# Stars

Document Sample

```					Bellwork – September 28,
2011

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
should…

- And listen
The Distance From the Sun to
the Earth

93,000,000
Step 1
• Move decimal left
• Leave only one number in front of
decimal
Step 2
• Write number without zeros
Step 3
• Count how many places you moved
decimal
• 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
3
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
3
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
Scientific Notation?

Measuring the Universe
Stars
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
Characteristics of Stars
• DISTANCE
– 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

http://hea-www.cfa.harvard.edu/CHAMP/EDUCATION/PUBLIC/ICONS/life_cycles.jpg
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
giant
• 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
nebula
• 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