Section 5: Comets, Asteroids, and Meteors - PowerPoint PPT Presentation

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Section 5: Comets, Asteroids, and Meteors

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Comet s Tail Comet s Orbit Comets move in an elliptical shaped orbit around the Sun. Asteroids A small and rocky space object. Most asteroids originate in the ... – PowerPoint PPT presentation

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Title: Section 5: Comets, Asteroids, and Meteors


1
Section 5 Comets, Asteroids, and Meteors
2
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.

3
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.
  • 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.

4
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5
Comets Dirty Snowballs
  • Comets are loose collections of ice, dust, and
    small rocky particles whose orbits are usually
    very long, narrow ellipses.

6
Structure of a Comet a few miles in diameter
  • A Comets Head
  • Outer layer Coma (water vapor, CO2, and other
    gases)
  • Solid inner core Nucleus (frozen ice, gas and
    dust )

7
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.

8
Comets Tail
9
Comets Orbit
  • Comets move in an elliptical shaped orbit around
    the Sun.

10
Asteroids
  • A small and rocky space object.
  • Most asteroids originate in the asteroid belt.
  • The asteroids orbit between the orbits of Mars
    and Jupiter.

11
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12
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).

13
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.

14
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.

15
Meteoroids
  • Meteoroid-chunk of rock or dust in space.
  • Meteoroids come from comets or asteroids.

16
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.

17
Meteorites
  • Meteoroids that pass through the atmosphere and
    hit Earths surface are called meteorites.
  • Classified by composition stony, iron ,or
    stony-iron.

18
Video Clip
  • http//pbs.panda-prod.cdn.s3.amazonaws.com/media/a
    ssets/wgbh/ess05/ess05_int_meteorshower/index.html

19
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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