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1 | | A white dwarf is about the size of |
| | A) | the Sun |
| | B) | the Earth |
| | C) | a small city |
| | D) | a basketball |
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2 | | A white dwarf forms when |
| | A) | the shell of a planetary nebula expands and dissipates, leaving behind the dead core of a red giant. |
| | B) | a massive star is destroyed in a supernova explosion, leaving behind a collapsed core made of neutrons. |
| | C) | an interstellar cloud collapses and starts burning hydrogen. |
| | D) | the helium fusion reactions in the core of a red giant experience a thermal runaway. |
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3 | | What would you think if someone claimed that they had discovered a 10 solar mass white dwarf? |
| | A) | That the white dwarf would be emitting X-rays. |
| | B) | That the person had made a mistake, as white dwarf stars cannot have less than 20 solar masses |
| | C) | That the person did not know what they were talking about due to the Chandrasekhar limit. |
| | D) | That such a white dwarf should have a red giant. |
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4 | | What is “degeneracy” pressure? |
| | A) | It is similar to gas pressure, but only affects protons. |
| | B) | It is pressure caused by the electrostatic repulsion of positrons. |
| | C) | The exclusion principle limits the number of electrons that can be put into a given volume, creating a pressure. |
| | D) | It is a pressure caused when atoms bounce of each other in a gas. |
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5 | | What happens if mass is added to a white dwarf (as from a nearby star)? |
| | A) | Its radius decreases. |
| | B) | Its density increases. |
| | C) | It may exceed the Chandrasekhar limit and collapse. |
| | D) | All of the above. |
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6 | | A neutron star is about the size of? |
| | A) | the Sun |
| | B) | the Earth |
| | C) | a small city |
| | D) | a basketball |
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7 | | A neutron star can form when |
| | A) | the shell of a planetary nebula expands and dissipates, leaving behind the dead core of a red giant. |
| | B) | a massive star is destroyed in a supernova explosion, leaving behind a collapsed core made of neutrons. |
| | C) | an interstellar cloud collapses and starts burning hydrogen. |
| | D) | the helium fusion reactions in the core of a red giant experience a thermal runaway. |
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8 | | What is a pulsar? |
| | A) | A rotating neutron star that emits radio waves in a narrow beam. |
| | B) | A star whose luminosity changes as it swells and shrinks rhythmically. |
| | C) | A star whose mass changes as it comes into contact with another star. |
| | D) | A planetary nebula. |
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9 | | Are all neutron stars pulsars? Are all pulsars neutron stars? |
| | A) | Yes; yes. |
| | B) | Yes; no. |
| | C) | No; yes |
| | D) | No; no. |
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10 | | Remember the principle of conservation of angular momentum? What happens to its angular momentum (L), and velocity as a star's radius (R) shrinks? The L _____ and the V _______. |
| | A) | decreases; stays the same |
| | B) | increases; stays the same |
| | C) | stays the same; decreases |
| | D) | stays the same; increases |
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11 | | What creates the beams of radiation seen in pulsars? |
| | A) | Charged particles ripped off the surface of a neutron star spiral around its magnetic field lines. This acceleration causes them to radiate. |
| | B) | The surface of a neutron star pulsates, throwing off waves of radiation. |
| | C) | Pulsars radiate just like main-sequence stars. |
| | D) | Pulsars do not radiate, because not even light can escape their strong gravity. |
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12 | | What is a black hole? |
| | A) | A white dwarf that no longer radiates light. |
| | B) | The collapsed core of a very massive star whose gravitational force is so great that not even light can escape it. |
| | C) | A very deep lunar crater. |
| | D) | The burned-out remnant of a low-mass star. |
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13 | | What evidence do astronomers have of black holes? |
| | A) | They have seen tiny dark spots drift across the face of some distant stars. |
| | B) | X-rays, perhaps from gas around a black hole, have been seen to disappear as a companion star eclipses the hole. |
| | C) | They have seen a star suddenly disappear as it became a black hole. |
| | D) | They have looked into a black hole with x-ray radar telescopes. |
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14 | | What is the Schwarzschild radius of a body? It is |
| | A) | the distance from its center at which nuclear fusion ceases. |
| | B) | the distance from its surface at which an orbiting companion will be broken apart. |
| | C) | the maximum radius a neutron star can have before it collapses. |
| | D) | the distance from body at which its escape velocity equals the speed of light. |
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15 | | What is the approximate Schwarzschild radius of a 10 solar mass black hole? |
| | A) | 0.3 km. |
| | B) | 3 km. |
| | C) | 30 km |
| | D) | 300 km |
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