11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its...

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11.2 Classifying Stars Our Goals for Learning • How do we classify stars? • Why is a star’s mass its most important property? • What is a Hertzsprung– Russell diagram?

Transcript of 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its...

Page 1: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

11.2 Classifying Stars

Our Goals for Learning

• How do we classify stars?

• Why is a star’s mass its most important property?

• What is a Hertzsprung–Russell diagram?

Page 2: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

What is the stellar Main Sequence?

Page 3: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Most of the brightest stars are reddish in color

Color and luminosity are closely related among the remaining “normal” stars

Page 4: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Main-sequence stars (like the Sun) are fusing hydrogen into helium in their cores

Luminous main-sequence stars are hot (blue)

Less luminous ones are cooler (yellow or red)

Page 5: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Why are some red stars so much more luminous?They’re bigger!

L = LuminosityT = Temperature

L=Area × T4

L=4πr2 × T4

(page 312)

Biggest red stars: 1000 Rsun

Smallest red stars: 0.1 RSun

(Ranking Task)

Page 6: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Which star is the least luminous?

A B C D E F

94%

3%0%0%2%0%

1. A

2. B

3. C

4. D

5. E

6. F

Page 7: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Which star is the most luminous?

A B C D E F

0% 0%

31%

1%

67%

0%

1. A

2. B

3. C

4. D

5. E

6. F

Page 8: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Temperatures and sizes of stars

Page 9: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

1) Hotter objects emit more light per area at all wavelengths

2) Hotter objects tend to emit light at shorter wavelengths and higher frequencies

Laws of Thermal Radiation

Page 10: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Why are some red stars so much more luminous?They’re bigger!

L = LuminosityT = Temperature

L=Area × T4

L=4πr2 × T4

(page 312)

Biggest red stars: 1000 Rsun

Smallest red stars: 0.1 RSun

(Ranking Task)

Page 11: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Activity 10, Part II (pages 32-34, questions 6-15)

Page 12: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

6) Stars E and F in Figure 2a are the same size. Which gives off more red light?

E F

Both

giv

e of

f the

s...

63%

2%

35%

1. E

2. F

3. Both give off the same amount of red light

Page 13: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

7) Stars E and F in Figure 2a are the same size. Which gives off more blue light?

E F

Both

giv

e of

f the

sa..

89%

0%10%

1. E

2. F

3. Both give off the same amount of blue light

Page 14: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

8) Which star from Figure 2a looks red, and which looks blue?

E lo

oks b

lue

and

F loo..

E lo

oks re

d and

F loo..

Both

look

red

Both

look

blue

86%

1%2%11%

1. E looks blue and F looks red

2. E looks red and F looks blue

3. Both look red

4. Both look blue

Page 15: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

11) In Figure 2b, how must star C be different from star E to account for their difference in energy output?

Sta

r C m

ust b

e co

oler..

.

Sta

r C m

ust b

e sm

alle

...

Both

1 a

nd 2

Eith

er 1

or 2

35%

26%

18%21%

1. Star C must be cooler than Star E

2. Star C must be smaller than Star E

3. Both 1 and 2

4. Either 1 or 2

Page 16: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

1) Hotter objects emit more light per area at all wavelengths

2) Hotter objects tend to emit light at shorter wavelengths and higher frequencies

Laws of Thermal Radiation

Page 17: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

14) In Figure 2c, which star has the higher surface temperature?

Sta

r D

Sta

r E

Both

hav

e th

e sa

me.

..

17%7%

75%1. Star D

2. Star E

3. Both have the same temperature

Page 18: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

1) Hotter objects emit more light per area at all wavelengths

2) Hotter objects tend to emit light at shorter wavelengths and higher frequencies

Laws of Thermal Radiation

Page 19: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

15) In Figure 2c, which star is larger?

Sta

r D

Sta

r E

Both

are

the

sam

e si

ze

28%

69%

3%

1. Star D

2. Star E

3. Both are the same size

Page 20: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

How do we classify stars?

Page 21: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Most of the brightest stars are reddish in color

Color and luminosity are closely related among the remaining “normal” stars

Page 22: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Main-sequence stars (like the Sun) are fusing hydrogen into helium in their cores

Luminous main-sequence stars are hot (blue)

Less luminous ones are cooler (yellow or red)

Page 23: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Properties of Main Sequence Stars - Review

Luminosity: from brightness and distance

10-4 LSun - 106 LSun

Temperature: from color and spectral type

2,000 K - 50,000 K

Mass: from period (p) and average separation (a) of binary-star orbit

0.08 MSun - 150 MSun

Page 24: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Main Sequence Stellar Properties Review

Luminosity: from brightness and distance

10-4 LSun - 106 LSun

Temperature: from color and spectral type

2,000 K - 50,000 K

Mass: from period (p) and average separation (a) of binary-star orbit

0.08 MSun - 150 MSun

(0.08 MSun) (150 MSun)

(150 MSun)(0.08 MSun)

Page 25: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Each star’s properties depend mostly on mass and age

Page 26: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Why is a star’s mass its most important property?

Page 27: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Core pressure and temperature of a higher-mass star need to be larger in order to balance gravity

Higher core temperature boosts fusion rate, leading to larger luminosity

Page 28: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

A star’s mass largely determines how much light it gives off (its luminosity) and for how long it

will shine (its lifetime).

Page 29: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

What can we learn about stars from a Hertzsprung-Russell Diagram?

Page 30: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Temperature

Lu

min

osi

tyAn H-R diagram plots the luminosity versus temperature of stars

Page 31: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.
Page 32: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Normal hydrogen-fusing stars reside on the main sequence of the H-R diagram

Page 33: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Stars with low temperature and high luminosity must have large radius

Large radius

Small radius

Page 34: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.
Page 35: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Temperature

Lu

min

osi

tyH-R diagram depicts: Temperature,

Colour,

Luminosit

y,

Radius,

Spectral Type

*Mass

*Lifespan

*Age

Page 36: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Temperature

Lu

min

osi

ty

Which star is the hottest?

A

BC

D

Page 37: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Which star is the hottest?

0%

0%

0%

0%

:10

1. A

2. B

3. C

4. D

Page 38: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Temperature

Lu

min

osi

tyWhich star is the hottest?

A

BC

A

D

A

BC

D

Page 39: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Temperature

Lu

min

osi

ty

Which star is the most luminous?

A

BC

D

Page 40: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Which star is the most luminous?

0%

0%

0%

0%

:10

1. A

2. B

3. C

4. D

Page 41: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Temperature

Lu

min

osi

tyWhich star is the most luminous?

C

A

BC

D

Page 42: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Temperature

Lu

min

osi

tyWhich star is a main-sequence star?

A

BC

D

Page 43: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Which star is a main sequence star?

0%

0%

0%

0%

:10

1. A

2. B

3. C

4. D

Page 44: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Temperature

Lu

min

osi

tyWhich star is a main-sequence star?

D

A

BC

D

Page 45: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Temperature

Lu

min

osi

tyWhich star has the largest radius?

A

BC

D

Page 46: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Which star has the largest radius?

0%

0%

0%

0%

:10

1. A

2. B

3. C

4. D

Page 47: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Temperature

Lu

min

osi

tyWhich star has the largest radius?

C

A

BC

D

Page 48: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Temperature

Lu

min

osi

ty

Which star is most like our Sun?

A

B

C

D

Page 49: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Which star is most like our Sun?

0%

0%

0%

0%

:10

1. A

2. B

3. C

4. D

Page 50: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Temperature

Lu

min

osi

tyWhich star is most like our Sun?

B

A

B

C

D

Page 51: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

What have we learned?

• How do we classify stars?• We classify stars according

to their spectral type and luminosity class.

• The spectral type tells us the star’s surface temperature

• The luminosity class how much light it puts out.

• Why is a star’s mass its most important property?

• A star’s mass at birth determines virtually everything that happens to it throughout its life.

Page 52: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

What have we learned?• What is a

Hertzsprung-Russell diagram?

• An H–R diagram plots stars according to their surface temperatures and luminosities.

Page 53: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

Activity #9, questions 10-15,pages 29-30

Page 54: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

10) Which star is larger, star S or star T?

Sta

r S

Sta

r T

They

are

the

sam

e si

ze

0% 0%0%

:10

1. Star S

2. Star T

3. They are the same size

Page 55: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

11) Which star is larger, star S or star X?

Sta

r S

Sta

r X

They

are

the

sam

e si

ze

Can

not a

nswer

with

...

0% 0%0%0%

:10

1. Star S

2. Star X

3. They are the same size

4. Cannot answer with information given

Page 56: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

12) Which star is larger, star X or star Y?

Sta

r X

Sta

r Y

They

are

the

sam

e si

ze

Can

not a

nswer

with

...

0% 0%0%0%

:10

1. Star X

2. Star Y

3. They are the same size

4. Cannot answer with information given

Page 57: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

14) Star Z has the same luminosity as star W but is smaller than star W.

It could be located…

Bet

wee

n S a

nd X

Bet

wee

n T a

nd Y

Bet

wee

n S a

nd T

Bet

wee

n X a

nd Y

1 o

r 2 a

bove

3 o

r 4 a

bove

0% 0% 0%0%0%0%

:10

1. Between S and X

2. Between T and Y

3. Between S and T

4. Between X and Y

5. 1 or 2 above

6. 3 or 4 above

Page 58: 11.2 Classifying Stars Our Goals for Learning How do we classify stars? Why is a star’s mass its most important property? What is a Hertzsprung–Russell.

15) Star S has a temperature twice as high as star W does. Using L=4πR2T4, which star is larger: star S or star W?

Sta

r S

Sta

r W

They

are

the

sam

e si

ze

0% 0%0%

:10

1. Star S

2. Star W

3. They are the same size


Stars, Galaxies, and the Universe Section 1 ... · Composition of Stars Astronomers use an instrument called a spectrograph to break a star’s light into a spectrum (just like a

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