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Introduction to the Solar System Grasping the size Scale of Solar SystemKhan Academy: http://www.khanacadem y.org/science/cosmology -and-astronomy/v/scaleof-solar-system Astronomical Unit: 1 (AU) = 149,597,870 km 92,955,807 miles Beyond the Solar System: http://scaleofuniverse.co m/ Survey of the Solar System Lesson 15: Chap 4, Secs 4.2-4.3 Origin of the Solar System and Other Planetary Systems 2 What’s our Motivation? Solar system is our “local neighborhood” Want to get to know what’s around you! You are here Survey of the Solar System Lesson 15: Chap 4, Secs 4.2-4.3 Origin of the Solar System and Other Planetary Systems 3 Lesson Overview How did the solar system form? What are interstellar clouds? What is a solar nebula? How did the solar nebula evolve into the Sun and planets? Are other solar systems out there? Survey of the Solar System Lesson 15: Chap 4, Secs 4.2-4.3 Origin of the Solar System and Other Planetary Systems 4 Introduction Two questions: How did the solar system form? and Are similar solar systems “out there”? There are various theories for how the solar system formed Survey of the Solar System Lesson 15: Chap 4, Secs 4.2-4.3 Origin of the Solar System and Other Planetary Systems 5 How did the solar system form? Good theories must answer key questions: Why is the solar system flat? Why do all the planets orbit in the same direction? Why do two types of planets exist? Why do all solar-system bodies appear to be less than 4.5 billion years old? Survey of the Solar System Lesson 15: Chap 4, Secs 4.2-4.3 Origin of the Solar System and Other Planetary Systems 6 How did the solar system form? Current hypothesis for formation of Solar System: Solar nebula hypothesis Proposes the solar system evolved from a rotating mass of gas and dust (an INTERSTELLAR CLOUD) The interstellar cloud flattened into a disk. The outer part became the planets and the inner part became the Sun. QuickTime Movie: How the solar system formed Survey of the Solar System Lesson 15: Chap 4, Secs 4.2-4.3 Origin of the Solar System and Other Planetary Systems 7 What are interstellar clouds? Beginning of solar system— interstellar cloud Interstellar clouds—vast collections of gases (mostly Hydrogen) Interstellar cloud that formed our solar system was probably several light years in diameter and 2 times the Sun’s mass. Photograph of an interstellar cloud (the dark region at top), which may be similar to the one that became our solar system. (Courtesy Anglo-Australian Telescope Board, photo by David Malin.) Survey of the Solar System Lesson 15: Chap 4, Secs 4.2-4.3 Origin of the Solar System and Other Planetary Systems 8 What are interstellar clouds? Contain tiny dust particles called interstellar grains Usually, contain elements like those found in the Sun Survey of the Solar System Lesson 15: Chap 4, Secs 4.2-4.3 Origin of the Solar System and Other Planetary Systems 9 How did the solar system form? How do we get from an interstellar cloud to our solar system? Solar nebula hypothesis Six steps to formation Survey of the Solar System Lesson 15: Chap 4, Secs 4.2-4.3 Origin of the Solar System and Other Planetary Systems 10 Survey of the Solar System Lesson 15: Chap 4, Secs 4.2-4.3 Origin of the Solar System and Other Planetary Systems 11 Step 1 Interstellar cloud starts collapsing into a solar nebula Occurs over several million years Collapsed disk is called the solar nebula Its bulge became the Sun; disk became the planets. Survey of the Solar System Sketch illustrates A. An interstellar cloud’s collapse B. Its flattening Lesson 15: Chap 4, Secs 4.2-4.3 Origin of the Solar System and Other Planetary Systems 12 What is a solar nebula? Before planets formed—inner part of disk was hot, outer disk was cold. A B A. The small blobs in this picture are protostars in the Orion nebula—a huge gas cloud about 1,500 light years from Earth. (Courtesy Space Telescope Science Institute.) B. Picture in false color of a disk of dust around the young star, b Pictoris, made at the ESO telescope. Dark circle blots out the star's direct light, which would otherwise overexpose the image. (Courtesy A. M. Lagrange, D. Mouillet, and J. L. Beuzit, Grenoble Observatory) Survey of the Solar System Lesson 15: Chap 4, Secs 4.2-4.3 Origin of the Solar System and Other Planetary Systems 13 Survey of the Solar System Lesson 15: Chap 4, Secs 4.2-4.3 Origin of the Solar System and Other Planetary Systems 14 Step 2: How did the solar nebula evolve into the Sun and planets? Basic elements in the solar nebula condensed into small particles. (Hydrogen, Iron, Water vapor, Silicon) On a hot day, water vapor from the air condenses on a cold glass of water, making a messy puddle if you don’t have a coaster. Survey of the Solar System Lesson 15: Chap 4, Secs 4.2-4.3 Origin of the Solar System and Other Planetary Systems 15 How did the solar nebula evolve into the Sun and planets? (cont’d) Step 2 (from previous): Basic elements in the solar nebula condensed into small particles. Materials condensed at different temperatures: At colder temperatures . . . Iron vapor condensed and became a solid at 1300 K. Silicate vapor condensed and became a solid at 1200 K. Water vapor condensed and became solid ice at 273 K. Hydrogen vapor condensed and became solid at 14 K. Survey of the Solar System Lesson 15: Chap 4, Secs 4.2-4.3 Origin of the Solar System and Other Planetary Systems 16 How did the solar nebula evolve into the Sun and planets? Step 3: Small particles gradually formed larger particles through accretion (sticking together). Step 4: Over time, the larger particles collided and stuck together to form planetesimals. Step 5: Over more time, planetesimals gently collided to form the planets. Survey of the Solar System Lesson 15: Chap 4, Secs 4.2-4.3 Origin of the Solar System and Other Planetary Systems 17 How did the solar nebula evolve into the Sun and planets? (cont’d) Step 3: Accretion Step 4: Forming planetesimals Step 5: Planetesimals forming planets Sketches showing (A) how dust grains may have grown into planetesimals and (B) how the planetesimals may have grown into planets. Survey of the Solar System Lesson 15: Chap 4, Secs 4.2-4.3 Origin of the Solar System and Other Planetary Systems 18 How did the solar nebula evolve into the Sun and planets? (cont’d) Sketches showing (A) how dust grains may have grown into planetesimals and (B) how the planetesimals may have grown into planets. Survey of the Solar System Lesson 15: Chap 4, Secs 4.2-4.3 Origin of the Solar System and Other Planetary Systems 19 Survey of the Solar System Lesson 15: Chap 4, Secs 4.2-4.3 Origin of the Solar System and Other Planetary Systems 20 How did the solar nebula evolve into the Sun and planets? (cont’d) Step 6: Planetary atmospheres formed. Outer planets were big enough so their gravity could capture lighter gases to form atmospheres. Inner planets created atmospheres by volcanic activity and perhaps from comets and asteroids that vaporized. Some planets were too small to keep gases on their surface Survey of the Solar System Lesson 15: Chap 4, Secs 4.2-4.3 Origin of the Solar System and Other Planetary Systems 21 Survey of the Solar System Lesson 15: Chap 4, Secs 4.2-4.3 Origin of the Solar System and Other Planetary Systems 22 Are there other solar systems out there? Survey of the Solar System Lesson 15: Chap 4, Secs 4.2-4.3 Origin of the Solar System and Other Planetary Systems 23 Are there other solar systems out there? Survey of the Solar System Lesson 15: Chap 4, Secs 4.2-4.3 Origin of the Solar System and Other Planetary Systems 24 Are there other solar systems out there? Survey of the Solar System Lesson 15: Chap 4, Secs 4.2-4.3 Origin of the Solar System and Other Planetary Systems 25 Lesson review How did the solar system form? A currently favored theory for the solar system’s origin is the solar nebula hypothesis. Six steps: Step 1: An interstellar cloud collapsed to form a solar nebula. Step 2: Basic elements condensed into small particles. Step 3: Small particles gradually formed larger particles through accretion. Step 4: Larger particles collided and formed planetesimals. Step 5: Planetesimals gently collided to form the planets. Step 6: Planetary atmospheres formed. Survey of the Solar System Lesson 15: Chap 4, Secs 4.2-4.3 Origin of the Solar System and Other Planetary Systems 26 Activity—Questions for review What is the currently favored theory for the solar system’s origin called? What are the six steps that formed the solar system? What is an interstellar cloud? What is a solar nebula? What is accretion? What are planetesimals? *What size planets have we found around other stars? Survey of the Solar System Lesson 15: Chap 4, Secs 4.2-4.3 Origin of the Solar System and Other Planetary Systems 27 Activity—Test yourself • The solar nebula hypothesis proposes that _______ ________ evolved from a rotating, mass of gas and dust (called an interstellar cloud). • *Interstellar clouds are vast collections of gases that contain about ___% hydrogen, ___% helium, and traces of the other elements.* • Basic elements (hydrogen, iron, etc.) in the solar nebula _______ into small particles. • Small particles in the solar nebula gradually formed larger particles through _________. • Over time, the larger particles in the solar nebula collided and stuck together to form __________ . • Planets formed from _______ ________ of the planetesimals. • *New planets found around other stars aren’t observed directly. Instead, we see their ________ ________ on their parent stars.* Survey of the Solar System Lesson 15: Chap 4, Secs 4.2-4.3 Origin of the Solar System and Other Planetary Systems 28