CP Space Science Unit (Textbook reference Chapters 12, 13, 14, 15 and 16)

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CP Space Science Unit(Textbook reference
Chapters 12, 13, 14, 15 and 16)
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Key Ideas

• Galaxies clusters of stars different shapes
• Stars Sun differ in size, temperature and
  color source for all bright objects
• Gravity planets, stars, solar system
• Know the appearance, composition, position and
  size, and motion of objects in our solar system
• Astronomical units for measuring

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What is astronomy?
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M33, The Pinwheel Galaxy in Triangulum by George
Greaney
What is astronomy?
M33, The Pinwheel Galaxy in Triangulum by George
Greaney
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Basically, if its off this planet its a study of
some realm of astronomy. As one might
imagine that covers an awful lot of subjects,
even more than we know right now.

• NGC 253, galaxy in Sculptor
• by George Greaney

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What is astronomy?
Galaxy M83 in Hydra by George Greaney
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• Stars
• Nebula
• Planets
• The Sun

• Star clusters
• Galaxies
• Galaxy clusters
• Dark matter
• Black holes

• The Great Andromeda Galaxy
• by George Greaney

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What is an astronomer?
Galileo Galilei (1564-1642)
A night watchman with a college education?
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An astronomer is a scientist, skilled in
mathematics, physics, and astronomy.
Most professional astronomers work for
universities or government agencies.
Galileo Observatory in Italy
Source The Berkeley Cosmology Group
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Few astronomers spend much time looking through
a telescope. Most operate telescopes from a
control room or even from their computer at
home via the Internet. Typical astronomers only
spend one or two weeks each year observing, and
the rest of their research time analyzing their
data.
Astronomer Serena Kim at work At Cerro Tololo in
Chili
Source Applied Theoretical and Computational
Physics DivisionLos Alamos National Laboratory
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Amateurs and their tools
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What is an amateurastronomer?
Although the term has different meanings for
different people, a basic definition would
include anyone who looks into the sky, and
wants to see or learn more.
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The Expanding Universe 15-5

• Theories on How the Universe Formed
• The Big Bang Theory
• Steady-State Theory and Plasma Theory
• Hubbles Law
• Age of the Universe

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What is space like?

• No air
• No gravity-when youre not very close to a
  planet, sun, or moon
• No wind
• No friction
• No real up or down
• No pressure

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What is a galaxy? (Textbook reference 15-4)

• A large group of stars outside of our own Milky
  Way
• Made of billions to trillions of stars
• Also may have gas and dust
• Spiral, or elliptical, or irregular shaped

Image at http//hubblesite.org/newscenter/archive/
releases/galaxy/spiral/2007/41/results/50/
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Spiral galaxy--Andromeda
NOAO/AURA/NSF Images at http//www.noao.edu/image_
gallery/html/im0606.html and http//www.noao.edu/i
mage_gallery/html/im0685.html
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Elliptical Galaxies
Images at http//hubblesite.org/newscenter/archive
/releases/galaxy/elliptical/2007/08/image/a/format
/large_web/results/50/ and http//hubblesite.org/n
ewscenter/archive/releases/galaxy/elliptical/1995/
07/results/50/
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Irregular Galaxies
NASA and NOAO/AURA/NSF Images at
http//hubblesite.org/newscenter/archive/releases/
galaxy/irregular/2005/09/results/50/ ,
http//www.noao.edu/image_gallery/html/im0560.html
, and http//www.noao.edu/image_gallery/html/im09
93.html
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Our Galaxy the Milky Way

• has about 200 billion stars, and lots of gas and
  dust
• is a barred-spiral (we think)
• about 100,000 light-years wide
• our Sun is halfway to the edge, revolving at half
  a million miles per hour around the center of the
  Galaxy
• takes our Solar System about 200 million years to
  revolve once around our galaxy

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The Milky Way
Image at http//news.nationalgeographic.com/news/b
igphotos/1945371.html
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Mapping the Milky Way
How do we know what our galaxy looks like?

• We can see
• stars
• star clusters
• nebulae
• galaxies

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Reviewing Galaxies

• Groups of stars, planets, and space debris
• Irregular, Elliptical, Spiral
• Milky Way is our galaxy

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Image of the Sun from Goddard Space Flight Center
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What is a Star? Our Sun is the closest star. At
the simplest, a star is just a ball of gas that
has condensed out of interstellar material. The
largest part of its lifetime is spent as a main
sequence star during which hydrogen is being
converted to helium balancing gravitational
contraction so that the radius and energy output
remain almost constant.
Source The British Astronomical Association
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Stars (Textbook reference 15-2 and 15-3)

• Bodies of gases that give off tremendous amounts
  of radiant and heat energy
• Constellations are groups of stars used for
  navigation, storytelling, honoring heroes

Life Cycle of a Star Video
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Nearby Stars Name Distance from
Earth Sun 93 million miles (8 light minutes)
Proxima Centauri 4.22 Light Years Alpha Centuri
A,B 4.39 Light Years Barnards Star 5.94 Light
Years Wolf 359 7.8 Light Years Lalande 21185
8.3 Light Years Sirius A,B 8.6 Light
Years
Image courtesy of Dave DockeryAstronomical
Society of Las Cruces Source The British
Astronomical Association
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Evolution of Stars
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How do Black Holes form?
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Black Holes

• Remains of a neutron star that has collapsed due
  to intense gravity
• Event horizon surface of a black hole from
  which light cannot escape

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Hertzsprung-Russell Diagram
Video on the Hertzsprung-Russell Diagram
The Doppler Effect Red Shift stars moving
away from Earth Blue Shift stars moving toward
Earth
Spectroscopy Video
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Hertzsprung-Russell Diagram
Images from http//www.nasa.gov/centers/goddard/ne
ws/topstory/2007/spectrum_plants.html and
http//sunearthday.gsfc.nasa.gov/2009/TTT/65_surfa
cetemp.php
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Using a Stars Spectrum

• We can use a stars spectrum to classify it.

NOAO/AURA/NSF image at http//antwrp.gsfc.nasa.gov
/apod/ap010530.html
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Time to Create a Stellar Graph

• Everyone will receive several stars
• Place them on the large paper, according to their
  color and their brightness
• This is a version of the Hertzsprung-Russell
  diagram.

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Measuring Distances

• Parallax (lets model it)
• As Earth orbits the Sun, we see nearby stars move
  relative to more distant stars
• How many degrees did the plate move, relative to
  the background?
• Can you calculate the distance to the plate?
• The angles involved for stellar observations are
  very small and difficult to measure. Proxima
  Centauri, has a parallax of 0.77 arcsec. This
  angle is approximately the angle subtended by an
  object about 2 centimeters in diameter located
  about 5.3 kilometers away.

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The Sun (Textbook reference 14-2

• The sun is an ordinary star.
• The sun is the biggest, brightest, and hottest
  object in the solar system.
• Its energy is the result of the fusion of
  hydrogen nuclei into helium nuclei.
• The sun is made of about 70 hydrogen and 28
  helium.

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Characteristics of the Sun

• Interior Core, Radiation Zone, Convection Zone
• Exterior Photosphere, Chromosphere, Corona
• Features Sunspots, Prominences, Solar Flares
• Central star in our solar system around which
  planets revolve
• Composed of gases (H2 and He) burning at
  15,000,000 o C

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The Sun Seasons (Textbook Reference 12-1)
Seasons Solstices sun directly
overhead two times a year (June 21 and December
21) Junelongest day, Decembershortest
day Equinoxes halfway between
solstices neither hemisphere is tilted toward
the sun daylight and darknessequal
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What causes the seasons?

1. 23.5 tilt of Earths axis
2. Direct vs. indirect sun rays
3. Length of daylight

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Fall

Summer
Sun
Winter
Spring
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The Sun Solar Energy (14-2)
Energy in the Atmosphere Energy reaches earths
atmosphere Reflected back or absorbed clouds,
dust and gases surface Energy is transferred
within the troposphere radiation heats land
and water reflected back into
atmosphere convection moves heat through the
troposphere warm air is replaced by
denser, cool air conduction transfers heat
from land and water directly into the
air nearest Earths surface
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Our Sun is a star that has already spent about 5
billion years on the main sequence.
Scientist believe our Sun is roughly
halfway through it's life.
Source The British Astronomical Association
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Earths Moon
Stars are the source of light for all objects in
outer space
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Phases of the Moon (Textbook reference 12-3)
waxing increasing waning
decreasing gibbous gt ½ crescent lt
½
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Lunar Phases

• New Moon

• Waxing Crescent

• First Quarter

• Waxing Gibbous

• Full Moon

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Lunar Phases

• Full Moon

• Waning Gibbous

• Last Quarter

• Waning Crescent

• New Moon

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Rotate vs. Revolve

• Rotation spin of an object on its axis
• Revolution orbit of an object around another
  object

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Moons Orbit and Phases
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Why does one side of the moon always face us?

• Moon rotates once every 27.3 days
• Moon revolves once every 29.5 days
• Moons rotation approximately equal to its
  revolution

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Eclipses

• Lunar Eclipse
• Solar Eclipse
• Total Eclipse

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A total eclipse of the sun occurs during the day!
Only the corona is visible.
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Tides

• Effect of gravity between the moon and the sun

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Spring Tides

• When the sun, the moon, and the Earth are all
  aligned in a 180o angle

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Neap Tide

• When the sun, the moon, and the Earth form a 90
  angle

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Stars are the source of light for all objects in
outer space

• Complete the standards-based reading handed out
  in class to address this concept
• Answer the assessment questions that accompany
  the handout

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SOLAR SYSTEM

• The Sun

• Eight Planets and Pluto

• Sixty-one satellites of the planets

• Many Comets and asteroids

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Formation of the Solar System(Textbook reference
15-5)
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A collapsing interstellar cloud

• Stars and planets form from interstellar clouds
• They appear dark because of dust blocking out the
  light
• The light can cause it to glow, or even become
  heated
• Stars and solar systems are born this way
• Collapse accelerates
• The collapse of this cloud is slow, but it
  accelerates and becomes denser at the center
• This collapse and spin results in a flattening at
  the equatorial plane

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• Matter condenses
• Our solar system may have formed this way when
  temperature and pressure caused hydrogen to fuse
  into helium
• The temperature differential allowed for
  different elements to concentrate in different
  areas around the sun
• This is why the inner planets are rocky and have
  a higher melting point
• Outer ones are less dense and made of ice and gas

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Planetesimals

• The planetesimals combined to get larger and in
  many cases to become the known planets.
• Gas giants form
• Jupiter was the first to form
• Icy planetesimals combined to form it
• Its mass (gravity) caused it to collect much of
  the debris
• The others formed the same way, but Jupiter took
  most of the extraneous material

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• Terrestrial planets form
• the merging of planetesimals in the inner portion
  of the disk
• Made of materials that resist vaporization
• Most of the gaseous material and smaller stuff
  consumed by the sun, hence fewer satellites.
• Debris
• All of the junk left over
• Some became comets
• Some ejected from solar system or destroyed in
  collisions
• The asteroid belt between mars and Jupiter is the
  rest

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The Greeks called the five points of light that
seemed to move among the stars ______, meaning
______.
PlanetsWandering Stars?

• planets
• wanderers

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The ancient Romans later called these planets

• Mercury
• Venus
• Mars
• Jupiter
• Saturn

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Greek Ideas Earth at the Center(Textbook
reference 14-1)

• Initially the geocentric theory stated that
  everything moved around the earth.
• Retrograde motion (apparent westward movement)
  led astronomers to find a different explanation

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Describe the ancient Greek beliefs of the solar
system.

• The ancient Greeks thought Earth was a stationary
  object and the sun, moon, and planets were on a
  rotating celestial sphere

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Checkpoint What is a geocentric system?

• A geocentric system is one in which Earth is at
  the center of a system of revolving planets.

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Figure 2 Interpreting DiagramsWhere is Earth
located in this illustration?

• The Earth is in the middle of the solar system
• The sun, moon, and a planet are orbiting Earth on
  a large circle, while moving on a smaller cirlce

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How is Ptolemys model of the solar system differ
from the Greeks before him?

• The Greeks before Ptolemy thought the universe
  was unchanging and the sun, moon, and planets
  moved together on a celestial sphere (like a
  carousel). Earth was stationary
• Ptolemy introduced the idea of the sun, moon and
  planets rotating on little circles which rotate
  on bigger circles

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Copernicuss Idea Sun at the Center

• The heliocentric model (Copernicus) put the sun
  at the center and planets in orbit around it.
• Proximity to the sun caused planets to move at
  different speeds
• This explained retrograde

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Heliocentric

• A description of the solar system which all
  planets revolve around the sun

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Guide For Reading How do the heliocentric and
geocentric descriptions of the solar system
differ?

• In a geocentric system, Earth is at the center of
  the revolving planets.
• In a heliocentric system, Earth and the other
  planets revolve around the sun.

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What two discoveries made by Galileo supported
the heliocentric description of the solar system?

• Jupiters four moons revolve around the planet.
• Venus goes through phases similar to those of
  Earths moon.

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Brahe, a ______ ______, made much more accurate
observations by carefully observing the positions
of the planets for almost _____ years.
Brahe and Kepler

• Danish astronomer
• 20

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What did Kepler discover about the orbits of the
planets?

• Kepler had discovered that the orbit of each
  planet is an ellipse.
• Ellipse an elongated circle or oval shape.

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The Space Program (textbook reference 13-2)

• Space Race began in 1957 with the launch of the
  Soviet satellite Sputnik I
• Satellite an object revolving around another
  object
• Humans in Space
• Soviets launched the first human in 1961
• The Moon Landing
• 1969, Apollo 11, and Neil Armstrong and Buzz
  Aldrin

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Exploring the Solar System (textbook reference
14-1 continued)
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Ellipse

• An elongated circle, or oval shape the shape of
  the planets orbit

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• Keplers Laws
• 1st law in general, the planets orbit the sun in
  an ellipse
• The eccentricity of the orbit is how squashed
  the orbit is
• 2nd law a line drawn from the sun to any planet,
  sweeps out equal areas in equal times (although
  the orbital distance may be different)
• 3rd law he defined the size of the ellipse and
  the orbital period (year)

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Which planets orbit did Kepler calculate to
discover that a planets orbit is not a circle?

• Mars

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Inertia and Gravity (textbook reference 12-2)
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Inertia

• Inertia tendency of a moving object to continue
  in a straight line or a stationary object to
  remain in place.

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The more _____ an object has, the more ______ it
has.

• mass
• inertia

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Gravity

• Gravity The attractive force between two
  objects its magnitude depends on their masses
  and the distance between them.

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The strength of gravity depends on the ______ of
the objects and the ______ between them.

• mass
• distance

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Figure 5 Interpreting Diagrams -What would
happen if a planet had no inertia?

• The planet would be pulled into the sun

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Figure 5 Interpreting Diagrams -What would
happen if a planet had no gravity?

• The planet would continue to travel straight off
  into space

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Guide For Reading What two factors keep the
planets in their orbits?

• Newton concluded that two factors inertia and
  gravity combine to keep the planets in orbit.
• Inertia keeps the planets the moving
• Gravity from the sun keeps the planets from
  traveling off in space

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Reviewing Gravity

• Gravity is the attractive force between 2 objects
• It is affected by mass and distance
• Gravity is what determines the orbit planets
  follow
• Newtons explanation of gravity supported
  Keplers laws of planetary motion.

Dark Matter helps Gravitational Pull
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Solar System Characteristics (Textbook reference
14-3)

• Inner Planets
• Mercury, Venus, Earth, Mars
• Terrestrial planets with atmosphere and crust

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The Inner Planets

• Terrestrial Planets
• 4 inner planets
• Similar densities to Earth
• Solid rocky surfaces

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Mercury

• closest to the sun
• 1/3 Earths size(or the size of Earths moon)
• no moons
• solid and covered with craters
• almost no atmosphere
• the eighth largest planet(second smallest planet)

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• Surface
• covered with craters and plains
• the plains formed much like the maria on the moon
• the craters are smaller with less ejecta
• Interior
• the density suggests a dense core similar to the
  Earth
• the magnetic field suggests its partially molten

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Venus

• Sixth largest planet
• Sister planet to Earth
• About three-fourths the size of Earth
• Has no moons or rings
• The brightest object in our sky besides the sun
  and moon because of proximity and albedo 75

• Surface is rocky and very hot (covered in
  craters, volcanoes and mountains)
• Atmosphere completely hides the surface and
  traps the heat.
• Probes and satellites have provided radar images
  of 98 of the surface

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Earth

• Third planet from the sun
• Fifth largest planet
• Liquid covers 71 percent of the Earths surface.
• The Earth has one moon.
• Only planet known to have life and liquid water
• Atmosphere composed of composed of Nitrogen
  (78), Oxygen (21), and other gases (1).

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Earth, from 6,100,000,000 km (3,700,000,000
miles) away can you find it?
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Mars

• Fourth planet from the sun
• A thin atmosphere that contains mostly carbon
  dioxide
• Appears as bright reddish color in the night sky
• Surface features volcanoes and huge dust storms
• Has 2 moons Phobos and Deimos

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Moons of Mars

• Phobos
• Deimos

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Solar System Characteristics(Textbook reference
25-4)

• Outer Planets
• Jupiter, Saturn, Uranus, Neptune, Pluto
• Jovian planets have ring systems and gas
  atmospheres (J, S, U, N)
• Pluto is neither terrestrial or Jovian

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The Outer Planets(Textbook reference 14-4)

• The Gas Giants
• These planets include Jupiter, Saturn, Uranus
  and Neptune
• All larger than Earth by 15-300 times

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Jupiter

• The largest planet (1/10 of the sun and 11X
  Earths)
• Better than 70 of the planetary mass of the
  solar system
• 52 albedo
• Has a banded appearance

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Jupiter

• Rings have 3 parts Halo Ring, Main Ring,
  Gossamer Ring
• Brightest planet in sky
• Strong magnetic field
• 60 moons, 5 visible from Earth

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• Density is relatively low for its size
• The is because of it composition (H and He in gas
  or liquid form.
• Rotation
• Shortest day in the solar system about 10hrs
• This fast spin distorts the shape
• This also contributes to its banded appearance
• Belts are low lying dark-colored clouds
• Zones are high light-colored clouds
• Moons
• More than 60, but some are very small
• Mostly composed of ice and rock
• Gravity assist

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Jupiters Red Spot

• the great spot is a storm of swirling gas that
  has lasted for better than 300 years
• Jupiter does not have a solid surface. The planet
  is a ball of liquid surrounded by gas.

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Moons of Jupiter

• Jupiter has four large Galilean moons, twelve
  smaller named moons and twenty-three more
  recently discovered but not named moons.
• Well take a look at the four large Galilean
  moons which were first observed by Galileo in
  1610.

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Io

• Io is the fifth moon of Jupiter. Its the third
  largest of Jupiters moons.
• Io has hundreds of volcanic calderas. Some of the
  volcanoes are active.

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Europa

• Europa is the sixth of Jupiters moons and is the
  fourth largest.
• It is slightly smaller than the Earths moon.
• The surface strongly resembles images of sea ice
  on Earth. There may be a liquid water sea under
  the crust.
• Europa is one of the five known moons in the
  solar system to have an atmosphere.

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Ganymede

• Ganymede is the seventh and largest of Jupiters
  known satellites.
• Ganymede has extensive cratering and an icy crust.

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Callisto

• Callisto is the eighth of Jupiters known
  satellites and the second largest.
• Callisto has the oldest, most cratered surface of
  any body yet observed in the solar system.

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Saturn

• Second largest planet
• Sixth from the sun.
• Slightly smaller than Jupiter
• Easily visible in the night sky
• Voyager explored Saturn and its rings.
• Made of materials that are lighter than water.
  (If you could fit Saturn in a lake, it would
  float!)

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Rings of Saturn

• 7 major rings made up of ringlets
• Gravity keeps the rings in place
• rings are not solid
• composed of small countless particles
• rings are very thin.
• Though theyre 250,000 km or more in diameter,
  theyre less than one kilometer thick

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• Moons
• 55 moons
• 31 moons
• Largest moon, Titan,
• Titan, the largest is bigger than Mercury
• Odd among moons because of content with dense
  atmosphere and methanes existence in 3 states

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Uranus

• 7th planet from sun
• Has a faint ring system (they are dark and hard
  to observe)
• 27 known moons
• Covered with clouds
• Uranus sits on its side with the north and south
  poles sticking out the sides.
• 4x larger and 15Xmass of the Earth

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Uranus

• Atmosphere
• Bluish appearance cause by methane gas
• Clouds are similar in appearance to the surface
• Liquid surface with a small solid core
• Rotation
• Almost a top to bottom rotation
• Poles vacillate between 42 years of darkness and
  light

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URANUS

• Uranus has more moons (15) than any other planet
  except Jupiter (16) and Saturn (23)!

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Neptune

• 4th largest planet
• 8th planet from sun
• Because of the orbits, from 1979 to 1999, Neptune
  was the ninth planet.
• Discovered through math
• 7 known moons
• Great Dark Spot thought to be a hole, similar to
  the hole in the ozone layer on Earth
• Like Uranus, the methane gives Neptune its color.

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Neptune

• Atmosphere
• Smaller and denser than Uranus but 4XEarth
• Similar in color to Uranus (twins??) but does
  have some color variation on surface
• Belts and zones give it texture
• Moons and Rings
• 13 moons Triton being the largest
• Triton has retrograde orbit
• Also has nitrogen geysers when heated by the sun
• Rings are invisible from Earth but exist

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The blue coloration of Neptune is probably due to
the presence of methane
Note the apparent storms
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Plutoa planet?

• Today, Pluto is called a "dwarf planet.
• A dwarf planet orbits the sun just like other
  planets, but it is smaller.
• A dwarf planet is so small it cannot clear other
  objects out of its path.

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Per NASA.gov.

• In 2003, an astronomer saw a new object beyond
  Pluto. The astronomer thought he had found a new
  planet. The object he saw was larger than Pluto.
  He named the object Eris (EER-is). Finding Eris
  caused other astronomers to talk about what makes
  a planet a "planet." There is a group of
  astronomers that names objects in space. This
  group decided that Pluto was not really a planet
  because of its size and location in space. So
  Pluto and objects like it are now called dwarf
  planets. Pluto is also called a plutoid. A
  plutoid is a dwarf planet that is farther out in
  space than the planet Neptune. The three known
  plutoids are Pluto, Eris and Makemake
  (MAH-kee-MAH-kee). Astronomers use telescopes to
  discover new objects like plutoids.

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Dwarf Planet Pluto

• Pluto, is one of three plutoids.
• It is a small (smaller than Earths moon), solid
  and icy
• It is so far from the sun that it has never been
  visited by spacecraft.
• It orbits the sun very slowly.

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Sample Quiz Questions
Question Which of the planets are rocky?
Answer The inner planets Mercury, Venus,
Earth and Mars
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Sample Question 2

• Which of the planets has the most satellites?

Saturn!
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Image by Dave DockeryAstronomical Society of
Las Cruces
What Are Comets, Asteroids and Meteors?
(textbook reference 14-5) Space Debris
Comet Ikeya Zhang
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Comets A comet is basically a ball of ice and
dust in space. The typical comet is less than
10 kilometers across. Most of their time is
spent frozen solid in the outer reaches of our
solar system.
Comet Hale Bopp
Image by Harvard-Smithsonian Center for
Astrophysics
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A comet orbits around the sun, in a wide,
elliptical path. When a comet gets within a few
million miles of the sun, it begins to melt,
leaving a tail of gas and dust that is blown by
solar winds
Source NASA
Comet Hale Bopp
Image by Harvard-Smithsonian Center for
Astrophysics
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Reviewing Comets

• Small icy bodies
• Travel past the Sun
• Give off gas and dust as they pass by
• Tail of gasses called a coma

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Asteroids

• Asteroid rocks orbiting in space
• Asteroid belt 100,000 asteroids located between
  Mars and Jupiter
• separates inner and outer planets

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Asteroids

• Small bodies
• Believed to be left over from the beginning of
  the solar system billions of years ago
• Largest asteroids have been given names

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Meteoroids

• Meteoroid smallest asteroids or comets
• Come from asteroids colliding in space
• Come from a comet breaking up and creating a
  cloud of dust continuing to move through the
  solar system

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Meteors

• Meteor meteoroid striking Earths atmosphere
• Meteorite meteor that hits Earths surface

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Solar SystemActivities

• Order the Planets 
• Fun with Planets
• Constellations of the Northern Sky
• Planets
• Solar System 

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Units of Time from Space

• Year 1 revolution of Earth
• Day 1 rotation of Earth
• Month 1 revolution and/or rotation of Moon

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Measuring Distances

• What is a Light Year?
• A light year is the distance light travels in a
  year. Light moves at a velocity of about 300,000
  kilometers (km) each second how far would it
  move in a year?
• About 10 trillion km (or about 6 trillion miles).
• Why do we use light years?
• Show me how far 5 centimeters is.
• Now show me 50 centimeters.
• Now tell me (without thinking about it, or
  calculating it in meters) how far 500 centemeters
  is. 2000? 20,000?
• We need numbers that make sense to us in
  relationship to objects we scale up and use
  meters and kilometers for large numbers.

144
Measurements in Space

• Light year distance light travels in one Earth
  year
• Astronomical Unit distance from Earth to Sun

http//www.youtube.com/watch?v3bmb0YE9VGM
145
Are We Alone in the Universe?(textbook reference
14-6)

• SETI http//www.seti.org/seti-institute/about-seti
  /scientists vs Pseudoscience http//www.chem1.com/
  acad/sci/pseudosci.html
• If it is just us, it seems like an awful waste
  of space.
• Ellie Arroway in Carl Sagans Contact