Astro 100 Spring 2019 Midterm 2n PDF

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Midterm #2 Astronomy 100 – Prof. Vahé Peroomian Spring Semester 2019 – March 7, 2019 Each of the 50 questions is worth 2 points. Please circle the correct answers below. The terrestrial planet cores contain mostly metal because B) the entire planets are made mostly of metal. C) metals condensed first in the solar nebula and the rocks then accreted around them. D) radioactivity created metals in the core from the decay of uranium. E) convection carried the metals to the core. 2) The core, mantle, and crust of a planet primarily have differences in their A) geological activity. B) color. C) strength. 3) Which of the following best describes convection? A) It is the process by which rocks sink in water. C) It is the process in which warm material gets even warmer and cool material gets even cooler. D) It is the process in which a liquid separates according to density, such as oil and water separating in a jar. E) It is the process in which bubbles of gas move upward through a liquid. 4) The two principal sources for the internal heating of terrestrial planets are A) convection and accretion. C) accretion and eruption. E) radiation and convection. 5) Which of the following has virtually no effect on the internal structure of a planet? A) its composition D) its mass The relatively few craters that we see within the lunar maria B) were formed by impacts that occurred before those that formed most of the craters in the lunar highlands. C) were created by the same large impactor that led to the formation of the maria. D) are volcanic in origin, rather than from impacts. E) are sinkholes that formed when sections of the maria collapsed.

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7) A planet is most likely to have tectonic activity if it has A) low surface gravity. B) high surface gravity. C) low internal temperature. E) a dense atmosphere. Why do we think Mercury has so many tremendous cliffs? A) They were probably carved in Mercury's early history by running water. C) They probably formed when a series of large impacts hit Mercury. D) They are probably volcanic in origin, carved by flowing lava. E) They were probably formed by convection occurring in Mercury's mantle. 9) How have we been able to construct detailed maps of surface features on Venus? A) by studying Venus from Earth with powerful telescopes B) by studying Venus with powerful telescopes on spacecraft that were sent to orbit Venus C) by making computer models of geological processes on Venus E) by landing spacecraft on the surface for close-up study 10) Spacecraft have landed on all the terrestrial worlds except C) Moon. D) Mars. 11) Which of the following gases best absorbs ultraviolet light? A) carbon dioxide B) nitrogen C) oxygen

12) Earth's atmosphere contains only small amounts of carbon dioxide because A) the Earth's volcanoes did not outgas as much carbon dioxide as those on Venus and Mars. B) most of the carbon dioxide was lost during the age of bombardment. C) chemical reactions with other gases destroyed the carbon dioxide and replaced it with the nitrogen that is in the atmosphere now. E) Earth doesn't have as strong a greenhouse effect as is present on Venus. 13) Which of the jovian planets have rings? A) Jupiter B) Saturn C) Uranus D) Neptune

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14) Why are Saturn's rings so thin? A) Saturn's gravity prevents particles from migrating upwards out of the rings. B) The "gap" moons shepherd the particles and maintain its thin profile. D) Solar radiation pressure keeps particles pressed into the rings. E) The current thinness is a short-lived phenomenon that is special to this time. 15) The photo on the right shows B) The Caloris Basin on Mercury C) Maxwell Montes on Venus D) The Grand Canyon on Earth 16) Which of the following statements about Titan is not true? A) It may have oceans of liquid methane. B) Its atmosphere is mostly nitrogen. C) Its temperature is too cold for liquid water to exist. D) Its surface is hidden from view by its thick atmosphere. 17) Which of the following is not due to tidal forces? A) the synchronous rotation of the Moon around Earth B) the volcanos on Io C) the synchronous rotation of the Galilean moons

18) How do the jovian planet interiors differ from one another? B) The core mass decreases with the mass of the planet. C) The composition changes from mostly ammonia in Jupiter and Saturn to mostly methane in Uranus and Neptune. E) All have about the same amount of hydrogen and helium but the proportion of rocks is greater in those planets closer to the Sun. 19) Jupiter and the other jovian planets are sometimes called "gas giants." In what sense is this term misleading? A) They are not in any sense "giants." D) Actually, it's a great description, because these worlds are big and gaseous throughout. 20) Which of the following is not a general characteristic of the four jovian planets in our solar system? A) They are much more massive then any of the terrestrial planets. C) They lack solid surfaces. !

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21) Which of the following applies to Europa? A) the most volcanically active body in the solar system C) probably a captured Kuiper Belt object D) the only moon of a jovian planet with an atmosphere thicker than Earth's atmosphere The first person to claim to see linear features on the surface of Mars was A) Angelo Secchi B) Percival Lowell D) William Herschel 23) The atmosphere of Mars is made mostly of A) nitrogen C) hydrocarbons D) ammonia 24) Seasons on Mars B) are exactly the same at the Earth D) are similar to those on the Earth but half as long 25) What do asteroids and comets have in common? B) They have similar densities. C) They have similar orbital radii. E) They have nothing in common with each other. 26) Why do asteroids and comets differ in composition? A) Asteroids and comets formed at different times. B) Comets formed from the jovian nebula, while asteroids did not. C) Comets are much larger than asteroids. E) Asteroids are much larger than comets. Where are the Trojan asteroids located? A) in orbits around Jupiter C) in the center of the asteroid belt D) in orbits that cross Earth's orbit E) in orbits that cross Mars's orbit 28) Using the transit method, how many times must a dip in the brightness of a star be observed before it can qualify as an actual planet detection? A) 1 time B) 2 times E) 5 times !

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29) What causes the "gaps" observed in the asteroid belt between Mars and Jupiter? A) There are very few asteroids with diameters between 1 and 100 kilometers, creating a gap in the size distribution. B) Asteroids cluster together due to their mutual gravity and this creates gaps in their distribution. D) There is a large population of asteroids too faint to see called the "gap" asteroids. E) There are either pure metal or pure rock asteroids, but no mixtures. Thus there is a "gap" in the composition of asteroids. 30) Which photo shows an object that looks most like a typical asteroid?

31) According to the nebular theory, how did the asteroid belt form? A) It is material left over from the interstellar cloud that never contracted with the rest of the gases to form the solar nebula. B) It is made of planetesimals that formed beyond Neptune's orbit and never accreted to form a planet. C) It consists of objects that fragmented from the protosun during a catastrophic collision early in the formation of the solar system. E) It is made of planetesimals formed in the outer solar system that were flung into distant orbits by encounters with the jovian planets. The graph on the right shows how a star's orbital speed varies with time due to the gravitational tug of an orbiting planet. These data were obtained by measuring __________. A) the precise brightness of the star divided by the precise brightness of the planet C) the orbital period of the planet that is orbiting the star D) the precise wavelengths of spectral lines in the spectrum of the orbiting planet

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33) The depth of the dip in a star's brightness due to the transit of a planet depends most directly on B) the planet's density. D) the size of the planet's orbit. E) the eccentricity of the planet's orbit. 34) What must be true about the orbit of a planet discovered by the transit method? B) The planet must be closer to its star than Mercury is to the Sun. C) As seen from Earth, the planet's orbit must be nearly perpendicular to our line of sight. D) The planet's orbit must be very close to circular. E) The planet's orbit must be very eccentric. 35) The planet COROT-14b is only slightly larger than Jupiter, but is several times more massive. Which is the most plausible explanation for its similar size to Jupiter? A) The mass measurement is mistaken, and it is actually about 10 times more massive than Jupiter. B) Planets that are close to a star are puffed up and therefore larger. C) It is made of elements other than hydrogen and helium which do not compress under their own gravity.

36) How do we think the "hot Jupiters" around other stars were formed? A) They formed as gas giants close to the star in the same orbits that they are seen today. B) They formed as dense, rocky planets close to the star in the same orbits that they are seen today. D) Many planets were formed around the star but coalesced into a single planet close in. 37) Direct detection of an extrasolar planet means ________. B) sending a space probe to the planet C) observing the planet's effect on its host star D) seeing the planet with the naked eye 38) A star is seen to have two transiting planets. Planet 1 transits every 3 months, and Planet 2 transits every 15 months. What can we infer about their orbits? A) Planet 1's semimajor axis is larger than Planet 2's. C) Planet 2's orbit is more eccentric than Planet 1's. D) Planet 1's orbit is more eccentric than Planet 2's. 39) The graph on the right shows the brightness of a star over the course of a transit. Which of the following do we learn about the planet? B) It is about 97.5% as bright as its star. C) It is about 2.5% as massive as the star. D) It has an orbital period of less than 2 hours.

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In order to be able to directly see the Sun's motion due to Jupiter's gravity, an observer at a distance of 10 light-years would need to be able to measure changes in its position of ________. A) 0.5 arcsecond B) 0.05 arcsecond C) 0.005 arcsecond 41) Which of the following is the phase of matter in the interior of the Sun? A) gas C) liquid D) solid E) a mixture of all of the above 42) Sunspots are cooler than the surrounding gas in the photosphere because A) they are regions where convection carries cooler material downward. C) magnetic fields trap ionized gases that absorb light. D) there is less fusion occurring there. 43) By what process does the Sun generate energy? B) nuclear fission C) chemical reactions D) gravitational contraction E) gradual expansion 44) Which of the following is not a method astronomers use to determine the physical conditions inside the Sun? A) building mathematical models that use the laws of physics B) detecting solar neutrinos generated in the Sun's core C) measuring Doppler shifts to observe solar vibrations 45) Imagine that you are trying to stop neutrinos with a lead shield. How thick would you need to make this shield to ensure that it can stop an average neutrino? B) about 700,000 kilometers (the radius of the Sun) C) about 150 million kilometers (the size of an astronomical unit) E) about 14 billion light-years (the size of the observable universe) 46) The light radiated from the Sun's surface reaches Earth in about 8 minutes. However, the energy of this light was released by fusion in the Sun's core about B) 11 years ago. C) several hundred years ago. D) several thousand years ago.

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Study the figure above and its axis labels. What is this graph showing us? A) The Sun pulsates much like a beating heart, but with each beat taking about a decade. B) The intensity of Sunlight varies significantly over time, and reached an unusually high peak around 1960. D) The latitude at which sunspots appear varies between 0 and 0.5 degrees. What observations characterize solar maximum? A) The Sun becomes much brighter. B) The Sun emits light of longer average wavelength. C) The Sun rotates faster at its poles. E) all of the above 49) What two physical processes balance each other to create the condition known as gravitational equilibrium in stars? A) the strong force and the weak force C) gravitational force and surface tension D) the strong force and the electromagnetic force 50) What is the solar wind? B) the uppermost layer of the Sun, lying just above the corona C) the strong wind that blows sunspots around on the surface of the Sun D) the wind that causes huge arcs of gas to rise above the Sun's surface

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