Test tomorrow will be Earth, Solar System 7, and Meteors, Asteroids,

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Test tomorrow will be Earth, Solar System (7),
and Meteors, Asteroids, Comets (10)

• Final is Mon, July 30, 910a - 1040

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Meteors, Asteroids, and Comets

• Chapter 10

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Meteors - terms

• Meteor - shooting star (a rock in the Earth's
  atmosphere)
• period when in Earth's atmosphere - when is
  making the light
• Meteoroid - a rock in space
• Before enters atmosphere
• Meteorite - a rock from space that made it to the
  Earth's surface
• After hits Earth
• KNOW terms / differences

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Meteors

• When encounters earth's atmosphere it compresses
  the air in front of it very fast becomes very
  hot
• Vaporizes most rocks before makes it the ground,
  although some do survive

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• Meteors are heated to 1.000s K
• Meteors can be large enough to be visible during
  the day (fireball)
• does not happen often
• Most burn up in the atmosphere and do not reach
  the surface
• KEY - are rocks debris that enter earth's
  atmosphere

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Question

• What is the difference between a meteor,
  meteoroid, and meteorite?
• meteor - when in atmosphere
• meteoroid - in space
• meteorite - after hits earth
• Can find wherever they fell but easier in
  glaciers in artic circle because glacier collects
  together drops when melts

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Asteroids

• Small, generally rocky bodies that orbit the Sun
• Many between Mars Jupiter
• Most lie in the asteroid belt
• Trojan asteroids - not specifically in belt, just
  in solar system in other places
• are not really close together - belt is actually
  large space

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• Ceres (first asteroid) - "missing planet"
• Asteroids are too small (most) to be spherical
• When object gets to large size the gravitational
  force pulls on opposite sides of rock it will
  collapse to a spherical which is nearly uniform
  in pull on all sides
• size from 1,000 km to 1 km and smaller
• found by taking pictures of sky on at different
  times comparing location - an asteroids moves
  much more quickly than the stars

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Origin of asteroids

• fragments of planetesimals
• gathered together through accretion, just like
  planets
• differentiation in large asteroids
• material radioactive if large enough sometimes
  heats up creates iron core like earth
• Jupiter's gravity disturbed accretion
• Prevented asteroids from gathering together into
  one planet
• Meteoroid asteroids are basically the same
  thing, but the first is close enough to hit earth

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Kirkwood Gaps

• Plot of of asteroids at a particular distance
  from the sun
• Certain locations have no asteroids at all
• Jupiter pulls on asteroids when both orbits lines
  up (inside orbit is faster) pulls out to
  location where not as regular a pull
• Important because show why asteroids are there
  why orbit where they do

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• Kirkwood gaps
• Where there are spaces because the asteroids
  jupiter line up durring peroidic orbits
• Trojan asteroids
• Stay same distance from jupitor
• Apollo asteroids
• Earth crossing
• about 700 exist (known)
• 1 collision about every 10,000 years

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Question

• What happens to most of the extra terrestrial
  material that collides with the Earth?
• most becomes dust before makes it to the ground

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Comets
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Comets

• More difficult to see now because of light
  pollution
• In the past, comet "a bad sign"
• Unpredictible, unlike other things in sky
• Reminded some of sword or knife
• Structure
• has small nucleus of gas ice - 10 km max
• has tail of gas - very large
• NOT made up of rocky-iron stuff but rocky-ice,
  unlike asteroids

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• Composition
• coma and tail - water, CO2, CO
• Evaporating H2O is broken up - creating Hydrogen
  cloud
• neucleus is frozen material
• Origin
• Oort Cloud - 150,000 AU - million year periods
  (some)
• know from outside frost line because made
  primarily of ice
• Tossed out by giant planets
• gravitational pull makes them leave cloud / belt
• Kuiper belt
• out by Pluto

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• Oort cloud comets come from so far that unlikly
  to come more than once because great distance
  takes so long to orbit

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Why leave Oort?

• know where came by orbit
• Oort come from any direction
• Kuiper come in same plane as planetial orbit
• Small interaction from distant sun can change
  orbit over long term
• Our sun moves in relation to other stars, just
  takes long time to see

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Comet's tails

• Sunlight strikes dust - reflection
• sun when sun reflects of dust
• Gas tail - fluorescence
• light from sun excites gas like in florucent
  light
• Tails point away from the Sun
• in different angles but still away (even when
  traveling away)
• because reaction of light solar wind

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• Dust tail curved because when released the dust
  is orbiting the sun travel at different speed
• Gas cloud is not orbiting but reacting to solar
  winds
• Farther from sun, harder to see comet
• at closest point gas tail points straight away
  from sun
• no way to see before they get close to sun no
  predictable pattern - see only once

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• Short period comets
• less than 200 year orbital period
• From Kuiper belt
• Eventually depleted due to repeated passes by the
  Sun or colides with Jupitor
• Haliey's comet is best example
• In same plane as rest of regularly orbiting parts
  of solar system
• Long Period comets
• One-time visits
• Because so far away
• meteor showers are caused when earth passes
  through dust of comet

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Meteor Showers

• Meteor showers are caused when earth passes
  through dust from comet it meets atmosphere
• Cannot predict intensity because dust clumps into
  higher density as orbits
• Named after constellation looks like comes from -
  that is in the same direction as the dust trail
• Showers are at same time every year because dust
  stays in same location along our orbit

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Question

• Which way does the tail of a comet point?
• Away from sun
• Why do comets have two tails?
• Dust reflects light gas florescence
• NOT created from speed of comet

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Giant Impacts

• Every few 1,000 years, Earth is hit by a huge
  meteoroid - 10 meters or more
• A 100 kg (_at_ 1 m) meteoroid is like 100 tons of
  dynamite - would make a 30-meter crater
• A 10-meter meteoroid is like a thermonuclear bomb

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Arizona

• Can detect after erosion surface changes
  because also creates underground disturbance

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Chicxulub, Yucatan
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Wolfe Creek, Australia
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Manicougan Lake in Quebec
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Plot

• How often they happen vs how much energy given
  off
• The more often happens, the less energy it gives
  off

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Question

• What are the two types of comets, and where do
  they come from?
• Oort cloud
• long period
• Kyper belt
• short period

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