CHAPTER 10 STARS
ANSWERS TO STOP & THINK AND
REFLECT & CONNECT
REFLECT AND CONNECT: STAR
PICTURES
PAGE 462
1. Look at the stars on the handout titled “Star Pictures”
a. What images or pictures can you envision in these stars? Imagine a picture in the stars
that is your own original constellation outline the picture on your handout
b. Select a name for your constellation. In your science notebook, write why you chose
that name and briefly describe your constellation.
2. On a clear night, what constellations are you able to see from your location? With the help
of figures 10.3 and 10.4, identify at least 3 constellations in your notebook.
3. What do you know about individual stars? List in your notebook three things you know
about stars and three things you would like to learn about stars.
a. Share your thoughts with your partner and listen as our partner reads his or her list
b. Add to your list anything you learned from your partner
4. The position of constellations change in the sky during the night and from season to
season. Yet the relative position of the stars remain the same. What does that say about
the motion of the Earth? Compose your answer either in words or in sketches of the
position of the Earth, the Sun, and stars at different times of the year.
REFLECT AND CONNECT: STAR
PICTURES ANSWERS
PAGE 462
4. The changes observed is the result of the rotation of the Earth. Just as the Moon and the
Sun seem to move across the sky, stars to the same, because the EARTH IS MOVING.
Constellations seem to move because the Earth revolves around the Sun, and as such
different groups of stars are brought into view as the seasons progress
REFLECT AND CONNECT: STARS AT A
GLANCE
PAGE 466
1. Why do you think your finger appears to shift in position when you look at it first with one
eye and then the other?
2. Compare the apparent shift of your finger at different distances. What did you notice about
the shift when your finger was closer to and further away from your eye? To answer that
question, complete the following sentence:
• As the distance from my eye to my finger increases……..
3. How might a similar process be useful to astronomers?
REFLECT AND CONNECT: STARS AT A
GLANCE ANSWERS
PAGE 466
1. Looking with one eye and then the other is actually looking at the same object from 2
different positions. If you look at your finger from a different positron, your finger will
shift with respect to the background.
2. As the distance from my eye to my finger increases, the apparent shift decreases. As the
distance from my eye to my finger decreases, the apparent shift increases.
3. If your fingers represent a star that is much closer than the background stars. The line on
the paper represents the backgrounds stars. Then fi astronomers could view these stars
from 2 different locations (as with different eyes) they can determine the distance to these
stars. There is a relationship between the distance from a nearby star to background distant
stars and the apparent shift in position when viewed from different locations.
REFLECT AND CONNECT: STELLAR
PARALLAX
PAGE 468;470
1. View a simulation of stellar parallax as directed by your teacher. Make sure you click and
drag the red star closer and farther from Earth. How is your model with your finger and
line similar to this simulation of stellar parallax? To answer that, draw a T-table in your
science notebook to organize your responses to Questions 1a-c. Label the top of the Ttable with 2 headings “My Model” and “Stellar Parallax Simulation”.
a. What does your finger represent?
b. What does the line represent?
c. What do your eyes represent?
2. Alpha Centauri, a nearby star is 4.36 (ly) from Earth, and Proxima Centauri is 4.22 ly from
Earth. When viewed from Earth in June and again in December, which star appears to shift
the greatest distance compared to very distant stars in the background? Explain. IF you are
not familiar with light years READ “Monster Units”
3. Both Alpha Centauri and Proxima Centauri are in the constellation Centaurus, the Centaur.
How would you respond to the student who said that all stars in a constellation are the same
distance from Earth?
REFLECT AND CONNECT: STELLAR
PARALLAX ANSWERS
PAGE 468;470
1. T-Table
My Model
Stellar Parallax
1. Index finger
Near Star
2.
Line
Distant background stars
3.
Eyes
Different locations of Earth in the sky
2. Proxima Centauri, is closer to Earth it would appear to shift the greatest distance when
compared to the background stars. Similarly, Alpha Centauri, would shift less. This is
because as a star’s distance from Earth increases, its parallax angle decreases, causing the
shift in position to appear less.
3. Stars in the same constellation are not all the same distance from Earth. Constellations are
not actual features in space but only human made patterns from the stars we see at night
REFLECT AND CONNECT: SPRINGING
INTO ACTION
PAGE 474
1. What variable changed the speed of the wave? Remember that there are variations in
almost every test due to experimental error. You are looking for significant change in
speed.
2. You learned earlier that the speed of light through an empty space is about 3x108 m/s.
The distance between Earth and the Sun is about 1.5x1011 m. If you were riding on a wave
of light from the Sun to Earth, how long would it take you to get to Earth? Use the
formula for speed to calculate that time needed to get to Earth. Convert your answers to
minutes. Show all of your calculations and give your answer in the proper unit.
3. Sound waves in air have a velocity of about 340 m/s. How does the speed of your wave
compare with the speed of sound? To compare, use the ratio to determine how much
faster sound travels than your wave travels.
• For example: if your wave has a speed of 3.4m/s, the ratio would be as follows
340m/s
3.4m/s =100
•
After dividing, you could say that the speed of sound is 100 times faster than the
speed of your wave. Now use this method with your data
REFLECT AND CONNECT: SPRINGING
INTO ACTION
PAGE 474 CONTINUED
4. How does the speed of sound compare with the speed of light? Using the same method
explained in Question 3, determine how much faster light waves travel compared to sound
waves. Be sure to show your work.
5. What features of thunderstorms help confirm your calculations in Question 4?
REFLECT AND CONNECT: SPRINGING
INTO ACTION ANSWERS
PAGE 474
1. The type of material through which the wave travels (medium) affects the speed of the
wave.
2. Calculations: time = distance/speed
• time = 1.5 x 1011m
= 500 s
8
3 x 10 m/s.
Then convert to minutes
500s x 1min = 8.3min
60s
3. For example: if your wave has a speed of 10m/s, the ratio would be as follows
340m/s
10 m/s =34
•
So you can say that the speed of sound is 34 times faster than the speed of the wave
REFLECT AND CONNECT: SPRINGING
INTO ACTION ANSWERS
PAGE 474 CONTINUED
4. Using the relationship
• 3 x 108 m/s = 880,000
340 m/s
• So you can say that the speed of light is 880,000 times faster than the speed of sound.
5. When you see lightning from a storm it takes several seconds before you hear the thunder.
STOP AND THINK: MUCH ADO ABOUT
WAVES
PAGE 480-481
1. Imagine that you are creating a wave on a spring by shaking your hand from side to side.
Without changing the distance your hand moves, you being shaking your hand faster and
faster. What happens to the amplitude, frequency, wavelength, and speed of your wave?
2. Waves are sent along a spring of fixed length. Explain how (or if) you could change the
variables listed in figure 10.16. Cite evidence for your answers from the activity. Copy the
chart in figure 10.16 to organize your response.
Variable
How to Change
Evidence from
activity
Speed
Frequency
Amplitude
Wavelength
3. Does a wave transfer matter, energy, or both? What is your evidence?
STOP AND THINK: MUCH ADO ABOUT
WAVES
PAGE 480-481 CONTINUED
4. If you add more total energy to a wave (as you did in Step 7), what happens to the
a. Frequency of the wave ?
b. Wavelength of the wave?
5. A wave moves 12m in 5 seconds. There are 6 complete waves produced in that distance
and time. Using this information, complete the tasks and answer the following questions
a. Sketch a picture of this wave and include all info given in the problem. Label you
sketch with the values given to you. This will help you to visualize the wave and solve
the following problem.
b. Calculate the speed using the equation: speed = distance/time
a. The info you need is given in the sentences above. Show all of your work and
use the correct units in your answer.
c. Now use your sketch and the info given to you to find the frequency and wavelength.
Then use the equation for speed= λ x f to calculate speed another way. Again, show
all your work and use proper units.
d. How do your 2 answers for the speed of a wave compare?
STOP AND THINK: MUCH ADO ABOUT
WAVES ANSWERS
PAGE 480-481
1. Since distance hand moves doesn’t change; amplitude doesn’t change. Frequency and
wavelength will change. Since you don’t change springs the speed stays the same.
2. T-Table.
Variable
How to Change
Evidence from activity
Speed
You cannot change the speed unless
you change the medium
Changing the medium was the only way
to change the speed
Frequency
Move hand up and down faster/slower
When making waves as fast as you
could
Amplitude
Can make amplitude bigger by moving
hands at greater distances up and down
When moving greater distance the
amplitude increased
Wavelength
Must move up/down quickly to
decrease and slowly to increase
When you increased frequency the
wavelength became shorter
3. Remember the tape? This represents that matter was NOT transferred. Evidence supports
that the tape returned to its original position while the ENERGY of the wave moved
through the slinky.
STOP AND THINK: MUCH ADO ABOUT
WAVES ANSWERS
PAGE 480-481 CONTINUED
4. If you add more total energy to a wave (as you did in Step 7), what happens to the
a. The frequency gets higher or increases
b. Wavelength gets shorter or decreases
5. A wave moves 12m in 5 seconds. There are 6 complete waves produced in that distance
and time. Using this information, complete the tasks and answer the following questions
b. Calculate the speed using the equation: speed = distance/time
• 12m/ 5s = 2.4m/s.
c. speed= λ x f to calculate speed another way.
• F= number of waves/second. 6 waves pass in 5 seconds. So the f = 1.2 Hz
• Now:
• 6 waves in 12 min; each wavelength must have a wavelength of 2m.
• Speed = wavelength x frequency
• Speed = 2m x 1.2Hz = 2.4 m/s
d. They are the same
REFLECT AND CONNECT: PART II
STARLIGHT- CELL PHONE CALLS
FROM OUTER SPACE
PAGE 487
1. What is the order of the 7 colors in the visible spectrum? Name them in order from
longest wavelength to shortest wavelength.
2. Using the EM spectrum (fig 10.21), consider X-rays and radio waves to answer the
following questions:
a. Which has the highest frequency?
b. Which has the longest wavelength?
c. Which has the greatest energy?
3. Make a T-table with 2 columns, labeling the headings “Red Light” and “Blue Light”. In
your table, indicate the differences, if any in the following:
a. Wavelength
b. Frequency
c. Energy
d. Speed
REFLECT AND CONNECT: PART II
STARLIGHT- CELL PHONE CALLS
FROM OUTER SPACE
PAGE 487
4. Do cell phones use only EM waves in their operation? Think of the different steps in a cell
phone conversation and think about the paths of all waves. Indicate in you answer all the
steps you can think of and all the different types of waves involved.
5. These activities were about waves and the fact that waves have similar properties whether
they are sound waves, waves on a Slinky, or light waves. In a Reflect and Connect question
in the Springing into Action! Activity, you imagined riding on a light wave from the Sun to
Earth and calculated that your journey would take just over 8 minutes. Would it make any
difference in time if you were riding a blue light wave versus a red light wave? Give
evidence to support your answer.
REFLECT AND CONNECT: PART II
STARLIGHT- CELL PHONE CALLS
FROM OUTER SPACE (ANSWERS)
PAGE 487
1. ROYGBIV in order from longest to shortest wavelength
• Significant: colors of the rainbow. The colors correspond to increasing frequencies
and decreasing wavelengths of light from red-violet.
2. Using the EM spectrum (fig 10.21), consider X-rays and radio waves to answer the
following questions:
a. X-Rays have the highest frequency
b. Radio waves have much longer wavelengths than X-Rays
c. X-rays have greater energy than radio waves
3. Make a T-table with 2 columns, labeling the headings “Red Light” and “Blue Light”. In
your table, indicate the differences, if any in the following:
Red Light
Blue Light
Longer Wavelength
Shorter Wavelength
Lower Frequency
Higher Frequency
Lower Energy
Higher Energy
Equal speed 3 x 108 m/s
Equal speed 3 x 108 m/s
REFLECT AND CONNECT: PART II
STARLIGHT- CELL PHONE CALLS
FROM OUTER SPACE
PAGE 487 CONTINUED
4. More involved than just EM waves zipping back and forth at 840MHz.
• Why?
• Eardrum cannot detect EM at that frequency
• Microwaves enter the cell phones, phones decode that signal and then recode the
signal that it can be resent as sound waves to your ear
• Small speaker sends the sound waves to your ear at the speed of sound.
• Brain processes sound waves and decides upon a response
• Speak w/ vocal chords vibrating at certain frequencies
• Sound waves trigger a receiver in the phone which then translates the signal to a
code in EM waves
• They are sent from the cell phone at the speed of light to a cell tower w/in a grid
where the waves are relayed to the original caller
5. Remember: that the speed of the wave is constant unless the medium thru which it travels
changes properties. It doesn’t matter if you ride a blue wave or a red wave. However, a
blue light wave would have a higher frequency and a shorter wavelength so it would “feel”
shorter
STOP AND THINK: PART I WATT’S UP?
PAGE 489: 491
1. How is the wattage of the bulb related to the brightness?
2. Could a lower wattage bulb ever appear brighter than a higher wattage bulb? Represent
your answer with a labeled sketch.
3. Some lamp manufacturers warn customers to use only low-wattage bulbs in their lamps.
Why do you think this is?
4. When you look at the bulb, energy enters your eyes. When you place your hand near the
bulb, energy hits your hand. Do your eyes or your hand receive all of the energy produced
by the bulb? Explain your reasoning?
5. You saw in your teacher’s demo that the energy output of a light bulb is not always obvious
when the light bulb is placed at different distances. You also felt the heat given off by the
bulbs.
a. Would you expect to feel more heat, or less heat, or the same amount of heat as you
move your hand further from the bulb?
b. What does this tell you about the amount of energy striking your hand as you move
closer to the bulb and farther from the bulb?
STOP AND THINK: PART I WATT’S UP?
PAGE 489: 491 (ANSWERS)
1. The higher the wattage of the light bulb, the brighter it appears
2. Yes. Show that if the lower wattage bulb were closer to the observer it appears brighter
than the higher watt bulb
3. Warnings are on lamps because using a bulb with a higher wattage could melt the lamp
4. Your eyes and hands only receive part of the energy emitted from the bulb. If someone
else was looking/feeling from the opposites side of the bulb they would feel another
portion of the energy. If you move farther way you receive less energy.
5. You saw in your teacher’s demo that the energy output of a light bulb is not always obvious
when the light bulb is placed at different distances. You also felt the heat given off by the
bulbs.
a. Less heat if you move farther from the bulb
b. Energy striking your hand increases as you move closer to the bulb and decreases as
you move farther from the bulb
STOP AND THINK: PART I WATT’S UP?
PAGE 489: 491
6. A friend see’s a very bright star in the constellation Orion and tells you that it is very bright
because it is much closer to Earth than the dimmer stars. Obviously, this friend is not in
your science class! Could this statement be true? Or are there other factors to consider?
Write a short paragraph explaining a better way to describe the apparent brightness of this
star.
7. Why do astronomers need to know the apparent brightness and luminosity of stars?
8. You learned in an earlier activity about how scientists use stellar parallax to determine
distances to stars. Does this method work for all stars? Explain.
STOP AND THINK: PART I WATT’S UP?
PAGE 489: 491 (ANSWERS)
1. The higher the wattage of the light bulb, the brighter it appears
2. Yes. Show that if the lower wattage bulb were closer to the observer it appears brighter
than the higher watt bulb
3. Warnings are on lamps because using a bulb with a higher wattage could melt the lamp
4. Your eyes and hands only receive part of the energy emitted from the bulb. If someone
else was looking/feeling from the opposites side of the bulb they would feel another
portion of the energy. If you move farther way you receive less energy.
5. You saw in your teacher’s demo that the energy output of a light bulb is not always obvious
when the light bulb is placed at different distances. You also felt the heat given off by the
bulbs.
a. Less heat if you move farther from the bulb
b. Energy striking your hand increases as you move closer to the bulb and decreases as
you move farther from the bulb
STOP AND THINK: PART I WATT’S UP?
PAGE 489: 491 CONTINUED
6. This very bright star could be closer but is not necessarily. The star could be the same
distance from Earth as a dim star but be more powerful-have more watts. The star could be
more distant than dimmer stars if the dimmer stars were much less powerful than the
brighter, more distant star.
7. Astronomers use the relationship between apparent brightness and luminosity of stars to
determine their distance from Earth.
8. No, parallax only works for nearby stars-stars with a few hundred ly. To find the distances
to stars beyond the capabilities of stellar parallax, astronomers turn to apparent brightness
and luminosity.
STOP AND THINK: PART II STARBURST
PAGE 497: 501
1. Create the T-Table (DIDN’T DO)
2. If the distance from the source of energy increases 4 times, what happens to the apparent
brightness, provided the luminosity stays the same
3. What would happened to the flux or apparent brightness if the distance were cut in ½?
4. In a previous analogy, apparent brightness and luminosity are compared to rain hitting a
windshield and rain falling from the clouds. As with all analogies and models, there are
strengths and weaknesses to the comparison. Make a T-table in your science notebook with
the headings “Strengths” and “Weaknesses”. Think about how the analogy is a good
comparison and list those as strengths. Also, consider how this analogy is not a good
example and list those reasons as weaknesses.
5. To find the distance to a star using the inverse square law, what 2 things do you need to
know?
6. How would scientists use the inverse square law to find the luminosity of a nearby star?
7. If the distance to Star A is 10 times greater than the distance to Star B, and the 2 stars have
the same luminosity, how would their apparent brightness compare?
STOP AND THINK: PART II STARBURST
PAGE 497: 501
1.
2.
3.
T-Table
The flux decreases by a factor of 16.
If the distance decreases by 1/2 , the flux increases by a factor of 4
4.
T-Table
Strengths
Weaknesses
Rain hitting the windshield simulates flux, which is like
brightness
The rain from a cloud falls in one direction (down), a light
travels in all directions
We see the rain hitting our windshield & we see apparent
brightness
Rain is matter, light is energy
Raindrops are particles, light acts like particles
The amount of rain per square meter (flux) doesn’t change
much, if any, with distance
Clouds are point sources of light
5.
6.
7.
You must know the apparent brightness (AB) and the luminosity (L)
If star is nearby (use parallax). AB could be measured w/ a light meter and then luminosity can be
calculated by:
• AB =
L
4 x π x d2
The apparent brightness of Star B would be 100 times (102) brighter than Star A
REFLECT AND CONNECT: PART III
COLORFUL CHARACTERISTICS
PAGE 508
1. Describe what you can learn about stars by looking at their spectra. Give examples of what
astronomers look for in spectra.
2. The Sun is a yellow-white star. What range of surface temperatures would you expect from
the Sun?
3. Spectral analysis of a particular star reveals that its light has a peak in intensity at a
wavelength of λ = 640nm. Draw a sketch graph of the spectrum from this star and
describe its temperature and color.
REFLECT AND CONNECT
PAGE 508
4. In each activity in this chapter, you learned certain characteristic properties of stars and the
info that scientists can lean from these properties. Make a chart in your notebook using the
guide in fig. 10.34. Fill in the chart with the properties that were addressed in each activity
and the significance of each property to astronomers you may look back in your
book/notebook to compose your answers.
Activity
Stars @ Glance & Stellar Parallax
Springing into Action! Much Ado
about Waves
Starlight: Cell Phone Calls from
Outer Space
Watts Up?
Starburst
Colorful Characteristics
Property/properties Sig. to Astronomers
REFLECT AND CONNECT: PART III
COLORFUL CHARACTERISTICS
PAGE 508 (ANSWERS)
1. Describe what you can learn about stars by looking at their spectra. Give examples of what
astronomers look for in spectra.
2. The Sun is a yellow-white star. What range of surface temperatures would you expect from
the Sun?
3. Spectral analysis of a particular star reveals that its light has a peak in intensity at a
wavelength of λ = 640nm. Draw a sketch graph of the spectrum from this star and
describe its temperature and color.
REFLECT AND CONNECT
PAGE 508 (ANSWERS)
4. In each activity in this chapter, you learned certain characteristic properties of stars and the
info that scientists can lean from these properties. Make a chart in your notebook using the
guide in fig. 10.34. Fill in the chart with the properties that were addressed in each activity
and the significance of each property to astronomers you may look back in your
book/notebook to compose your answers.
Activity
Stars @ Glance & Stellar Parallax
Springing into Action! Much Ado
about Waves
Starlight: Cell Phone Calls from
Outer Space
Watts Up?
Starburst
Colorful Characteristics
Property/properties Sig. to Astronomers
REFLECT AND CONNECT: PUTTING IT
ALL TOGETHER
PAGE 511
1. From a star’s spectrum, astronomers can;
• Id the elements present in the star
• Notice the strength of the hydrogen lines
• Measure the wavelength emitted with the highest intensity
• Determine the surface temperature of stars based on the wavelength of greatest
intensity
• Id the color of the star
• Classify the star based on surface temperature and absorption lines
• Astronomers look for absorption line spectra to determine the elements present.
They measure relative intensities of the wavelengths to determine the surface
temp. and color of the star
2. Use Wien’s Law to answer this question. T range is from 5,000K to 6,000K
3. Graphs
REFLECT AND CONNECT
PAGE 508
Activity
Property/properties
Sig. to Astronomers
Stars @ Glance & Stellar Parallax
Apparent shift in position of
the stars with respect to
background stars when viewed
from different perspectives
Astronomers can determine the distances to nearby
stars using parallax
Springing into Action! Much Ado
about Waves
Speed, frequency, wavelength,
and amplitude
The speed of a wave is constant in constant
medium. Waves transfer energy, not matter.
Frequency of a wave and wavelength are inverse
relationships
Starlight: Cell Phone Calls from Outer
Space
Light as a form of EM
radiation
Astronomers use the formula c = f x λ to determine
wavelength or frequency. Wavelength and frequency
of EM radiation determine the properties of that
radiation such as color. Info astronomers use to
analyze stars comes in the form of EM radiation
Watts Up?
Apparent Brightness (AB),
luminosity
Astronomers use AB w/ a light meter and can
determine luminosity of near stars using parallax.
Distance to stars is important to know to compare
AB and luminosity
Starburst
Inverse square law, Cepheid
variable stars
Astronomers can use the inverse square law and
Leavitt’s work with Cepheid variable stars to
determine luminosities and distances of stars too
distant to use parallax
Colorful Characteristics
Spectra, intensity, color,
wavelength, and temperature
Astronomers use these properties of stars to
determine such things such as elements that make up
the star, the color of the star, and the temperature of
the star
4. T-Table.
REFLECT AND CONNECT: PUTTING IT
ALL TOGETHER
PAGE 511
1. Even though there did not appear to be a relationship between distance and temperature,
why is it important to know the distance to stars when trying to understand their
characteristics?
2. Recall that in Part I of the previous activity, you compared properties of distance, apparent
brightness, and luminosity. You also felt the temperature of the air around different
wattages of bulbs. What data could you have collected in Part I and plotted on a graph that
would have resemble the data you used to make your HR diagram?
3. One of the first things scientist do when they look at unfamiliar things is to classify them.
Why would astronomers want to classify stars?
REFLECT AND CONNECT: PUTTING IT
ALL TOGETHER
PAGE 511 (ANSWERS)
1. Remember from earlier activities that a stars apparent brightness is related to its distance
from Earth. If astronomers determine distance, they can factor it into their observations
of star’s brightness. They can determine a star’s luminosity, or total power output. This is
an inherent feature of the star that is independent of distance. Luminosity tells
astronomers how much power a star produces and how large a star is.
2. Remember that taking data on the wattage of the bulb and the temp at a specified distance
from the bulb would give data similar to what you graphed for stars. Plotting this data
would show similar relationships. These experiences w/ the light bulbs would model stars
that would fall in the main sequence.
3. Scientist classify things so they can determine patterns or relationships that exists between
characteristics. Those with similar characteristics can be placed into groups. When groups
overlap scientists can make predictions about relationships and test those predictions with
new members of the groups. Scientists use relationships to develop ideas about how stars
are born, live, and die.