What%20will%20I%20learn%20Today?%20I%20will%20be%20able%20to%20describe%20how%20astronomers%20determine%20the%20composition%20and%20surface%20temperature%20of%20a%20star

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What will I learn Today?I will be able to
describe how astronomers determine the
composition and surface temperature of a star

• Standards
• Students know the Sun is a typical star and is
  powered by nuclear reactions, primarily the
  fusion of hydrogen to form helium.
• Students know the evidence indicating that the
  planets are much closer to Earth than the stars
  are.
• Homework
• Sentence and define vocabulary for chapter 27.1

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Chapter 27.1 Vocabulary

• Star
• circumpolar
• Red shift
• Light years
• Parallax
• Apparent magnitude
• Absolute magnitude
• H-R diagram
• Main sequence stars

• Giants
• Supergiants
• White dwarfs

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Chapter 27.1 Notes

• Characteristics of stars

• The sun is our closest star
• A star is a body of gas that gives off a
  tremendous amount of light and heat
• From earth stars look like tiny white lights, but
  if you look closely they shine different colors
  (blue, yellow, orange, red and white)
• Stars also vary in mass and composition

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Chapter 27.1 Notes

• Composition and temperature

• The light of stars is analyzed through a
  spectrometer, which breaks the light into
  different wavelengths or colors
• The display of colors and lines is called the
  spectrum
• There are three types of spectra emission
  (bright light), Absorption (dark line) and
  continuous

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Chapter 27.1 Notes

• Composition and temperature

• The dark lines are what tell us what makes up a
  star, the types of materials that can found in
  the star
• Stars are mainly Hydrogen and Helium, but also
  have carbon, oxygen, nitrogen, and calcium
• The temperature range of stars is 2,800c to
  24,000c, with some blue stars reaching 50,000c

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Chapter 27.1 Notes

• Motion

• There are two types of motion with stars apparent
  and actual
• Actual motion can be seen with only high powered
  telescopes, because of the great distances
• Apparent motion can be seen every night as you
  see stars move across the sky
• Stars also appear to shift as our seasons change
  or as we move around the sun they become visible
  to us

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Chapter 27.1 Notes

• Motion

• There are some stars that seem to always be out
  or never drop below the horizon, these are the
  circumpolar or the little dipper
• Star have three actual motions
• First they turn on there axis
• Second, most rotate around another star
• Third, they move toward or away from earth
• Light has a Doppler effect just like sound
• Blue means, it is moving closer to you
• Red means, it is moving farther away from you

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Chapter 27.1 Notes

• Distance to the stars

• Star distance is measured in light-years
• Light travels at 300,000 km/s or in one year 9.5
  trillion miles
• The closest star is Proxima Centauri at 4.2 light
  years, Sirius the brightest star is 9 light
  years, and Polaris or Northern Star is 700 light
  years away
• Distance is measured using a process known as
  parallax
• The shift of a star from January to June can be
  used to determine distance to within 1,000 light
  years
• The closer a star is the bigger the shift

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Chapter 27.1 Notes

• Distance to the stars

• Another method is to use the brightness of stars
  for more distance stars
• They estimate the true brightness by using the
  spectrum
• They then compare it to its apparent brightness
• Cepheid are stars that pulse in brightness on a
  cycle of time
• From 1 day to 100 days
• The longer the cycle the brighter the star

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Chapter 27.1 Notes

• Stellar Magnitudes

• We can see about 6,000 stars with our eyes
• A good telescope will allow you to see about
  3,000,000,000 (billion) stars
• The Hubble telescope can see about
  1,000,000,000,000 (Trillion) stars
• Stars are broken into two different scales, how
  bright they appear from earth and the other
  measure is how bright they would be if all stars
  were the same distance

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Chapter 27.1 Notes

• Apparent Magnitude

• This is how bright a star appears from earth

Object mV
Sun -26.8
Full Moon -12.5
Venus at brightest -4.4
Jupiter at brightest -2.7
Sirius -1.47
Vega 0.04
Betelgeuse 0.41
Polaris 1.99
Naked eye limit 6
Pluto 15.1
Hubble Space Telescope 31
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Chapter 27.1 Notes

• Absolute Magnitude

• This is how bright the star would be if it was
  32.6 light years away from the earth
• If we take the sun with an apparent magnitude of
  -26.8 and moved it 32.6 light years away, it
  would have an absolute magnitude of 5
• So if the apparent is less (-26.8) then the
  absolute (5) the star is closer then 32.6 light
  years
• If the apparent is (6) more then the absolute
  (2) the star is farther then 32.6 light years
• 3.26 is one parsec a star that has a parallax
  of one second

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Chapter 27.1 Notes

• Classification of stars

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Chapter 27.1 Notes

• Classification of stars

• When you classify stars by there temperatures and
  absolute magnitude a pattern develops
• The line through the graph is called the main
  sequence of stars, most stars visible at night
  are in this group
• It starts in the lower right hand corner with
  cool, dim and red stars
• It then moves up to the upper left corner with
  hot, bright, and blue stars
• The upper right is cool bright stars
• The lower left are hot and dim stars, called
  white dwarfs (about the size of earth)

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Chapter 27 activity

• Procedure
• Stand directly in front of and directly facing
  the red cup at a distance of several meters.
• Close one eye and sketch the position of the red
  cup relative to the background and white cups.
• Take several steps back and to the right of your
  original position, repeat step 2
• Take several steps directly back and make another
  sketch.
• Repeat step 4 once again.

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Chapter 27 activity - analysis

1. Compare your drawings. Did the red cup change
   position as you viewed it from different
   locations? Explain
2. What kind of results would you expect if you
   continued to repeat step 5 at greater and greater
   distances? Explain
3. If you noted the positions of several stars with
   a powerful telescope, what would you expect to
   observe about their positions if you sighted the
   same stars several months later? Explain

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Chapter 27.2 Vocabulary

1. Nebula
2. Protostar
3. Planetary nebula
4. Novas
5. Supernova
6. Neutron star
7. Pulsars
8. Black hole

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Chapter 27.2 Notes

• Stellar Evolution

• Nebula a cloud of gas and dust
• Protostar a shrinking spinning region of gas
  that flattens into a disk with a central
  concentration
• Stars exists for billions of years. Stars form in
  nebula that usually are composed of 70 hydrogen,
  28 helium, and 2 heavier materials.
• Gravity pulls it all together. Matter gets warmer
  with increased pressure, Over millions years,
  until 10,000,000C fusion begins. More than one
  star can form, as well as planets

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Chapter 27.2 Notes

• Main Sequence stars

• Second and longest stage of a stars life
• Energy generated in the core through fusion of
  hydrogen into helium, 1g of hydrogen can generate
  enough power to keep a 100 watt bulb burning for
  3,000 years.
• The energy bubbles upward like boiling water,
  gravity prevents the expansion of the star.
• These two forces keep the star at a stable size,
  as long as it has enough hydrogen to convert to
  helium.

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Chapter 27.2 Notes

• Giants Supergiant

• Third stage of a stars life
• All atoms of hydrogen have fused into helium
  therefore the core will contract under the force
  of gravity.
• Temp increases and helium fusion begins, carbon
  formed
• Hydrogen fusion continues in the areas
  surrounding the core and the star expands into a
  giant 10 or more times larger then our sun, a
  supergiant is 100 times

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Chapter 27.2 Notes

• White Dwarf Stars

• Planetary nebula a expanding shell of gas left
  from a dying star.
• The end of helium fusion is the end of the giant
  stage of a medium size star.
• The outer gas layers are lost and the core
  revealed, it will heat and illuminate the
  expanding gases.
• It takes billions of years for a white dwarf to
  cool into a black or brown dwarf, the universe is
  too young to have any in it yet.

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Chapter 27.2 Notes

• Novas

• Nova a white dwarf that explodes as it cools,
  becoming a thousand times brighter for a short
  time.
• Some white dwarfs do not just cool, they have one
  or more large explosions.
• Astronomers think this may be caused by a
  companion star that is having material taken from
  it by the white dwarf.

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Chapter 27.2 Notes

• Supernovas

• Supernova a star that explodes with such
  tremendous force that it blows itself apart.
• A star with 10 to 100 times of our sun and the
  explosions can be 100 times brighter than novas.
• They can release as much energy as our sun would
  over 500 million years.
• These massive stars continue to fuse heavier
  materials until the core turns into iron, this
  core then contracts from gravity and explodes

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Chapter 27.2 Notes

• Neutron Stars

• Neutron star an extremely small and dense ball
  of neutrons.
• Pulsars two beams of radiation that sweep
  across space like a lighthouse
• Formed from a supernova, as the star collapses
  only neutrons are left. A spoonful would weigh
  100 million tons on earth
• Some give off radiation at the poles called
  pulsars, we can detect these as radio waves.

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Chapter 27.2 Notes

• Black Holes

• Black hole a hole in space with such gravity
  that light can not escape
• The most massive stars form black holes
• They are invisible to the eye, astronomers look
  for companion stars that are influenced by the
  gravity or the energy of the materials being
  pulled into the Black Hole
• Massive Black holes may be at the center of
  galaxies.

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Chapter 27.3 Vocabulary

1. Constellations
2. Galaxies
3. Spiral galaxy
4. Barred spiral galaxy
5. Elliptical galaxy
6. Irregular galaxy
7. Open cluster
8. Globular clusters
9. Binary stars

1. Quasars

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Chapter 27.3 Notes

• Star Groups
• Constellations

• You see what appear to be single stars, yet only
  1 in 4 is actually a single star. 1/3 are double
  and the rest are triple or more star groups or
  clusters.
• Constellation a pattern of stars
• There are 88 recognized constellation.
• They are used as a star locator map, the star are
  labeled by apparent magnitude and the
  constellation they appear in.
• Some stars are bright enough to have been given
  their own names - Antares

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Chapter 27.3 Notes

• Galaxies

• Galaxy A large scale group of stars
• The major component of the universe, a typical
  galaxy is 100,000 light years in diameter and has
  about 100 billion stars.
• Galaxies also contain gas and dust or nebulae,
  some are bright because they reflect light or
  from the gas within them. The dark areas absorb
  light from distant stars.
• Estimates of 50 billion to 1 trillion galaxies in
  the known universe.

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Chapter 27.3 Notes

• Galaxies
• Types of Galaxies

• The two closest to the Milky Way is the large
  Magellanic Cloud and the small Magellanic Cloud
  at 150,000 light years
• There are 17 other galaxies within 3 million
  light years and this makes up the Local Group.
• Spiral galaxy -
• Barred spiral galaxy -
• Elliptical galaxy -
• Irregular galaxy -

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Chapter 27.3 Notes

• The Milky Way

• Our sun is one of billions stars that circle the
  galactic center. It is 2,000 light years thick at
  the center.
• We are 30,000 light years from the center in a
  spiral arm.
• We revolve around the center at 250km/s, it takes
  200 million years to complete a revolution

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Chapter 27.3 Notes

• Star Cluster
• Binary stars

• Open clusters -
• Globular clusters -
• Difference globular clusters have more stars,
  are in the core of the galaxy and a spherical
  shape. Open cluster are a loose grouping and are
  in the spiral arms.
• Binary stars -
• Used to determine stellar mass
• Consist of two stars, a multiple star system has
  more then two in orbit around each other.

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Chapter 27.3 Notes

• Formation of the Universe

• The big bang theory that the universe formed
  from a single point of matter.
• Then 12 to 15 billion years ago the Big Bang
  occurred propelling matter and energy outward in
  all directions.
• As they moved away from the center gravity began
  to have an effect and formed galaxies
• Quasars
• These may be the oldest objects in our universe