Moons

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Moons

• Satellites are natural or artificial bodies that
  revolve around larger bodies like planets

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Luna The moon of Earth

• Where did our moon come from?

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Three major theories

• 1. Captured Theory Earths gravitational pull
  captured the moon causing it to orbit the Earth.
• Disproved
• 2. Double Planet Theory When the Earth formed
  from a spinning disk of material , not all of the
  material coalesced to form Earth. A small portion
  was left orbiting to form the moon.
• Disproved

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• 3. Impact Theory When Earth was still mostly
  molten, a large body (size of Mars) collided with
  Earth. Ejecting debris into orbit around Earth.
  Over time the debris began to join together to
  form the Moon.

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Moon statistics
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We know

• Lunar rocks suggests the composition of the moon
  is very similar to that of earths mantle.
• Lunar rocks found to be 4.6 billion years
• Surfaces that have no atmosphere preserve a
  record of almost all impacts of other objects.

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Phases of the Moons

• As a month progresses, the Moon appears to go
  through phases.
• In other words, the amount of the Moon that we
  can see changes over time in a cyclic period that
  repeats itself approximately once a month. (The
  actual period of this cycle is 27 Earth days 8
  hours.)
• The cause of these phases is the relative
  positions of the Sun, Earth, and Moon

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• Crescent Moon - when we can see only a sliver of
  the moon's disk (the side of the moon facing us)
• Full Moon - when the moon's disk is light because
  the Earth is between the sun and the moon
• Gibbous Moon - when we can see roughly
  three-quarters of the moon's disk
• Half Moon - (also called quarter moon) when we
  can see one half of the moon's disk (this is
  one-quarter of the entire moon's surface)

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• New Moon - when the moon's disk is dark (and
  invisible to us) because the moon is between the
  sun and the Earth
• Quarter Moon - (also called half moon) when we
  can see one half of the moon's disk (this is
  one-quarter of the entire moon's surface)
• Waning Moon - when the moon seems to be getting
  smaller, going from full to gibbous to half to
  crescent to new
• Waxing Moon - when the moon seems to be getting
  bigger, going from new to crescent to half to
  gibbous to full

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What is an Eclipse?

• An eclipse occurs when the shadow of one
  celestial body falls on another.

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Lunar eclipse

• Happens when the earth comes between the sun and
  the moon causing the shadow of Earth fall on the
  moon.
• Earths atmosphere filters the blue light causing
  the moon to appear red.

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Solar Eclipse

• The disk of the moon covers the disk of the sun.
• Because the moons orbit is not completely
  circular, sometimes the moon is farther away from
  the Earth, a thin ring of sunlight may show
  around the outer edge of the sun. This is called
  a annular eclipse.

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Extra moon facts

• On Earth we always see the same side of the moon,
  due to its period of rotation being the same as
  its period of revolution.
• One lunar day is 27 Earth days 8 hours.
• If you lived on the far side of the moon, you
  would see the sun for half of each lunar day, you
  would never see the Earth.

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• The moons tilt is 5 degrees off in respect to
  the orbit of the earth around the sun.
• This is enough to place the moon out of the
  Earths shadow for most full moons and the Earth
  out of the moons shadow for most new moons.

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Moons of other Planets

• Range is size
• Jovian (Gas) planets have multiple moons
• Very in orbit

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Mars

• Two moons
• Phobos
• Deimos
• Irregular shaped
• Small
• Dark color material
• Possibly captured asteroids

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Jupiter

• Has dozens of moons
• Four largest Ganymede, Callisto, Io, Europa were
  discovered by Galileo in 1610
• Io and Europa are in a gravitational tug of war.
  
• This constant tugging causes Io to heat up.
• Io is the most volcanically active body in the
  solar system

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Saturn

• Has dozens of moon
• Made of ice
• Titan (largest moon) discovered in 1655
• Similar to Earths atmosphere
• Atmosphere is orange

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Uranus

• More than 20 moons
• Miranda has some of the most unusual features
• Includes smooth, cratered plains
• Regions with grooves and cliffs
• Its patchwork terrain indicates that it has had a
  violent history

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Neptune

• Eight known moons
• Triton travels retrograde rotation
• Ice volcanoes geysers