Astronomy #3 – Flashcards
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What is parallax? A. The distance to an object, measured in parsecs B. The difference between the apparent and absolute magnitude C. The apparent shift in position of an object caused by a change in the observer's position D. The shift in angular position of an object as the object actually moves in space
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C. The apparent shift in position of an object caused by a change in the observer's position
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Parallax measurements of the distances to the nearest stars use ________ as a baseline. A. Earth's orbit B. Earth's diameter C. Earth-Moon distance D. About the length of a football field
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A. Earth's orbit
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The relative brightness of the stars as we see them in our sky is represented by their A. Absolute magnitudes B. Apparent magnitude C. Surface temperature D. Luminosity
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B. Apparent magnitude
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Star A and Star B have same temperatures, but Star A is more luminous than Star B. Based on this information, which of the following must be the case? A. Star A is smaller than Star B B. Star A is larger than Star B C. Star A and Star B have same size D. Star A is more massive than star B
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B. Star A is larger than Star B
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Luminosity (absolute brightness) of a star depends on its _________ A. Temperature B. Radius C. Distance from us D. Both A and B E. Both A and C
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D. Both A and B
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Star A and Star B have the same size, but Star A is more luminous than Star B. Based on this information, which of the following must be the case? A. Star A is cooler than Star B B. Star A is hotter than Star B C. Star A and Star B have the same temperature D. Star A is more massive than Star B
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B. Star A is hotter than Star B
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Which of the following stars has the hottest stellar surface temperature? A. M6 B. A0 C. G5 D. B2 E. K9
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D. B2
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Which of the following stars is reddish in color? A. F6 B. A0 C. G5 D. B2 E. K9
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E. K9
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A star has a parallax angle of 0.2 arcseconds, which means it is a distance of A. 2 parsecs B. 2 light years C. 5 parsecs D 5 light years
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C. 5 parsecs
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80% of ______ type stars have orbiting companions A. O and B B. A and F C. F and G D. K and M
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A. O and B
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In which binary system can we observe both the stars separately and follow their orbits around each other? A. Visual binary system B. Spectroscopic binary system C. Eclipsing binary system
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A. Visual binary system
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The H-R diagram is a diagram plotting the stars according to their A. Apparent brightness and temperature B. Spectral type and temperature C. Brightness and luminosity class D. Luminosity and temperature E. Mass and diameter
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D. Luminosity and temperature
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Which of the following is a main sequence star hotter than the Sun? (Note: the Sun is a G2V star) A. B2II B. G2II C. G2III D. G1V E. O2II
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D. GIV
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The star Aldebaran is cooler and much more luminous than the Sun. Where do you expect to find Aldebaran in the H-R diagram? A. Top left B. Top right C. Center D. Bottom right E. Bottom left
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B. Top right
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How can we explain the fact that hydrogen Balmer lines are essentially absent in the hot O type and the cool M stars? A. O type stars do not contain hydrogen B. In cool stars hydrogen combines to form large molecules C. In O stars hydrogen in ionized and in M stars the electrons of hyrogen are in level 1, not level 2 D. All of the above
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C. In O stars hydrogen is ionized and in M stars the electrons of hydrogen are in level 1, not level 2
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The spectrum of a star shows the 656 nm absorption line shifted to 654 nm. Which of the following can we conclude about this star? A. This star is approaching us with an approximate speed of 1,800 km/sec B. The star is receding with an approximate speed of 1,800 km/sec C. The star is approaching us with an approximate speed of 900 km/sec D. The star is receding with an approximate speed of 900 km/sec E. The star is spinning rapidly
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C. the star is approaching us with an approximate speed of 900 km/sec.
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Binary star systems are very important becaue they allow A. Measurement of star masses B. Measurement of the speed of stars C. More precise measurement of the distance of stars D. More precise measurement of the temperature of stars E. More precise measurement of the spectral of stars
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A. measurement of star masses
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What is the difference between spectroscopic and visual binaries? A. Spectroscopic binaries have double spectral lines but do not move B. Visual binaries are pairs of stars in the same region in the sky but are not gravitationally interacting C. A visual binary does not show changes in the spectral lines D. In a visual binary we can see two distinct stars; in spectroscopic binaries, the images of the two stars can not be resolved
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D. In a visual binary we can see two distinct stars; in spectroscopic binaries, images of the twos stars can not be resolved
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A visual binary star system has rotation period P = 10 years. The semi-major axis of the orbit of one of the stars is 5 AU. What is the combined mass of the binary star system? A. 0.4 solar masses B. 4 solar masses C. 8 solar masses D. 40 solar masses E. 200 solar masses
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C. 8 solar masses
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The study of eclipsing binary stars is very important because it allows astronomers to determine A. The distance between two stars B. The speed of stars is from the Doppler shift of their spectral lines C. The diameters of stars D. The luminosity of each star E. The brightness of each star
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C. The diameters of stars
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Stars on the main sequence have different luminosities because A. They have different chemical compositions B. They have different ages C. They are at different distances from the Sun D. They have different masses E. They have different apparent magnitudes
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D. They have different masses
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If a main sequence, giant, and supergiant all have the same spectral class, what characteristic is known to make these stars different? A. Luminosity B. Distance C. Surface temperature D. Color E. It shows that the more massive stars are cooler
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A. Luminosity
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Which of the following is not true for a pulsating star? A. The surface temperature of a pulsating star changes periodically B. The outer layers of a pulsating star expand and contract periodically C. The luminosity changes periodically D. They are usually members of an eclipsing binary star system E. They show periodic shifts in their spectral lines
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D. They are usually members of an eclipsing binary star system
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What can we conclude about a star because its luminosity varies in an irregular pattern? A. A star is very young B. The star is very old C. The star is rotating D. A or B
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D. A or B
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If the distance between the Earth and a star is measured using parallax measurements, how far apart in time should the two measurements be made to make the parallax measurement as accurate as possible? A. Instantaneously B. A day C. Six months D. A year
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B. A day
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The luminosity of a star is determined by the star's ____ and ____ A. Brightness; temperature B. Apparent brightness; surface temperature C. Diameter; surface temperature D. Distance; surface temperature E. Diameter; distance
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C. Diameter; surface temperature
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A star of apparent magnitude six appears ____ times brighter than a star of apparent magnitude 7 A. 1 B. 2 C. 2.51 D. 1/2 E. 10
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C. 2.51
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Analysis of stellar spectra shows that most stars consist of 71% ____, 27% ____ and a 2% mix of the other elements A. Hydrogen; oxygen B. Hydrogen; helium C. Helium; hydrogen D. Oxygen; nitrogen
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Hydrogen; helium
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Star A is located at the top left of the H-R diagram and has the same luminosity as Star B which is located at the top right of the H-R diagram. How must these stars differ? A. Star A is hotter and bigger than Star B B. Star A is cooler and bigger than Star B C. Star A is hotter and smaller than Star B D. Star A is cooler and smaller than Star B
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C. Star A is hotter and smaller than Star B
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An M type star 1000 times more luminous than the Sun will be located near the ____ part of the H-R diagram A. Top left B. Top right C. Center D. Bottom right E. Bottom left
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B. Top right
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The hydrogen absorption lines are the strongest in ____ type stars A. A B. B C. O D. G
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A. A
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In ____ stars most of the electrons in the hydrogen atoms are above level two and in ____ stars most of the electrons are below level 2, therefore the ____ are essentially absent in both types A. Type M; type O; Balmer lines B. Type O; type M; Balmer lines C. Type A; type; M; emission lines D. Type M; type A; absorption lines
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B. Type O; type M; Balmer lines
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____ binary star systems are important because they allow astronomers to determine the mass and the ____ of stars in the system A. Eclipsing; temperature B. Spectroscopic; diameter C. Spectroscopic; temperature D. Eclipsing; diameter E. Visual; temperature
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D. Eclipsing diameter
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White dwarfs have ____ spectral lines than red giants A. Narrower B. Stronger C. Weaker D. Wider
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D. Wider
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If Star A is twice as far as Star B, and they are identical in all other ways, then the brightness of Star A would be A. One-fourth the brightness of Star B B. One-half the brightness of Star B C. The same brightness of Star B D. Twice the brightness of Star B E. Four times the brightness of Star B
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A. One-fourth the brightness of Star B
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How does Rigel, a bluish star, surface temperature compare to Betelgeuse, a reddish star A. Rigel's surface temperature is less than Betelgeuse's B. Rigel's surface temperature is greater than Betelgeuse's C. They have the same surface temperature because they are both members of the constellation Orion D. It is impossible to say without knowledge of the sizes of the stars
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B. Rigel's surface temperature is greater than Betelgeuse's
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If two stars are stacked vertically in an H-R diagram then they necessarily differ in their A. Distance B. Luminosity class C. Spectral class D. Temperature
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D. Luminosity class
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(T or F) The hottest (O and B type) stars are usually binary stars, while the coolest (M type) stars are usually single stars
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True
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(T or F) Nearby stars have nearby parallax angles, therefore their distance in parsecs is smaller
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True
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(T or F) The luminosity of a star allows astronomers to determine the radius and distance of the star
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True
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(T or F) The apparent magnitude of a star tells us how bright the star would appear if placed at a distance of 10 pc from the Sun
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False
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(T or F) A star with an apparent magnitude of 10 is visible by the naked eye
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False
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One parsec is equal to 3.26 light years
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True
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The sequence OBAFGKM orders the stars in decreasing temperature and decreasing mass
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False
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A star approaching the Earth will show spectral lines that are shifted to longer wavelengths
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False
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The study of eclipsing binary star systems provides information about the radii of stars
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True
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Stars with surface temperatures near 10,000 K have the strongest hydrogen absorption lines in their spectra
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True
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Two stars that have the same absolute magnitude also have the same luminosity
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True
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In the H-R diagram, stars of luminosity class A1 are located near the center
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False
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Stellar luminosities vary much more than stellar masses
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True
