Chapter 16: The Solar System Part 2

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Chapter 16 The Solar System Part 2

• Alyssa Jean-Mary

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The Outer Planets Jupiter

• Jupiter is a mammoth planet that was named after
  the most important of the Roman gods. The symbol
  of Jupiter is a stylized lightning bolt, since
  lightning was supposed to come from the god
  Jupiter. Electrical discharges actually regularly
  occur in the atmosphere of Jupiter, which are
  detected on the earth by the bursts of radio
  waves that they produce. Thus, Jupiters symbol
  is appropriate.
• The period of rotation for Jupiter is a little
  less than 10 hours. This means that points on
  Jupiters equator travel at the enormous speed of
  45,000km/h. In perspective, points on the earths
  equator travel at the speed of only 1670km/h.
  Because Jupiter has such a fast rotation, it
  bulges much more at the equator that the earth
  does, and thus has much less of a spherical shape.

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The Outer Planets Jupiter Its Clouds

• Like Venus, Jupiter is shrouded in clouds. The
  clouds around Jupiter are more spectacular,
  however. These clouds are responsible for the
  relatively high reflectivity of Jupiter. This
  reflectivity, along with its size, make Jupiter a
  bright object in the sky, even though it is far
  from the sun. The clouds occur in alternate light
  and dark bands. The colors, which are mostly in
  the yellow-orange-red family, and markings of the
  bands change slightly from time to time.
• The Great Red Spot is one of such markings. It is
  about 25,000km long and 10,000km high, which is
  actually as large as two earths. Although the
  size, shape, and color of this marking varies, it
  doesnt seem to be a temporary phenomenon, since
  it was definitely identified as long ago as 1831.
  The nature and origin of the Great Red Spot is
  uncertain, but one possible explanation is that
  it is a king of permanent hurricane into which
  energy is constantly fed by the Jovian wind
  system. Its red color could be due to
  phosphorous, which would be present as a result
  of the breakup of the phosphorus compounds that
  are believed to contribute to the colors of the
  bands that circle Jupiter.

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The Outer Planets Jupiter Its Satellites

• Jupiter has 61 known satellites. Of these, the
  four that were discovered by Galileo in 1610 are
  the easiest to see. These are Io, Europa,
  Ganymede, and Callisto.
• The innermost satellite is Io. Io is slightly
  larger than our moon, and its surface contains
  many active volcanoes. It is actually the most
  volcanically active body in the solar system. The
  energy that is involved in this activity comes
  from the gravitational pulls of Jupiter and two
  of Jupiters other satellites, Ganymede and
  Europa. Io flexes by nearly 100m, which heats up
  its interior, thus powering the over 100 active
  volcanoes. These volcanoes belch white-hot lava
  and jets of sulfurous gas. Loki, which is the
  most vigorous of the volcanoes, pours out more
  heat than all the active volcanoes on earth
  combined.
• The other satellites of Jupiter are coated with
  ice. Europa is smaller than the moon, Ganymede is
  larger than Mercury, and Callisto is bit more
  modest in size. Unlike Callisto, both Europa and
  Ganymede show signs of geological activity.
• The satellites of Jupiter besides these four are
  very small, being only 2 to 250km across. Some of
  these satellites revolve backward around
  Jupiter, meaning that they move from east to west
  instead of from west to east as most other
  satellites do.
• Jupiter also has a ring, but this ring is so
  faint that it can only be detected by spacecraft.
  This ring seems to consist of dust that was
  knocked off the innermost satellites by
  micrometeoroid impacts and debris from volcanic
  eruptions on Io.

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The Outer Planets Jupiter Its Structure

• The volume of Jupiter is about 1300 times the
  volume of the earth, but its mass is only 318
  times as great as the mass of the earth. Thus,
  Jupiter has a low density, a density that is only
  a quarter of the density of the earth. This means
  that Jupiter cannot be composed of rock and iron
  like the earth is. Jupiter actually consists
  chiefly of hydrogen and helium, which are the two
  lightest elements.
• Jupiter most probably has a relatively small
  rocky inner core that is probably the size of the
  earth. This inner core is probably surrounded by
  a large outer core that is composed of liquid
  hydrogen. The hydrogen is assumed to be under
  such an enormous amount of pressure that it
  behaves like a liquid metal. The interior is
  believed to be as hot as 20,000C. This is not
  hot enough for nuclear reactions involving
  hydrogen to occur, because if it was, it would
  turn Jupiter into a star. But, if Jupiter had a
  mass that is 80 times greater than its current
  mass, then the internal temperatures of Jupiter
  would be high enough to make Jupiter a miniature
  star. The entire core is surrounded by a dense
  layer of liquid hydrogen and helium. This layer
  gradually turns into a gas with increasing
  distance from the core. The outer part of the
  atmosphere of Jupiter contains such gases as
  ammonia, methane, and water vapor, in addition to
  hydrogen and helium.

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The Outer Planets Jupiter Spacecraft Visits

• The spacecraft that have passed close to Jupiter
  have provided a wealth of information
• Jupiter has a magnetic field that is many times
  stronger than the magnetic field of the earth.
  Jupiters magnetic field traps high-energy
  protons and electrons from the sun in belts that
  extend outward. Even though the earth also has
  such belts, they are 10,000 times weaker than the
  belts of Jupiter. It is possible that this field
  is connected to the metallic nature of part of
  the volume of Jupiter, with the metal being the
  highly compressed liquid hydrogen, instead of the
  molten iron that is present in the core of the
  earth.
• Jupiter actually radiates over twice as much
  energy as it receives from the sun. In
  perspective, Venus, Earth, and Mars radiate only
  as much energy as the sun provides. Thus, it
  seems that Jupiter is still cooling down, with
  the extra heat being left over from the planets
  formation.

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The Outer Planets Saturn

• Saturn is the most striking and beautiful of the
  planets in the solar system. Saturn was named
  after the Roman god of sowing seed, who is the
  father of Jupiter. Saturn is called Kronos in
  Greek mythology, and thus, its symbol is a
  stylized K. There are festivals of worship to
  Saturn, which are called saturnalia. These
  festivals are always splendid occasions of joy
  and revelry. Saturday was actually named after
  this Roman god.

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The Outer Planets Saturn Its Like and Unlike
Jupiter

• Although Saturn is smaller and less massive, it
  resembles Jupiter in many ways
• It consists largely of hydrogen and helium.
• It radiates more heat than it receives from the
  sun.
• It is flattened at the poles by rapid rotation.
• It has a strong magnetic fild.
• It has a dense atmosphere.
• It is surrounded by banded clouds, in which
  gigantic thunderstorms occur.
• Auroras occur in the atmosphere.
• In some ways, however, Saturn is different than
  Jupiter
• The core of Saturn seems to have less liquid
  metallic hydrogen than the core of Jupiter. Thus,
  it might have a large rocky kernel at the center
  of the core.
• Since Saturn is farther from the sun than
  Jupiter, it is considerably colder, with its
  surface temperature being only about -180C.

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The Outer Planets Saturn Its Satellites

• Saturn has at least 39 satellites. These
  satellites range in size from 6km across to
  5140km across.
• Titan, who is 5140km across, is Saturns largest
  satellite. It is only slightly smaller that
  Jupiters satellite Ganymede. Titan is the only
  satellite in the solar system that has an
  atmosphere. This atmosphere seems to consist
  largely of nitrogen, with some methane and small
  amounts of other organic compounds. The
  atmosphere of Titan is more like the atmosphere
  on the earth than the atmosphere of any other
  body in the solar system. Floating in this
  atmosphere are reddish clouds of organic
  compounds. These clouds probably send showers of
  methane rain and perhaps snow from time to time
  to the surface of Saturn, thus feeding the liquid
  methane oceans that cover much of the surface of
  Titan. If Titan have been warmer, life might have
  developed there, since chemical processes are
  slow at low temperatures. If it took a half
  billion years for life to come into being on the
  earth, the solar system is not old enough for
  this process to have occurred on Titan since its
  temperature is about -176C.

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The Outer Planets Saturn Its Rings 1

• A number of rings surround Saturn at its equator.
  Two of these rings are bright and the rest of
  them are faint. The rings are inclined by 27
  with respect to the plane of the orbit of the
  earth. Therefore, we see the rings from different
  angels as Saturn revolves around the sun, a
  process that takes 29.5 years. The rings are
  edgewise to the earth twice in each period of
  revolution. When the rings are edgewise, they
  are practically invisible, which suggests that
  they are very thin. Actually, they are only tens
  of meters thick. In perspective, since the outer
  bright ring is 270,000km in diameter, a sheet of
  paper would appear fat by comparison. The rings
  of Saturn are seen in their fullest glory when
  they are tipped by 27.

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The Outer Planets Saturn Its Rings 2

• The rings of Saturn are not solid sheets. They
  actually consist of a multitude of small bodies.
  Each of these bodies are miniature satellites
  that revolve around Saturn. One reason for this
  conclusion is that stars can be seen though the
  rings. Another reason for this conclusion is
  based on the measurements taken of the
  Doppler-effect. These measurements show that the
  inner part of each ring moves faster than the
  outer part. If the rings were solid sheets, the
  outer part of the ring would actually move faster
  than the inner part.
• The rings of Saturn are also not gaseous. This is
  because they reflect sunlight and radar signals
  very well.
• When spacecraft provided a vast amount of
  information about Saturn, it was found that the
  rings are composed of particles of chunks of rock
  and ice that range in size from small stones to
  boulders. The information also showed that the
  rings that we see from the earth are not uniform,
  but are actually split into thousands of narrow
  ringlets. In one of the outer, faint rings, two
  of the ringlets that make it up seem to be
  braided around each other. This may be a result
  of the gravitational pulls of two small
  satellites, one with an orbit just inside the
  ringlets and one with an orbit just outside the
  ringlets.

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The Outer Planets Uranus and Neptune Discovered

• Uranus and Neptune were discovered by a
  telescope
• Uranus was found in 1781 by William Herschel, a
  great English astronomer. Herschel first thought
  that Uranus was a comet, since it couldnt be a
  star since it appeared as a disk instead of a
  point of light. But, observations were made over
  a period of time that showed that its position
  changes relative to the stars. From these
  observations, its orbit was calculated, thus
  showing that it is a planet. In Greek mythology,
  Uranus personifies the heavens and is the father
  of Saturn, and thus the grandfather of Jupiter.
• Neptune was discovered in 1846. It was discovered
  because the predictions that were made for the
  orbit of Uranus, and thus its positions in the
  sky, were not followed by Uranus. Thus,
  calculations were done to establish that another
  body is affecting Uranus, which is why it was not
  following its predicted path. These calculations
  predicted where this other body would be in the
  sky, and were thus what ultimately led to the
  discovery of Neptune. Neptune is the Roman god of
  the sea.

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The Outer Planets Uranus and Neptune

• Uranus rotates about an axis that is only 8 from
  the plane of its orbit. Thus, you can think of
  Uranus as spinning on its side. The reason for
  this is most likely because a large object, an
  object that is about the size of the earth,
  collided with Uranus, early in the history of the
  solar system. This tilt causes summer at a
  particular place on Uranus to be a 42 year period
  of continuous sunshine and winter at a particular
  place on Uranus to be a 42 year period of
  continuous darkness.
• When spacecraft passed near Uranus and Neptune,
  photographs were taken that showed that both
  Uranus and Neptune have several rings around
  them. These rings consist of small particles,
  just like the rings of Saturn, but the rings are
  too narrow to be seen from the earth. Photographs
  from the spacecraft also showed that Uranus has
  24 known satellites, and Neptune has 8 known
  satellites.
• The spacecraft also found that the atmosphere of
  Neptune is in much more violent motion than the
  atmosphere of Uranus. Strong, turbulent winds
  blow across Neptune. Also, a hurricane that is
  nearly the width of the earth can be seen. This
  hurricane is called the Great Dark Spot because
  of its appearance, and it is much like the Great
  Red Spot on Jupiter. Near Neptunes south pole is
  a smaller hurricane. Both of these hurricanes are
  accompanied by white cirrus clouds of methane
  ice. Since Neptune is father away from the sun
  than Uranus is, and thus receives less solar
  energy, it is unknown why Neptune has stormier
  weather than Uranus does.

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The Moon

• The light that comes from the moon is actually
  reflected sunlight.
• The diameter of the moon is 3476, which is a
  little more than a quarter of the diameter of the
  earth. The moon is thus one of the largest
  satellites in the solar system.
• The moon revolves around the earth every 27 1/3
  days, and it rotates on its axis as it is
  revolving the earth. Since the rotation of the
  moon keeps pace exactly with its revolution, the
  moon turns around completely only once during
  each revolution around the earth. Thus, the same
  side of the moon is always facing us, with the
  other side always being hidden from us. The
  rotation and revolution of the moon are
  synchronized because of tidal bulges that were
  raised in the moon by the gravitational pull of
  the earth, which are much like the those that
  occur on the water on the earth due to the
  attraction of the moon. The rotation of the earth
  on its axis is actually slowing down due to
  friction between these water bulges and the
  bottom of the oceans. In the past, a similar
  friction that involved its tidal flexing also
  slowed down the rotation of the moon. It was
  slowed to the point where the tidal bulges are
  locked in place along a line between the moon and
  the earth. Most of the other large satellites in
  the solar system are synchronized in the same way.

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The Phases of the Moon 1

• If the earth was not revolving around the sun,
  the moon would be seen in the same place in the
  sky relative to the stars and at the same time of
  day every 27 1/3 days. But the earth is revolving
  around the sun, and it is carrying the moon with
  it, even as the moon is revolving around the
  earth. Thus, to us, the amount of time it takes
  the moon to revolve around the earth appears to
  be 29.5 days instead of 27 1/3 days. The
  following can be said the moon revolves around
  the earth every 27 1/3 days relative to the stars
  and every 29.5 days relative to the sun. Since
  time on Earth is relative to the sun, the moon is
  seen to return to the same place in the sky and
  at the same time of day every 29.5 days.
• During each of the 29.5 day period, the moon goes
  though a cycle of phases. The first phase is a
  thin crescent in the western sky at sunset that
  falls soon below the horizon. After this, the
  illuminated part of the moon grows wider each
  night, with the moon moving eastward relative to
  the stars. After two weeks, the moon is full and
  also rises in the east at sunset to light up the
  sky the entire night. After this, the illuminated
  part of the moon grows narrower each night,
  until, after two more weeks, it is again a thin
  crescent that rises just before sunrise. Then,
  the moon disappears altogether for a few nights,
  until it is again seen as a crescent at sunset.

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The Phases of the Moon 2

• During each of the 29.5 day period, the moon goes
  though a cycle of phases. The first phase is a
  thin crescent in the western sky at sunset that
  falls soon below the horizon. After this, the
  illuminated part of the moon grows wider each
  night, with the moon moving eastward relative to
  the stars. After two weeks, the moon is full and
  also rises in the east at sunset to light up the
  sky the entire night. After this, the illuminated
  part of the moon grows narrower each night,
  until, after two more weeks, it is again a thin
  crescent that rises just before sunrise. Then,
  the moon disappears altogether for a few nights,
  until it is again seen as a crescent at sunset.
• When the moon is full, it is on the opposite side
  of the earth from the sun. When the moon is not
  visible, which is called the dark of the moon
  or the new moon, it is approximately between the
  earth and the sun. The moon is actually not
  completely invisible at this time in its
  revolution there is actually a ghostly glow
  because of earthshine, which is sunlight that is
  reflected from the surface of the earth reaches
  the moon. Earthshine is affected by the clouds,
  the surface ice, and the whitecaps on ocean
  waves.

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The Properties of the Moon
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Eclipses 1

• When the earth is between the sun and the moon,
  why does light reach the moon? When the moon is
  between the sun and the earth, why does light
  reach the earth?
• The orbit of the moon is actually titled at an
  angle of 5.2 to the orbit of the earth. Thus,
  the moon is normally either slightly above or
  slightly below the direct line between the sun
  and the earth. When the moon does pass
  approximately directly before or behind the
  earth, an eclipse occurs. If the earth is between
  the sun and the moon, then it is an eclipse of
  the moon, and if the moon is between the sun and
  the earth, then it is an eclipse of the sun.

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Eclipses 2

• Even though the diameter of the sun is about 400
  times greater than the diameter of the moon,
  total eclipses of the sun still occur because the
  sun is also about 400 times as far away from the
  earth during much of its revolution around the
  sun. When a total eclipse of the sun occurs, the
  diameters of both the sun and the moon as seen
  from the earth are the same. When the moon is not
  quite aligned with the sun, partial eclipses of
  the sun can occur, with only part of the sun
  being obscured.
• When the moon is farthest from the earth, the
  diameter of the moon appears to us to be smaller
  than the diameter of the sun. Thus, even if the
  moon lies directly between the sun and the earth,
  the moon cannot block the entire sun. Here, an
  annular eclipse of the sun occurs. In an annular
  eclipse, a ring of sunlight appears around the
  rim of the moon.

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Eclipses