astro final 2

astro final 2 - 1. A binary star system has an orbital...

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1. A binary star system has an orbital period of 1 year. It is most likely that this system would be observed to be (a) a visual binary. (b) a spectroscopic binary. (c) an eclipsing binary. (d) a wide binary. (e) a close binary. 2. In a certain eclipsing binary system, primary minimum occurs when star X is eclipsed by star Y. What can we say about the temperatures of the two stars? (a) star X is hotter than star Y. (b) star X is cooler than star Y. (c) stars X and Y are the same temperature. (d) not enough information given, need to know the size of each star. (e) not enough information given, need to know the luminosity of each star. 3. Mass exchange in close binary systems can produce (a) X-ray emission from an accretion disk. (b) recurrent novae if one partner is a white dwarf. (c) modification of the evolutionary status of both stars. (d) some (but not all) of the three responses is correct. (e) all of the three responses is correct. 4. Observations of a binary star system show that the orbital period is increasing. Astronomers conclude that (a) the more massive star is transferring matter to the less massive star. (b) the less massive star is transferring matter to the more massive star. (c) both stars are gaining mass from the interstellar medium. (d) one of the stars is going to explode as a type Ia supernova. (e) one of the stars is a compact object (a white dwarf, neutron star, or black hole). 5. The explosive burning of hydrogen on the surface of a white dwarf produces (a) a type Ia supernova. (b) a pulsar. (c) an X-ray burster. (d) a nova. (e) a millisecond pulsar. 6. When a black hole is part of a close binary star system, the system may be a strong source of X-rays. Where do the X-rays come from? (a) the companion star, which is heated by the black hole. (b) from the black hole itself. (c) from planets which are captured by the black hole. (d) from infalling matter that heats up when it strikes the black hole at the Schwarzschild radius. (e) a disk of hot matter around the black hole. 7. The 21-centimeter line of atomic hydrogen (a) is strongly absorbed by dust. (b) provides the ONLY evidence that our Sun orbits the center of the Galaxy. (c) is emitted primarily by the hot gas in the dark halo of our Galaxy. (d) has been only rarely observed by radio astronomers. (e) is our best tool for mapping the structure and rotation of our Galaxy.
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8. The hydrogen in an H II region is mostly (a) in molecular form. (b) ionized. (c) neutral. (d) excited. (e) tied up in dust particles. 9. What kind of object creates an evacuated, very hot bubble in the interstellar gas? (a) a red giant star. (b) a black hole. (c) a supernova. (d) a globular cluster. (e) a reflection nebula. 10. When our Galaxy is mapped using star counts, absorption by dust makes the Galaxy appear
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astro final 2 - 1. A binary star system has an orbital...

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