Download Stars - Science

1. Uri looks through a telescope for two stars. He knows that both stars have the
same absolute brightness and that the second star is twice as far from Earth as
the first star. How bright will the second star appear compared to the first star?
A.
B.
C.
D.
It will
It will
It will
It will
appear brighter than the first star.
appear dimmer than the first star.
appear as bright as the first star.
appear redder than the first star.
2. Chaya analyzes the data for two stars. Both stars are the same color, but the
first star has an absolute brightness greater than the second star. What should
Chaya conclude about the stars?
A.
B.
C.
D.
The first star is larger than the second star.
The first star is smaller than the second star.
The first star is hotter than the second star.
The first star is cooler than the second star.
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3. Stars can be many different colors. Which star in
the chart has the highest surface temperature?
A. Star A
B. Star B
C. Star C
D. Star D
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What are stars?
• Giant balls of flaming gases
– mostly hydrogen and helium
How big is Earth compared to our Star?
How are stars classified?
Characteristics of Stars
(click for video)
Temperature
Color
Size
Absolute brightness (luminosity)
Apparent magnitude (brightness)
Characteristics of Stars
• Magnitude (brightness)
– A measure of brightness
of celestial objects
– Apparent magnitude
(brightness)
• How bright a star appears
to be from Earth
– Absolute brightness
• How bright a star actually is
Of all the stars in the
background, which is
the brightest?
What type (apparent of
absolute can you use
to answer the question
above?
Characteristics of Stars
• Temperature & Color
– The color of a star indicates the temperature of
the star (Think of a candle, the hottest colors at
the bottom.)
The coolest stars
are red.
Medium
temperature stars
are orange and
yellow.
The hottest stars
are blue.
H-R Diagram of stars help Astronomers to classify stars based on
temperature, absolute brightness (luminosity), and
sometimes size.
big &
cool
big &
hot
Units
Of
Sun’s
small &
hot
small &
cool
Hertzsprung-Russell Diagram
Looking at stars of the
same temperature,
how is size related
absolute brightness
(luminosity)?
Hint: Compare white
dwarfs to stars of
the same
temperature.
2. Class “K” stars can be separated
into three groups. They all share a
similar temperature, but have
different absolute magnitudes
(brightness). How can astronomers
distinguish these stars from one
another?
1. Using the H-R Diagram above,
describe the characteristics of a
Class “O” Main sequence star.
3. Explain how a star with a low
absolute brightness can have a higher
apparent brightness than a star with a
high absolute brightness.
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