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62 Cards in this Set
- Front
- Back
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Venus appears now with magnitude -4.5, and the red giant Betelgeuse in Orion has magnitude +0.5. Which looks brighter? cannot tell with the information given they show the same brightness Venus looks brighter Betelguese looks brighter |
Venus looks brighter |
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With data from the previous problem, how much greater is the intensity of light seen on Earth from the brighter of the two objects? cannot tell with the information given they give the same intensity 5 times higher intensity 10 times higher intensity 100 times higher intensity |
100 times higher intensity |
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The visible surface of the full moon emits thermal radiation with maximum intensity at about 10^5 Angstroms (10^4 nanometers) wavelngth. What is the temperature there? 100 K 300 K 1000 K 3000 K |
300 K |
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Say we observe thermal radiation from two stars and see that it fits the shape of Planck's backbody. curve. One star has a temperature 2000K (a red giant) and the other has a temperature 10,000 K (a bue giant). By what factor does the total thermal radiation emitted per square meter of surface differ between the two stars? x5 x25 x125 x625 x3125 |
x625 |
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The thermal radiation spectrum and the line emission spectrum from an object cannot overlap in wavelength T/F |
False |
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The thermal radiation spectrum and the line absorption spectrum from an object must overlap in wavelength. T/F |
False |
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How does the thermal radiation spectrum of hydrogen at 3000 K compare to that of iron at 3000 K? |
the brightness vs. wavelength graph for hydrogen has the same shape as for iron |
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How does the line emission spectrum of hydrogen compare to that of neon? |
the hydrogen lines' wavelengths can be explained by the Bohr model because hydrogen has only a single electron, while the neon lines (with 10 electrons) are harder to explain the hydrogen and neon line emission spectra are each unique and bear no obvious resemblance to each other |
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Dark absorption lines in the spectrum of an astrophysical object tell us that: |
relatively cool gas lies between us and the emitting surface of the object |
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Space probes typically move away from Earth at about 40 km/sec (25,000 mph). The speed of light is 3x108 m/s. By roughly what fraction are radio transmissions from such a probe redshifted? 0.1 0.01 0.001 0.0001 0.00001 |
0.0001 |
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By studying the redshifts of its spectral lines, we can determine whether a distant galaxy is moving away from us, or we are moving away from it. T/F |
False |
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By studying the redshifts of its spectral lines, we can determine whether a distant galaxy is rotating left-to-right or right-to-left on the sky. T/F |
True |
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Which of the following wavelength bands of electromagnetic radiation are mostly transmitted through the atmosphere? |
visible light radio |
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The solar corona: (2 things) |
is the outermost layer of the Sun visible only during an eclipse or with a special instrument |
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The solar chromosphere: (3 things) |
emits mainly the red Lyman alpha line of hydrogen visible only during an eclipse or with a special instrument is only about 7000 km thick |
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The solar photosphere: (1 thing) |
emits most of the sun's light |
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the solar core: (1 thing) |
is the place where nuclear fusion occurs |
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Are there more prominences and solar flares when the sunspot number is high, or fewer? |
more |
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The number of visible sunspots varies with time in a way without any discernible regularity. T/F |
False |
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The technique called helioseismology gives information about the deep interior of the Sun by observing what? |
Doppler shifts from oscillations of the Sun's visible surface |
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Which of the following are true of the solar wind? |
it consists mostly of ionized gas it causes the Aurora Borealis it can cause disruption of communications and electronic systems |
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Why was nuclear fusion originally proposed as the source of the Sun's energy? |
heating due to gravitational contraction could not provide enough energy to power the sun for its long lifetime |
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Which of the following objects were used to test General Relativity in 1919? |
The sun A star close to the sun in the sky |
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Study of the spectra of stars around the beginning of the [x] -th century allowed them to be classified into "types" in order of their [y]
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x = 20 y = temperature |
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The parallax angle for determining a star's distance from us is measured |
between the directions to the star in observations separated by six months usually by comparing its position to much more distant stars |
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The distance to a star with parallax 0.1 arc second is about how many light years? |
33 |
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The distances to most of the stars in our galaxy are known from parallax measurements. T/F |
False |
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A given star's luminosity wouldn't change if it was moved twice as far from Earth as it is now. T/F |
True
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We can calculate a star's luminosity if we know its [x] brightness and its [y]
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x - apparent y - distance/parallax |
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A star's distance from us can be estimated just from its spectrum and its apparent magnitude. T/F |
True |
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The Hertzsprung-Russel (HR) diagram has [x] on the horizontal axis and [y] on the vertical. |
x = temperature y = luminosity |
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If we plot many stars in an HR diagram, they appear randomly distributed in the plane T/F |
False |
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Stars move down along the main sequence as they go through their hydrogen-burning lives T/F |
False
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The Main Sequence on an HR diagram looks like:
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a group of stars stretching from high temperature and high luminosity to low temperature and low luminosity |
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White dwarfs on an HR diagram look like: |
a group of stars at low luminosity and high temperature |
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Red Giants on an HR diagram look like: |
group of stars at high luminosity and low temperature |
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The masses of many stars can be determined by applying [x] 's Law to [y] star systems. |
x = kepler y = binary |
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True binary stars in orbit around each other are rare T/F |
False |
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The most accurate star mass measurements require a binary system of which type(s)? |
spectroscopic eclipsing |
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The [x] of a star determines where it lies along the Main Sequence |
x = mass |
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Once identified, Cepheid variable stars allow us to determine their [x] by measuring the [y] of their brightness variations |
x = luminosity y = period |
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Cepheid variables are so bright that they can even be picked out in other nearby galaxies T/F |
True |
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What very interesting number you deduce about another galaxy if you can identify one or more Cepheid variables in it? |
the distance to the galaxy |
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All variable stars are either eclipsing binaries or Cepheid variables T/F |
False |
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The member stars of many star clusters are all about the same age T/F |
True
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Globular clusters are full of hot, young stars (just like Hollywood!) T/F |
False
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For a time, measurements indicated that globular clusters were older than the universe itself T/F |
True |
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When the Sun runs out of hydrogen fuel in its core, hydrostatic equilibrium will be upset and its size will initially do what? |
Shrink |
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Gravitational heating then causes fusion of [x] to begin in a shell outside the core, and eventually fusion of [y] in the core itself. |
x = hydrogen y = helium |
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Next, the large amount of fusion energy released in the shell causes the outer envelope of the star to do what? |
expand to ten times its original size |
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The resulting star is called a(n) [x] |
red giant |
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A planetary nebula then forms because the expanded envelope of the star incinerates its planetary system. T/F |
False |
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For a star with mass similar to that of the Sun, carbon and oxygen never undergo fusion in the core because what phenomonon prevents further collapse? |
electron degeneracy pressure |
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The core of a star with mass similar to that of the Sun is finally left as a(n) [x] dwarf with density about a [y] times the density of normal matter. |
x = white y = million |
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Higher mass stars don't stop with carbon and oxygen cores, but continue fusing carbon and oxygen into higher elements T/F |
True |
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No further fusion can take place after what element is reached? |
Iron |
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The reason fusion stops at the above element (iron) is that: |
further fusion does not release any energy |
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When no further fusion can take place, a supernova explosion can still occur with what as the energy source? |
gravity |
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Just after a supernova explosion, which of the following may be left? |
neutron star black hole shock waves and glowing gas |
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Although theorists are confident they occur, there is no observational evidence for supernova explosions. T/F |
False |
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Although theorists are confident they exist, there is no observational evidence for neutron stars. T/F |
False |
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Black holes are most readily observed when they are the [x] companion in a [y] star system |
x = unseen/invisible y = binary/double/multiple |
