Astronomy New for Final – Flashcards
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Where did the elements heavier than hydrogen and helium come from?
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They were produced inside stars
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Why did the solar nebula heat up as it collapsed?
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As the cloud shrank, its gravitational potential energy was converted into kinetic energy and then into thermal energy
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Why did the solar nebula flatten into a disk?
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It flattened as a natural consequence of collisions between particles in the nebula, changing random motions into more orderly ones
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What happened during the accretion phase of the early solar system?
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Particles grew by colliding and sticking together
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According to our theory of solar system formation, why do all the planets orbit the sun in the same direction and in nearly the same plane?
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The laws of conservation of energy and conservation of angular momentum ensure that any rotating object, collapsing cloud will end up as a spinning disk
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What percentage of the solar nebulas mass consisted of hydrogen and helium gases?
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98 percent
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Why are the inner planets made of denser materials than the outer planets?
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In the inner part of the nebula only metals and rocks were able to condense because of the high temperatures, where as hydrogen compounds, although more abundant, were only able to condense in the cooler outer regions
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At first, the Sun's only present-day rotation seems to contradict the prediction of the nebular theory because
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the theory predicts that the Sun should have been rotating fast when it formed, but the actual rotation is fairly slow
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According to our theory of solar system formation, why does the Sun rotate slowly today?
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The Sun once rotated much faster, but it transferred angular momentum to charged particles caught in its magnetic field and then blew the particles away with its strong solar wind
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According to the nebular theory, how did the Oort cloud form?
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It is made of planetismals formed in the outer solar system that were flung into distant orbits by encounters with the jovian planets
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According to the nebular theory, what are asteroids and comets?
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They are leftover planetismals that never accreted into planets
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What is the most likely reason that there are no giant planets beyond Neptune?
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By the time planetismals grew to large enough mass to hold onto an atmosphere, the solar nebula had been blown away
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Which of the following is the origen of almost all the large moons around the jovian planets?
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They were formed by condensation and accretion in a disk of gas around the planet
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The nebular theory of the formation of the solar system successfully predicts all but one of the following. Which one does the theory not predict?
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the equal number of terrestrial and jovian planets
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Suppose you find a rock that contains some potassium-40 (half life of 1.3 billion years). You measure the amount and determine that there are 5 grams of potassium-40 in the rock. By measuring the amount of its decay product (argon-40) present in the rock, you realize that there must have been 40 grams of potassium -40 when the rock solidified. How old is the rock?
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3.9 billion years
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The age of our solar system is approximately
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4.6 billions years
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Which of the following is not evidence supporting the giant impact theory for the formation of the Moon?
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Scientists have found several meteorites that appear to be the remains of the object that caused the giant impact
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According to our theory of solar system formation, why do we find some exceptions to the general rules and patterns of the planets?
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Most of the exceptions are the results of giant impacts
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According to the nebular theory, how did the Kuiper belt form?
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It is made of planetismals that formed beyond Neptune's orbit and never accreted to form a planet
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What kind of material in the solar nebula could remain solid at temperatures as high as 1500 K, such as existed in the inner regions of the nebula?
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Metals
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Rank the five terrestrial in order from size smallest to largest
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Moon, Mercury, Mars, Venus, Earth
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What is differentiation in planetary geography?
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The process by which gravity separates materials according to density
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Under what circumstances can differentiation occur in a planet?
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The planet must have a molten interior
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The terrestrial planet cores contain mostly metal because
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metals sank to the center during a time when the interiors were molten throughout
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Which internal energy source is the most important in continuing to heat the terrestrial planets today
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radioactivity
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Heat escapes from a planet's surface into space by thermal radiation. Planets radiate almost entirely in the wavelength range of the
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infrared
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Which of the following best describes why the smaller terrestrial worlds have cooler interiors than the larger ones?
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They have relatively more surface area compared to their volumes
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Why does Earth have the strongest magnetic field among the terrestrial worlds/
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It is the only one that has a partially molten metallic core and reasonably rapid rotation.
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Which of the following most likely explains why Venus does not have a strong magnetic field?
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It's rotation is too slow
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Which two properties are most important in determining the surface temperature of a planet?
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Distance from the sun and astmosphere
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Which of the following does not have a major effect in shaping planetary surfaces?
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Magnetism
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The relatively few craters that we see within the lunar maria
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were formed by impacts that occurred after those that formed most of the craters in the lunar highlands
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When we see a region of a planet that is not as heavily cratered as other regions, we conclude that
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the surface in the region is younger than the surface in more heavily cratered regions
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Volcanism is more likely on a planet that
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has high internal temperatures
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Shallow-sloped shield volcanoes are made from lava that
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has a medium viscosity
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Streep-sided stratovolcanoes are made from lava that
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has a high viscosity
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Which of the following describes tectonics?
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the disruption of a planets surface by internal stresses
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Which of the following best describes erosion?
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the wearing down or building up of geological features by wind, water, ice and other phenomena of planetary weather
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Which of the following describes volcanism?
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the eruption of molten rock from a planets interior to its surface
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Which of the following describes impact cratering
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the excavation of bowl-shaped depressions by asteroids or comets striking a planets surface
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How did the lunar maria form?
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Large impacts fractured the moons lithosphere, allowing lava to fill the impact basins
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The Caloris Basin on Mercury covers a large region of the planet, but few smaller craters have formed on top of it. From this we conclude that
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The Caloris Basin formed toward the end of the solar systems period of heavy bombardment
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Why do we think Mercury has so many tremendous cliffs?
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They were probably formed by tectonic stresses when the entire planet shrank as its core cooled
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Which of the following show evidence of ancient river beds?
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Mars
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What drives the motion of tectonic plates on Earth?
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convection cells in the mantle
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Which of the following correctly describes the meaning of albedo?
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The higher the albedo, the more light the surface reflects and the less it absorbs
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Which of the following worlds has the most substantial atmosphere?
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Venus
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Which of the following worlds has the least substantial atmosphere?
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Mercury
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Why does Venus have such a great difference in temperature between its "no atmosphere" temperature and its actual temperature?
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It has a large amount of greenhouse gases in its atmosphere
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What are greenhouse gases?
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gases that absorb infrared light
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How does the greenhouse effect work?
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Greenhouse gases transmit visible light, allowing it to heat the surface, but then absorb infrared light from Earth, trapping the heat near the surface
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What is the exosphere?
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The highest layer in the atmosphere
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What is the troposphere?
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the lowest layer in the atmosphere
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The sky is blue because?
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molecules scatter blue light more effectively than red light
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Sunsets are red because
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sunlight must pass through more atmosphere then, and the atmosphere scatters even more light at bluer wavelengths, transmitting mostly red light
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Radio communication between distant places on Earth is possible because the
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ionosphere reflects radio signals
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There are no aurora on Venus because it
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lacks a strong magnetic field
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What is the difference in meaning between the terms weather and climate?
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Weather refers to short term variations in conditions, and climate refers to long term variations in conditions
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The strength of the Coriolis effect depends on
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a planets size and rotation rate
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Why doesn't Venus have seasons like Mars and Earth do?
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Its rotation axis is not tilted
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Where is most of the water on Mars?
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in its polar caps and subsurface ground ice
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Why isn't Earth's atmosphere mostly hydrogen?
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Light gases such as hydrogen move faster than heavier gases and escape from Earth's gravitational field
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Why does the burning of fossil fuels increase the greenhouse effect on Earth?
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Burning releases carbon dioxide into the atmosphere
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What are oxidation reactions?
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reactions that remove oxygen from the atmosphere, such as fire and rust
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What are fossil fuels?
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the carbon rich remains of plants that died millions of years ago
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What is differential rotation?
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rotation where a body rotates faster or slower at its equator than it does at its poles
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Why do jovian planets bulge around the equator, that is have a "squashed" appearance?
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their rapid rotation flings the mass near the equator outward
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Which of the following does not yield information of jovian planet interiors
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spectroscopy of the cloud layers
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Why is Jupiter denser than Saturn?
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The extra mass of Jupiter compresses its interior to a greater extent than that of Saturn
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Why is Neptune denser than Saturn?
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It has a different composition than Saturn, including a higher proportion of hydrogen compounds and rocks
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How do the jovian planet interiors differ/
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All have cores of about the same mass, but differ in the amount of surrounding hydrogen and helium
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The belts and zones of Jupiter are
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alternating bands of rising and falling air at different latitudes
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What is Jupiter's Great Red Spot?
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a long lived, high pressure storm
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Why do Uranus and Neptune have blue methane clouds but Jupiter and Saturn do not?
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Methane does not condense into ice in the warmer atmospheric temperatures of Jupiter and Saturn
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The four Galilean moons around Jupiter are
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a mixture of rock and ice, with the ice fraction increasing with distance from Jupiter
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Why are there no impact craters on the surface of Io?
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Io did have impact craters but they have all been buried in lava flows
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The fact that most moons always show the same face to their planet is
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a natural consequence of tidal forces acting on the moons
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What is the most important reason why an icy moon is more likely to be geologically active than a rocky moon of the same size?
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Ice has a lower melting point than a rock
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Why do astronomers believe Triton may have been a planet that was captured by Neptune?
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It orbits Neptune in the opposite direction of Neptune's rotation
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Why are Saturn's rings so thin?
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Any particle in the ring with an orbital tilt would collide with other ring particles, flattening its orbit
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Planetary rings are
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all of the above
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Which of the jovian planets have rings?
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all of the above
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Which previously unknown planets location was predicted from mathematical calculation of orbital motions?
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Neptune
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Which of the following planets cannot be seen with the naked eye?
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Neptune
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Which moon has the most substantial atmosphere?
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Titan
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How big is the largest asteroid?
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about 1000 km in diameter
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What is the average distance between asteroids in the asteroid belt?
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1,000,000 km
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Why didn't the material in the asteroid belt form a planet?
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Orbital resonances with Jupiter disrupted the orbits of the asteroids and prevented them from forming a planet
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What are the Trojan asteroids?
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They are asteroids in the 1:1 resonance with Jupiter in Jupiter's orbit
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Why are most meteorites found in Antarctica?
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Meteorites are dark and easy to spot against the ice in Antarctica
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What are the most common types of meteorites?
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stony primitive meteorites
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What is the orientation of a comets plasma tail?
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The plasma tail extends from the nucleus in the opposite direction of the sun
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What produces meteor showers?
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Meteor showers are caused by the passage of Earth through the debris left by a comet in it's orbit
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Comets are often described as
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dirty snowballs
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Where do the Kuiper belt comets come from?
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The formed in the Kuiper belt
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How is Pluto different from other objects in the Kuiper belt?
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none of these
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What is a dwarf planet/
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A dwarf planet is any object orbiting the Sun that is large enough to be round but not one of the eight planets
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What is the largest dwarf planet discovered to date?
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Eris
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What is Comet SL9?
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It is a comet that was seen crashing into Jupiter
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Which of the following is not evidence for a large impact on Earth 65 million years ago?
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globally distributed meteorites with a radiometric age of 65 million years
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How large was the object that caused the Tunguska impact?
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about 40 m across
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How often does an impact large enough to cause tsunamis and widespread devastation strike Earth?
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about once in a million years
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How would the impact history on Earth have been different if Jupiter didn't exist?
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There would be more impacts from comets and fewer from asteroids
