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13 Cards in this Set
- Front
- Back
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Which of these groups of particles has the greatest mass?
a helium nucleus with two protons and two neutrons four electrons four individual protons |
four individual protons
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Which of these layers of the Sun is coolest?
photosphere chromosphere corona |
photosphere
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Which of these layers of the Sun is coolest?
core radiation zone photosphere |
photosphere
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Why do sunspots appear darker than their surroundings?
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They are cooler than their surroundings.
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At the center of the Sun, fusion converts hydrogen into
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helium, energy, and neutrinos.
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Solar energy leaves the core of the Sun in the form of
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photons
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How does the number of neutrinos passing through your body at night compare with the number passing through your body during the day?
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about the same
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All stars are born with the same basic composition, yet stars can look quite different from one another. Which two factors primarily determine the characteristics of a star?
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its mass and its stage of life
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Based on the definition of apparent brightness, which units are appropriate for its measurement?
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Watts are the units of its total luminosity, not the amount of light we receive here on Earth.
Joules are a unit of energy, and when talking about brightness we are more interested in the rate at which energy from the star is reaching Earth. ******Apparent brightness is defined as the power of starlight reaching us per unit area. Power has units of watts and area has units of square meters.******** |
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Star A is identical to Star B, except that Star A is twice as far from us as Star B. Therefore:
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Luminosity is an intrinsic property, so two identical stars will always have the same luminosity. But apparent brightness follows an inverse square law with distance, so the fact that Star A is twice as far away makes it 22 = 4 times dimmer.
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A star with a parallax angle of 1/20 arcsecond is _________.
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This is true because distance in parsecs = 1/(parallax angle in arcsecond). Note that 20 parsecs is equivalent to 20 ( 3.26 = 65.2 light-years.
20 parsecs away |
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The star Vega has an absolute magnitude of about 4 and an apparent magnitude of about 0. Based on the definitions of absolute and apparent magnitude, we can conclude that ______.
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Vega is nearer than 10 parsecs from Earth.
Absolute magnitude is the magnitude it would have if it were a distance of 10 parsecs (32.6 light-years) away. Since its absolute magnitude is larger (meaning dimmer) than its apparent magnitude, the star must be less than 10 parsecs away. |
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Which of the following statements about spectral types of stars is not generally true?
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The spectral type of a star can be used to determine its distance.
Spectral type tells us surface temperature, but to calculate the star's distance we need to know its luminosity and apparent brightness (and then use the inverse square law for light). |
