1. Small Bodies in the Solar System

2. Small Planetary Bodies
In addition to planets & moons, the solar system contains many other types of objects:
including comets,
asteroids, and
meteoroids.

3. Comet Structure Nucleus
gas and dust released & form atmosphere around the comet called the coma

4. Comet’s Tail Dust Tail Usually white Ion Tail (ionized gas)
Usually blue

5. Comet’s Tail A comet's tail points away from the Sun due to solar wind
Tail gets longer when it is closer to the Sun.

6. Kuiper Belt Short-period < 200 years
Oort cloud not actually seen, billions to 2 trillion objects, made out of water, ammonia & methane
2000 AU ~ 1 ly thick

7. Oort Cloud Long-period > 200 years
Oort cloud not actually seen, billions to 2 trillion objects, made out of water, ammonia & methane
2000 AU ~ 1 ly thick

8. Comet’s Orbit Eccentricity How “oval shaped” 0 = circle
1 = very long oval
Speed
~ 40 km/s (86,400 miles/hr)

9. Halley’s ~76 years
Tempel ~5.5 years
Hyakutaka ~17,000 years

10. Comet’s Orbit
Perihelion – nearest sun
Aphelion – furthest sun

11. Asteroid Belt

12. Asteroids Size Meters – 900 km (too small to be planet) Shape
Irregular
Larger ones are more spherical
Content
Lighter – more rock
Darker – more metal

13. Asteroids > 200 asteroids > 60 miles (100 km) in diameter.
Sometimes considered planetoids or minor planets
Most located in asteroid belt (between Mars & Jupiter)
> 200 asteroids > 60 miles (100 km) in diameter.
> 750,000 asteroids > .6 mile (1 km) in diameter and
1,000,000 of smaller ones.
Speed ~ 25 km/s (54,000 miles/hr)

14. Asteroids Ceres – largest asteroid in asteroid belt 580 miles across
Considered dwarf planet

15. Asteroids
A large asteroid may have hit the Earth when the dinosaurs were alive.
~65 million years ago.

16. Asteroids Many will drop out of orbit
Collision w/ other asteroid & may head toward Earth.
< 10 km across, burn up in atmosphere.
> 10 km across, will hit surface of planet.
Hundreds of millions of years ago, collisions with asteroids more often.

17. Meteoroids…
Meteoroid - A small particle from an asteroid or comet orbiting the Sun. 
Meteor - A meteoroid that is observed as it burns up in the Earth's atmosphere – a shooting star.
Meteorite - A meteoroid that survives and impacts the Earth's surface

18. Meteoroids…
Size
Pebble to boulder (smaller than asteroids, most weigh < 1g)
Shape
Irregular
Content
From asteroids & comets, so likely metal & rock

19. Meteor Heats up to > 2,000˚C.
Creates a streak of light called a “shooting star”.
Fireballs - larger meteors -> brighter flash
On average, 1/ 10 minutes, or about 6/hour
Speed ~ km/s (~ 20 – 155,000 miles/hr)

20. Meteor Showers Usual rate = 6/hour
Meteor Shower = rate may be as high as 60/hour
Occur when Earth passes through the tail or debris of a comet
Perseids (mid-August)
Leonids (mid-November)

21. Meteorite
Meteorites could be fragments from collisions involving asteroids.
weigh few pounds & cause little damage.
Impact craters
Earth – not many, thick atmosphere
Moon & Mercury – lots, no atmosphere
Where to find –
Antarctica & Desert

22. Meteorites 3 Types Iron – chunks of iron and nickel
Stony – silicate masses that resemble Earth rocks
Stony-iron – iron–stone mixtures

23. meteorite for sale