Exam 1 Study Guide

EAPS 105, The Planets Exam 1 Study Guide Know the following: Unit 1: Solar System Origins 1. The percent of the Solar System’s mass contained in the Sun.  99.9% of solar system’s mass is in the Sun 2. The percent of the mass of our Solar System’s planets contained in Jupiter.  70% of mass of the planets is in Jupiter 3. What is an astronomical unit (AU).  The distance from the Sun to the Earth (150 million km) 4. The distance from the Sun that Jupiter is compared to Earth (in AU).  Jupiter is 5 AU and Earth is 1 AU from the sun 5. Whether the distance from the Earth to the Moon is changing.  The moon is moving away from the Earth at 4cm/year 6. What most of the objects that you can see in the night sky with your naked eye are.  Stars are the most visible thing you can see 7. Where the first helium atoms originated from.  The high pressure and temperature of the early universe caused hydrogen ions to fuse (fusion) into helium 8. Why fusion produces heat.  The lost mass is converted to energy (heat and light) 9. The difference between hydrogen ions and molecular hydrogen.  Hydrogen ion – protons; molecular hydrogen – cooled hydrogen ions (give off no light) 10. Why nuclear fusion produces heat and light.  The mass of the helium plus neutron that results from fusion has less mass than the original two hydrogen atoms, and that lost mass is converted into energy 11. What the James Webb telescope focused on to create the Deep Field image.  It focused on the darkest path of sky to what was there. 12. The elements fused within a low-mass star like the Sun.  Hydrogen fuses to helium, helium fuses to beryllium, helium and beryllium fuse to carbon, then helium and carbon fuse to oxygen 13. The two forces that maintain balance within a star.  Gravity and fusion 14. The fate of the core within a low-mass star like our Sun when fusion begins to shut down.  Inner regions will collapse into a white dwarf 15. The fate of the outer regions of a low-mass star when fusion begins to shut down.  Expansion of outer regions cause them to disperse non-violently into space (outgassing) 16. Why the emitted light of dying stars is redder.  Cooler temperatures cause the star’s light to shift into the redder part of the spectrum, the star expands and becomes redder. 17. What planetary nebulae are.  Relatively small gas clouds of ionized hydrogen (they glow, but are not planets) 18. The fate of our Sun.  It will become a white dwarf 19. The fate of the largest stars.  They will become a neutron star or black hole 20. How mass affects the longevity of stars.  Mass is density -> smaller stars live longer because they burn fuel very slowly 1

21. Characteristic of a red dwarf stars.  Low mass and coolest, have a red appearance, make up 75% of all stars, live for a trillion years, best stars to look for extraterrestrial life on orbiting planets 22. The heaviest element that can be fused in the core of a high mass star.  Iron 23. Why supernovas occur.  When fusion ceases in a massive star the core collapses extremely fast and causes a shock wave of high pressure that causes the outer part of the star to explode 24. What supernovas do that fusion in the cores of stars cannot.  They cause the fusion of elements heavier than iron 25. The processes that can generate a supernova.  1) white swarf accretes material and then it compresses, heats up, and explodes 2) collision of two neutron stars 26. Why low mass stars have heavy elements.  They inherited them from previous supernovas 27. Where the atoms in your body come from (generally, not specifically).  Remnants of stars 28. The correct sequence of the Solar Nebula Hypothesis (start anywhere in the cycle)  Dense cloud -> accretion disk -> stellar system -> mass loss -> diffuse cloud 29. The source of material in current nebula.  From supernova remnants 30. Where stars are born.  Clumps within molecular clouds contract to generate pressures sufficient to initiate the fusion of hydrogen into helium, giving off light and heat 31. The type of nebula comprised of hot hydrogen ions (H+) that glow.  Emissions nebulas 32. How the force of gravity between two objects is affected by their distance.  The closer objects get, the greater the gravitational force 33. Why nebula clumps contract.  Because of gravity, but angular momentum causes the clumps to spin more rapidly as they contract 34. How concentrating the mass of a rotating object influences its rotation rate.  Clumps with small radius spin faster (more density = faster spin) 35. What an accretionary disc is.  New stars surrounded by a spinning disc of gas, this is where planets form 36. Why already spinning nebula clumps flatten into accretionary discs.  The law of gravity make them contract into stars, then the collision of objects perpendicular to the plane of rotation make the disc flat Unit 2: Planet Formation 37. What meteoroids are.  Small rocks traveling through space that haven’t reached Earth’s atmosphere 38. What meteors are.  Small rocks from space that light up the night sky as they burn up in Earth’s atmosphere 39. What meteorites are.  Small pieces of rock that survive passage through the atmosphere to be picked up on the surface 40. Why a fusion crust forms on a meteorite.  From the melting caused when a meteor passes through the atmosphere 41. The easiest place to find meteorites.  Antarctica because flowing glaciers collect and deposit them 2

 The cores of the ice giants did not grow fast enough to attract a large amount of hydrogen and helium, so the cores are much more massive than they appear because they are highly compressed 60. The characteristics of an accretionary disc that increase with distance from the Sun.  The availability of mass to build planets (material to accrete) increases with distance from the sun 61. Why gas giants need to form in the first 3-10 million years of the Solar System.  Because solar wind pushes hydrogen and helium out of the accretionary disc once the star is 3-10 million years old 62. Why the cores of Uranus and Neptune grew slower than that of Saturn and Jupiter.  Either: collisions between objects happened less frequently in the larger volume of larger orbits, less material available because density of accretion disc dropped off very rapidly beyond Saturn, or Jupiter/Saturn captured and ejected material from the orbits of Uranus and Neptune, stunting their growth 63. Why Uranus and Neptune are called Ice Giants.  They collected a lot of ices to develop large, icy mantles. Their mantles are comprised of very hot liquid water, ammonia, methane, and other volatiles 64. Uranus' original name for 70 years.  George 65. Why Ceres is a sphere.  Because it is so big, gravity was strong enough to overcome the strength of rock and ice and pulled Ceres’ body into a sphere 66. Why Haumea is an oblate spheroid.  It rotates so fast that inertia causes it to be very elongated 67. Why the heights of plateaus and mountains on celestial bodies are limited.  The rocks have limited strength which leads to a limit of how high topography can grow before pressure caused by gravity causes rocks to break or flow 68. Why Mars has taller and deeper topography than Earth and Venus.  Mars has a smaller gravity 69. Whether surface gravity always points toward the center of a celestial body.  Gravity does not always point downwards if a body is too small to pull itself into a sphere Unit 3: Planetary Motions 70. Where the angular velocity of a rotating accretionary disc is fastest.  Dust within the accretion disc rotates faster the closer it is to the disc center - thus, the planets that accrete from this dust orbit faster the closer they are to the disc center 71. What conservation of angular momentum leads one to expect regarding the spin of planets.  Planets accrete from the rotating accretion disc, so the angular momentum is carried into the planets causing them to spin. We expect them to spin in the same direction they orbit, and their axis of rotation should be perpendicular to the plan of the solar system (aka ecliptic) but this is not the case. 72. Why the axes of rotation of the planets are not found to align perpendicular to the ecliptic.  Gravitational interactions with each other, violent impacts, changes in the distribution of mass within the planet 73. Why the tilt of Mars varies significantly more than the tilt of Earth.  Smaller than earth so easily influenced by changes to its mass distribution and gravitational influences of Jupiter and Saturn, closer to Jupiter and Saturn, does not have a large stabilizing moon, more massive volcanism that changes distribution of Mars' mass 74. Why the spin rates of the giant planets are faster than that of Earth.  The more massive the planet is, the faster they spin -> the more angular momentum was transferred from the accretion disc 4

75. Why Mercury and Venus spin so slowly.  They are tide locked by the sun 76. The differences between neap and spring high tides.  Spring tides occur with new and full moons, neap tides occur during first or third quarter moons 77. The number of times the Moon rotates about its spin axis during each orbit around the Earth.  Exactly 1 time since it is tidally locked with the Earth 78. What tidally locking means with regards to observing Earthrise from the lunar surface.  The moon rotates about its spin axis exactly once during each orbit around the earth, meaning that the same side of the moon always faces the earth (the near side) -> this means we 79. Why the Moon is fully tidally locked but Mercury is not.  Mercury is not completely tidally locked to the Sun because Mercury has an elliptical orbit while the moon has a circular orbit 80. The center of Aristotle’s universe.  The Earth 81. Copernicus’ great contribution to science.  Said the sun was the center of the universe, not the earth 82. The major breakthrough that allowed Kepler to explain the orbits of celestial bodies.  Planet orbits were better described as being elliptical as opposed to circular 83. How eccentricity, e, varies from a circle to an infinite ellipse.  E is 0 at a circle and 1 to an infinite ellipse 84. How Neptune was discovered.  Urbain le Verrier realized that Uranus did not follow Kepler’s 2 nd law and he realized this was only possible if another planet’s gravity was tugging on Uranus. So using just math, Le Verrier told Galle where to find Neptune. 85. What Kepler’s second law says about how the speed of a planet varies in its orbit.  The speed of a planet increases as it approaches the Sun (due to Sun’s gravity) and decreases as it moves away from the Sun (decelerated by Sun’s gravity) 86. According to Kepler’s 3 rd Law, the factors that influence the time it takes a planet to orbit.  The period for a planet to orbit the sun increases greatly with the radius of its orbit 87. The two forces that determine a planet or moon’s orbital parameters.  Centrifugal force and gravity 88. What happens if you launch from a planet with too little angular velocity.  Gravity will pull you straight back down (crash into earth) 89. What happens if you launch from a planet with too much angular velocity.  You escape Earth’s gravity and head into the solar system (hyperbolic orbit) 90. The geometry that defines the transition to an escaped orbit.  Parabola is the escape trajectory (e=1, 11.2 km/s) o Ellipse, circle are the geometry that is for an orbit. Hyperbola is not orbiting 91. How we know that our 2017 interstellar visitor Oumuamua was not here to stay.  Because its trajectory was in the shape of a hyperbola (not orbiting) 92. The manner in which angular velocity varies with orbital height for Earth satellites.  Orbital distance can be changed by changing the orbital speed (satellites orbit more slowly the more distant they orbit).  Satellites can move into a circular orbit by firing the engines at the same height until it eventually orbits in a circle not an ellipse 93. The parameters used to measure the mass of a planet based on the orbit of a moon.  Orbital distance (r) and angular velocity (omega) of one of its moon (and gravity, the constant) 94. What a hot Jupiter is. 5