Transcript Chapter J1

Chapter J1
Section 3 Mapping the Stars
Objectives
• Explain how constellations are used to organize
the night sky.
• Describe how the altitude of a star is measured.
• Explain how the celestial sphere is used to
describe the location of objects in the sky.
• Compare size and scale in the universe, and
explain how red shift indicates that the universe is
expanding.
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Chapter J1
Section 3 Mapping the Stars
Patterns in the Sky
• Constellations Help Organize the Sky A
constellation is a region of the sky. Each
constellation shares a border with neighboring
constellations.
• Seasonal Changes As Earth revolves around
the sun, the apparent locations of the
constellations change from season to season.
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Chapter J1
Section 3 Mapping the Stars
Spring Constellations in the Northern Hemisphere
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Chapter J1
Section 3 Mapping the Stars
Finding Stars in the Night Sky
• You can describe the location of a star or planet by
using an instrument called an astrolabe and the
following points of reference:
• The zenith is the point in the sky directly above on
observer on Earth.
• The altitude is the angle between an object in the sky
and the horizon.
• The horizon is the line where the sky and the Earth
appear to meet.
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Chapter J1
Section 3 Mapping the Stars
Zenith, Altitude, and Horizon
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Section 3 Mapping the Stars
Finding Stars in the Night Sky, continued
• Using an astrolabe allows you to describe where
a star or planet is relative to you. Scientists need
a different method that describes location
independently of the observer’s location.
• Astronomers describe the location of a star or
planet in terms of the celestial sphere.
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Chapter J1
Section 3 Mapping the Stars
The Celestial Sphere
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Section 3 Mapping the Stars
Describing a Star’s Position
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Visual Concept
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Chapter J1
Section 3 Mapping the Stars
The Size and Scale of the Universe
• In the 1600s, Nicolaus Copernicus noticed that
the planets appeared to move relative to each
other but that the stars did not. Thus, he thought
that the stars must be much farther away than the
planets.
• Measuring Distance in Space A light-year is a
unit of length equal to the distance that light
travels in 1 year.
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Section 3 Mapping the Stars
The Size and Scale of the Universe,
continued
• It is important to consider scale when thinking
about the universe. Although stars looks tiny in
the night sky, remember that they are actually a
lot larger than Earth.
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Chapter J1
Section 3 Mapping the Stars
The Doppler Effect
• What Is the Doppler Effect? Have you ever
noticed that when a driver in an approaching car
blows the horn, the horn sounds higher pitched as
the car approaches and lower pitched after the
car passes? This effect is called the Doppler
effect.
• An Expanding Universe The Doppler effect has
been used to discover that galaxies are rapidly
moving apart from each other.
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Chapter J1
Section 3 Mapping the Stars
Red Shift
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Visual Concept
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Chapter J1
Standardized Test Preparation
Reading
Read each of the passages. Then, answer the
questions that follow each passage.
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2. Why don’t upright objects cast a shadow when the
sun is at its zenith?
F because the sun is directly overhead
G because the summer solstice is occurring
H because the sun is below the horizon
I because the sun is at its zenith on the longest day
of the year
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INTERPRETING GRAPHICS
The diagram on the following slide shows a galaxy
moving in relation to four observers. The concentric
circles illustrate the Doppler effect at each location.
Use the diagram to answer the questions that follow.
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1. Which of the following observers would see the light
from the galaxy affected by redshift?
A observers 1 and 2
B observer 3
C observers 3 and 4
D observers 1 and 4
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1. Which of the following observers would see the light
from the galaxy affected by redshift?
A observers 1 and 2
B observer 3
C observers 3 and 4
D observers 1 and 4
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2. Which of the following observers would see the light
from the galaxy affected by blueshift?
F observer 1
G observers 2 and 4
H observers 3 and 4
I observer 2
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2. Which of the following observers would see the light
from the galaxy affected by blueshift?
F observer 1
G observers 2 and 4
H observers 3 and 4
I observer 2
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3. How would the wavelengths of light detected by observer
4 appear?
A The wavelengths would appear shorter than they really
are.
B The wavelengths would appear longer than they really are.
C The wavelengths would appear unchanged.
D The wavelengths would alternate between blue and red.
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3. How would the wavelengths of light detected by observer
4 appear?
A The wavelengths would appear shorter than they really
are.
B The wavelengths would appear longer than they really are.
C The wavelengths would appear unchanged.
D The wavelengths would alternate between blue and red.
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MATH
Read each of the following questions, and choose the
best answer.
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1. If light travels 300,000 km/s, how long does light
reflected from Mars take to reach Earth when Mars is
65,000,000 km away?
A 22 s
B 217 s
C 2,170 s
D 2,200 s
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1. If light travels 300,000 km/s, how long does light
reflected from Mars take to reach Earth when Mars is
65,000,000 km away?
A 22 s
B 217 s
C 2,170 s
D 2,200 s
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4. If the altitude of a star is 37°, what is the angle
between the star and the zenith?
F 143°
G 90°
H 53°
I 37°
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4. If the altitude of a star is 37°, what is the angle
between the star and the zenith?
F 143°
G 90°
H 53°
I 37°
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5. You are studying an image made by the Hubble
Space Telescope. If you observe 90 stars in an area
that is 1 cm2 , which of the following estimates is the
best estimate for the number of stars in 15 cm2 ?
A 700
B 900
C 1,200
D 1,350
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5. You are studying an image made by the Hubble
Space Telescope. If you observe 90 stars in an area
that is 1 cm2 , which of the following estimates is the
best estimate for the number of stars in 15 cm2 ?
A 700
B 900
C 1,200
D 1,350
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