Module 29: The Solar System

Standards Overview

  • SC.8.E.5.1: Recognize that there are enormous distances between objects in space and apply knowledge of light and space travel to understand this distance.
  • SC.8.E.5.3: Distinguish the hierarchical relationships between planets and other astronomical bodies relative to the solar system, galaxy, and universe, including distance, size, and composition.
  • SC.8.E.5.4: Explore the Law of Universal Gravitation by explaining the role that gravity plays in the formation of planets, stars, and solar systems and in determining their motions.
  • SC.8.E.5.7: Compare and contrast the properties of objects in the Solar System including the Sun, planets, and moons to those of Earth, such as gravitational force, distance from the Sun, speed, movement, temperature, and atmospheric conditions.
  • SC.8.E.5.8: Compare various historical models of the Solar System, including geocentric and heliocentric.

Models of the Solar System

  • Geocentric Model (Earth-Centered):

    • Key Contributors:
    • Ptolemy: Developed a model with epicycles to explain retrograde motion of planets.
    • Aristotle: Provided a philosophical basis for the geocentric model, supported by observations.
    • Plato: Suggested a perfect circular motion for celestial bodies.

  • Heliocentric Model (Sun-Centered):

    • Key Contributors:
    • Copernicus: Proposed the heliocentric model as a simpler explanation for planetary movements.
    • Newton: Formulated the Law of Universal Gravitation, providing the basis for understanding planetary motion.
    • Kepler: Introduced laws of planetary motion, specifically that orbits are elliptical.
    • Galileo: Used telescopic observations to provide evidence for the heliocentric model.

Key Terms

  • Epicycles: Small circles on which planets move, used to explain retrograde motion in the geocentric model.
  • Celestial Sphere: An imaginary sphere surrounding the Earth with celestial bodies projected onto it.
  • Prime Mover: A concept describing a first cause or primary source of motion in the universe.
  • Retrograde Motion: The apparent backward movement of planets against the background stars.

Size and Distance in the Solar System

  • Astronomical Unit (AU):
    • Definition: 1 AU = 150,000,000 km or 93 million miles.
  • Relative Distances: Understand distances between various planets in AU.
  • Relative Sizes: Know the comparative sizes of the planets.

Planets in the Solar System

  • Order by Distance from the Sun:
    • Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.
  • Order by Size:
    • Jupiter, Saturn, Uranus, Neptune, Earth, Venus, Mars, Mercury.
  • Number of Planets: 8 major planets in total.
  • Key Objects:
    • Asteroid Belt: Located between Mars and Jupiter.
    • Kuiper Belt: Extends from Neptune’s orbit to about 50 AU from the Sun.
    • Oort Cloud: A theorized cloud of icy objects surrounding the solar system.

Main Characteristics of Planets

  • Inner vs. Outer Planets:
    • Inner Planets (Terrestrial): Mercury, Venus, Earth, Mars - primarily composed of rock and metal.
    • Outer Planets (Gas Giants): Jupiter, Saturn; Ice Giants: Uranus, Neptune - composed mainly of gases and ices.
  • Average Temperatures: Know the average surface temperatures of each planet.
  • Rotations/Revolutions:
    • Understand the length of days (rotation) and years (revolution) in comparison to Earth.
  • Planetary Rules: Familiarize with basic rules applicable to planetary systems.
  • Dwarf Planets: Definition and locations of dwarf planets like Pluto, Eris, etc.

Other Objects in the Solar System

  • Satellites: Natural satellites, commonly referred to as moons, orbiting planets.
  • Meteoroid, Meteor, Meteorite:
    • Meteoroid: A small rocky or metallic body in outer space.
    • Meteor: A meteoroid that enters the Earth's atmosphere and glows as it vaporizes.
    • Meteorite: A meteoroid that survives its passage through the atmosphere and lands on Earth.
  • Asteroids: Small rocky bodies, primarily found in the asteroid belt.
  • Asteroid Belt: A region of space between Mars and Jupiter where the majority of the solar system's asteroids are located.
  • Dwarf Planets: Smaller celestial bodies that orbit the Sun, do not clear their orbits of other objects.
  • Oort Cloud: A hypothetical shell of icy objects surrounding the solar system at the farthest reaches.
  • Star (Sun): The Sun is a star at the center of the solar system.
  • Comets: Icy bodies that release gas or dust; parts include:
    • Coma: A cloud of gas and dust surrounding the nucleus.
    • Gas Tail: Comes from the solar wind pushing away gases from the comet.
    • Debris Tail: Contains dust particles drifting away from the comet.

Laws of Motion

  • Law of Universal Gravitation:
    • Responsible for gravitational interactions between bodies; largely attributed to Isaac Newton.
  • Space-Time: Concepts introduced by Einstein that discuss how gravity affects time and space.
  • Escape Velocity: The minimum speed required for an object to break free from the gravitational attraction of a celestial body.
  • Kepler’s Laws: Planets orbit the Sun in elliptical paths, not circular.
    • First Law: The orbit of a planet is an ellipse with the Sun at one focus.
    • Second Law: A line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time.
    • Third Law: The ratio of the squares of the periods of any two planets is equal to the ratio of the cubes of their average distances from the Sun.