1. Meteors, Asteroids, & Comets
(Power Point 12)
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”?
Why do the meteors heat up in the atmosphere?

8. Meteor Showers
Earth passes through dust particles left behind by a comet.
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)
Kirkwood Gaps
3 asteroid orbits/1 Jupiter orbit (3:1)

16. Practice Characterize the objects in the asteroid belt.
Compare and contrast asteroids to planets in our solar system.
How would you explain the absence of asteroids in certain orbits (Kirkwood gaps), to a friend?

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

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

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

20. 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?

21. What is the structure of a comet?
Comets are leftover icy planetesimals.
Ices
(NH3, CH4, CO2, & H2O)
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)

22. Comet Halley's Nucleus
APOD 2010 January 4

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

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

25. 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.

26. Image Credit: NASA

27. 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?

28. Animation by Dakota Dillard
Animation by Dakota Dillard

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