Chapter
23.4
Minor Members of
the Solar System
Students will be able to…
•Identify where most asteroids are located
•Describe the structure of a comet
23.4 Asteroids: Microplanets
Definition - An asteroid is a small, rocky body whose
diameter can range from a few hundred kilometers to
less than a kilometer.
Do asteroids have an atmosphere? None of the asteroids have atmospheres.
What is another name for asteroids? Asteroids are also known as planetoids or minor planets.
23.4 Asteroids: Location
Most asteroids lie between the orbits of
Mars and Jupiter. They have orbital periods
of three to six years.
Asteroids
• Why is there an asteroid belt?
• One theory suggests that they are the remains of a planet that was destroyed in a massive collision long ago.
• More likely, asteroids are material that never coalesced into a planet.
• In fact, if the estimated total mass of all asteroids was gathered into a single object, the object would be less than 932 miles across -- less than half the diameter of our Moon
Name: Gaspra
Size: 17 x 10 km
This image was taken in October
1991, when the Galileo spacecraft
passed within 1600 km on its way
to Jupiter. (Courtesy Nasa/JPL)
Name: Ida
Size: 56 x 24 km
Location: Asteroid Belt
Image obtained in 1993
when Galileo passed within
2400 km (Courtesy
Nasa/JPL).
Some examples of asteroids
- Asteroids are big and meteoroids are small
(pebbles)
Meteoroids come from:
1) left over solar system debris
2) asteroids collide
3) comet debris.
Asteroids vs. Meteoroids
- When a meteoroid strikes our atmosphere at high
velocity, friction causes this chunk of space matter to
heat up and create a streak of light known as a meteor
(shooting star).
Asteroid, Meteoroid, Meteor, and Meteorite
- If the meteoroid does not burn up completely, what's
left strikes Earth's surface and is called a meteorite.
These rocks have helped identify the age of the solar
system (4.6 billion years old).
Asteroid, Meteoroid, Meteor, and Meteorite
Major Meteor Showers
23.4 Comets
Comets are small bodies made of rocky
and metallic pieces held together by frozen
gases.
Comets generally revolve about the sun in
elongated orbits (highly elliptical).
23.4 Parts of a Comet
• A coma is the fuzzy, gaseous component of a comet’s
head (atmosphere).
• A small nucleus (body) with a diameter of only a few
kilometers can sometimes be detected within a coma.
• As comets approach the sun, some, but not all, develop
a tail that always points away from the sun.
23.4 Parts of a Comet
23.4 Comets
Kuiper Belt or Oort Cloud
• Where most comets are located.
• This area is found beyond Neptune
Comets
Comets
• Astronomers believe
that comets are leftover
debris from the outer
planets about 4.6 billion
years ago.
• Some scientists believe
that comets originally
brought to Earth some
of the water and the
carbon-based
molecules that make up
living things.
23.4 Comets
Halley’s Comet
• The most famous short-period comet is Halley’s
comet. Its orbital period is 76 years.
• From July 16 through July 22, 1994, pieces of an
object designated as Comet P/Shoemaker-Levy
9 collided with Jupiter. This is the first collision of
two solar system bodies ever to be observed
• Comet Shoemaker-Levy 9 consisted of at least
21 fragments
• http://www.windows.ucar.edu/tour/link=/co
mets/comet_model_interactive.html