3 c1 s3 galaxies
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Galaxies
Seeing the Universe
Section 3
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What Exactly are They?
Galaxies are groups of stars, gas, anddust held together by gravity.
May contain as many as one trillion stars
They vary in size but our galaxy (theMilky Way) is 100,000 light yearsacross
The closest galaxy to the Milky Wayis Andromeda
2 million li ht ears awa
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Types of Galaxies
Spiral have spiral arms that windoutward from inner regionsThe Milky Way and Andromeda are spiral
(so is the picture in the background) Some are barred spirals where the
arms extend from a central bar ofstars
Elliptical shaped like large 3-Dellipses (like a football). Some are large enough that several
Milky Ways could fit inside of them
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Irregular just like it sounds, theydont have a definite shape and dontfit easily into other classifications
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EllipticalGalaxy
Notice otherspiral galaxiesin the
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An irregular
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The Milky Way
Our home galaxy is 100,000 lightyears across
Our solar system is about 30,000 Ly
from the center and makes one full orbitin 240 mil yearsThis means that were travelling at 235 km/s
If theres low light pollution, you cansee the Milky Way on a clear night
It looks like a band of misty lightstretching through the night sky
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The Milky Way as seenfrom a road in Death
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Expansion of the Universe
What does an ambulance sound likeas it passes you?
Have you noticed the drop in pitch as it
travels away from you?This is called the Doppler effect
Light from other stars does the same
thing!
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The Doppler Shift
Just like sound waves, light that travelstoward us is compressed and light thattravels away is elongated
Think about the ambulance, the pitchlowers because the sound waves are beingstretched out
Light that is moving away from us
(stretched) is shifted toward the redend of the color spectrum
Light that is moving toward us(compressed) is shifted toward the blue
end
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Elongated
Compressedwaves
Shifted
Shifted blue
Normal
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Red Shift
Edwin Hubble discovered that allgalaxies outside of our Local Grouphave a red shift
What direction are all of these galaxiesmoving then?
If they all have red shifted light, they
all must be moving away from theEarth
Scientists determined that if theyre
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The Big Bang Theory
States that the universe began 12-15billion years ago in a massiveexplosion
The entire universe began to expandeverywhere at the same time
As matter cooled, it clumpedtogether to form hydrogen andhelium gasses Eventually, gravity caused this matter to
compact and form the first stars
The first stars were born after about one
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Faith and the Big Bang
Faith is being sure of what we hopefor, and certain of what we cannotsee Heb. 11:1
Take comfort in the complexity of lifeand the universe itself
The Bible says that the wisdom of men
is like foolishness to God. 1 Cor. 1:25,3:19
The goal of science is to explainEVERYTHING and scientists are going to
do just that.
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