large perihelion changes • Jupiter shields inner solar system from inner 20,000 AU of Oort Cloud

  7. 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

  8. Inner Oort Cloud • Strength of shower depends on: • Stellar encounter • Population of Inner Oort Cloud • Inner Oort Cloud population very sensitive to Sun’s birthplace environment (Kaib & Quinn, submitted) No Cluster 30 stars/pc3 100 stars/pc3

  9. Shower Simulations • Each simulation contains ~106 comets • These are run for 40 Myrs and include one very close stellar passage, many weaker encounters and galactic tide • Formation environment and stellar encounter parameters are varied • Flux of objects coming into the inner 5 AU is monitored

  10. Results 30 stars/pc3 No Cluster Encounter: 1 MSun, 3000 AU, 10 km/s

  11. Conclusions • Close stellar passages can raise the long-period comet flux by a factor of 200-400 for 105 years • To assess affect on Earth we need better measurement of LPC size distribution and current LPC flux • New generation surveys (LSST, Pan-STARRS) will better determine the background flux in the coming years

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