1. Meteors, Asteroids, & Comets
(Power Point 10)
Comet Lovejoy 2015
Image Credit: Sky & Telescope

2. Student Learning Objectives
Construct a model of the Solar System; its creation, contents, and evolution.
Classify & describe meteors, meteoroids, and meteorites
Differentiate between meteors, asteroids, and comets
Identify the locations of groups of small objects in our solar system

3. What is the origin of meteors?
Meteors are bits of matter that have two possible origins.
Asteroid Collisions
(bits of rock are ejected)
Single Meteor
Comet trails
(bits of comet along path)
Meteor Shower
Image Credit: NASA

4. Meteor Photo from ISS
Image Credit: NASA

5. Classifying Rocky Debris
Object
Location
Description
Meteoroid
Space
Orbit Sun
Meteor
Earth’s Atmosphere
“Shooting Star”
Meteorite
Earth’s Surface
Impact Earth (2/year)

6. “Falling Stars” Meteors are fast! (22,000 - 89,000 mph) KE is huge!
Meteors heat up in the Earth’s atmosphere (bright)

7. Practice
What quantity causes the KE of a meteor to be “huge”, mass or speed?
Explain why meteors heat up in the atmosphere?
What is the primary difference between a meteoroid, meteor, and meteorite?

8. Meteor Showers
When Earth passes through dust particles left behind by a comet, there is a meteor shower.
The dust particles enter Earth’s atmosphere from the same direction (radiant).
Image Credit: NASA

9. Meteor Shower Radiant
Image Credit: NASA

10. Image Credit: NASA

11. Practice What is the correct name for a “falling star”?
What is the probability of being hit by an object falling from the sky?

12. K-T Event
Sixty-five million years ago, about 70% of all species disappeared within a very short period. This was called the Cretaceous-Tertiary Mass Extinction, or K-T Event. Many theorize that this was the result of a giant impact.

13. What are the locations of asteroid groups?
Asteroids are leftover rocky planetesimals.
Most asteroids are located in the main asteroid belt between 2.3 and 3.3 AU.
Irregular shapes
Many sizes
Rotations 3-20 hours
Some binary systems
Some differentiated
Image Credit: NASA

14. Image Credit: NASA

15. 3 asteroid orbits/1 Jupiter orbit (3:1)

16. Reason for Kirkwood Gaps
The gaps result from orbital resonances with Jupiter.
These gaps have been cleared of asteroids by Jupiter’s dominant gravitational influence.

17. Practice Characterize the objects in the asteroid belt.
Compare and contrast asteroids to planets in our solar system.
What is required for a gap in the asteroid belt to occur?

18. Apollo Asteroids
Apollo asteroids orbit within the inner solar system, crossing Earth’s orbit.
Impact Earth
(1/250,000 years)
Image Credit: COSMOS

19. Trojan Asteroids Trojan asteroids are located on Jupiter’s orbit.
One group ahead
One group behind
Image Credit: Facweb

20. Artist’s conception of Trojan Asteroids
Image Credit: JPL/NASA

21. Practice
What is the origin of a single meteor? What is the origin of a meteor shower?
Why are asteroids irregularly shaped, not spherical like planets?
Meteorites are found with different compositions. Why? What process could explain this?

22. What is the structure of a comet?
Comets are leftover icy planetesimals.
Mostly ices
NH3 CH4 CO2 H2O
Some silicates
The nucleus is an irregularly shaped solid ball of ices with dust grains.
The coma is a sphere of tenuous gas and dust that surrounds the nucleus. (Ices vaporize)

23. Comet Halley's Nucleus
APOD 2010 January 4

24. The coma stretches into two tails.
Gas tail points away from Sun (ionized gasses)
Dust tail follows orbit of comet

25. Animation by Dakota Dillard
Animation by Dakota Dillard

26. Three Month Composite of Comet Holmes
APOD 2008 February 5

27. Location of Comets Beyond Neptune
Kuiper Belt (30-55 AU)
Oort Cloud (5, ,000 AU)
Distant enough that a passing star can alter the orbit

28. Image Credit: NASA

29. Practice Which tail is typically seen with your eyes?
Does a comet always have a tail?
Not all comets return to the inner solar system. What are the possible reasons for this?
Have we ever landed on a comet?

30. Animation by European Space Agency (ESA)
Animation by European Space Agency (ESA)