This document discusses minor members of the solar system including comets, meteors, and asteroids. It explains that comets are balls of ice, rocks, and dust with a nucleus, coma, and dust and ion tails. Edmond Halley discovered that some comets have predictable orbital periods, such as the comet that bears his name which returns every 76 years. Meteoroids are small rocks or metals in space that become meteors when entering Earth's atmosphere, sometimes forming meteor showers. Those that reach the surface are meteorites. Asteroids are chunks of rock or metal found mainly in the asteroid belt between Mars and Jupiter.

1. HEAVENLY BODIES

2. Learning Objectives
At the end of our discussion you should be able to:
1. Demonstrate understanding of the characteristics of comets,
meteors, and asteroids;
2. Compare and contrast comets, meteors, and asteroids;
3. Predict the appearance of comets based on recorded data of
previous appearances;
4. Explain the regular occurrence of meteor showers;
5. Discuss whether or not beliefs and practices about comets and
meteors have scientific bases;

3. OUTER SPACE
Simulation

4. Minor Members of the Solar System
Comets
Balls of ice, rocks, and dust particles in outer space

5. Minor Members of the Solar System
Comets
In 1705, British astronomer Edmond
Halley (1656–1742) discovered that
one comet has an eccentric orbit
and returns to the inner part of the
solar system every 76 years. This
comet was posthumously named
after him.

6. Parts of a Comet
Nucleus - mainly of ice, dust, and a small
rocky core.
Coma - cloud that forms when ice on the
surface of the nucleus begins to turn into gas
as the comet gets closer to the sun.
Dust Tail - formed when the sun’s radiation
pushes dust particles away from the coma
Ion Tail - formed when charged particles
from the sun convert the comet’s gases into
ions

7. Conceptual Check
What are the comets believed to be composed of?

8. Kuiper Belt and Oort Cloud

9. How far have you travelled already?

10. Astronomical Distance
One light-year is equal to 9.4605284 × 1012 km.

11. The perihelion is
the point in the
orbit of a planet,
asteroid, or
comet that is
nearest to the
sun.
Aphelion -
farthest

12. Collision
Comets sometimes collide with other
planets and their satellites. Collisions occur when a
comet orbits near a planet or satellite and is
attracted or pulled by the planet’s gravitational
force.

13. Meteoroids, Meteors and Meteorites
Meteoroids are small chunks of rocks
or metals traveling in outer space.
It contain iron and nickel, similar to some
rocks on Earth.

14. Meteoroids, Meteors and Meteorites
A meteoroid that has entered
Earth’s atmosphere is called a meteor.

15. Meteoroids, Meteors and Meteorites
A meteor shower is a phenomenon
that is caused by streams of meteoroids that
enter Earth’s atmosphere.
Usually, meteor showers
are named after the
constellation (stellar pattern)
from where they appear to
originate.

16. Conceptual Check
Why is Earth’s atmosphere so
important?

17. Meteoroids, Meteors and Meteorites
A meteor that is too large to be stopped
completely by the atmosphere may strike Earth
with its cosmic velocity.
A meteor that reaches
Earth’s surface without being
completely vaporized is called
a meteorite.

18. Asteriods
Asteroids are chunks of rocks or
metals that vary in size.

19. Asteriods
Asteroids are
found between the
orbits of Mars and
Jupiter. This area is
called the asteroid
belt

20. Activity
Answer Chapter Test on pages 145-147 of
your textbook.