Download Characteristics of Stars

Name
Date
Stars, Galaxies, and the Universe
■
Class
Adapted Reading and Study
Characteristics of Stars
(pages 752–759)
Classifying Stars
(pages 753–754)
Key Concept: Characteristics used to classify stars
include color, temperature, size, composition, and
brightness.
• A star’s color gives clues about the star’s temperature.
The coolest stars appear red. The hottest stars appear
blue.
• Very large stars are called giant stars or supergiant
stars. Our sun is a medium-sized star. Most stars are
smaller than the sun.
• Stars differ in their chemical make-ups. Astronomers
use spectrographs to find out what elements are in a
star. A spectrograph (SPEK truh graf) is a device that
breaks light into colors. Scientists compare a star’s light
with the light produced by different elements to find out
what elements are in the star.
Answer the following questions. Use your textbook and the
ideas above.
1. Is the following sentence true or false? A star’s color
gives clues about the star’s temperature.
2. Circle the letter of a device that breaks light into colors.
a. spectrograph
b. telescope
c. observatory
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358
Name
Date
Stars, Galaxies, and the Universe
■
Class
Adapted Reading and Study
3. Complete the concept map about characteristics used
to classify stars.
Characteristics
used to classify stars
include
Color
Composition
Size
a.
b.
Brightness of Stars
(pages 754–755)
Key Concept: The brightness of a star depends upon
both its size and temperature.
• Stars differ in how bright they are. A hot star shines
brighter than a cool star. A large star shines brighter
than a small star.
• A star’s apparent brightness is the brightness you see
from Earth. A hot, large star that is very far from Earth
does not look very bright. But the sun looks very bright
because it is so close to Earth.
• A star’s absolute brightness is the brightness the star
would have if all stars were the same distance from
Earth.
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
359
Name
Date
Stars, Galaxies, and the Universe
■
Class
Adapted Reading and Study
Answer the following questions. Use your textbook and the
ideas on page 359.
4. Circle the letter of each characteristic that affects a
star’s brightness.
a. composition
b. size
c. temperature
5. Complete the table about the two ways that brightness
can be described.
Ways That Brightness Can Be Described
Brightness
Description
a.
the brightness you see
from Earth
b.
the brightness a star
would have if all stars
were the same distance
from Earth
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
360
Name
Date
Stars, Galaxies, and the Universe
■
Class
Adapted Reading and Study
Measuring Distances to Stars
(pages 756–757)
Key Concept: Astronomers use a unit called the lightyear to measure distances between the stars.
• A light-year is the distance that light travels in one year.
That distance is about 9.5 million kilometers.
• A light-year is a unit of distance, not time. You could also
measure distance on Earth in terms of time. For
example, if it takes you 1 hour to ride your bike to the
mall, you could say the mall is “1 bicycle-hour” away.
Answer the following questions. Use your textbook and the
ideas above.
6. The distance that light travels in one year is a(an)
.
7. Is the following sentence true or false? A light-year is a
unit of distance, not time.
Key Concept: Astronomers often use parallax to
measure distances to nearby stars.
• Parallax is the change in an object’s position you seem
to see when you change your own position. The object
does not really change position. It only seems to change
because you change your position.
• Astronomers use parallax. They measure how far a star
seems to move when Earth moves from one side of the
sun to the other. The distance the star seems to move
tells an astronomer how far the star is from Earth.
Answer the following questions. Use your textbook and the
ideas above.
8. The change in an object’s position you seem to see
when you change your own position is
.
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
361
Name
Date
Stars, Galaxies, and the Universe
■
Class
Adapted Reading and Study
9. Circle the letter of what astronomers use parallax for.
a. to measure distances to nearby stars
b. to compare the brightness of stars
c. to determine the elements found in stars
The Hertzsprung-Russell Diagram
(pages 758–759)
Key Concept: Astronomers use H-R diagrams to
classify stars and to understand how stars change
over time.
• The Hertzsprung-Russell diagram, or the H-R
diagram, shows how the surface temperature of stars is
related to their absolute brightness.
• The points on the H-R diagram form a pattern. Most
stars on the H-R diagram fall into a band that spreads
from the top left corner of the diagram to the bottom
right corner. This band is called the main sequence.
Stars in the main sequence are called main-sequence
stars. About 90 percent of all stars are main-sequence
stars.
• The brightest stars are located near the top of the H-R
diagram. Stars that are not bright are located at the
bottom.
Answer the following questions. Use your textbook and the
ideas above.
10. The Hertzsprung-Russell diagram shows how the
surface temperature of stars is related to absolute
.
11. Most stars are
stars.
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
362
Name
Date
Stars, Galaxies, and the Universe
■
Class
Adapted Reading and Study
12. The picture shows a H-R diagram. The dots represent
stars. Draw a line on the diagram to show about where
the main sequence is.
Absolute
Brightness
High
Low
High
Surface
Temperature
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
363
Low