The Planets

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The Planets

• The Solar System is made up of 8 planets, 3
  dwarf planets (Pluto, Ceres and Xena) countless
  asteroids and comets. The sun is by far the
  dominant body in the solar system. It has a
  thousand times the mass of Jupiter, which in
  itself has more mass than all the planets
  combined. It is the Suns gravitational
  attraction therefore that controls the motion of
  the planets, asteroids and comets. Lets have a
  quick look at these nine planets before you
  create a detailed chart comparing some of their
  more important facts. Key words and terms will be
  introduced throughout this presentation.

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Planets and Sun to scale
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• Mercury
• Its symbol represents a wand with two serpents
  on it, carried by the God Mercury
• God of Commerce and Thievery (once called
  Vulcan)
• Smallest planet, too small to have an atmosphere
  
• Nearest to the sun
• The Composition of the planets (atmosphere and
  surface) can be confirmed by Spectroscopy.
  Different substances absorb sunlight at specific
  wavelengths. A Spectrum analysis will tell us
  what a planet is made of.

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• Venus
• Its symbol represents a hand mirror. Venus is
  the goddess of love
• Due to its thick atmosphere and Greenhouse
  Effect, it is the hottest planet
• It is the closest planet to Earth in distance
• It is third to the Sun and the moon in
  brightness at night. It is called the Evening
  Star
• Its rotation is extremely slow - 243 of our
  days. Its rotation is slower than its revolution
• After the moon it was the first planet to be
  visited by an earth probe.
• Known to have volcanic activity.

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• Earth
• The word means ground. Its symbol is that of a
  circle with the equator and Prime Meridian drawn
  on them
• Of course it is the only planet to have life on
  it. It is a dynamic planet - tectonic and
  erosional forces are constantly changing its
  surface.
• Its tilt allows the earth to have seasons - more
  on this later
• The plain of the Earths orbit is called the
  Ecliptic. The moon can hide behind the Sun only
  when it crosses this place exactly. The Moons
  orbit about the Earth is inclined 5.20 to the
  ecliptic and the orbits of the planets lie within
  3.50 of the ecliptic.

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• Mars
• Its symbol represents a shield with a sphere
• Named after the god of war
• It is also called the Red Planet - red colour
  due to iron ore content (rust)
• It is most similar to Earth (in composition and
  tilt). Once believed to contain liquid water
  (Channels can be seen on its surface) and even
  LIFE!
• Most peoples favourite planet - folklore and
  science fiction
• Has frozen water in the polar regions - Ice Caps
• Two moons Phobos (fear) and Deimos (panic).

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• Asteroids or Planetoids
• The word Asteroid means star-like
• They are found in a large unusual gap between
  Mars and Jupiter
• There is a theory as to the origin of the
  Asteroids called
• Bodes law
• Titius Progression Planet Actual
  Distance from sun (AU)
• (04) / 10 0.4 Mercury 0.387
• ( 34 ) / 10 0.7 Venus 0.723
• ( 64) / 10 1.0 Earth 1.00
• (124) /10 1.6 Mars 1.524
• (244) /10 2.8
• (484) /10 5.2 Jupiter 5.203
• (964) /10 10.0 Saturn 9.539
• (1924) /10 19.6 Uranus 19.18
• (3844) /10 38.8 Neptune 30.6
• (7684) /10 77.2 Pluto 39.4

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• AU Astronomical unit (distance from the earth
  to the sun)
• 1.495978893 x 10 cm 93,000,000 miles
• Notice that Neptune and Pluto do not fit
• There is no planet at the 2.8 position
• The Asteroids or minor planets are found there
• The belief is that the gravitational pull of
  Jupiter and the Sun broke up a planet that once
  existed at the 2.8 position
• This broken planet left 1,700 smaller pieces
  revolving around the sun called The Asteroid Belt
• The two largest asteroids are called CERES (has
  been upgraded to Dwarf planet) and EROS. Ceres is
  480 miles in diameter, others average 50 miles
  wide

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• 2000 cross the earths orbit
• It is estimated that 5 asteroids of 1 km or
  greater in size will strike the earth every 1
  million years
• An asteroid collision is believed to be the
  reason for the mass extinction of the dinosaurs

NOTE The orbits of the planets are not perfect
circles, they are egg shaped or Elliptical. The
more elongated the ellipse the more Eccentric
the orbit.
A - Perihelion B - Aphelion
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Remember Pluto is now not a planet, but it is
interesting to see the shape of its orbit.
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• Jupiter
• Its symbol is that of a great thunderbolt in the
  shape of a Z to represent Zeus (King of the
  Greek gods). Jupiter is the name of the King of
  the Roman gods.
• The first outer planet, the first of the gas
  giants, Jupiter and the other large planets are
  called Jovian planets.
• It is the largest planet
• Known for it great red spot, believed to be a
  continuous storm on the planet
• Jupiter rotates in just under ten hours!

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• It has rings
• Four of its 16 moons were discovered by Galileo
  Galilei in 1610 (Io, Europa, Ganymede, Callisto)
• Io has active volcanoes and even an atmoshere.
• Europa has water as solid, some even think as a
  liquid.

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• Saturn
• Named after the god of time. Its symbol is a
  cane shaped like a sickle
• Most recognizable and beautiful due to the
  magnificent rings that surround the planet,
  believed to be a broken up moon. The rings are in
  3 major parts separated by a division called
  Cassinis division.
• One of Saturns moons is actually bigger than
  the planet Mercury.
• Its density is lighter than water. Saturn can
  float!
• It has 18 moons or satellites. Titan has a
  substantial atmosphere.

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• Uranus
• Named after the god of the sky. Its symbol
  represents the sky
• Discovered in 1781 by telescope, barely bright
  enough to see with the unaided eye.
• It also has rings as well
• Due to its tilt (980) Uranus nights could last
  up to 21 years.
• It has a bluish green colour due to its methane
  atmosphere.

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Since we have mentioned the tilt of a number of
planets here is a diagram that shows all of the
tilts.
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• Neptune
• Named after the god of the sea, so naturally its
  symbol is a trident
• The last of the gas giants
• It was discovered in 1846. It cannot be seen
  without a telescope.
• Neptune is blue in colour. Its methane
  atmosphere is denser than that of Uranus.
• Because of Plutos very elliptical orbit (It
  actually crosses Neptunes orbit) Neptune was
  further away from the sun for a number of years.

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• Pluto A Dwarf Planet
• Named after one of the people that discovered
  it. Pluto represents the god of the underworld.
• Discovered in 1930
• Downgraded to Dwarf planet because it is too
  small in 2006
• Due to its tremendous distance from the sun very
  little is known about Pluto
• Theory goes that it was a rogue planet captured
  by our Suns gravitational pull
• Pluto has a moon called Charon, some say that
  they are double planets.
• Only planet not visited by an earth probe.

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• The Kuiper Belt
• Theorized to exist in 1951. The first object to
  be found there was in 1992.
• Today there are more than 240 objects found in
  the belt
• Some comets (short period) are found here. Just
  outside the Kuiper Belt is another zone that is
  believed to house most of the long period comets
  called the Oort cloud. These comets have very
  eccentric orbits thus passing by the earth once
  every 75 to 100 years (Eg. Halleys Comet)
• Xena the third Dwarf planet is found here.

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The End!