The universe and galaxies
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The Universe and Galaxies. Glencoe Ch.26 Sec. 3: pages 831-835. I. What is the universe?. universe - sum of all matter and energy that ever has, does, and ever will exist everything physical that exists in space and time

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The universe and galaxies

The Universe and Galaxies

Glencoe Ch.26 Sec. 3:

pages 831-835


I what is the universe

I. What is the universe?

  • universe - sum of all matter and energy that ever has, does, and ever will exist

  • everything physical that exists in space and time

    - cosmology – the study of how the universe began, what it is made of and how it continues to evolve and change


Of what is the universe made composed

- Of what is the universe made / composed?

  • stars, planets, rocks, comets, asteroids, dark matter, dark energy


Of what is the universe made composed1

- Of what is the universe made / composed?

- Dark matter – theoretical unseen and undetectable mass that adds to the gravity of a galaxy

- Dark energy – theoretical energy that might be causing accelerated expansion of the universe


Most things we see in space are stars

Most things we see in space are stars

- stars - huge balls of hot gases that emits light

- stars are grouped together by the millions and billions into galaxies


A astronomical distance

A. Astronomical distance

- measured in light years (ly)  a distance measurement

- light year - the distance light travels in one year

 1 light year = 9.5x1015m

 light travels at 3.0x108m/s


B seeing the past

B. Seeing the past

- time is required for light to travel through space

- light travels a little over 8 minutes from the sun to earth

- the farther away an object/star is, the longer it takes for light to get to us, and the older the light is when it gets to us = “Light is OLD”

- we see the past of other stars in the night sky


Ii galaxies

II. Galaxies

- galaxy - grouping of millions or billions of stars, and dust and gas held together by gravity

  • there are an estimated 100 billion galaxies in the universe

    A. 3 Types of Galaxies - classified by shape


Ii galaxies1

II. Galaxies

1. Spiral - disk shaped with spiral arms of dust and gas (fig 26-15, pg. 831)

- dust and gas provide a place for new

stars to form

- young stars are

bluish in color 

gives spiral

galaxies a blue tint

- looks like a pin wheel


Spiral galaxies

Spiral Galaxies


Ii galaxies2

II. Galaxies

2. Elliptical (fig. 26-16, pg. 832)  most common type of galaxy

  • spherical and egg shaped

     NO spiral arms,

    little dust and gas

  • generally have older

    stars (reddish in color)


Elliptical galaxy

Elliptical Galaxy


Ii galaxies3

II. Galaxies

- Range of sizes

a. Giant - trillions of stars, millions of light years in diameter

b. Dwarf - millions of stars, thousands of light years in diameter


Ii galaxies4

II. Galaxies

3. Irregular (fig. 26-17, pg. 832)  least common type of galaxy

- NO well defined shape or structure

  • some have little

    dust or gas, some

    have lots of dust

    and gas


Irregular galaxies

Irregular Galaxies


B milky way galaxy

B. Milky Way galaxy

- the galaxy we live in

- consists of stars, and, clouds of dust and gas between stars (interstellar matter)

- all the stars we see at night are in the Milky Way galaxy (about 400 billion stars)


Milky way galaxy side view

Milky Way Galaxy – side view

  • a huge spiraling disk of stars and interstellar matter (fig. 26-20 pg. 834)  1000 l.y. thick


Milky way galaxy overhead view

Milky Way Galaxy – overhead view

- A huge bulge in

the center

 10,000 l.y. thick


Where are we in the galaxy

Where Are We In The Galaxy?

  • Our solar system

    is about halfway

    between the

    center and the

    edge of the

    galaxy (26,000

    light years from

    the center)


B milky way galaxy1

B. Milky Way galaxy

  • the nearest galaxy to ours is the Andromeda

    galaxy  2.6 million l.y. away


C gravity holds galaxies together

C. Gravity holds galaxies together

- dust and gases and stars are attracted to each other by gravity

  • galaxies are grouped

    into clusters group

    of galaxies bound

    together by gravity


C gravity holds galaxies together1

C. Gravity holds galaxies together

- Milky Way and Andromeda galaxies are in a cluster of ~45 galaxies called the “Local Group”

  • Superclusters - have

    thousands of galaxies

     largest structure

    in the universe


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