Goal/Purpose:

The purpose of this lesson is for students to explore some facts, myths, and legends
linked to the appearance of comets throughout history.

Desired Learning Outcomes:

1. Identify one fact, legend and/or myth associated with comets.

2. Identify a property of comets and explain how that property makes comets
visible.
3. Describe the path of a comet and explain how this affects its reappearance.

Prerequisites:

Before attempting to complete this lesson, the student should:

 Understand that the solar system consists of planets, moons, asteroids,

comets, and the Sun.
 Understand the difference between a fact, a legend and a myth.

New Vocabulary:
Asteroid —
A small solar system object composed mostly of rock. Many of these objects
orbit the Sun between Mars and Jupiter. Their size can range anywhere from 10
meters in diameter to less than 1,000 kilometers.
Coma —
The cloud that forms around a comet's nucleus. This cloud is made by solar
wind striking the surface of the nucleus, causing a mixture of gas and dust to
form around it.
Comet —
A small solar system object consisting of ice and other compounds. A comet
will form a coma and sometimes a visible tail whenever it orbits close to the
Sun.
Dust Tail —
This type of comet tail forms when the solar wind separates dust from the
coma, pushing it outward away from the Sun in a slightly curved path.
Gas-Ion Tail —
This type of comet tail forms when the solar wind separates gases from the
coma, pushing them outward away from the Sun in a straight path.
Inner Solar System —
The path of the solar system between the Sun and the orbit of Jupiter
Meteor —
 The flash of light that we see in the night sky caused by the friction of a
meteoroid passing through the atmosphere.
Meteor Shower —
Many and sustained flashes of light that are seen in the night sky as a result of
the Earth passing through the former path of a comet. The debris released by
the comet causes the meteor shower.
Meteorite —
Any part of a meteoroid that that survives its fall through the atmosphere and
lands on the Earth.
Meteoroid —
An interplanetary chunk of matter that is smaller than a kilometer in diameter
and most frequently measured in millimeters.
Naked-eye Visibility —
Being able to see a celestial object, such as a comet, without the aid of
telescopes, binoculars or other astronomical devices.
Comet Nucleus —
The solid rocky part of a comet.
Orbit —
The path followed by one celestial object around another celestial object, such
as Earth’s path around the Sun or the Moon’s path around Earth.
Period —
The time needed for one complete trip or cycle. For example, the period for the
Earth to travel around the Sun is 365 days.
Solar Wind —
A stream of charged particles ejected from the surface of a star.

General Misconceptions:

Misconception: Comets are not a part of the solar system. 

Reality: Comets are part of the solar system. They are believed to originate from one
of two locations within the solar system: the Kuiper belt and the Oort Cloud.

Misconception: Comets are similar to asteroids.

Reality: Comets and asteroids have a very different make-up. Asteroids are composed
of rocky and metallic material while comets are composed of water ice, dust, and
carbon- and silicon-based compounds.

Misconception: All comets look the same and don’t change their appearance.
Reality: Comets have a coma and one, two, or three tails when near the Sun, and no
coma or tail when far way from the Sun.

Misconception: Pluto is the most-distant and last object in the solar system.

Reality: Beyond Pluto’s orbit is a group of icy objects known as the Kuiper belt, from
which short-period comets emerge. Further still is a sphere of icy bodies, called the
Oort Cloud, from which long-period comets emerge. Short-period comets visit the
inner solar system frequently while the long-period comets visit infrequently.

Misconception: There is empty space between the planets.

Reality: There is gas and dust, also known as the interplanetary medium, between the
planets. Comets are responsible for depositing some of the gas and dust found in the
inner solar system.

Preparation Time:

1. Provide time to download computer software to support the lesson.

2. Allow time to preview the activity and to read the science background pages.

Execution Time:

The amount of time needed to complete this activity will vary depending on the length
of available teaching time, the ratio of computers to students in the class and
how/what you have your students do. The navigation through the activity is quite
simple but you might want to use an overhead, an LCD, or a TV monitor to show the
activity to the class ahead of time. The following is an estimated time:

 "Comet Facts, Myths, and Legends" should take about 20 minutes to

read.

Physical Layout of Room:

Teachers may decide whether students will work in small groups of two or three, or
individually. To maximize learning, no more than three students should share a
computer. Adaptations can be made to accommodate classrooms with a single
computer with Internet access. These might include using an overhead projector with
an LCD to project the computer image onto a screen, or hooking up a computer to a
television monitor.

You can also do "Comet Facts, Myths, and Legends" off-line. Different software
programs provide off-line access to the Internet. The programs allow you to save Web
pages to your local hard drive. Using your Web browser, you can open the Web pages
locally and experience the lesson as if you were on the Internet. Using this option,
however, will deny students access to the rest of the pages available on the World
Wide Web.

Materials:
This activity requires a computer with a color monitor and Internet connection. The
Web browser must be capable of running Netscape's Navigator 3.0 (or better) or
Internet Explorer 4.0 (or better). For additional information, read the Computer Needs
section.

Procedure / Directions:

This is a self-directed computer activity. Students may work independently or in small

groups to complete the activity.

Suggested Engagement Activities:

1. Project images of comets, which can be found at the Space Telescope

Science Institute's Web site, http://www.stsci.edu, onto a screen or
television monitor. In a class discussion, ask students to describe what
they already know about comets and planets, and what they can learn
from the images.
2. Organize an informal debate or discussion on the topic, Comet
Collisions with Earth: Fact or Myth?

Evaluation / Assessment:

Share the learning outcomes with your students ahead of time. Following the activity,
ask students to answer one or more of the following questions, which are derived from
the outcomes and based on the reading:

1. Identify a fact associated with comets.

2. Identify a legend associated with comets.
3. Identify a myth associated with comets.
4. Comets are small solar system objects, yet ancient cultures knew about comets.
Identify one property of comets that explains why humanity has known of
comets for so long.
5. Describe the path of a comet and explain how this affects its reappearance.
6. Short-period comets tend to originate from the Kuiper belt — a region beyond
the orbit of Neptune and similar in shape to the Asteroid belt. Long-period
comets tend to originate from the Oort Cloud — a spherical region well beyond
the orbits of Neptune and Pluto. Based on the reading, explain where each of
the following comets is likely to have originated: Hale-Bopp, Swift-Tuttle,
Hyakutake, and Halley’s comet. Explain your choices.

Solutions:
1. Identify a fact associated with comets.

Some possible answers are included here but there are other correct answers.
Comets travel far beyond the orbit of the Moon. Comets move in elliptical
orbits around the Sun. Comets return to the inner solar system at predictable
times. Edmund Halley correctly predicted the return of the comet named for
him. Comets leave a trail of debris behind them. For a long time afterwards,
whenever the Earth passes through the left-behind trails, the debris strikes our
atmosphere and causes meteor showers.

2. Identify a legend associated with comets.

Some people in ancient times thought that a comet was a curse. To save himself
from the "curse of the comet," Emperor Nero of Rome had all possible
successors to his throne executed.

The famous Bayeux Tapestry, which commemorates the Norman Conquest of

England in 1066, depicts an image of Halley's comet bright in the sky before
the Battle of Hastings. Some people thought this meant that King Harold would
lose his throne to William, the Duke of Normandy. He did.

3. Identify a myth associated with comets.

Most astronomers in the 1500's and early 1600's thought that a comet appeared
once and was never seen again. They believed that a comet approached the Sun
in a straight line, spun around it, and then disappeared into space in a straight
path. Another myth claims that the gas from a comet tail is poisonous and can
affect people on Earth if its path crosses the planet.

4. Comets are small solar system objects, yet ancient cultures knew about comets.
Identify one property of comets that explains why humanity has known of comets
for so long.

Students will probably identify the tail as the primary feature that makes
comets visible. Comets have bright tails when near the Sun — this makes them
visible. Comets are composed of ice and dust, which changes to gas when their
elliptical orbits bring them close to the Sun. The gas creates a coma and
flowing tail(s).

5. Describe the path of a comet and explain how this affects its reappearance.

Comets move in orbits around the Sun. Since the path is a complete oval,
comets return to the inner solar system at predictable times.
 6. Short-period comets tend to originate from the Kuiper belt — a region beyond the
orbit of Neptune similar in shape to the Asteroid belt. Long-period comets tend to
originate from the Oort Cloud — a spherical region well beyond the orbits of
Neptune and Pluto. Based on the reading, explain where each of the following
comets is likely to have originated: Hale-Bopp, Swift-Tuttle, Hyakutake and
Halley’s Comet. Explain your choices.

Comets from the Kuiper belt tend to have short periods - like Halley's Comet,
which reappears every 76 years or comet Swift-Tuttle, which reappears every
120 years. Comets from the Oort Cloud tend to have long periods, like Comet
Hale-Bopp with its 2,400-year period or Hyakutake, which will not appear
again for another 14,000 years.

Follow-up Activities / Interdisciplinary Connections:

You can find other images of comets and planets at the Space Telescope Science
Institute. These images could be shown directly to the class using an overhead
projector, an LCD, or a TV monitor. Paper-copy versions of images taken by the
Hubble Space Telescope and other NASA missions also are available at your closest
NASA Educator Resource Center.

Connections to other disciplines can be used to broaden classroom discussion of

Comets Facts, Myths, and Legends.

Biology: Some scientists think that a comet or asteroid collided with the Earth and
killed the dinosaurs millions of years ago. Research and discuss this idea.

English: Ask students to write a poem or a story about a comet.

Social Studies: Ask students to research the relevance of comets in different cultures.

Have them search for references to comets and the myths that might be associated
with the appearance of a particular comet.

Art: Have students study art that includes comets and/or create a picture showing what
it might look like if a very bright comet were in the sky around their school.

One-Computer Classroom:

It is recommended that teachers project the images from the computer onto a
classroom screen using an overhead, LCD or television screen. To facilitate a more
organized and predictable large-group presentation and avoid last-minute glitches,
consider bookmarking the activity (such as one of the pages you wish to use) and
downloading it onto your hard disk. This will eliminate the inconvenience of
unexpectedly losing your connection to the Internet.

Classrooms without Computers:

Here are some suggestions:

1. If you have access to a computer with World Wide Web capabilities at

home or in the school library, you may print selected parts of the activity
as paper copies or transparencies.
2. If your school has one or more computers located outside your
classroom, students may experience the activity individually or in small
groups as a learning station.
3. Some students might have computers at home with access to the Internet.
If that's the case, you might consider assigning Comets Facts, Myths,
and Legends as homework or extra credit.
4. NASA offers FREE comet and solar system-related lithographs and
posters, which are available at your closest NASA Educator Resource
Center. They can be used as teaching tools in the classroom.

Home Schooler:

This lesson is easily followed without additional teacher support if the prerequisites
are met. Parents can preview the lesson and examine the teacher pages ahead of time.
A wealth of information can be found at HubbleSite, the Hubble Space Telescope's
Web site at the Space Telescope Science Institute. Here you can find background
information on the telescope, pictures and news releases of past and present stories,
education activities, and other science resources.

More information for the home-schooled can be found at:

 American Homeschool Association Web Page (http://www.home-ed-

magazine.com/AHA/aha.html)
 Yahoo Homeschooling Directory
(http://dir.yahoo.com/Education/Theory_and_Methods/Homeschooling/)
 The "Home Schooling Trading Post" (http://www.startup-
page.com/homeschl.htm)
 The Home School Learning Network
(http://www.homeschoollearning.com)
 Griffith, Mary. The Homeschooling Handbook. Prima Publishing, CA,
1997.