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Mr. Fetch’s Earth Science Classroom
Galaxies and the Universe
Mr. Fetch’s Earth Science Classroom
The Big Picture
Place these in order from smallest to largest: Place these in order from smallest to largest: Place these in order from smallest to largest: Place these in order from smallest to largest:
solar systemsolar systemsolar systemsolar system
planetsplanetsplanetsplanets
galaxiesgalaxiesgalaxiesgalaxies
universe universe universe universe
Our solar system is Our solar system is Our solar system is Our solar system is part of the Milky Way galaxypart of the Milky Way galaxypart of the Milky Way galaxypart of the Milky Way galaxy, which is , which is , which is , which is part of part of part of part of
the universethe universethe universethe universe. We are a very small part of the big picture.. We are a very small part of the big picture.. We are a very small part of the big picture.. We are a very small part of the big picture.
There are over There are over There are over There are over 40 billion40 billion40 billion40 billion galaxies in the universe, all many light galaxies in the universe, all many light galaxies in the universe, all many light galaxies in the universe, all many light
years away.years away.years away.years away.
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Mr. Fetch’s Earth Science Classroom
The Big Picture
Light Year (ly): Light Year (ly): Light Year (ly): Light Year (ly): distance light travels in one yeardistance light travels in one yeardistance light travels in one yeardistance light travels in one year....
A light year is not a measure of time. A light year is not a measure of time. A light year is not a measure of time. A light year is not a measure of time.
Light travels Light travels Light travels Light travels 9.5 trillion kilometers9.5 trillion kilometers9.5 trillion kilometers9.5 trillion kilometers in one year. Thatin one year. Thatin one year. Thatin one year. That’’’’s a lot!s a lot!s a lot!s a lot!
Star: 4.3 ly away Star: 4.3 ly away Star: 4.3 ly away Star: 4.3 ly away ����
It will take light It will take light It will take light It will take light
_______________ _______________ _______________ _______________
years to reach our years to reach our years to reach our years to reach our
eyes. (Proxima eyes. (Proxima eyes. (Proxima eyes. (Proxima
Centauri)Centauri)Centauri)Centauri)
Mr. Fetch’s Earth Science Classroom
What is a galaxy?
A galaxy is a cluster or A galaxy is a cluster or A galaxy is a cluster or A galaxy is a cluster or group of stars, gas, and dustgroup of stars, gas, and dustgroup of stars, gas, and dustgroup of stars, gas, and dust held together held together held together held together
by gravity.by gravity.by gravity.by gravity.
There are There are There are There are three major typesthree major typesthree major typesthree major types of galaxies: of galaxies: of galaxies: of galaxies:
Spiral GalaxiesSpiral GalaxiesSpiral GalaxiesSpiral Galaxies
Elliptical GalaxiesElliptical GalaxiesElliptical GalaxiesElliptical Galaxies
Irregular Galaxies.Irregular Galaxies.Irregular Galaxies.Irregular Galaxies.
---- We live in the We live in the We live in the We live in the Milky WayMilky WayMilky WayMilky Way galaxy. galaxy. galaxy. galaxy.
---- All the stars you can see with your eyes are part of the Milky All the stars you can see with your eyes are part of the Milky All the stars you can see with your eyes are part of the Milky All the stars you can see with your eyes are part of the Milky Way.Way.Way.Way.
---- Galaxies are huge: Galaxies are huge: Galaxies are huge: Galaxies are huge: 1000 to 1,000,000 light years1000 to 1,000,000 light years1000 to 1,000,000 light years1000 to 1,000,000 light years wide.wide.wide.wide.
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Mr. Fetch’s Earth Science Classroom
Spiral Galaxies
Galaxies in the shape of a Galaxies in the shape of a Galaxies in the shape of a Galaxies in the shape of a pinwheel with spiral armspinwheel with spiral armspinwheel with spiral armspinwheel with spiral arms. . . .
It must have 4 parts:It must have 4 parts:It must have 4 parts:It must have 4 parts:
1.1.1.1. Spiral ArmsSpiral ArmsSpiral ArmsSpiral Arms: makes up most of the galaxy where an abundance : makes up most of the galaxy where an abundance : makes up most of the galaxy where an abundance : makes up most of the galaxy where an abundance
of of of of gas and dustgas and dustgas and dustgas and dust (nebula) (nebula) (nebula) (nebula) aid in start formationaid in start formationaid in start formationaid in start formation....
Mr. Fetch’s Earth Science Classroom
Spiral Galaxies
Galaxies in the shape of a Galaxies in the shape of a Galaxies in the shape of a Galaxies in the shape of a pinwheel with spiral armspinwheel with spiral armspinwheel with spiral armspinwheel with spiral arms. . . .
It must have 4 parts:It must have 4 parts:It must have 4 parts:It must have 4 parts:
2.2.2.2. Central BulgeCentral BulgeCentral BulgeCentral Bulge: the : the : the : the centercentercentercenter of the galaxy where of the galaxy where of the galaxy where of the galaxy where very little gas very little gas very little gas very little gas
and dustand dustand dustand dust means that means that means that means that no new starsno new starsno new starsno new stars are forming.are forming.are forming.are forming.
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Mr. Fetch’s Earth Science Classroom
Spiral Galaxies
Galaxies in the shape of a Galaxies in the shape of a Galaxies in the shape of a Galaxies in the shape of a pinwheel with spiral armspinwheel with spiral armspinwheel with spiral armspinwheel with spiral arms. . . .
It must have 4 parts:It must have 4 parts:It must have 4 parts:It must have 4 parts:
3.3.3.3. Halo: Halo: Halo: Halo: surrounding layer of old starssurrounding layer of old starssurrounding layer of old starssurrounding layer of old stars that have formed a long that have formed a long that have formed a long that have formed a long
time ago.time ago.time ago.time ago.
Mr. Fetch’s Earth Science Classroom
Spiral Galaxies
Galaxies in the shape of a Galaxies in the shape of a Galaxies in the shape of a Galaxies in the shape of a pinwheel with spiral armspinwheel with spiral armspinwheel with spiral armspinwheel with spiral arms. . . .
It must have 4 parts:It must have 4 parts:It must have 4 parts:It must have 4 parts:
4.4.4.4. RotationRotationRotationRotation: the galaxy is : the galaxy is : the galaxy is : the galaxy is rotatingrotatingrotatingrotating, which explains the , which explains the , which explains the , which explains the spiral armsspiral armsspiral armsspiral arms
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Mr. Fetch’s Earth Science Classroom
Elliptical Galaxies
Elliptical galaxiesElliptical galaxiesElliptical galaxiesElliptical galaxies are large are large are large are large ballballballball----shaped circles of starsshaped circles of starsshaped circles of starsshaped circles of stars....
They are large, They are large, They are large, They are large, 3333----D ellipsesD ellipsesD ellipsesD ellipses. . . .
They are similar to They are similar to They are similar to They are similar to giant footballgiant footballgiant footballgiant football in space.in space.in space.in space.
Elliptical galaxies have Elliptical galaxies have Elliptical galaxies have Elliptical galaxies have very little very little very little very little
gas and dustgas and dustgas and dustgas and dust which means which means which means which means stars stars stars stars
are not formingare not formingare not formingare not forming in them. in them. in them. in them.
Mr. Fetch’s Earth Science Classroom
Elliptical Galaxies
Most are tiny
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Mr. Fetch’s Earth Science Classroom
Irregular Galaxies
These galaxies are not spiral or elliptical. These galaxies are not spiral or elliptical. These galaxies are not spiral or elliptical. These galaxies are not spiral or elliptical.
They are They are They are They are irregularly shapedirregularly shapedirregularly shapedirregularly shaped....
They contain They contain They contain They contain lots of gas and lots of gas and lots of gas and lots of gas and
dustdustdustdust which means that lots of which means that lots of which means that lots of which means that lots of
stars are formingstars are formingstars are formingstars are forming. . . .
D. Hunter (Lowell Observatory), Z. Levay (STScI)
Local G
roup Gala
xies S
urvey Team,
NOAO, A
URA, N
SF
Mr. Fetch’s Earth Science Classroom
The Milky Way
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Mr. Fetch’s Earth Science Classroom
The Milky Way
The Milky Way is The Milky Way is The Milky Way is The Milky Way is 75,000 ly75,000 ly75,000 ly75,000 ly across.across.across.across.
The The The The sunsunsunsun is located is located is located is located in the diskin the diskin the diskin the disk about about about about 2/3 out from the center2/3 out from the center2/3 out from the center2/3 out from the center....
At the center, there is a massive At the center, there is a massive At the center, there is a massive At the center, there is a massive black holeblack holeblack holeblack hole. . . .
Mr. Fetch’s Earth Science Classroom
The Milky Way
“face-on”
� view
“edge-on”
� view
25 kpc = 25 kiloparsecs = 25,000 parsecs
75,000 light-years
8.5 kpc
(2/3 of the
way out)
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Mr. Fetch’s Earth Science Classroom
The Big Bang Theory: 10 billion to 20 billion years ago:
•••• The Big Bang TheoryThe Big Bang TheoryThe Big Bang TheoryThe Big Bang Theory states that a long time ago there was, states that a long time ago there was, states that a long time ago there was, states that a long time ago there was,
for some reason, an for some reason, an for some reason, an for some reason, an expansion of spaceexpansion of spaceexpansion of spaceexpansion of space....
•••• The universe was The universe was The universe was The universe was very hot and very densevery hot and very densevery hot and very densevery hot and very dense. All the . All the . All the . All the matter was matter was matter was matter was
crammed into a single pointcrammed into a single pointcrammed into a single pointcrammed into a single point about the size of a grain of sand.about the size of a grain of sand.about the size of a grain of sand.about the size of a grain of sand.
•••• SomethingSomethingSomethingSomething caused space to start caused space to start caused space to start caused space to start expanding outwardexpanding outwardexpanding outwardexpanding outward from from from from
this single point.this single point.this single point.this single point.
Mr. Fetch’s Earth Science Classroom
The Big Bang Theory: 10 billion to 20 billion years ago:
•••• Over time the universe has cooled, but is Over time the universe has cooled, but is Over time the universe has cooled, but is Over time the universe has cooled, but is still expanding still expanding still expanding still expanding
todaytodaytodaytoday. . . .
(What proof do we have?(What proof do we have?(What proof do we have?(What proof do we have?
Stay Tuned!) Stay Tuned!) Stay Tuned!) Stay Tuned!) …………
•••• After about After about After about After about 1 billion years1 billion years1 billion years1 billion years, the first , the first , the first , the first stars and galaxies started stars and galaxies started stars and galaxies started stars and galaxies started
to formto formto formto form. . . .
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Mr. Fetch’s Earth Science Classroom
The Big Bang Theory: 10 billion to 20 billion years ago:
•••• All All All All galaxies in spacegalaxies in spacegalaxies in spacegalaxies in space are not moving through space, they are are not moving through space, they are are not moving through space, they are are not moving through space, they are
moving moving moving moving withwithwithwith spacespacespacespace as the space expands. as the space expands. as the space expands. as the space expands.
•••• They are actually in fixed positions.They are actually in fixed positions.They are actually in fixed positions.They are actually in fixed positions.
•••• Like raisins inLike raisins inLike raisins inLike raisins in rising raisin breadrising raisin breadrising raisin breadrising raisin bread. The raisins . The raisins . The raisins . The raisins do not movedo not movedo not movedo not move
through the bread, but through the bread, but through the bread, but through the bread, but expand with it.expand with it.expand with it.expand with it.
•••• No matter where you are, you see all No matter where you are, you see all No matter where you are, you see all No matter where you are, you see all galaxies moving away galaxies moving away galaxies moving away galaxies moving away
from you.from you.from you.from you.
•••• No geometric center to the universe, and thus no edges. No geometric center to the universe, and thus no edges. No geometric center to the universe, and thus no edges. No geometric center to the universe, and thus no edges.
Mr. Fetch’s Earth Science Classroom
The Big Bang Theory: 10 billion to 20 billion years ago:
The “raisin bread” analogyraisins � galaxies, dough � space
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Mr. Fetch’s Earth Science Classroom
The Big Bang Theory: 10 billion to 20 billion years ago:
The “raisin bread” analogyraisins � galaxies, dough � space
Mr. Fetch’s Earth Science Classroom
The Big Bang Theory: 10 billion to 20 billion years ago:
The “raisin bread” analogyraisins � galaxies, dough � space
Note: raisins are not moving through dough.
Rather, blobs of dough are expanding, and
pushing the raisins farther apart.
Note: galaxies are not moving through space.
Rather, blobs of space are expanding, and
pushing the galaxies farther apart.
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