The Origin Of The Solar System 3f6l58

THE STRUCTURE AND ORIGIN OF THE SOLAR SYSTEM

Comparative Planetology • By studying the differences and similarities between the planets, moons, asteroids and comets, we can gain a fuller understanding of the solar system as a whole.

General Properties of Terrestrial Planets

General Properties of Jovian Planets

• Exploring Our Solar System- Planets and Space for Kids - FreeSchool.mp4

The Origins of the Solar System: Four Challenges 1) 2) 3) 4)

Patterns of Motion Categorizing Planets Asteroids and Comets Exceptions to the Rules

Challenge 1: Patterns of Motion • All planets orbit the Sun in the same direction --counterclockwise when seen from high above the Earth’s North Pole. • All planetary orbits lie nearly in the same plane. • Almost all planets travel on nearly circular orbits, and the spacing between planetary orbits increases with distance from the Sun according to a fairly regular trend.

Challenge 1: Patterns of Motion - Continued • Most planets rotate in the same direction in which they orbit- counterclockwise when seen from above the Earth’s North Pole – with fairly small axial tilts (i.e. < 25o)

• Almost all moons orbit their planet in the same direction as the planet’s rotation and near the planet’s equatorial plane. • The Sun rotates in the same direction in which the planets orbit.

Challenge 2 • The second challenge for any theory of solar system formation is to explain why the inner and outer solar system planets divide so neatly into two classes. • Terrestrial Planets • Jovian Planets

Challenge 2: Categorizing Planets

• Terrestrial Planets: Earth-like planets. • These include Mercury, Venus, Earth and Mars. • Jovian Planets: Jupiter-like planets.

• These include Jupiter, Saturn, Uranus, and Neptune.

Challenge 3 Cosmic Debris • In order for a theory to be complete, it must also address the issue of Asteroids and Comets. • Asteroids are small, rocky bodies that orbit the Sun primarily in the asteroid belt. • Comets are small, icy bodies that spend most of their lives well beyond the orbit of Pluto. (Oort Cloud)

• We generally recognize them only on the rare occasions when one visits the inner solar system.

• We know today that comets are orbiting the Sun primarily in two broad regions. – The Kuiper (Koy-per) belt: (Begins in the vicinity of the orbit of Neptune ~ 30AU) – The Oort Cloud: Huge spherical region centered on the Sun and extending perhaps half way to nearest stars.

• The Third Challenge for any theory of solar system formation is to explain the existence and general properties of the large numbers of asteroids and comets. – Why are there so many? – How did their existence come about?

Challenge 4: Exceptions to the Rule Some objects don’t fit into the general pattern:

• Mercury and Pluto have larger eccentricities. • Pluto and Uranus are substantially tilted. • Venus rotates backwards.

Four Major Characteristics of the Solar System 1. Large bodies in the solar system have orderly motions. 2. Planets fall into two main categories: Small, rocky terrestrial planets. Large, hydrogen rich gas giants (Jovian planets). 3. Swarms of asteroids and comets populate the solar system 4. Several notable exceptions to these general trends stand out: Planets with unusual axial tilts or surrounding large moons. Moons with unusual orbits.

Theories on the Origin of the Solar System • • • • •

Vortex Theory Collision Theory Kant-Laplace Nebular Theory Jeans Jeffrey Tidal Theory Solar Nebular Theory

Vortex Theory • Rene Descartes • The Solar System was formed into bodies with nearly circular orbits due to whirlpool-like motion in the pre-solar materials

Descartes Vortex Theory.mp4

Collision Theory • George Louis Leclerc, Comte de Buffon • Planets were formed by the collision of the sun with a giant comet.

Kant-Laplace Nebular Theory • Immanuel Kant, Pierre Simon Laplace • Nebula begins to collapse due to gravitational pull • Contraction proceeded and the nebula spun more rapidly • The spinning cloud flattens with a bulge at the center • The local regions continue to collapse

The Kant-Laplace Nebular Theory.mp4

Jeans-Jeffrey’s Tidal Theory • James Hopwood Jeans and Harold Jeffrey • Tidal theory proposed that the planets were formed from the substance that was torn out of the sun. • As a speeding massive star ed near the sun, it pulled off material due to gravitational attraction.

The Solar Nebular Theory • In the past few decades, a tremendous amount of evidence has accumulated in of one model. • This model is called the Nebular Theory. • This Theory holds that our solar system formed from a giant, swirling interstellar cloud of gas and dust.

SOLAR NEBULA THEORY.mp4

Nebular Model

Original Cloud is large and diffuse with little rotation

The cloud heats up and spins faster and faster as it contracts

This results in a spinning, flattened disk, with mass concentrated near the center

Theories on the Origin of the Solar System.mp4