The Solar System

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The Solar System
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What is the Solar System?

• The solar system includes our sun, and all the
  matter that orbits the sun.
• Planets, moons, dust and other debris
• People used to believe that everything they saw
  in the sky revolved around earth and therefore
  the entire Universe was our solar system.

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Aristotle

• Greek Philosopher (384-322 BCE)
• Came up with the idea that the earth was in the
  center of the solar system
• Geocentric Model
• Determined Universe to be spherical and limited
  in size
• This idea was adopted by the church and remained
  untested for 1000 years.
• His model was not very accurate and did not
  explain a lot of the variation seen in planets
  and comets.

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Ptolemy

• Greek Astronomer (87-150 CE)
• Ptolemy looked at the motion of the stars and the
  planets and came up with ideas that helped
  Aristotles model work better
• Ptolemys system had the planets spinning in
  large circles as they orbited earth.
• This system more accurately predicted the motion
  of the planets but was very complex.

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Aristarchus

• Greek Astronomer (310-230 BCE)
• First to suggest a Heliocentric model of the
  solar system.
• Few people believe in him as at the time they
  believed their Gods lived on Earth so it must be
  the center of the known Universe.

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Nicolaus Copernicus

• Polish Astronomer (1473-1543 BCE)
• First astronomer to formulate a scientifically
  based sun-centered model of the cosmos.
• Delayed publishing his work until he was near
  death, likely due to fear of condemnation from
  the Church.
• Nearly 60 years later the Church banned his book.
  It remained banned until 1835.

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Tycho Brahe

• Danish Nobleman (1546-1601)
• Known for his accurate and complete astronomical
  and planetary observations
• Religious beliefs led Tycho to attempt to use his
  data to blend Ptolemy and Copernicuss views.
• He believed the sun revolved around the earth and
  the planets revolved around the sun.
• The stars lay beyond all of this and also
  revolved around earth.
• His assistant, Johannes Kepler, would later
  develop his own theory on the solar system.

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Johannes Kepler

• German mathematician and astronomer. (1571-1630)
• Used Brahes extensive observations to develop
  the most accurate model of the Universe based on
  his Three Laws of Planetary motion
• 1. All planets move in ellipses with the sun at
  one focus.
• 2. A planet moves faster as it gets closer to
  the sun.
• 3. The further a planet is from the sun, the
  slower it revolves.

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Galileo Galilei

• Italian physicist, mathematician, astronomer, and
  philosopher (1564-1642)
• Was the first astronomer to use the telescope to
  make observations that helped to prove Copernicus
  and Kepler right.
• Found four of Jupiters Moons
• Found objects outside of our solar system that
  did not revolve around either the sun or earth.
• Was sentenced to house arrest for his beliefs by
  the Inquisition

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What is in our Solar System?

• 8 Planets
• 166 known planetary moons
• Billions of small bodies including
• 4 dwarf planets and their 4 moons
• Asteroids
• Meteoroids
• Kuiper Belt objects
• Comets
• Interplanetary Dust

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Types of Planets

• The planets are divided into 2 groups based on
  their location and composition
• Inner planets
• Mercury, Venus, Earth, Mars
• Small and Rocky with few moons
• Outer Planets
• Jupiter, Saturn, Uranus, Neptune
• Huge, gaseous, ringed, many moons

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NTK Terms

• Astronomical Unit - Distance from the earth to
  the sun (150,000,000 km) (AU)
• Revolution - A celestial bodys movement around
  another object, usually in an ellipse
• Rotation - The spinning of a celestial body like
  a top.
• Earth Day - the amt of time it takes earth to
  rotate once (24 hours)
• Earth Year- the amt of time it takes the earth to
  revolve once (365 days)

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Mercury

• Closest planet to the sun.
• 0.39 AU
• The sun looks 3 times bigger
• Smallest planet in our solar system
• About 40 the diameter of Earth
• Has no atmosphere
• Is heavily cratered like the moon

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Mercury

• Takes 88 Earth days to revolve around the sun
• 116 Earth days to rotate once
• Used to be larger, its liquid core shrunk as it
  solidified, leaving large cracks on the surface.
• Has no Moons

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Mercury

• Temperature Range -168 427C
• Has polar ice caps
• Was named after the Roman winged messenger to the
  Gods as it is the fastest planet.

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Venus

• Second planet from the sun.
• 0.72 AU
• Just slightly smaller than earth (5)
• Has a very hot, dense, atmosphere that contains
  sulfuric acid clouds
• Sustains an average temperature of 450C likely
  due to runaway greenhouse gases.

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Venus

• Revolves around sun in 225 Earth Days
• Rotates very slowly, 243 Earth Days
• Surface is protected by the thick atmosphere from
  meteors so it looks much like Earths
• No moons or ice caps
• Named after the Roman goddess of Love
• Brightest object in night sky aside from moon.

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Earth

• Third planet from the sun
• 1 AU
• Largest of the Inner Planets (12,000km dia.)
• Has an atmosphere containing mostly nitrogen(78)
  and oxygen (21)
• Temperature ranges from -88 to 58C
• Earth is tilted from its axis of revolution by 23

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Earth

• Earth revolves around the sun in 365.24 Earth
  days.
• The Earth rotates in one Earth day or 23.93
  hours.
• Has a molten core.
• Has polar ice caps.
• Has a moon (Luna or Moon)
• Roughly 25 the size of earth.

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Mars

• The fourth planet from the sun
• 1.5 AU
• Roughly half the size of Earth
• Has a very thin atmosphere composed mostly of
  carbon dioxide
• Temperature ranges from -140 to 20C
• Called Red Planet due to iron oxide in the
  crust
• Named after the Roman god of war.
• Home to largest volcano in solar system, Olympus
  Mons

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Mars

• Mars revolves around the sun in 687 Earth Days.
• Mars rotation takes just slightly over one earth
  day (24.6 hours)
• Mars has polar ice caps made of dry ice.
• Mars has two tiny moons
• Phobos(22km) and Deimos(13km)

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Jupiter

• 5th planet from the sun
• 5.2 AU
• The largest of the planets (88,700km wide)
• Is comprised almost entirely of hydrogen and
  helium. If it were considerably larger, it could
  have become a star.
• The gas is compressed to a liquid in the center.
• There is likely a molten rocky core, possibly
  from impacts with other objects.
• Surface temp -153C (Core is hotter due to
  pressure from gravity

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Jupiter

• Jupiter takes about 12 years to revolve around
  the sun.
• Jupiter rotates in only 9.8 hours.
• Jupiter has a giant storm on its surface called
  the Great Red Spot
• Jupiter has 63 named satellites
• Io and Europa are two well known moons
• Jupiter has rings, but they are very faint
• Jupiter was named after the principle Roman God
  (Greek equivalent Zeus)

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Saturn

• Saturn is the 6th planet from the sun
• 9.5AU
• Second largest planet (75,000km wide)
• Hydrogen and Helium with a liquid center and a
  molten rock core.
• Has a surface temperature of -185C (Core hotter
  due to pressure from gravity)

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Saturn

• Revolution takes 29 Earth Years
• Rotation takes 10.2 Hours
• Saturn has beautiful rings composed mostly of ice
  and dust.
• Saturn has 60 identified moons (52 named)
• Titan is the largest moon
• Named after the Roman god of agriculture, who
  happened to be Jupiters father.

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Four of Saturn's moons Dione, Titan, Prometheus
(edge of rings), Telesto (top center)
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Uranus

• Uranus is the 7th planet from the sun
• 19 AU
• Third largest planet (51,000km wide)
• Composed of Hydrogen, Helium and Methane
  (blue-green color)
• Also likely to have liquid center with molten
  rock core.
• Surface temperature of -114C

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Uranus

• It takes 84 Earth years to revolve around the
  sun.
• Rotates in just 18 hours.
• Has 11 rings that run up and down because Uranus
  is tilted nearly 90
• Has 27 known moons
• Titania is the largest
• Was named after the greek god of the sky.
  (Saturns Father)

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Neptune

• Neptune is the eighth and farthest planet from
  the sun -30 AU
• Neptune is nearly equal in size to Uranus
• 50,000 km wide.
• Composed of hydrogen, helium, and methane
  (blue-green color)
• Also has liquid center and molten rocky core
• Surface temperature of -125C

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Neptune

• It takes Neptune 165 Earth years to orbit the
  sun.
• It takes only 19 hours to rotate
• Has several faint rings
• Named after the Greek god of the sea.
• Has 13 known moons
• Triton is the largest.

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What else is in our solar system?

• Asteroids
• Meteoroids
• Kuiper Belt Objects
• Comets.

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Asteroids

• Asteroids are large chunks of rock that orbit the
  sun
• Larger than a meteor(10m)
• Have no ice
• Most are located between the inner planets and
  outer planets in the Asteroid Belt
• Largest known is Ceres at 950km across

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Left to right 4 Vesta, 1 Ceres, Earth's Moon
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Meteoroids

• Small sand to boulder sized debris in the solar
  system.
• Anything smaller is considered interplanetary
  dust.
• Tend to be debris from things like comets or
  collisions with planets.
• These meteoroids clump together as they orbit.

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Meteors

• Meteors are meteoroids that enter Earths
  atmosphere.
• When earth passes through a clump of meteoroids,
  a meteor shower occurs.
• Meteor showers are regular and predictable.
• If the meteor hits the ground it is referred to
  as a meteorite.

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Kuiper Belt Objects

• Kuiper Belt is a region of space extending beyond
  Neptune. (30-55AU)
• Composed of small bodies of rock and ice
• Very similar to comets, though without the
  eccentric orbit.
• Pluto is the most well known KBO
• If we wanted to include Pluto as a planet we
  would have to include the 70,000 other pluto-like
  objects in the Kuiper Belt.

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Comets

• Comets are small bodies in the solar system that
  orbit the sun. (100m to 40km)
• As they approach the sun ice begins to sublimate,
  causing a visible coma and tail to form that
  points away from the sun.
• Comets have very elliptical orbits
• As comets lose ice they also loose debris
• Eventually they run out of ice and lose the coma
  and tail.
• Comets all together form the Oort Cloud which is
  estimated to end around 50,000 AU from the sun.

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