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Astronomy 100
Chapter 2-The Sky
| Question | Answer |
|---|---|
| The Greek-letter designation indicates a star's | relative brightness and constellation |
| In the constellation Orion, we receive more light from the star Rigel than we do from the star Betelguese. Why does this figure have the alpha and beta designations as shown? | This is one exception to the way in which brightness has been assigned in this system |
| Which statement below most accurately describes modern constellations? | They are 88 well-defined regions on the celestial sphere |
| The precession of Earth's rotational axis causes the location of the | all of the above |
| The apparent visual magnitudes of four stars are listed below. Of these four stars, which one appears dimmest in the sky? | +2.8 |
| At what location on Earth is an observer if the celestial equator passes through the point directly overhead? | At Earth's equator |
| The bowl of the Big Dipper is about 10 degrees wide. Use this figure to determine the angular separation between Polaris and the upper pointer star of the Big Dipper. | About 30 degrees |
| If Earth's rotational period changed to 16 hours, and Earth's shape remained the same, how would this affect Earth's precession? | The precession cycle would be longer than it is now |
| Which of the following is an asterism? | the Big Dipper |
| If the apparent visual magnitude of the sun is -26.5 and that of the full moon is -12.5, what is the approximate light-intensity ratio of sunlight to full moonlight received on Earth? | About 400,000 |
| On a clear, very dark night far from city lights, how many stars are visible to the naked human eye? | A few thousand |
| How many apparent brightness classes did Hipparchus assign to stars? | 6 |
| If the tilt of Earth's axis were to change from 23.5 degrees to 0 degrees, what celestial circles would coincide for all observers? | The celestial equator and the ecliptic |
| At what location on Earth is an observer who has the south celestial pole directly overhead? | At Earth's South Pole |
| From which of the following countries is the north celestial pole never above the horizon? | Australia |
| What is the faintest apparent magnitude that can be detected by the human eye on a clear, very dark night? | 6 |
| The apparent visual magnitude of star A is 2 and the apparent visual magnitude of star B is 1. Based on this information, which statement below must be true? | Light output and distance cannot be determined from a star's apparent visual magnitude alone |
| You observe that the north celestial pole is 42 degrees above the horizon. What does this information tell you? | That your latitude is 42 degrees north |
| Which pair of apparent visual magnitudes listed below indicates that we receive about 16 times as much visible light from star W as we do from star X? | m star W = 2, and m star X = 5 |
| When you observe a star on the celestial equator over a period of a few hours, you notice that it | moves from east to west relative to the horizon |
| The remaining 48 ancient constellations that we still recognize today are located | at mid and northern celestial latitudes |
| From what location on Earth are all constellations circumpolar? | Both North and South Poles |
| What is responsible for the motion described in the previous question? | Earth's rotation on its axis |
| What is the most likely Greek-letter name of the second brightest star in the constellation Lyra? | beta Lyrae |
| Use this figure to determine which constellation will be the nearest to the north point on the horizon 15 hours into the future. | Perseus |
| From what location on Earth are no constellations circumpolar? | The equator |
| Why does Earth's rotational axis precess? | The sun and moon pull on Earth's equatorial bulge |
| If Earth's equatorial bulge was larger and more massive, and Earth's rotation rate remained the same, how would this affect Earth's precession? | The precession cycle would be shorter than it is now |
| In this figure it is apparent that the radius of the precession circle is 23.5 degrees. At what latitude on Earth is the entire precession path currently above the horizon? | At all locations north of 23.5 degrees north latitude |
| Notice in this figure that the magnitude scale is "awkward" in that the smaller, or more negative, magnitude number corresponds to a brighter star. Why does the scale have this "awkward" direction? | The system was originally set up as a set of classes with first class as the brightest |
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