Orbits

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Orbits Objects in Space
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What is an orbit?

• An orbit is a regular, repeating path that one
  object in space takes around another one. An
  object in an orbit is called a satellite. A
  satellite can be natural, like the Earth or the
  Moon. It can also be man-made, like the Space
  Shuttle or the ISS.NASA

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Satellites

• A satellite is actually trying to travel in a
  straight line to conform to Newton's 1st law of
  motion (an object will remain at rest or in
  uniform motion in a straight line unless acted
  upon by an external force).
• However, the Earth's gravity is, at the same
  time, pulling the satellite down (the external
  force in Newton's law).

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Satellites and Orbits

• Imagine a firing a gun horizontally.
• The bullet will eventually fall to Earth. But
  what if the bullet were travelling fast enough
  that it passed the horizon before starting to
  drop?
• As the bullet fell to Earth, the curvature of the
  Earth would mean the ground was curving away
  underneath it.

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Satellites and Orbits

• Now, apply that to a satellite. If the satellite
  is travelling fast enough, the curvature of the
  Earth will cause the ground to fall away from
  beneath the satellite as gravity is pulling it
  down. This process continues, causing the
  satellite to orbit the Earth.

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Orbits and Forces
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LEO
Low Earth Orbit (LEO) Orbiting at an altitude of
600-1,000 km.
Path of Satellite
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Types of Earth Orbits

• LEO (Low Earth Orbit)
• 520-1,500 km altitude
• Orbital period ninety minutes

• MEO (Medium Earth Orbit)
• 20,000 km altitude
• Between LEO and GEO
• Orbital period 5-6 hours

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Types of Earth Orbits

• HEO (High Earth Orbit or Highly Elliptical Orbit)
• 40,000 km altitude (at perigee)
• Large dwell time over one hemisphere
• Orbital period 12-24 hours

• GEO (Geosynchronous or Geostationary Earth Orbit)
• 36,000 km altitude
• Orbital period 24 hours (matches Earths
  rotation)

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Planetary Orbits

• How do the planets stay in orbit around the sun?
• The solar system was formed from a rotating cloud
  of gas and dust which spun around a newly forming
  star, our sun, at its center.
• The planets all formed from this spinning
  disk-shaped cloud, and continued this rotating
  course around the sun after they were formed.

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Planetary Orbits

• The gravity of the sun attracts the planets and
  keeps the planets in their orbits. The stay in
  their orbits because there is no other force in
  the solar system which can stop them.  
• In fact, the planets are constantly falling
  toward the sun in much the same way that a thrown
  ball falls down to the ground.

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Planetary Orbits

• When you throw a ball. it moves away from you and
  falls to the ground. 
• If you throw the ball slowly, it lands on the
  ground a few feet from you.
• If you throw it faster, it will fall farther
  away.
•  
• The faster you throw the ball, the farther it
  goes.

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Planetary Orbits

• Now imagine throwing the ball so fast that its
  path has the same shape as the curvature of the
  Earth.
• Since the Earth is round, the ball you threw
  would fall all the way around the planet. 
• If it goes fast enough to keep going around and
  around, the ball would stay in orbit.  The
  planets stay in orbit around the sun in the same
  way.

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Our Solar System

• Our solar system is made up of
• Sun
• Eight planets (Poor Pluto ?)
• Their moons
• Asteroids
• Comets

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Planets

• A "planet is a celestial body that
• (1) is in orbit around the Sun,
• (2) has sufficient mass for its gravity to
  assume a nearly round shape
• (3) has cleared the neighborhood around its
  orbit.
• it has enough gravity that it does not share its
  orbit space with any other similarly sized body
  other than its own moons. (Pluto shares its
  orbit so its now a dwarf planet)

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Inner Planets

• The inner four rocky planets at the center of the
  solar system are
• Mercury
• Venus
• Earth
• Mars

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Outer Planets

• The outer planets composed of gas are
• Jupiter
• Saturn
• Uranus
• Neptune

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Comets

• The word "comet" comes from the Greek word for
  "hair.
• Our ancestors thought comets were stars with what
  looked like flowing hair trailing behind.

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Comets Dirty Snowballs

• Comets are loose collections of ice, dust, and
  small rocky particles whose orbits are usually
  very long, narrow ellipses.

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Structure of a Comet

• A Comets Head
• Outer layer Coma (water vapor, CO2, and other
  gases)
• Solid inner core Nucleus (frozen ice, gas and
  dust )

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Comets Tail

• As a comet approaches the sun and heats up, some
  of its gas and dust stream outward, forming a
  tail.
• Most comets have 2 tails
• gas (ion), tail
• dust tail
• Tails point away from the sun because of the
  force of the solar wind.
• A comets tail can be more than 100 million
  kilometers long.

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Comets Tail
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Comets Orbit

• Comets move in an elliptical shaped orbit.

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Origin of Comets

• Most comets are found in 2 regions of the solar
  system Kuiper belt and Oort cloud.
• Kuiper belt-doughnut-shaped region that extends
  beyond Neptunes orbit to about 100 times Earths
  distance from the sun.
• populated with frozen bodies left over from the
  solar system's formation
• Oort cloud-spherical region of comets that
  surrounds the solar system out to more than 1,000
  times the distance between Pluto and the sun.

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Famous Comets

• Comet Halley is perhaps the most famous comet in
  history.
• Each time this comet's orbit approaches the Sun,
  its 15-km (9-mile) nucleus sheds about 6 m (7
  yards) of ice and rock into space. This debris
  forms an orbiting trail that, when falling to
  Earth, is called the Orionids meteor shower.
• Halleys comet reappears every 76 years. Its next
  appearance is in 2061.

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Comet Hale-Bopp

• July 23, 1995- an unusually large and bright
  comet was seen outside of Jupiter's orbit by Alan
  Hale of New Mexico and Thomas Bopp of Arizona.
• Exceptionally large size.
• It was visible even through bright city skies,
  and may have been the most viewed comet in
  recorded history.
• It will not appear again for another 2,400 years.

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Other Famous Comets

• Comet Hyakutake-On January 30, 1996, Yuji
  Hyakutake (pronounced "hyah-koo-tah-kay"), an
  amateur astronomer from southern Japan,
  discovered a new comet using a pair of
  binoculars.
• Comet Shoemaker-Levy 9-Between July 16 and July
  22, 1994, more than 20 fragments of Comet
  Shoemaker-Levy 9 collided with the planet
  Jupiter. Astronomers Carolyn and Eugene Shoemaker
  and David Levy discovered the comet in 1993. It
  was the first collision of two Solar System
  bodies ever to be recorded.

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Asteroids

• A small and rocky space object that orbits the
  sun.
• Most asteroids are found in the asteroid belt.
• The asteroid belt is located between the orbits
  of Mars and Jupiter.
• Also called a minor planet or planetoid
• Smaller than planets but larger than meteoroids

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How many asteroids are there?

• There are about 40,000 known asteroids that are
  over 0.5 miles (1 km) in diameter in the asteroid
  belt About 3,000 asteroids have been cataloged.
• There are many smaller asteroids (100,000).
• Asteroids are made of metals, silicate, iron,
  nickel, and carbon.
• The first one discovered (and the biggest) is
  named Ceres it was discovered in 1801.
• Asteroids range in size from tiny pebbles to
  about 578 miles (930 kilometers) in diameter
  (Ceres).

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ASTEROIDS BECOMING MOONS

• Asteroids can be pulled out of their solar orbit
  by the gravitational pull of a planet. They would
  then orbit that planet instead of orbiting the
  Sun.
• Astronomers theorize that the two moons of Mars,
  Phobos and Deimos, are captured asteroids.

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Asteroid Strike

• Scientists hypothesize that one or more large
  asteroids hit Earth 65 million years ago and
  caused extinction of the dinosaurs.
• Scientists also hypothesize that the largest mass
  extinction, 250 million years ago, killing off
  90 of all species was also caused by a large
  asteroid.

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Meteoroids

• Meteoroid-chunk of rock or dust in space.
• Meteoroids come from comets or asteroids
• Smaller than an asteroid.

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Meteor

• When a meteoroid enters Earths atmosphere,
  friction with the air creates heat and produces a
  streak of light that you can see in the sky.
• A meteor is a meteoroid that enters Earths
  atmosphere and burns up.

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Meteorites

• Meteoroids that pass through the atmosphere and
  hit Earths surface are called meteorites.
• Classified by composition stony, iron ,or
  stony-iron.

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What do we do if an NEO (Near-Earth-Object) is
approaching?

• Unknown Still being experimented.
• Scientist are calculating ways to use nuclear
  energy to divert an incoming object.
• High energy x-ray pulses produce a shock wave to
  push the NEO in the opposite direction.

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Review

• Comet A comet is a relatively small solar system
  body that orbits the Sun. When close enough to
  the Sun they display a visible coma (a fuzzy
  outline or atmosphere due to solar radiation) and
  sometimes a tail.
• Asteroids are small solar system bodies that
  orbit the Sun. Made of rock and metal, they can
  also contain organic compounds. Asteroids are
  similar to comets but do not have a visible coma
  (fuzzy outline and tail) like comets do.
• Meteoroid is a small rock or particle of debris
  in our solar system. They range in size from dust
  to around 10 meters in diameter (larger objects
  are usually referred to as asteroids).
• Meteor A meteoroid that burns up as it passes
  through the Earths atmosphere is known as a
  meteor. If youve ever looked up at the sky at
  night and seen a streak of light or shooting
  star what you are actually seeing is a meteor.
• Meteorite A meteoroid that survives falling
  through the Earths atmosphere and colliding with
  the Earths surface is known as a meteorite.