HSU Astronomy Chapter 10 – Flashcards
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A star in the lower left part of the Hertzsprung-Russell diagram, compared to a star in the middle of the diagram, is
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smaller
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An astronomer is measuring the brightness of a particular star through a telescope, using different filters in the visual (yellow-green), violet, and ultraviolet regions. What is the name of the technique being used by this astronomer?
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Photometry
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An object which is too massive to be a planet but not massive enough to be a star is called
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A brown dwarf
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At what stage of its evolutionary life is the Sun?
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Main sequence, middle age.
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If a star is 100 light years away, what is its approximate distance in parsecs?
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30 parsec
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If the surface temperature of a star is very low, which of the following atomic or molecular constituents will produce the most prominent absorption lines in its spectrum?
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TiO
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Spectral types of stars (e.g., O, B, A, F, G, K, M) define uniquely their
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surface temperatures.
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Suppose you observe a previously undiscovered star and find its apparent magnitude. To determine its absolute magnitude you need to know the stars
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distance
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The Hertzsprung-Russell diagram is a plot of
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absolute magnitude (or intrinsic brightness) against temperature of a group of stars.
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The Sun's classification in terms of its surface temperature, as determined from absorption lines in its spectrum, is
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G2
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The absolute magnitude of a star is
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equal to the apparent magnitude if the star is 10 parsecs away.
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The chemical makeup of the Sun's surface can be determined
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by solar spectroscopy.
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The most likely places where stars and planetary systems are forming in the universe are
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in nebulae composed of gas and dust.
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The spectral class of the star Enif is K2, while that of the Sun is G2. Which of the following conclusions can be drawn about Enif from this information?
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It is cooler than the Sun.
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The surface temperature of a nearby star can best be determined from spectral classification by examining
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the pattern of spectral absorption lines from various atoms.
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What is a protostar?
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A small interstellar cloud, before it collapses to become a star.
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What is a red giant?
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A star that is burning hydrogen into helium in a shell around the core.
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What is a white dwarf star?
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A star of about the same size (diameter) as the Earth.
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What is the most abundant element in the universe?
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Hydrogen
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When observed through a set of photometric filters, the brightness of a distant star is seen to be brightest through the ultraviolet filter, less bright through the blue filter, and faintest through the yellow filter. What conclusion can be drawn from this information, assuming no absorption of light between the star and Earth?
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The star has a very high surface temperature.
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Where are the most massive stars to be found in the main sequence of a Hertzsprung-Russell diagram?
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The upper, left end.
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Where on the Hertzsprung-Russell diagram do most local stars in our Universe congregate?
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On the main sequence, where stars are generating energy by fusion reactions.
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Which of the following four spectral classifications represents the coolest stellar surface temperature?
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G4
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Which important stellar parameter can be best determined by observations of binary stars?
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Steller Mass
