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Vagabonds of the Solar System

Vagabonds of the Solar System. Lecture 27. Main-belt asteroids 2.0 – 3.5 AUs. Distribution of Asteroids. Kirkwood gaps were created by repeated gravitational influence by Jupiter. Families of Asteroids.

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Vagabonds of the Solar System

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  1. Vagabonds of theSolar System Lecture 27

  2. Main-belt asteroids 2.0 – 3.5 AUs

  3. Distribution of Asteroids Kirkwood gaps were created by repeated gravitational influence by Jupiter

  4. Families of Asteroids • Asteroids form “groups or families” and have unique sets of orbits rather than have a continuous range of all orbits. • Most notable family is “Trojan Asteroids”

  5. Trojan Asteroids

  6. Various sizes UL: HST image of Ceres (largest asteroid). UR: Radar map of a medium sized asteroid. LL: Flyby spacecraft image of an asteroid (Mathilde, ~50km).

  7. Chicxulub Impact (= dinosaur killer, K-T impact) • ~180km in diameter • Recent discovery (1978) • Equals to the energy of 10,000+ times of all nuclear weapon detonations

  8. Global Iridium layer at the K-T boundary

  9. KT impact  Dinosaur killer Estimated size of 10-20km asteroid

  10. Some recent impacts! • Arizona (Barringer Crater) • ~4,000 ft diameter • 50m size iron meteor collided at a speed of ~20km/sec. • ~50,000 yrs ago • Tunguska (June 30, 1908, Siberia) • Burst meteor in the air (~5 miles) • About 1,000 times stronger than the Hiroshima bomb. • Knocked down about 80 million trees within 15miles

  11. Shoemaker-Levy • broken up comet collide Jupiter (1996)

  12. Happens frequently… • A chain of impact craters on Ganymede Estimated size distribution of main-belt asteroids

  13. Torino scale A method for categorizing the impact hazard of near-Earth objects (NEOs). assessing the seriousness of collision predictions by combining probability statistics and known kinetic damage potentials into a single threat value. • Apophis: Highest ever Torino scale (“4”) • Initial calculation of 2.7% chance to hit the Earth in 2029. • Current calc = 1 in 12.3 million chance to hit the Earth in 2037. NASA can't pay for a killer asteroid hunt cost to find 90% of asteroids, comets (larger than 1km) would be about $1 billion

  14. Recent passby of a NEO : 2005 Yu55 0.5km asteroid passed by the Earth in early 2011 November. How small can asteroids be?

  15. Meteors and meteorites. • Iron meteorites Widmanstattenpattern meteoroid  meteor  meteorite • Stony Asteroid

  16. Comet : Chunk of ice and dust

  17. Comet Halley Comet’s tails

  18. Origin of long-period comets

  19. Cosmic Messengers

  20. Signal from Pioneer • A signal from the Pioneer 10 spacecraft, sent from a distance of more than 6 billion kilometers. The spacecraft transmitted the signal with a power of only one watt (about the power of an X-mas tree light)!

  21. In summary… Important Concepts Important Terms Lagrange point Trojan asteroids Kirkwood gap Widmanstatten pattern Near Earth Objects Torino scale meteoroid, meteor, meteorite • K-T impact • Different kinds of meteorites • Comets (from Kuiper Belt and Oort cloud) • Gas and dust tails of comets • Chapter/sections covered in this lecture : Chapter 15

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