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					Bellwork – September 28,

What is scientific notation?
    Scientific Notation

 A short-hand way of writing
 large or very small numbers
without writing all of the zeros.
Let’s Practice:
For the first one I will work
through the problem. You

- Put down your pencil
- And listen
The Distance From the Sun to
          the Earth

                Step 1
• Move decimal left
• Leave only one number in front of
               Step 2
• Write number without zeros
              Step 3
• Count how many places you moved
• Make that your power of ten
The power of
ten is 7 because
the decimal
moved 7 places.
• 93,000,000 ---
  Standard Form

• 9.3 x 107 ---
  Scientific Notation
            Practice Problem
With your shoulder partner, write in scientific
notation. Decide the power of ten.

  1)   98,500,000 = 9.85 x  10?        9.85 x 107

  2)   64,100,000,000 = 6.41 x 10?     6.41 x 1010

  3)   279,000,000 = 2.79 x 10?        2.79 x 108

  4)   4,200,000 = 4.2 x 10?           4.2 x 106
     More Practice Problems
On these, with your shoulder partner, decide
where the decimal will be moved.
 1) 734,000,000 = ______ x 108
 2) 870,000,000,000 = ______x 1011
 3) 90,000,000,000 = _____ x 1010

1) 7.34 x 108   2)   8.7 x 1011   ) 9 x 1010
    Complete Practice Problems
Write in scientific notation on YOUR OWN
1) 50,000
2) 7,200,000
3) 802,000,000,000

) 5 x 104
1           2)   7.2 x 106   ) 8.02 x 1011
 Scientific Notation to
    Standard Form
Move the decimal to the right
3.4 x 105 in scientific notation
3.40000 --- move the decimal

340,000 in standard form
    Write in Standard Form

• 6.27 x 106   • 6,270,000
• 9.01 x 104   • 90,100
Today we are going to begin talking
about stars. So why did we start with
Scientific Notation?

Measuring the Universe
          What is a star?
• “The objects that heat and light the
  planets in a system”
• A star is a ball of plasma held
  together by its own gravity:
  – Nuclear reactions occur in stars
  – Energy from the nuclear reactions is
    released as electromagnetic radiation
   Characteristics of Stars
 – Measured in light-years
   • The distance which a ray of light would
     travel in one year.
   • About 6,000,000,000,000 (6 trillion) miles
   • 186,000 miles per second
    Main Sequence Stars
A major grouping of stars that forms a
 narrow band from the upper left to the
 lower right when plotted according to
luminosity and surface temperature on
   the Hertzsprung-Russell diagram.
               Life Cycle of Stars
     Life Cycle of ALL Stars
• Begin their lives as clouds of dust and gas
  called nebulae.
• Gravity may cause the nebula to contract
• Matter in the gas cloud will begin to condense
  into a dense region called a protostar.
• The protostar continues to condense, it heats
  up. Eventually, it reaches a critical mass and
  nuclear fusion begins.
• Begins the main sequence phase of the star
• Most of its life is in this phase
        Life Cycle of Stars
Life span of a star depends on its size.
  – Very large, massive stars burn their fuel
    much faster than smaller stars
  – Their main sequence may last only a few
    hundred thousand years
  – Smaller stars will live on for billions of
    years because they burn their fuel much
    more slowly
• Eventually, the star's fuel will begin to
  run out.
    Life Cycle of Low & High
           Mass Stars
• It will expand into what is known as a red
• Massive stars will become red supergiants
• This phase will last until the star exhausts
  its remaining fuel
• At this point the star will collapse
Life Cycle of Low Mass Stars
• Most average stars will blow away their
  outer atmospheres to form a planetary
• Their cores will remain behind and burn
  as a white dwarf until they cool down
• What will be left is a dark ball of matter
  known as a black dwarf
  Life Cycle of Massive Stars
• If the star is massive enough, the
  collapse will trigger a violent explosion
  known as a supernova
• If the remaining mass of the star is
  about 1.4 times that of our Sun, the
  core is unable to support itself and it
  will collapse further to become a
  neutron star
 Life Cycle of Massive Stars
      The matter inside the star will be
 compressed so tightly that its atoms are
compacted into a dense shell of neutrons.
 If the remaining mass of the star is more
 than about three times that of the Sun, it
    will collapse so completely that it will
    literally disappear from the universe.
What is left behind is an intense region of
          gravity called a black hole.
Life Cycle of Stars

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