Astronomy Homework 4

[QUESTION] Listed following are statements that, based on our current theory of solar system formation, apply either to the formation of terrestrial planets or of jovian planets, but not both. Match these to the appropriate category. [1] Terrestrial Planets [2] Jovian Planets [-] accreted from planetesimals of rock and meta [-] large moons formed in surrounding disks of material [-] formed in a region of the solar system with lower orbital speeds [-] accreted from icy planetesimals [-] surfaces dramatically altered during the heavy bombardment [-] ejected icy planetesimals that are now Oort cloud comets [-] formed in regions cold enough for water to freeze

[ANSWER] [1] Terrestrial Planets [-] accreted from planetesimals of rock and meta [-] surfaces dramatically altered during the heavy bombardment [2] Jovian Planets [-] large moons formed in surrounding disks of material [-] formed in a region of the solar system with lower orbital speeds [-] accreted from icy planetesimals [-] ejected icy planetesimals that are now Oort cloud comets [-] formed in regions cold enough for water to freeze

[QUESTION] Provided following are stages that occurred during the formation of our solar system. Rank these stages from left to right based on when they occurred, from first to last. [-] Clearing the solar nebula. [-] Contraction of the solar nebula. [-] Accretion of planetesimals. [-] Large cloud of gas and dust. [-] Condensation of solid particles.

[ANSWER] [First Stage] [-] Large cloud of gas and dust. [-] Contraction of the solar nebula. [-] Condensation of solid particles. [-] Accretion of planetesimals. [-] Clearing the solar nebula. [Last Stage] [EXPLANATION] Once the solar wind helped clear away the remaining gas in the solar nebula, the era of planet formation was essentially over. Remember that all these stages occurred over a period of millions of years, ending about 4 1/2 billion years ago.

[QUESTION] How many Earths could fit inside Jupiter (assuming you could fill up all the volume)? The equation for the volume of a sphere is V=(43)πr3. (The radius of Jupiter is RJupiter = 71492 km.)

[ANSWER] 1410

[QUESTION] How many Jupiters could fit inside the Sun? The equation for the volume of a sphere is V=(43)πr3.

[ANSWER] 919

[QUESTION] The dwarf planet Eris was discovered in 2005, orbiting the Sun at an average distance about twice that of Pluto. In which of the following ways do Pluto and Eris differ from the terrestrial and jovian planets in our solar system? [-] Both Pluto and Eris are smaller than any of the terrestrial planets. [-] Both Pluto and Eris travel in more elliptical orbits than any of the terrestrial or Jovian planets. [-] Both Pluto and Eris are denser than any of the terrestrial planets. [-] Both Pluto and Eris are less massive than any of the terrestrial or Jovian planets. [-] Both Pluto and Eris have more hydrogen gas than any of the Jovian planets.

[ANSWER] [-] Both Pluto and Eris are smaller than any of the terrestrial planets. [-] Both Pluto and Eris travel in more elliptical orbits than any of the terrestrial or Jovian planets. [-] Both Pluto and Eris are less massive than any of the terrestrial or Jovian planets.

[QUESTION] Match the words in the left-hand column to the appropriate blanks in the sentences in the right-hand column. Use each word only once. [WORDS] [-] Jupiter [-] Venus [-] Uranus [-] Mars [-] Neptune [-] Saturn [-] Mercury [-] Earth [1] ______ is about 30 times as far from the Sun as our own planet. [2] ______ is the planet with the highest average surface temperature. [3] The planet with the lowest average density is ______. [4] The planet that orbits closest to the Sun is ______. [5] The only rocky planet to have more than one moon is ______. [6] ______ is the jovian planet that orbits closest to the Sun. [7] ______ has a rotational axis that is tilted so much it lies nearly in the plane of its orbit. [8] Most of the surface of ______ is covered with liquid water.

[ANSWER] [1] Neptune [2] Venus [3] Saturn [4] Mercury [5] Mars [6] Jupiter [7] Uranus [8] Earth

[QUESTION] Leftover ice-rich planetesimals are called [A] Comets. [B] Asteroids. [C] Meteorites

[ANSWER] [A] Comets.

[QUESTION] About how old is the solar system? [A] 4.5 million years [B] 4.5 billion years [C] 4.5 trillion years

[ANSWER] [B] 4.5 billion years

[QUESTION] Which of the following three kinds of objects resides closer to the Sun on average? [A] Comets. [B] Asteroids. [C] Jovian planets.

[ANSWER] [B] Asteroids.

[QUESTION] Our Moon is about the same size as moons of the other terrestrial planets. [A] TRUE [B] FALSE

[ANSWER] [B] FALSE

[QUESTION] The most abundant ingredient of the Sun and Jupiter is: [A] Ionized metal. [B] Hydrogen. [C] Ammonia.

[ANSWER] [B] Hydrogen.

[QUESTION] According to our theory of solar system formation, what are asteroids and comets? [A] Chunks of rock or ice that condensed after the planets and moons finished forming [B] Leftover planetesimals that never accreted into planets [C] The shattered remains of collisions between planets [D] Chunks of rock or ice that were expelled from planets by volcanoes

[ANSWER] [B] Leftover planetesimals that never accreted into planets

[QUESTION] Compared to terrestrial planets, Jovian planets are __________. [A] More massive and higher in average density. [B] More massive and lower in average density. [C] Less massive and lower in average density. [D] Less massive and higher in average density.

[ANSWER] [B] More massive and lower in average density. [EXPLANATION] Note that while jovian planets are lower in average density than terrestrial planets, the densities in their deep interiors are quite high, in some cases higher than the densities found at the centers of the terrestrial worlds.

[QUESTION] Assuming that other planetary systems form in the same way as our solar system formed, where would you expect to find terrestrial planets? [A] Terrestrial planets will likely be located farther from the planetary system's star than any jovian planets. [B] Terrestrial planets will likely be located nearer the planetary system's star than any jovian planets. [C] There is no way to know where terrestrial planets are likely to be.

[ANSWER] [B] Terrestrial planets will likely be located nearer the planetary system's star than any jovian planets. [EXPLANATION] Based on what we find in our own solar system, we expect terrestrial planets to form close to a star and jovian planets to form farther out.

[QUESTION] What is the giant impact hypothesis for the origin of the Moon? [A] The Moon originally was about the same size as Earth, but a giant impact blasted most of it away so that it ended up much smaller than Earth. [B] The Moon formed from material blasted out of Earth's mantle and crust by the impact of a Mars-size object. [C] The Moon formed when two gigantic asteroids collided with one another. [D] The Moon formed just like Earth, from accretion in the solar nebula.

[ANSWER] [B] The Moon formed from material blasted out of Earth's mantle and crust by the impact of a Mars-size object.

[QUESTION] Which lists the major steps of solar system formation in the correct order? [A] collapse, accretion, condensation [B] collapse, condensation, accretion [C] accretion, condensation, collapse

[ANSWER] [B] collapse, condensation, accretion

[QUESTION] Which terrestrial planets have had volcanic activity at some point in their histories? [A] Only Earth. [B] Earth and Mars. [C] All of them.

[ANSWER] [C] All of them.

[QUESTION] The solar nebula was 98 % ... [A] Rock and metal. [B] Hydrogen compounds. [C] Hydrogen and helium.

[ANSWER] [C] Hydrogen and helium.

[QUESTION] According to our theory of solar system formation, what three major changes occurred in the solar nebula as it shrank in size? [A] Its mass, temperature, and density all increased. [B] Its gas clumped up to form the terrestrial planets, nuclear fusion produced heavy elements to make the Jovian planets, and central temperatures rose to more than a trillion Kelvin. [C] It got hotter, its rate of rotation increased, and it flattened into a disk. [D] Its mass did NOT increase.

[ANSWER] [C] It got hotter, its rate of rotation increased, and it flattened into a disk.

[QUESTION] The planet in our solar system with the highest average surface temperature is __________. [A] Mercury [B] Neptune [C] Venus [D] Earth

[ANSWER] [C] Venus

[QUESTION] Which jovian planet does NOT have rings? [A] Neptune. [B] Uranus. [C] Jupiter. [D] All the Jovian planets have rings.

[ANSWER] [D] All the Jovian planets have rings.

[QUESTION] Which planet is approximately halfway between Pluto's orbit and the Sun? [A] Mars, the fourth planet from the Sun. [B] Jupiter, the fifth planet from the Sun. [C] Saturn, the sixth planet from the Sun. [D] Uranus, the seventh planet from the Sun.

[ANSWER] [D] Uranus, the seventh planet from the Sun. [EXPLANATION] Notice that Uranus is located at an average distance of 19.2 AU, which is close to half of Pluto's average distance of 39.5 AU. Many people are surprised to realize that Uranus, the seventh planet from the Sun, is only half as far as Pluto. As you can see in the figure, this surprising fact arises because the outer planets are much more widely spaced than the inner planets.