1. Theme 10 – Leftovers: Meteors and Asteroids ASTR 101 Prof. Dave Hanes

2. Meteors: Individual, or in Groups - not “falling stars!”

3. To Be Precise Meteoroid = the pebble out in space Meteor = the luminous event we see (the trail of the “falling star”) Meteorite = any surviving lump that we find on the ground

4. What We Are Seeing Most meteors are small (tiny pebbles, or even grains, of rocky material) They enter Earth’s atmosphere at very high speed (many tens of km/sec) Air resistance slows them and heats both the pebble and the column of air – this is what we see, not the pebble itself

5. Some Can be Very Bright

6. A Range of Sizes (‘Pebbles’ burn up!) A Range of Sizes (‘Pebbles’ burn up!)

7. Ahnigito (“The Tent”) Meteorite 31 tonnes; fell ~ 10,000 years ago

8. Duck!

9. Finding Them on the Ground Various types: stony (undistinguished!) carbonaceous chondrites, iron (very distinctive!), …

10. A Good Hunting Ground!

11. Meteor Showers Not all meteors come in singly.

12. Remants of Evaporated Comets A comet breaks up The rubble gets spread out

13. Moving ‘Gravel Pits’ - and a trick of perspective

14. The Shower has a‘Radiant’ - hence the name (e.g. the Perseids, in August)

15. The Leonids in 1833 and 2001

16. Asteroids

18. We Can Visit Them (Vesta and Ceres)

19. Finding New Ones

20. ‘Earth-Crossing’ Orbits

21. We Do Get Hit! [here, about 30,000 years ago]

22. The Speed is the Key Factor All of the kinetic energy (the energy of motion) is released when the moving object hits the target. A 1-gram pebble moving 100 km/sec has as much kinetic energy as a 10-ton truck moving along the highway at 100 km/hour http://www.popularmechanics.com/technology/engineering/gonzo/beh old-the-900-mph-supersonic-ping-pong-bazooka-15097897

24. The Same Basic Physics! http://www.youtube.com/watch?v=Pi-NIeJ26BI http://www.youtube.com/watch?v=Pi-NIeJ26BI

26. Local Examples

27. Relatively Recently, in Russia

28. Very Recently in Chelyabinsk, Russia Even a ‘miss’ can be quite destructive http://www.youtube.com/watch?v=dBvotWfR3j4/

29. Back to Tunguska

30. How about biggerstill?