Astronomy 1020Spring_2015

Day-18Stellar Astronomy

Course Announcements

•Exam-2 – Fri. 3/6 Chapters 5 & (some of) 6• I will collect the L-T books at this time.•Smartworks Chapters 5: Due Wed. 3/4•Smartworks Chapters 6: Due Mon. 3/16•APSU Research and Creativity Forum April 11-12, 2014

• Abstracts are due: 4:30pm Fri., March 21

•Mar. 2 – Last day to drop with an automatic “W”•Apr. 2 – Last day to drop a class.

Luminosity is the total energy (light) emitted by an object in each second.Stefan-Boltzmann lawLuminosity depends on an surface

area (A), and its temperature (T4); Surface Area ∝ R2

Luminosity = 4π R2 T4

Big and Hot objects have greater luminosity than small cool objects

Lecture Tutorial Luminosity: (pg 55)

Work with a partner!Read the instructions and questions carefully.Discuss the concepts and your answers with

one another. Take time to understand it now!!!!

Come to a consensus answer you both agree on.

If you get stuck or are not sure of your answer, ask another group.

20,000 10,000 5,000

Lum

inos

ity (

sola

r un

its)

Temperature (K)

4

2

1

3

5

10,000

100

10

1

0.1

0.01

0.001

0.0001

1,000

Hertzsprung-Russell Diagram

Which star is Hot and Dim?

Temperature (K)

20,000 10,000 5,000

Lum

inos

ity (

sola

r un

its)

Temperature

(K)

4

2

1

3

5

10,000

100

10

1

0.1

0.01

0.001

0.0001

1,000

Which star is Cool and Dim?

Temperature (K)

20,000 10,000 5,000

Lum

inos

ity (

sola

r un

its)

Temperature (K)

4

2

1

3

5

10,000

100

10

1

0.1

0.01

0.001

0.0001

1,000

Which star is Largest?

20,000 10,000 5,000

Lum

inos

ity (

sola

r un

its)

Temperature (K)

4

2

1

3

5

10,000

100

10

1

0.1

0.01

0.001

0.0001

1,000

Which star is smallest?

Temperature (K)

20,000 10,000 5,000

Lum

inos

ity (

sola

r un

its)

Temperature (K)

4

2

1

3

5

10,000

100

10

1

0.1

0.01

0.001

0.0001

1,000

Brightness is the amount of light arriving at a particular place.

Decreases as the distance from a light source increases, obeying an inverse square law.

The light spreads out over a greater area.

24 r

LB

Lecture - Tutorial: Blackbody Radiation (pg. 59)

Work with a partner!Read the instructions and questions

carefully.Discuss the concepts and your answers with

one another. Take time to understand it now!!!!

Come to a consensus answer you both agree on.

If you get stuck or are not sure of your answer, ask another group.

Energy

Output per

second

V I B G Y O

R

Star A

Star B

Wavelength

Star C

V I B G Y O R

Star D

V I B G Y O R

Star A Star A

Which has the longer peak wavelength?

1. Star A

2. Star C

3. SameStar C

Wavelength

V I B G Y O R

Energ

y

Output

per

secon

d

Star A

Which has the lower surface temperature?

1. Star A

2. Star C

3. SameStar C

Wavelength

V I B G Y O R

Energ

y

Output

per

secon

d

Star A

Which star looks red?

1. Star A

2. Star C

3. Both

4. Neither

Star C

Wavelength

V I B G Y O R

Energ

y

Output

per

secon

d

Star A

Which has the greater energy output?

1. Star A

2. Star C

3. SameStar C

Wavelength

V I B G Y O R

Energ

y

Output

per

secon

d

Star A

Which star is larger?

1. Star A

2. Star C

3. SameStar C

Wavelength

V I B G Y O R

Energ

y

Output

per

secon

d

Star A

Which star is larger?

1. Star A

2. Star D

3. Same

Star D

WavelengthV I B G Y O R

Star A

Energy Output per second

Try to determine EVERYTHING about how these four stars compare!! Temp, Energy output, color, size

(area)…..

Object

A WavelengthV I B G Y O R

visible

range

Ene

rgy

Out

put p

er s

econ

d

Object C

WavelengthV I B G Y O R

visible

range

Ene

rgy

Out

put p

er s

econ

d

Object

B WavelengthV I B G Y O R

visible

range

Ene

rgy

Out

put p

er s

econ

d

Object D

WavelengthV I B G Y O R

visible

range

Ene

rgy

Out

put p

er s

econ

d