1. Small objects in the Solar System
Meteors, Comets, : we see them without a telescope
Asteroids: small rocky objects mostly between Mars and Jupiter – too faint to see without a telescope
Kuiper belt objects: even fainter objects beyond Pluto, debris left over from solar system formation
Make a dry ice comet as class intro, bring hula hoop, meteor kit
Collect HW: reading on asteroids & dinosaurs
Image of comet Wild 2, visited by Stardust, return Jan 2006
Image of comet Wild 2, visited by Stardust mission, return Jan 2006

2. Meteors: debris from comets, chips of asteroids
Meteors (shooting stars) can appear at any time, from any direction.
Meteor: The bright tail of hot debris from the rock
Meteorite: A rock from space that reaches Earth’s surface

3. Peekskill, NY:
October 9, 1992

4. If a meteor does not burn up completely, and reaches the ground it is a meteorite
Most of these are probably remnants of asteroids
Most common are iron
Less common: stony (easily missed, more fragile)
Samples to examine:

5. Asteroids: small bodies that orbit the sun between the orbit of Mars and Jupiter – largest about 500 miles diameter
Jupiter’s gravity, stirs up the asteroid orbits and prevents their planet formation.
The first, named Ceres, discovered in 1800 in search for presumed planet between Mars and Jupiter

6. Asteroids: remains of a planet that did not combine?
Iridium and osmium are the densest elements, and both are believed to have dropped below the Earth's crust toward the core when the Earth was young and molten. The concentration of iridium in meteorites matches the concentration of iridium in the Earth as a whole.
Small rocky or iron objects (a few 100 to a few km in diameter) mostly in orbit between Mars and Jupiter

7. Comets

8. Comets:
Large ( many km diameter) dirty snowballs, orbiting the sun in highly elliptical orbits. So where do we see them?
We only see them when they come close to the sun and evaporation and sublimation creates a long tail.
The tail always points away from the sun, even when comet moving away from sun
They move among the stars, fastest when closest to the sun. (Why?)

9. When a comet nears the Sun, its ices can sublimate into gas and carry off dust, creating a coma and long tails.

11. A Comet’s Tail

12. Comets; they appear in the sky for days or weeks – do not flash across the sky!
Comets: their orbits around the sun are very elliptical Some have short periods ( years) like Comet Halley Others have periods of thousands of years, such as Comet ISON, in a sky near you now…
Bradfield, april 26 , april 25 am

13. Where do comets come from?
Many ordinate in a region called the Oort cloud which is located beyond the orbit of the planet Pluto
Others originate in the Kuiper Belt beyond the orbit of Neptune
This region is filled with billions of comets

14. Oort Cloud and Kuiper belt
The Kuiper belt is composed of small bodies, and a reservoir of short period comets: best known KBO is… Pluto!
Oort Cloud and Kuiper belt

15. Only a tiny number of comets enter the inner solar system - most stay far from the Sun
Oort cloud:
On random orbits extending to about 50,000 AU
Kuiper belt:
On orderly orbits from AU in disk of solar system

16. Gravity from Jovial () planets can influence the path of comets and Asteroids. They could protect us or steer one in our direction

17. Take away
In addition to the 8 planets there are many small objects down to dust grain size, orbiting the sun with us: meteors, asteroids, comets, Kuiper Belt Objects (KBO’s).
They are clues to the formation of the solar system.