Meteors, Asteroids, & Comets
(Chapter 19)
Comet Lovejoy 2015
Image Credit: Sky & Telescope
Student Learning Objectives
• Classify & describe meteors, asteroids, and
comets
• Identify the locations of these objects in our
solar system
What is the origin of meteors?
These bits of matter
have two origins.
1. Asteroid Collisions
(bits of rock are ejected)
Single Meteor
2. Comet trails
(bits of comet along path)
Meteor Shower
Classifying Rocky Debris
Object
Location
Description
Meteoroid
Space
Orbit Sun
Meteor
Earth’s
Atmosphere
“Shooting Star”
Earth’s Surface
Impact Earth
(2/year)
Meteorite
Astronaut Photographs Perseid Meteor... From Space
Aug 14, 2011 Discovery News
“Falling Stars”
Meteors are fast!
 22,000 - 89,000 mph
 KE huge
 Meteors heat up in the
Earth’s atmosphere
 Heat makes meteor
bright
Meteor showers come from
the same direction.
(radiant)
http://stardate.org/nightsky/meteors
Practice
1) What is the correct name for a “falling star”?
2) What is the probability of being hit by an
object falling from the sky?
http://geology.com/meteor-impact-craters.shtml
http://neo.jpl.nasa.gov/orbits/
http://szyzyg.arm.ac.uk/~spm/neo_map.html
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.
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
 Rotation 3-20 hours
 Some binary systems
 Some differentiated
APOD
APOD
Kirkwood Gaps
Apollo Asteroids
Apollo asteroids orbit
within the inner solar
system, crossing
Earth’s orbit.
Impact Earth
(1/ 250,000 years)
Trojan Asteroids
Trojan asteroids are
located on Jupiter’s
orbit.
 One group ahead
 One group behind
Asteroids maintain well established orbits.
No. Collisions = 1 per Million years
Collisions result in debris with different
compositions. Why?
Practice
1) What is the origin of a single meteor?
2) What is the origin of a meteor shower?
3) Why are asteroids irregularly shaped, not spherical
like planets?
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)
Comet Halley's Nucleus
APOD 2010 January 4
The coma stretches into
two tails.
 Gas tail points away from
Sun (ionized gasses)
 Dust tail follows orbit of
comet
http://www.st-andrews.ac.uk/~bds2/ltsn/ljm/JAVA/COMETORB/COMET.HTM
Three Month Composite of Comet Holmes
APOD 2008 February 5
Location of Comets
Outermost region of our
solar system
Kuiper Belt
(30-55 AU)
Beyond Neptune
Oort Cloud
(5,000-100,000 AU)
A passing star can alter
the comet orbit
Practice
1) Which tail is typically seen with your eyes?
2) Does a comet always have a tail?
3) Not all comets return to the inner solar system. What
are the possible reasons for this?