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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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