What is at the center of the Milky Way?
A: A supermassive (> 1 million solar masses) black hole
B: A cluster of young, hot stars zooming around
C: The center of the bulge/bar
D: The loud radio source known as Sag A*
E: All of the above
Ans: E: All of the above
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Several surprising discoveries were made as astronomers began detecting exoplanets. Which statement is correct?
A. There are terrestrial planets larger than Earth. B. Gas giants can orbit extremely close to their star. C. Some exoplanets have extremely elliptical orbits. D. All of these choices are correct. E. None of these choices are correct.
Most stars in the Milky Way's halo are
A) very old. B) found inside molecular clouds. C) very young. D) blue or white in color.
Copernicus' Heliocentric theory explains that
A) the Sun lies at one focus of an ellipse. B) all planets lie between the Sun and Earth. C) Mars will retrograde when it reaches a certain position on its epicycle. D) Venus retrogrades when she overtakes us at inferior conjunction. E) planetary orbits are elliptical in shape.
Resistance and Resistivity: A wire of resistivity ? must be replaced in a circuit by a wire of the same material but four times as long. If, however, the total resistance is to remain as before, the diameter of the new wire must
A. be the same as the original diameter. B. be one-half the original diameter. C. be one-fourth the original diameter. D. be two times the original diameter. E. be four times the original diameter.