Chapter 4 41087 - AST 115 - A
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This 6 page Class Notes was uploaded by Ashley Notetaker on Monday September 21, 2015. The Class Notes belongs to 41087 - AST 115 - A at Missouri State University taught by Robert S Patterson in Fall 2015. Since its upload, it has received 67 views. For similar materials see Basic Astronomy in Physics 2 at Missouri State University.
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Date Created: 09/21/15
Our Solar System Consists of one starthe sun and everything that orbits it planets moons various debris asteroids comets meteoroids Hydrogen and Helium make up 98 of mass in the Universe Big Bang Created all the matter and energy space and time Only hydrogen helium and a small amount of lithium were created directly from the Big Bang The first stars were made only out of Big Bang gases Stars shine because when hydrogen fusion occurs some of the hydrogen s mass is converted into electromagnetic energy photons Part of it eventually leaks out of the stars surface causing the star to shine Thermonuclear Fusion Gravity compresses the matter so much that hydrogen is transformed into helium How Other Elements were made If a star has enough mass the pressure from gravity will force the elements to transform to heavier ones Including neon aluminum silicone calcium and iron Helium subsequently fuses to create oxygen and carbon Super nova Explosion of a star This can emit nickel copper zinc silver and gold Planetary nebula More energetic expulsion As matter is ejected from stars small partials of dust can be left behind Over time enough dust and gas from stars were collected to make clouds full of hydrogen helium and some metals These clouds created molecules of water carbon dioxide methane and ammonia The clouds don t collapse to form stars because the partials of the clouds move fast enough and therefore aren t hot enough to avoid being pulled together from gravity Jeans Instability When gravitational force is stronger than the thermal force and part of an interstellar cloud to collapse and form stars or planets 3 Ways this happens 1 Winds from nearby stars compress dust and gas in the cloud 2 The force from a nearby supernova compresses dust and gas 3 Clouds collide and compress each other Dense core Regions of interstellar clouds that collapse to become a star or planet Solar nebula Dense core of our Solar System Protoplanetary disks Disks of material encircling a protostar or newborn star Building Materials of the Solar System Metals A elements other than Hydrogen and Helium Avg Density 10gcmquot3 Rocks Sillicates and oxygen Avg Density 3gcmquot3 Ices H20 C02 ammonia methane Avg Density 1gcmquot3 Gases Hydrogen and Helium Avg Density lt 1gcmquot3 Regularities of the Solar System The orbits of the 8 major planets are 1 Nearly all in the same plane the ecliptic 2 All Planets orbit in the same direction counterclockwise 3 Orbits are early circular but still ellipses 4 Regular spacing between planets but not equal Irregularity All the planets except Venus and Uranus rotate in the same direction It is unknown why Venus does this Uranus rotates on its side Therefore it must have gotten knocked over on its side from a collision early on in development This all shows that the planets must have formed from a spinning disk of dust AKA the nice model Nice Model Universe began in an extremely hot dense state about 14 billion years ago Only energy existed After a few minutes the temperature dropped low enough for matter to form from energy Essentially only Hydrogen and Helium formed 9 billion years later the Sun and Planets formed from material in an interstellar cloud The Sun and Planets formed around the same time Small amounts of heavier elements may have been formed from past Super Nova explosions After being compressed probably from a super nova explosion nearby the solar nebula began gravitational contractioncollapse Spinning nebula flattened into disk with central concentration the protosun is the central concentration Gravitational construction of the protosun released energy to heat it to a temperature which causes hydrogen fusion This turned the protosun into the sun we have today Gas ice and dust in the disk slowly accreted to produce the planets Accretion The gradual clumping of small particle to make larger ones the snowball effect This occurs due to the attraction of charged particles like static Inner part of the disk warmed by radiation from the protosun no gases or ices Beyond the snowline gases and ices were present Snowline The distance from the sun in which ice stays frozen Solar Nebula Theory The age of the solar system Formation of Outer Planets Jupiter formed 1st and used up most of the available raw material Then Saturn Neptune and Uranus formed In that order The Jovians are believed to have formed from seeds consisting of rocky metallic objects similar to the current terrestrial planets formed by millions of years of accretion Jupiter originally formed a 3AU and now sets at 5AU Outside the snowline Jupiter accumulated Hydrogen and Helium Saturn was formed next much closer to Jupiter than it is now Uranus and Neptune had less hydrogen and helium available after Jupiter and Saturn They are made of mostly water and ice Neptune was originally formed in front of Uranus Uranus and Neptune are known as ice giants Jupiter and Saturn are known as the gas giants Resonance When the period of 2 orbits are related by whole numbers Gravitational interplay or resonance allowed the Jovians to migrate to their current positions This is why Neptune is now the furthest planet Formation of the Inner Planets Formed after Jovians by collisions from planetesimals of rockymetal materials Either they were made from seeds in nearly circular orbits Or the collision process favored the survival of planetesimals in low eccentricity orbits One of the last major collisions with Earth led to the creation of the moon Terrestrials reached current diameters 41 billion years ago All water on Earth s surface came from icy planetesimals from beyond the snowline Only Earth retains significant amounts of water Properties of the Planets of the Solar System Planet Diameter Mass Average Density Earth 10 Earth 10 MassVolume gmcmquot3 Mercury 4 006 54 Venus 1 8 52 Earth 10 10 55 Mars 5 1 39 Jupiter 11 318 13 Saturn 95 95 7 could float in water Uranus 4 15 13 Neptune 39 17 16 Terrestrial Vs Jovian Planets Terrestrial Jovian Location Inner Planets Outer Planets Diameter Small Large Mass Low High Average Density High Low Moons Few Many Rings None All have rings Atmosphere Thin Thick Rotation Rate Slow Fast Debris in the Solar System Solid debris had been sent to the inner solar system Icy debris was propelled out beyond Neptune s orbit Kuiper belt Contains many comets in the plane of the ecliptic KBO Kuiper belt objects Mostly comets some w very elongated orbits that occasionally bring them closer to the Sun than Earth The Sun then vaporizes some of the ice giving comets the appearance of a tail Pluto is the 2ncl largest KBO and the 1st that was discovered Asteroid Belt Located between Mars and Jupiter where most asteroids are found This debris could have formed into a planet if not for Jupiter s gravitational pull Late Heavy Bombardment Debris flung from the giant planets knocked planetesimals from the asteroid belt out of orbit This is how the moon got many of its craters Solar System Today Asteroid Space debris primarily composed of rock and metal that is larger than 10m Meteoroid Space debris primarily composed of rock and metal that is smaller than 10m Comet Space debris composed of roughly equal rock and ice Crater Scars from where space debris struck a celestial body Planet Three requirements 1 Celestial body that orbits the Sunother star Has enough mass so that its own gravitational attraction makes it spherical 3 Has enough gravitational attraction to clear neighborhood of orbiting debris Dwarf Planet Satisfies requirements 1 amp 2 but not 3 Dwarf planets are smaller have less mass and therefore less gravitational attraction Moonnatural satellite An object orbiting a larger body that is orbiting the Sunanother star Small Solar System Body SSSB Everything not a planet dwarf planet moon or part of a ring system Development of the Sun Over 100 million years of planets forming the Sun s core was getting hotter Eventually it got hot enough for hydrogen fusion to occur This fusion generates energy in the form of gamma rays The gamma rays slamming gasses into the protosun created enough pressure inside the protosun to stabilize preventing it from expanding or contracting This is when the protosun became the sun The Sun shines due to some energy photons leaking out of the core Hydrogen fusion sti happens This happening over the past 45 billion years has maintained the Sun s size and temperature Sun like stars take about 100 million year to form
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