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

The New Solar System

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