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Astronomy 100-09 > Astronomy 100-09 Exam 2 Fall 2022 > Flashcards

Astronomy 100-09 Exam 2 Fall 2022 Flashcards

1
Q

the sun: what is the photosphere?

A

the photosphere is the sun’s visible disk that is produced by a thin layer of the sun

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2
Q

the sun: what are granulation and sun spots? ( surface phenomena)

A
  • granulation: tops of convective cells
  • sun spots: regions of intense magnetic energy and allow for convection allowing gas to cool down
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3
Q

the sun: what temperature is the suns surface?

A

11,000 degrees f or 5800 k

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4
Q

the sun: does the sun have a solid definite surface?

A

no

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5
Q

the sun: any possible fuel for the Sun must account for what 2 things?

A

-energy output per time (i.e. luminosity)
-duration of output

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6
Q

the sun: what is the formula for duration ( solar energy generation)

A

duration= amount of fuel / rate of consumption

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7
Q

the sun: what was the first clue to actual energy source came in 1905?

A

E=mc^2

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8
Q

the sun: what 3 things to you need enough of to sustain thermonuclear fusion?

A

temperature, pressure and density

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9
Q

the sun: what is hydrostatic equilibrium?

A

outward pressure is balanced by inward gravitational force

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10
Q

the sun: what is the random walk?

A

high density of plasma in the core and radiative envelope causes
repeated scattering of light as it passes amongst the atoms

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11
Q

light: what can we say about light as a physical phenomenon?

A
  • fastest phenomena in the universe
    186,000 mi/s or 299,792 km/s
    -speed of light in a vacuum is a universal constant
  • white light is composed of a spectrum
    roygbv ( red orange yellow green blue violet )
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12
Q

light: what is Newton’s definition of light?

A

-“corpuscular” theory; light is composed of undetectable particles
-explains propagation through a vacuum

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13
Q

light: what is Huygens’s definition of light?

A

-wave theory; light is a form of wave
* diffraction
* interference

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14
Q

light: what is Maxwell’s definition of light?

A

electromagnetic wave theory; light propagates as an oscillating electromagnetic field

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15
Q

light: what is a wavelength?

A

distance between two identical points on the waveform

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16
Q

light: what is the standard wavelength unit and what power does it equal to?

A
  • the standard unit for wavelength is angstrom
  • 10^-10 m
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17
Q

light: what do blue and red colors represent in wavelengths?

A
  • red: longer wavelengths
    -blue: shorter wavelengths
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18
Q

light: what is frequency and what is the formula?

A

-frequency (v): number of waves per second that pass a
stationary point
- v= c / wavelength

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19
Q

light: is wavelength and frequency inversely related?

A

yes
- high frequency means lower wavelength
- low frequency means long wavelength

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20
Q

light: how is frequency measured?

A

-measured in cycles per second: 1 Hertz (Hz) = 1/s
visible light estimates to 600 million MHz

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21
Q

light: how did Einstein define photons?

A

-light is composed of “packets of energy” (i.e. particles)
-every photon has a discrete amount of energy and momentum

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22
Q

light: what is the formula for photons?

A

E= hc / wavelength = hv

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23
Q

light: what does h represent and what does it equal to?

A
  • Planck’s constant
  • 6.626 x 10^-27 erg x s
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24
Q

light: what does 1 watt equal to?

A

10^7 ergs/s

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25
Q

light: what do visible photons equal to?

A

10^-12 erg

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26
Q

telescopes: why do astronomers use telescopes?

A

light gathering power and angular resolution

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27
Q

telescopes: what is light gathering power and what is the formula?

A

-greater area allows telescope to “catch” more light, it provides brighter images
- 𝐴𝑟𝑒𝑎∝𝐷𝑖𝑎𝑚𝑒𝑡𝑒𝑟2

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28
Q

telescopes: what is angular resolution and what is the formula?

A
  • (a”) describes the ability to resolve very fine detail and very small angles
  • a”= 2.516 x10^5 9(wavelength) / D (telescope diameter)
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29
Q

telescopes: what does a” represent?

A

minimum angle that can be resolved, expressed in seconds of arc

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30
Q

telescopes: what is seeing?

A

-the distortion, or smearing, of an image caused by turbulence in Earth’s atmosphere above the telescope
⇒ Scintillation = “twinkling”

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31
Q

astronomical detectors: what consist of astronomical detectors?

A

1.) the human eye
2.) photographic plates
3.) photomultiplier tubes
4.) charged coupled devices

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32
Q

astronomical detectors: was the human eye the first astronomical detectors and characteristics ?

A
  • yes, the human eye was the first astronomical detector
  • characteristics
    • wide dynamic range
    • poor efficiency ( estimates to 1%)
    • fair color response within very narrow range of wavelength
    • highly subjective
    • very short integration time ( estimates 0.1 to 0.2 seconds)
33
Q

astronomical detectors: what are photographic plates and their characteristics?

A
  • photochemical detectors; first used in astronomy in late 19th century
    -photons striking silver molecules (emulsion) cause
    chemical reactions and change opacity
  • characteristics
    • Poor efficiency (estimates to 3% up to 10%)
    • Excellent resolution
    • Fair color response
    • Very objective
34
Q

astronomical detectors: what are the advantages and disadvantages of photographic plates?

A
  • advantages
    *ability to expose for long periods of time
    *permanent, accurate, objective record of the observation
  • disadvantages
    *suffer from reciprocity failure
35
Q

astronomical detectors: what are photomultiplier tubes?

A

-employ a quantum mechanical principle
- the photoelectric effect; first developed
in 1907 (Joel Stebbins & F. C. Brown)
-when photons strike certain metals they liberate
electrons, which enables an electric current
⇒ The brighter the light, the greater the current

36
Q

astronomical detectors: what are the advantages of photomultiplier tubes?

A
  • excellent dynamic range
  • moderate efficiency (up to 35%)
  • poor color response
  • very poor resolution
37
Q

analysis of light: is speed of light the fastest phenomena in the universe and what is the speed of light in miles and km?

A
  • yes
  • c = 186,000 mi/s
  • c = 299,792 km/s
38
Q

analysis of light: what does the analysis of light reveal?

A
  • the analysis of light reveals the physical properties of the
    object or medium that is emitting or absorbing the light
  • note: the analysis of reflected light is very different from
    the analysis of emitted or absorbed light
39
Q

analysis of light: what is temperature?

A

-temperature: a measure of thermal energy content
-Kelvin scale (K)
-0 K =Zero energy
-K = °C + 273

40
Q

analysis of light: what is Stefan-Boltzmann Law and the formula?

A

-Stefan-Boltzmann Law : relates the amount of energy a
body radiates to its temperature
- F(energy flux)= 5.67 x 10^5 ( Boltzmann constant) temperature ( kelvin)^4

41
Q

analysis of light: what is Wien’s Law and the formula?

A
  • Wien’s displacement law: relates wavelength of brightest emission ( wavelength max) to temperature
  • wavelength max = 0.29/ t ( temperature)
42
Q

analysis of light: if something is blue that means it’s temperature is?

A
  • hotter
43
Q

analysis of light: if something is red that means it’s temperature is?

A
  • cooler
44
Q

analysis of light: what is a blackbody?

A

-Blackbody: a hypothetical object that perfectly absorbs
all incident radiation and emits light solely according to
its temperature
- not the same thing as a black hole
-stars so not radiate exactly as a blackbody

45
Q

analysis of light: what is a continuous spectrum and how is it produced?

A
  • a continuous spectrum is a long colorful spectrum usually with no lines
  • hot solids, and gasses under high pressure, produce a continuous spectrum
46
Q

analysis of light: what is an emission spectrum and how is it produced?

A
  • mainly black spectrum with thin color lines ( bright line spectrum)
  • hot, low pressure, gasses seen in front of a cooler
    background produce an emission spectrum
47
Q

analysis of light: what is an absorption spectrum and how is it produced?

A
  • mainly a colorful spectrum with thin black lines ( dark line spectrum)
    -low pressure gasses seen in front of a hot blackbody
    produce an absorption spectrum
48
Q

analysis of light: does every element create a different spectrum and how?

A
  • yes
  • the pattern of spectral lines depends on the states in
    which the electrons exist inside of the atoms
49
Q

analysis of light: what is atomic transition?

A

-atomic transition: spectral lines are produced by electrons jumping between these levels
- photons absorbed or emitted by an atom have energies
that exactly match the energy differences between any
two electron energy levels

50
Q

analysis of light: what type of lines does absorption spectrum produce?

A
  • absorption lines are produced by upward transitions
51
Q

analysis of light: what type of lines does an emission spectrum produce?

A

-emission lines are produced by downward transitions

52
Q

analysis of light: what is the doppler effect?

A
  • doppler effect: The observed wavelength of a spectral line is affected by relative motion between the source and the observer
53
Q

analysis of light: what is redshift?

A
  • redshift: when the wavelength subtracted by rest wavelength is greater than zero
  • the source is receding ( decreasing or getting farther)
54
Q

analysis of light: what is blueshift?

A
  • blueshift: when the wavelength subtracted by the rest wavelength is less than zero
  • the source is approaching ( increasing or getting closer)
55
Q

analysis of light: what is the doppler shift?

A
  • red and blue shift
  • these shifts are called a doppler shift; they affect the
    entire spectrum and allow astronomers to measure an
    object’s radial velocity
56
Q

analysis of light: what is radial velocity?

A
  • radial velocity: the component of an object’s relative motion that is toward or away from the observer (i.e. parallel to the line of sight)
57
Q

analysis of light: what is proper motion?

A
  • proper motion: the component of an object’s relative motion that is toward or away from the observer (i.e. parallel to the line of sight)
58
Q

stars: what is apparent magnitude?

A
  • apparent magnitude: how bright a star (or other object) appears to an observer; is directly measurable
  • 1 (bright) ⇒ 6 ( faint)
59
Q

stars: what is parallax?

A
  • parallax (pi” or p): the apparent angular shift of a “nearby” object wrt a distant background due to the observer’s own change in position
60
Q

stars: what is the small angle approximation formula?

A

r ( distance pc)= 1/ pi” ( parallax in arc seconds)

61
Q

stars: what is parsec and what does it equal?

A
  • parsec (pc): the distance of an object with a parallax of
    1 second of arc; the distance at which 1 AU subtends an
    angle of 1 second of arc
  • 1 pc = 3.26 ly
    3.1 = 10*13 km
    = 20 trillion miles
62
Q

stars: what is absolute magnitude and what 2 things are required to measure absolute magnitude?

A
  • absolute magnitude: a star’s true brightness; expressed as how bright the star appears from a distance of 10 pc
  • distance and apparent magnitude are needed to determine absolute magnitude
63
Q

stars: what is inverse square law and formula?

A
  • inverse square law: the intensity of light (i.e. brightness)
    radiated uniformly by a point source decreases inversely
    with the square of the distance
  • I ( intensity or brightness) ∝ 1 / r^2 ( distance)
64
Q

stars: what is luminosity (L)?

A
  • luminosity: total amount of energy radiated per second (ergs/s; or Watts); intrinsic to a star
65
Q

stars: what is photometry?

A
  • photometry: measures brightness of starlight very accurately in specific ranges of color (i.e. wavelengths)
66
Q

stars: what are the categories for stars?

A
  • blue = hot stars
  • red = cool stars
  • O ( hot) (2-9) mostly atoms ionized
  • B (0-9)
    -A (0-9) mostly hydrogen lines
  • F(0-9)
    -G (0-9) many metal lines
  • K(0-9)
  • M ( cool) (0-9) few atoms
67
Q

stars: what two things rely on temperature?

A
  • spectral type and luminosity
68
Q

Hertzsprung-Russell (H-R) Diagram: what is the Hertzsprung-Russell (H-R) Diagram?

A
  • c. 1911 Hertzsprung and Russell plotted stars according to
    their calculated Mv and their observed spectral type
  • for stars known with measured parallax⇒ distance
  • distance combined with apparent magnitude
69
Q

Hertzsprung-Russell (H-R) Diagram: the diagram shows the relationship between what two physical properties?

A
  • luminosity and temperature
70
Q

Hertzsprung-Russell (H-R) Diagram: what is main sequence?

A
  • main sequence: the majority of all stars adheres to this relationship; shows the most common relationship between luminosity and temperature
71
Q

Hertzsprung-Russell (H-R) Diagram: what are giants?

A
  • giants: populate only the upper right portion of the H-R diagram; commonly called red giants, cool but bright stars
72
Q

Hertzsprung-Russell (H-R) Diagram: what are white dwarfs?

A

white dwarfs: populate the lower left portion of the H-R diagram, hot and faint stars

73
Q

Hertzsprung-Russell (H-R) Diagram: what are the 5 classes of luminosity?

A

1.) super giants ( brightest at given spectral type )
2.) luminous giants
3.) giants
4.) sub giants
5.) main sequence ( faintest at given spectral type )

74
Q

binary stars: what are binary stars?

A
  • binary stars: two stars, gravitationally bound together, in mutual orbits around each other
75
Q

binary stars: what are visual binaries?

A
  • visual binaries: both stars can be resolved through a telescope as separate points of light
76
Q

binary stars: what are spectroscopic binaries?

A
  • spectroscopic binaries: stars are not resolved as separate points of light, but two sets of spectral lines are present, which vary over time as a result of a doppler shift
77
Q

binary stars: what are eclipsing binaries?

A
  • eclipsing binaries: when the orbit is seen nearly or exactly edge-on, eclipses are seen as the stars alternately pass in front of each other
78
Q

binary stars: what do the eclipses cause?

A
  • the eclipses cause a periodic change in the total light
    received from the system; observations reveal a light curve
79
Q

binary stars: what are first and second eclipses?

A

-primary eclipse: hotter star is eclipsed
-secondary eclipse: cooler star is eclipsed

Astronomy 100-09 (3 decks)

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