Chapter 10: Measuring Stars Planetarium Extra Credit Opportunity! - - PowerPoint PPT Presentation

chapter 10 measuring stars
SMART_READER_LITE
LIVE PREVIEW

Chapter 10: Measuring Stars Planetarium Extra Credit Opportunity! - - PowerPoint PPT Presentation

Chapter 10: Measuring Stars Planetarium Extra Credit Opportunity! Chapter 10 Reading Assignment due today at (see the syllabus) 10:45am Sept. 26th or 28th at 6:45 pm for Chapter 11 Reading Assignment due Tuesday, the Night Vision show


slide-1
SLIDE 1

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10

Chapter 10: Measuring Stars

1

Chapter 10 Reading Assignment due today at 10:45am Chapter 11 Reading Assignment due Tuesday, October 1st Are your grades in Canvas correct??? Planetarium Extra Credit Opportunity! (see the syllabus)

  • Sept. 26th or 28th at 6:45 pm for

the “Night Vision” show at the Clark Planetarium Free tickets available from me, $2 otherwise

slide-2
SLIDE 2

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10

What’s easy to measure for stars?

2

  • Their positions on the celestial sphere
  • Their spectra (brightness as a function of wavelength)
  • ~Changes in position and spectrum~
  • Their distance
  • Their size (resolving them)
  • Their mass

What’s hard to measure for stars?

slide-3
SLIDE 3

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10

How do we measure distances on the Earth?

3

slide-4
SLIDE 4

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10

Parallax

4

1) Calibration: hold your pinky finger at arm’s length, close one eye, and measure its width (this is about 1 degree in angle) 1 unit 1/2 unit 1/4 unit 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 Example: Cuzco is about 1.5 units long

slide-5
SLIDE 5

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10

Parallax

5

2) Close your left eye and center a finger or pen on the “1” line 1 unit 1/2 unit 1/4 unit 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27

slide-6
SLIDE 6

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10

Parallax

6

3) Open your left eye, close your right eye, and measure how far your finger moved 1 unit 1/2 unit 1/4 unit 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 Example: Cuzco appeared to move 9.25 units

slide-7
SLIDE 7

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10

Parallax

7

4) Divide the apparent movement by the width of your pinky to get the angle in degrees 1 unit 1/2 unit 1/4 unit 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 Example: 9.25 / 1.5 = 6.2 degrees

slide-8
SLIDE 8

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10

Parallax

8

5) Divide 110 inches by the number of degrees to get the distance to your finger! 1 unit 1/2 unit 1/4 unit 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 Example: 110 inches / 6.2 degrees ~ 18 inches

slide-9
SLIDE 9

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10

Parallax

9

5) Divide 110 inches by the number of degrees to get the distance to your finger! 1 unit 1/2 unit 1/4 unit 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 2.5in

slide-10
SLIDE 10

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10

Parallax

10

Place your finger about 1 foot away and repeat the test. What distance did you get? 1 unit 1/2 unit 1/4 unit 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 2.5in

slide-11
SLIDE 11

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10 11

Parallax

slide-12
SLIDE 12

Fall 2019: Chapter 10 ASTR/PHYS 1060: The Universe 12

Which star is the most luminous?

A B C

slide-13
SLIDE 13

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10

Distance and Brightness gives Luminosity

13

Star’s Brightness Star’s Luminosity 4 π distance2

=

slide-14
SLIDE 14

Fall 2019: Chapter 10 ASTR/PHYS 1060: The Universe 14

A B Which case for the red star would have the larger parallax?

slide-15
SLIDE 15

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10

What’s easy to measure for stars?

15

  • Their positions on the celestial sphere
  • Their spectra (brightness as a function of wavelength)
  • ~Changes in position and spectrum~
  • Their distance
  • Their size (resolving them)
  • Their mass

What’s hard to measure for stars?

slide-16
SLIDE 16

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10

Emission and Absorption Lines

16

Emission sticks up Absorption sticks down Electron Nucleus

Higher energy electron = Further from nucleus

Change in electron’s energy = Energy of Emitted Light

Electrons and Emission

slide-17
SLIDE 17

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10

Each atom has a unique set of energy levels

17

slide-18
SLIDE 18

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10

Remember: Light is “Quantized”

18

slide-19
SLIDE 19

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10

Spectra Lab: Emission Tubes

19

slide-20
SLIDE 20

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10

Spectra Lab: Emission Tubes

20

slide-21
SLIDE 21

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10

Spectra Lab: Blackbody Emission

21

slide-22
SLIDE 22

Fall 2019: Chapter 10 ASTR/PHYS 1060: The Universe 22

If you see a star bluer than the sun, would you expect it to have a lower or higher luminosity? If a star is very faint, what color would you expect it to be?

In small groups, discuss this question and your reasoning:

slide-23
SLIDE 23

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10

Spectra Lab: Blackbody Emission

23

slide-24
SLIDE 24

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10 24

Typical stellar spectrum has many absorption lines, which we graph

slide-25
SLIDE 25

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10

Chapter 10: Measuring Stars

25

Chapter 11 Reading Assignment due Tuesday, October 1st Are your grades in Canvas correct??? Planetarium Extra Credit Opportunity! (see the syllabus)

  • Sept. 26th or 28th at 6:45 pm for

the “Night Vision” show at the Clark Planetarium Free tickets available from me, $2 otherwise

slide-26
SLIDE 26

Fall 2019: Chapter 10 ASTR/PHYS 1060: The Universe 26

slide-27
SLIDE 27

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10

What kind of spectrum does the Moon have?

27

A) Emission Line B) Blackbody C) Absorption Line

slide-28
SLIDE 28

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10

Annie Jump Cannon Classifies the Stars

28

  • one of “Pickering’s Women,” a

Harvard “Calculator”

  • part of the effort to catalog every star

in the sky down to 9th magnitude

  • defined the classification scheme for

stellar spectra

  • manually classified over 350,000

stars

  • realized stellar types correlated with

temperature (but not in the original

  • rder)
slide-29
SLIDE 29

Fall 2019: Chapter 10 ASTR/PHYS 1060: The Universe 29

Balmer series (n=x -> n=2)

slide-30
SLIDE 30

Fall 2019: Chapter 10 ASTR/PHYS 1060: The Universe 30

Balmer series (n=2 -> n=x)

Small Numbers

  • f Atoms in E2

Large Numbers

  • f Atoms in E2

More Violet Light More Red Light

slide-31
SLIDE 31

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10

If temperature is what we want, why use spectra?

31

Dust preferentially absorbs bluer light (uniformly), so a star’s color will change (but the relative strengths of its lines will not)

slide-32
SLIDE 32

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10

Color and temperature are connected

32 1 μm = 1000 nm

Temperature [in K]

Wien's Law:

λmax = 2900 μm⋅K

Stefan-Boltzmann Law: Luminosity per unit area = constant × Temperature4

slide-33
SLIDE 33

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10

Binary Stars

33

slide-34
SLIDE 34

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10

Weighing stars in a Binary

34

slide-35
SLIDE 35

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10

What’s easy to measure for stars?

35

  • Their positions on the celestial sphere
  • Their spectra (brightness as a function of wavelength)
  • ~Changes in position and spectrum~
  • Their distance
  • Their size (resolving them)
  • Their mass

What’s hard to measure for stars?

slide-36
SLIDE 36

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10

Hertzsprung-Russell (HR) Diagram

36

Spectral Type, Color, Temperature

  • n the x-axis

Luminosity (intrinsic brightness)

  • n the y-axis
slide-37
SLIDE 37

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10

Globular Cluster Color-Magnitude Diagram

37

Bluer Redder Fainter Brighter

slide-38
SLIDE 38

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10

Gaia CMDs

38

66 million stars

slide-39
SLIDE 39

ASTR/PHYS 1060: The Universe Fall 2019: Chapter 10 39

Hydrogen-burning stars fall on the Main Sequence in a specific place determined by their mass

slide-40
SLIDE 40

Fall 2019: Chapter 10 ASTR/PHYS 1060: The Universe 40

Star P: Spectral Type: B5 Luminosity: 300 Lsun Star Q: Spectral Type: K3 Luminosity: 0.008 Lsun 100 1000 P Q 0.01 0.001