The Solar System

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Chapter 20

• The Solar System

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Solar System
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Solar System
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Section 20-1 Observing the Solar System

• Geocentric System Ptolemy developed the
  Geocentric Theory that the Earth is at the center
  of the revolving planets.
• Heliocentric System Later, during the 1500s,
  Nicolaus Copernicus developed a new model, the
  Heliocentric System, which is the Earth and the
  other planets revolve around the sun.

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20-1 Galileo

• Galileo lived nearly 100 years later after
  Copernicus. He made two discoveries supporting
  the Heliocentric Theory
• First, he saw four moons revolving around around
  Jupiter.
• Second, he saw that Venus goes through phases
  similar to those of Earths moon.

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20-1 Kepler

• Kepler discovered that the orbit of each planet
  is an ellipse. An ellipse is an elongated
  circle, or oval shape. However, he could not
  explain how the planets stayed in orbit.

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20-1 Newton

• The English scientist Isaac Newton provided the
  answer. Newton concluded two factors
• Inertia a moving object will continue to move
  until a force acts to stop its motion. This
  tendency of a moving object to continue in a
  straight line or of a stationary object to remain
  in place is the objects inertia.
• Gravity the force that attracts all objects
  toward each other.
• Newton figured out that Earth keeps pulling the
  moon toward it with gravity, while the moon keeps
  moving ahead because of its inertia.

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20-2 The Sun

• The suns mass is 99.8 percent of all the mass in
  the solar system.
• Because the sun is so large, its gravity is
  strong enough to hold all of the planets and
  comets in orbit.
• The sun has an interior and an atmosphere. The
  sun is a ball of glowing gas that is about ¾
  hydrogen, and ¼ helium.

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The Sun
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20-2 Nuclear Fusion

• The suns energy comes from nuclear fusion.
• In the process of nuclear fusion, hydrogen atoms
  join together to form helium. The temperature
  inside the core reaches about 15 million degrees
  Celsius. The energy produced by nuclear fusion,
  including light and heat, moves from the core
  through the suns atmosphere and into space.
  Some of the light and heat reaches Earth, giving
  Earths its main source of energy.

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The Suns Makeup
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20-2 The Suns Makeup

• The suns atmosphere has three layers
• The Photosphere the inner layer of the suns
  atmosphere that makes light. Photolight.
• The Chromosphere At the beginning and end of a
  solar eclipse, you can see a reddish glow around
  the photosphere. This glow comes from the
  middle layer of the suns atmosphere.
  Chromocolor.
• The Corona In the middle of a total solar
  eclipse, the moon also blocks light from the
  chromosphere. At these times an even fainter
  layer, the corona, is visible. The corona sends
  out a stream of electrically charged particles
  called solar winds, which sometimes reaches
  Earths North and South Poles, creating rippling
  sheets of light in the sky called auroras.

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20-2 Suns Features

• Features on or above the suns surface include
• Sunspots areas of gas on the sun that are cooler
  than the gases around them. The cooler gases
  give off less light, causing dark spots.
• Prominences Reddish loops of gas.
• Solar Flares the energy heats gas on the sun to
  millions of degrees Celsius, causing the gas to
  explode out in space.

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The Suns Spots
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Sun Prominences
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Sun Flares
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Solar Eclipse
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20-3

• The Inner Planets

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Terrestrial Planets

• Mercury
• Venus
• Earth
• Mars

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Mercury

• Mercury is the closest planet to the sun. The
  planets interior is probably made of iron and
  nickel. The side facing the sun reaches
  temperatures of 430 C during the day, and at
  night 170 C.
• Mercury has no moons.

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Mercury
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Venus

• Venus is similar in size to Earth. Venus rotates
  east to west, the opposite direction from most of
  the planets, this is called retrograde rotation.

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Venus
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Mars

• Mars is called the red planet. Its surface is
  covered with red dust. Mars is being
  investigated for life, astronomers may have found
  water in the form of ice. Mars also has seasons,
  tilted on its axis like Earth.
• Mars also has two moons Phobos and Deimes.

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Mars
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Mars Moons

• phobos" is Greek for "fear

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Mars Moons

• deimos" is Greek for "panic

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20-4

• The Outer Planet

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The Four Outer Planet

• The four outer planets, called gas giants, due to
  their largeness and surfaces not being solid, gas
  balls.
• Jupiter
• Saturn
• Uranus
• Neptune

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Gas Giants

• Gas grants have so much mass, they have a
  stronger gravitational force this prevents
  their gases from escaping.

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Jupiter
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Jupiter Red Spot
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Jupiter

• Jupiter is the most massive planet. Its
  atmosphere is colorful with a Great Red Spot,
  which is an area of swirling clouds. Jupiter has
  17 moons.

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Jupiter

• Scientists have spotted what appear to be
  thunderheads on Jupiter bright white cumulus
  clouds similar to those that bring thunderstorms
  on Earth

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Jupiters Moon Io
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Jupiter Volcano Hot Spots
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Saturn
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Saturn

• 2nd largest planet. Saturn is the least dense
  planet in the Solar System. Saturn has hundreds
  of rings and are made of chunks of ice and rock.
• Saturn has 19 moons.

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Uranus

• Uranus looks bluish because of the methane gas in
  its atmosphere.
• Uranus rotates from top to bottom and has 18
  moons.

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Uranus
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Neptune

• Neptune has 8 moons and its atmosphere contains
  visible clouds.

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Neptune
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Pluto

• Smallest planet with one moon Charon.
• Pluto revolves around the sun only once every 248
  Earth Years.

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Pluto
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The Planets in Order

• Sun
• Mercury
• Venus
• Earth
• Mars
• Jupiter
• Saturn
• Uranus
• 
  Neptune
• 
  Pluto

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20-5 Comets

• Comet called the dirty snowball, is about the
  size of an Earth mountain. Comets are chunks of
  ice and dust whose orbits are usually very long,
  narrow ellipses.
• When a comet gets to close to the sun, the ice
  turns to gas, releasing dust. The gas and dust
  form an outer layer called the coma. The inner
  layer of the comet is called the nucleus. The
  coma and the nucleus make up the comets head,
  which is the brightest part of the comet. Some
  of the gas is pushed away from the sun by the
  solar wind. This forms the comets tail.
• In 1705, Edmond Halley calculated that every 76
  years the same comet would reappear. He
  predicted it would resurface in 1758, and when it
  did, it was named Halleys comet.

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Diagram of a Comet
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Comet Diagram
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Comet
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Halleys Comet
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Tail of Halleys Comet
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20-5 Asteroids

• Between 1801 and 1807, astronomers discovered
  four small objects between Mars and Jupiter.
  Over the next 80 years, they found 300 more.
  These objects are called asteroids.
• Most asteroids revolve around the sun between the
  orbits of Mars and Jupiter. This region in the
  solar system is known as the asteroid belt.

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Asteroids
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Asteroids Vesta
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20-5 Meteors

• A meteoroid is a chunk of rock or dust in space.
  Meteoroids usually come from comets or asteroids.
  
• When a meteoroid enters Earths atmosphere,
  friction makes it burn up and produce a streak of
  light you see in the sky a meteor.
• Meteorites are pieces of rock, made mostly of
  iron and nickel, that fall all over Earth, that
  did not burn up. Their sizes are usually
  extremely large, which makes it easier to
  identify them as meteorites than rock.

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Meteors
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Nasa Photo Journal

• http//photojournal.jpl.nasa.gov/index.html

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Nasa Live

• http//www.nasa.gov/home/index.html?skipIntro1