Download Evolution of a Planetary System

Sample Lesson for Grades 5-6 from
Evolution of a Planetary System
The Life in the Universe Series was created by
children, teachers, and scientists at the SETI Institute
for grades 3-9, with funding from
the National Science Foundation (NSF)
and the National Aeronautics and Space Administration (NASA).
Edna DeVore
Director
Education and Public Outreach
Pamela Harman
Manager
Education and Outreach
SETI Institute
515 North Whisman Road
Mountain View, CA 94043
650-961-6633 phone
650-961-7099 fax
[email protected]
http://www.seti.org
Life in the Universe Series - Book 2
Mission 4
Investigating Types of Stars
Is Our Sun Unique?
__________________________________________________________________
Overview
In Mission 3, the students did an experiment in which they simulated the
formation of our Solar System. In Mission 4, they will learn about properties of
different types of stars.
Is the bright, yellow Sun the only kind of star that might have planets orbiting it?
How would planetary systems be different for other colors or types of stars? In
this activity, your students will experiment to find out that a star's color is
determined by its temperature. White stars are hotter than yellow stars, and red
stars are the coolest. White stars burn up the fastest, yellow stars have a longer
lifetime, and red stars live the longest. If two stars are the same size, the hotter
one will radiate more energy than the cooler one.
Concepts
• There are many different colors, sizes, and temperatures of stars.
• The largest, hottest stars are white (and blue; still other large stars are cool and
red.) Medium sized stars are cooler, and are yellow or orange. The smallest,
coolest stars are red. All stars are hot.
• Star types are catalogued by the letters O B A F G K M which can be
remembered by the sentence, "Oh Be A Fine Girl (or Guy) Kiss Me!" These
star types span the range of star temperatures. Spectral type is determined strictly
by temperature: O-type stars are the hottest stars and M-type stars are the coolest.
(We study types A, G, and M today.)
• A star "burns" by converting hydrogen to helium at its center.
• The larger, hotter stars, such as O, B, and A-type stars, use up their hydrogen
fuel and burn out faster. Smaller, cooler stars burn slower and live longer. Atype stars probably do not live long enough for life to evolve on any nearby
planet as it has on the Earth.
Adapted from The SETI Academy Planet Project -Evolution of a Planetary System
SETI Institute, Teacher Ideas Press, Englewood, CO, 1(800)237-6124
2
Life in the Universe Series - Book 2
Skills
• Measure with a radiometer.
• Time an experiment.
• Take averages.
• Compare models and simulations to real objects.
What You Need
PART ONE
It is ideal if a Star Center station can be set up for every group of 5-6 students.
However, if your materials budget allows you to set up only a single station,
arrange other projects to engage the students while groups wait their turn.
For Each Station:
› 1 Clear 200 watt light bulb
› 1 Ceramic light bulb socket
› 1 Rotary-dialed dimmer switch
(that can be installed into lamp wire)
› Electrical tape
› 3 to 6 Feet of lamp wire
› 1 Electrical Plug
› 1 Wire cutters
› 1 Wire strippers
› 1 Blade screwdriver
› 1 Phillips screwdriver
› 1 Fine point permanent marker
› 1 30 cm Metric ruler or Meter stick
› 1 "New" Radiometer
older radiometers lose their vacuum seal)
› 1 Stopwatch
› Optional: Clear plastic box to protect radiometer
For the Class:
›
›
›
›
›
Butcher paper
Marking pens
Optional: "Life Story of the Earth" Image Transparencies
Optional Overhead projector
Optional: Calculator
For Each Student:
› Student Logbook and pencil
Adapted from The SETI Academy Planet Project -Evolution of a Planetary System
SETI Institute, Teacher Ideas Press, Englewood, CO, 1(800)237-6124
3
Life in the Universe Series - Book 2
4
Getting Ready
PART ONE
One or More Days Before Class:
1. Build your Star Center(s). Refer to Figure 4.1, Star Center Assembly.
First consider where you will want to locate your Star Center(s). Use enough
lamp wire to span the distance from the Star Center to a wall socket easily.
Attach the ceramic light bulb socket to one end of the lamp wire, following the
directions on the box. Then use electrical tape to cover any exposed wire and/or
metal on the bottom of the socket. Splice in the dimmer switch about a foot from
the socket, using the directions on the package. Attach the plug at the end of the
lamp wire. Use electrical tape to cover any exposed wire and/or metal.
Figure 4.1. Star Center Assembly.
plug
dimmer
light bulb
socket
2. Calibrate your dimmer switch. Screw your clear 200 watt bulb into the
socket, and plug in the Star Center. Set out the 30 cm ruler and place your
radiometer at the end of it as shown in Fig. 4.2, Star Center Set-Up (or mark 30
cm on a meter stick, and place the radiometer at 30 cm away from the bulb).
Figure 4.2. Star Center Set-Up.
dimmer
bulb and socket
radiometer
plug
STAR
CENTER
DIRECTIONS
30 cm ruler
Adapted from The SETI Academy Planet Project -Evolution of a Planetary System
SETI Institute, Teacher Ideas Press, Englewood, CO, 1(800)237-6124
Life in the Universe Series - Book 2
Use the permanent marker to draw an arrow on the body of the dimmer, as
shown in Figure 4.3, Calibrating the Dimmer Switch. The arrow will show the
students where to set the dial for each of their measurements (A, G, and M).
Figure 4.3. Calibrating the Dimmer Switch.
Calibration for the A type Star: Turn the switch up to its highest setting.
Mark the dial with a small line that lines up with the arrow, and write "A" by the
mark.
Calibration for the M type Star: While watching the bulb, slowly spin the
dimmer down to a point where the filament glows orange/red. When it is at a
very low setting it will flicker. Turn it up until the flicker is less noticeable. Test
your radiometer to see if it's vanes turn at this setting. If not, turn the dimmer up
until the radiometer does turn, or replace your radiometer (it may be too old).
Make a mark for the M star at the lowest setting that will turn the radiometer's
vanes.
Calibration for the G type Star: Turn the dimmer all the way up to its highest
point again, and then turn it down until the bulb glows yellow. This should be
about midway between your A and M marks. Make a mark for the G star.
Teacher's Note: Starting from the lowest setting and turning towards the
highest, gives very different readings. Encourage your students to use a
consistent method to collect this data, i.e., starting from highest to lowest.
4. Optional: Radiometers are made from very thin glass, and therefore are
breakable. Some teachers have found it useful to glue their radiometer into a
small clear plastic box.
Just Before the Lesson:
1. Set up one or more Star Centers as shown in Fig. 4.2, Star Center Set-Up.
Put the Star Centers in places that do not have another source of heat, such as a
sunny window, an incandescent light, or a heater.
2. Before each use of a completed Star Center, try your radiometer(s) with each
dimmer setting to be sure it will still turn at the 30 cm distance. If you have an
older radiometer, it may tend to turn more slowly because air has leaked in.
If necessary, you can shorten the distance at which students make their
measurements, as long as the measurements for all bulbs are made at the same
distance.
3. Draw a chart like Table 4.1 on the butcher paper or blackboard for students to
record their data. Hang the chart at the front of the room.
Table 4.1. Radiometer Turns in 10 Seconds.
Adapted from The SETI Academy Planet Project -Evolution of a Planetary System
SETI Institute, Teacher Ideas Press, Englewood, CO, 1(800)237-6124
5
Life in the Universe Series - Book 2
Star Types
Group 1
Group 2
Group 3
Group 4
Group 5
Average
A (White)
6
G (Yellow)
M (Red)
Classroom Action
PART ONE
1. Review. Remind the students that in the last Mission, they learned how
planets may form around a star. But are all stars the same? Now we will study
how stars can vary in their color and temperature. Star types were first invented
to identify stars with different colors. For example, our Sun is a G type star.
What color is it? Yellow.
Star types are catalogued by the letters O B A F G K M which can be
remembered by the sentence, "Oh Be A Fine Girl (or Guy), Kiss Me!" These
star types span the range of star temperatures. Spectral type is determined strictly
by temperature: O-type stars are the hottest stars and N-type stars are the coolest.
We will study three types of stars: white (A), yellow (G), and red (M).
2. Mission Briefing. Have the students refer to the Mission Briefing in their
Student Logbook, as one student reads it aloud.
“In order to decide which types of stars to search first for planets that could
have life, we would like you to conduct some experiments to determine some
of the ways that stars differ.”
3. "What Do You Think?" Activity/Discussion. Let the students write their
opinions on the pre-activity questions ("What Do You Think?"). Then invite
them to share their answers with the class in a discussion.
4. Demonstration. Show the students the Star Center you set up at the front of
the classroom. Explain that a single bulb can represent three different star types
by using a dimmer switch at three different settings. The three bulb settings
represent stars that are white (A), yellow (G), and red (M).
Tell students that the light bulb they see in the Star Center represents a star—a
burning ball of gases very far away. We are going to observe how the color
changes as the temperature of the bulb is changed.
Turn the lights off in the classroom and turn the bulb on to its highest, brightest
setting. Ask the students what color the bulb is. White. Begin dimming. The
color will become noticeably more yellow. Continue slowly dimming the bulb,
stopping each time there is a change in color, to ask students what color they see.
At the end, ask the students: "What colors did you see?" White, yellow, red and
colors in-between. Point out that white, yellow and red are three types of stars:
A, G and M respectively.
Their Student Logbook has a chart that gives facts about each of the basic types
of stars. You may want to refer to this chart.
Adapted from The SETI Academy Planet Project -Evolution of a Planetary System
SETI Institute, Teacher Ideas Press, Englewood, CO, 1(800)237-6124
Life in the Universe Series - Book 2
Tell the students that their job is to measure the heat (infrared radiation) produced
by the model A, G and M type stars. A radiometer is used to measure heat
(infrared radiation). The faster the radiometer spins, the more heat (infrared
radiation) is being radiated by the bulb. (For an explanation of how a radiometer
works, see the Appendix.)
Go over the directions in the Student Logbook, demonstrating each step.
Emphasize that they cannot begin counting until the radiometer reaches full
speed, which takes about thirty seconds. It is important not to bump the
radiometer, since it is very fragile. In order to stop the radiometer vanes between
measurements, tilt the radiometer slightly for a few seconds and then gently let it
down again.
Mention safety considerations:
• No more than one group at the Star Center at one time.
• Do not touch the bulbs.
• Handle the radiometers very carefully.
• Do not remove the radiometers from the Star Center.
5. Activity. Give the students time to complete their observations and datataking. Provide other activities for early finishers. When groups finish, they
should record their data on the class data chart that you have drawn on the
butcher paper or on the black board.
Closure
1. Data. Have a student or teams of students use a calculator to average the
results from the various groups. Ask the students for the conclusions that they
can draw from this experiment. Go over the questions on the data sheet. The
students will find that the A-type star is hottest (gives off the most infrared
radiation) and the M-type star is coolest (gives off the least infrared radiation).
2. Lecture. You may also wish to emphasize that all stars are really hot. Even
the coolest M star, at 3,300 °C is at least 13 times hotter than the hottest kitchen
ovens can get. Also, the temperatures listed are surface temperatures of stars.
Temperatures at the center or cores of stars are much hotter.
3. Discussion. Ask the students look at Question 3 in the "What Do You
Think Now" section of their Student Logbook. Invite discussion. Some
students may realize that if our Sun were an A-type star and the Earth were the
same distance from it, it would be too hot to live on Earth. Others may point out
that the Earth could orbit at a comfortable distance from an A-type star, much
further than its current position, but that sunlight would be white, not yellow.
4. Optional Transparencies. Using transparencies, quickly review the Video
Image show with emphasis on the Timeline will provide the students with the
information that it took over three billion years for complex life to appear on
Earth. Use information about the lifetimes of stars of different types from Table
4.3, "Types of Stars Information Table". Direct the students' attention to the
Timeline that they created during their last Mission. Ask the students: "How
long did it take for complex life to evolve on the Earth?" Over three billion
years! Have the students notice the "lifetime" column in table 4.3, and then ask
them what would happen if the Earth orbited an A-type star. Complex life would
probably have never evolved on Earth, as an A -type star would "burn out" long
Adapted from The SETI Academy Planet Project -Evolution of a Planetary System
SETI Institute, Teacher Ideas Press, Englewood, CO, 1(800)237-6124
7
Life in the Universe Series - Book 2
before complex life could get started. Since an A-type star only lives 100 million
years complex life could never have evolved on our planet!
5. "What Do You Think Now?" Have students answer the post activity
questions on the Logbook sheet ("What Do You Think Now?") After students
have completed their answers, invite students to share their responses.
6. Preview. Tell the students that in the next Mission, we will finding out how a
life-bearing planet orbiting other star types, such as A-type and M-type stars,
could still be at a comfortable temperature. (Keep the completed "Radiometer
Turns in 10 Seconds" Table 4.1 for the next Mission.)
Going Further
DEMONSTRATION: LIFETIMES OF STARS
Set up three Star Centers where they can be seen clearly from all over the room
and where it won't be bumped or handled by students. Announce that you are
going to demonstrate the comparative lifetimes of the three stars. Turn on the
dimmer setting on the first to A-type star, the second to G, the third to M and set
a timer for 5 minutes. Explain that the time scale you are using is 5 minutes =
100 million years (0.1 billion years). At this scale the White A-type star would
live for 5 minutes. A Yellow G-type star for 8 hours. And a Red M-type star
for almost a week (80 hours). Mark your calendar or have a student in charge of
turning off the 'stars' at the appropriate times. (If you have only one star center,
do the lifetimes in series.)
ACTIVITY: MORE RADIOMETER STUFF!
Have the students use the radiometer to measure infrared radiation from various
things: our sun, other lights, fluorescent lights, heaters, and so forth. What
conclusions can they draw?
ACTIVITY: COLORFUL STARS AT NIGHT
Do some observations of the night sky; try to find stars that are red, white,
yellow, or blue and classify them by star type. Use a star chart to get the star's
name and look it up in a stellar atlas.
ACTIVITY: ASTROPHOTOGRAPHY
Take a long exposure (2 seconds) of a familiar constellation from a very dark
area. If you move the camera while you take the picture you can streak the stars
which will show you what colors they are. From your developed picture
determine what types of stars you were looking at.
Adapted from The SETI Academy Planet Project -Evolution of a Planetary System
SETI Institute, Teacher Ideas Press, Englewood, CO, 1(800)237-6124
8
Life in the Universe Series - Book 2
9
Name
Date
Mission 4
Investigating Types of Stars
Dr. Laurance Doyle
Stellar Astronomer on the
SETI Academy Team.
Mission Briefing. “In order to decide which types of stars to search first for planets that could have
life, we would like you to conduct some experiments to determine some of the ways that stars differ.”
What do you think?
1. From Earth, stars appear to be different colors: blue, white, yellow, orange, and red. What might cause
one star to be a different color than another star?
2. What other ways might stars be different?
3. The Earth orbits a yellow star. What things would be different on Earth and in our Solar System if our
star was red?
Adapted from The SETI Academy Planet Project -Evolution of a Planetary System
SETI Institute, Teacher Ideas Press, Englewood, CO, 1(800)237-6124
Life in the Universe Series - Book 2
10
Name
Date
Mission 4: Investigating Types of Stars
Star Center Instruction Sheet
1. Turn the dimmer switch all the way off. Place one end of the ruler or measuring stick at the base of the
socket. Place the radiometer at the other end.
lightbulb
ruler
or
30 cm measuring stick
2. Stop the radiometer's vanes. Turn the dimmer switch to the A star mark. Wait 30 seconds. Looking
from the top follow one blade around with your finger. Have your partner time 10 seconds, saying "Start"
and "Stop." Count how many times the vanes go around during the ten seconds. Record the number of turns
in 10 seconds below:
A Star:
_______ turns in 10 seconds
Color
G Star:
_______ turns in 10 seconds
Color
M Star:
_______ turns in 10 seconds
Color
3. Turn the dimmer knob down to the G star mark. Stop the radiometer's vanes. Set it back down at the end
of the ruler. Wait 30 seconds. Time, count and record the turns of the radiometer vanes just like you did for
the A star.
4. Now take the same measurements for the M star. Don't forget to stop the radiometer fully, then wait 30
seconds for it to reach full speed. Record your data. Add all your data to the class chart.
Adapted from The SETI Academy Planet Project -Evolution of a Planetary System
SETI Institute, Teacher Ideas Press, Englewood, CO, 1(800)237-6124
Life in the Universe Series - Book 2
11
Name
Date
Mission 4
Investigating Types of Stars
What do you think, now?
After completing your investigation, please answer these questions:
1. From Earth, stars appear to be different colors: blue, white, yellow, orange, and red. What causes one star
to be a different color than another star?
2. What other ways are stars different?
3. The Earth orbits a yellow star. What things would be different on Earth and in our Solar System if our
star was white? (Consider what you learned from the Video Image show about how long it was before
complex life appeared on Earth.)
Type
O
B
A
F
G
K
M
Color
blue
blue-white
white
yellow-white
yellow
orange
red
Temperature
35,000°C
21,000°C
10,000 °C
7,500°C
6,000 °C
4,700 °C
3,300 °C
Lifetime
10 million years
40 million years
100 million years
5 billion years
10 billion years
50 billion years
100 billion years
Adapted from The SETI Academy Planet Project -Evolution of a Planetary System
SETI Institute, Teacher Ideas Press, Englewood, CO, 1(800)237-6124