The Solar System

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The Solar System
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Overview of the Solar System

• Basics
• Source Nine Planets - A Multimedia Tour of the
  Solar System By Bill Arnett

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The solar system

• consists of the Sun
• the nine planets
• about 90 satellites of the planets
• a large number of small bodies (the comets and
  asteroids)
• and the interplanetary medium.

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The nine planets are

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

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The orbits of the planets

• are ellipses with the Sun at one focus though
  all except Mercury and Pluto are very nearly
  circular.
• The orbits of the planets are all more or less in
  the same plane (called the ecliptic and defined
  by the plane of the Earths orbit).

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How do they orbit

• They all orbit in the same direction
  (counter-clockwise looking down from above the
  Suns north pole)
• all but Venus Uranus and Pluto also rotate in
  that same sense.

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The Nine Planets
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Classification

• Traditionally the solar system has been divided
  into planets (the big bodies orbiting the Sun)
• their satellites (a.k.a. moons variously sized
  objects orbiting the planets) asteroids (small
  dense objects orbiting the Sun) and comets (small
  icy objects with highly eccentric orbits).

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The Big Questions

• What is the origin of the solar system It is
  generally agreed that it condensed from a nebula
  of dust and gas. But the details are far from
  clear.

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Big questions continued

• What conditions allow the formation of
  terrestrial planets It seems unlikely that the
  Earth is totally unique but we still have no
  direct evidence one way or the other.

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Big questions continued

• Is there life elsewhere in the solar system If
  not why is Earth special
• Is there life beyond the solar system
  Intelligent life
• Is life a rare and unusual or even unique event
  in the evolution of the universe or is it
  adaptable widespread and common

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The Earth
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Earth

• is the third planet from the Sun and the fifth
  largest.
• orbit 149600000 km
• (1.00 AU) from Sun
• diameter 12756.3 km
• mass 5.972e24 kg

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The Earth is divided

• into several layers which have distinct chemical
  and seismic properties

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Earths division

• (depths in km)
• 0- 40 Crust
• 40- 400 Upper mantle
• 400- 650 Transition region
• 650-2700 Lower mantle
• 2700-2890 D layer
• 2890-5150 Outer core
• 5150-6378 Inner core

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The crust

• varies considerably in thickness
• it is thinner under the oceans
• thicker under the continents.
• The inner core and crust are solid the outer
  core and mantle layers are plastic or semi-fluid.

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Most of the mass

• of the Earth is in the mantle
• most of the rest in the core
• the part we inhabit is a tiny fraction of the
  whole

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Parts of earth

• (values below x1024 kilograms)
• atmosphere 0.0000051
• oceans 0.0014
• crust 0.026
• mantle 4.043
• outer core 1.835
• inner core 0.09675

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71 of the Earths surface

• is covered with water.
• Earth is the only planet on which water can exist
  in liquid form on the surface.

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Liquid water is essential

• for life as we know it.
• The heat capacity of the oceans is also very
  important in keeping the Earths temperature
  relatively stable.

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Liquid water

• is also responsible for most of the erosion and
  weathering of the Earths continents a process
  unique in the solar system today (though it may
  have occurred on Mars in the past).

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The Earths atmosphere

• is 77 nitrogen 21 oxygen with traces of
  argon carbon dioxide and water.

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The tiny amount of

• carbon dioxide resident in the atmosphere at any
  time is extremely important to the maintenance of
  the Earths surface temperature via the
  greenhouse effect.

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The greenhouse effect

• raises the average surface temperature about 35
  degrees C above what it would otherwise be (from
  a frigid -21 C to a comfortable 14 C)
• without it the oceans would freeze and life as we
  know it would be impossible.

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The Moon
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The Moon

• is the only natural satellite of Earth
• orbit 384400 km from Earth
• diameter 3476 km
• mass 7.35e22 kg

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The moon

• is the second brightest object in the sky after
  the Sun. As the Moon orbits around the Earth once
  per month the angle between the Earth the Moon
  and the Sun changes we see this as the cycle of
  the Moons phases. The time between successive
  new moons is 29.5 days (709 hours)

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The Moon was first visited

• by the Soviet spacecraft Luna 2 in 1959. It is
  the only extraterrestrial body to have been
  visited by humans.
• The first landing was on July 20 1969 the last
  was in December 1972.
• The Moon is also the only body from which samples
  have been returned to Earth.

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The gravitational forces

• between the Earth and the Moon cause some
  interesting effects. The most obvious is the
  tides.

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The Moons gravitational attraction

• is stronger on the side of the Earth nearest to
  the Moon and weaker on the opposite side.
• Since the Earth and particularly the oceans is
  not perfectly rigid it is stretched out along the
  line toward the Moon.

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The Moon has

• no atmosphere. But evidence from suggested that
  there may be water ice in some deep craters near
  the Moons south pole which are permanently
  shaded. There is apparently ice at the north pole
  as well.

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A piece of the moon
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The End